Become a Site Supporter and Never see Ads again!

Author Topic: MXL 990, 991 and Oktava 319 Mods  (Read 62142 times)

0 Members and 1 Guest are viewing this topic.

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
MXL 990, 991 and Oktava 319 Mods
« on: September 21, 2009, 10:55:37 PM »
Attached are pictures of the finished mods to these mics. I didn't post pictures of the internal mods to the Oktava's since the are not as easy to take a part and it was an after thought to shoot them.

I have used the mics on a few live sessions with very good results. One live session will be released as an upcoming cd. I'll let folks know when it becomes available.

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
MXL 990 991-Oktava 319 part 2
« Reply #1 on: September 21, 2009, 10:58:49 PM »
More pics

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
MXL 990 991 Oktava Part 3
« Reply #2 on: September 21, 2009, 10:59:50 PM »
More Pics

Offline Fatah Ruark (aka MIKE B)

  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 9960
  • Gender: Male
  • I dream in beige.
    • sloppy.art.ink
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #3 on: September 21, 2009, 11:05:46 PM »
FYI:

You can post those other pictures as a REPLY to this thread. It will be easier for people to search for in the future.

Very cool stuff though!
||| MICS:  Beyer CK930 | DPA 4022 | DPA 4080 | Nevaton MCE400 | Sennheiser Ambeo Headset |||
||| PREAMPS: DPA d:vice | Naiant Tinybox | Naiant IPA |||
||| DECKS: Sound Devices MixPre6 | iPod Touch 32GB |||
|||Concert History || LMA Recordings || Live YouTube |||

Offline Kindguy

  • Team Bama
  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 6390
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #4 on: September 23, 2009, 05:32:55 AM »
What mod is on the 319?
TDS!

DPA 4023> aeta PSP-2> Apogee Mini Me > R-44

http://www.basicallyfrightened.com/

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #5 on: September 25, 2009, 09:47:21 PM »
Physical:
1) one layer of screen removed
2) foam around base of LD to remove reflective sound
3) Side metal brasing on basket removed
4) Resonator filter around LD removed

Electrical:
1) Many caps and resitors replaced with higher compliance and better grade.
2) 1o db pad and high pass filters removed.


Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #6 on: September 26, 2009, 06:18:17 AM »
How difficult was it to remove the inner layers of mesh from the MXL 990?

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #7 on: September 26, 2009, 10:55:14 AM »
Simple! Needle nose pliers and pull. Also, I would take off the brass ring that surround the SD. I'm not sure why they have it there but my guess was to create a shadow and make it look like a LD.

FYI The 990/901 and 993 share the same cap, circut topolgy and components. They are identical mics. However, the 990 is side address, or course. So you can skip paying any extra for the 603's and go directly to the 990/991 for usually half the price of 603's.

Look for Frank Vagnola and Bucky Pizerelli CD to be release soon. On that session I used the 991 as ORTF, and the 990 as spaced Omni along with the other tracks in the multi track mix. I think you will like what you hear.

Ray
« Last Edit: October 02, 2009, 11:09:12 PM by raymonda »

Offline michaeljoly

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 6
  • Microphone Modification Design & Engineering
    • OktavaMod - Boutique Mics
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #8 on: October 02, 2009, 04:12:39 AM »
In all of these mics, upgrading to a faster FET with less capsule capacitive loading, then biasing for optimum operation makes a big difference as well. There is one manufacturer making a particular version a very stable capacitor that is my choice for the critical capsule to FET input location (no, its not a WIMA Polypro). Its also possible to squeeze 1 uF coupling caps into the 603 bodies for better bass extension.

Similar comments about the 990. In addition I prefer to modify the capsule into a little "saddle" with tapered edges to reduce diffraction effects. Hard to tell from your photos, but the mesh can be completely removed from the capsule to reduce top end resonance in the 990 application because of the sheilding effects of the headbasket.

I didn't realize you Tapers are such crafty DIY'ers!
« Last Edit: October 02, 2009, 04:21:54 AM by michaeljoly »

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #9 on: October 02, 2009, 11:06:56 PM »
Hey Mike,

Great to have you step in side since your work on the Oktava's and MXL's inspired me to work on mine to begin with. I hold your work and technical experience in high esteem.

I left the screens on the 990's because I change the caps, depending on the purpose, from omni to card and it can help protect it from foreign objects and fat fingers.

Thanks for the recomendation of further improvements, which I'll certainly act on. 
« Last Edit: October 02, 2009, 11:14:52 PM by raymonda »

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #10 on: October 02, 2009, 11:18:45 PM »
Quote from: michaeljoly link=topic=127204.msg1690345#msg1690345 date=1254471159
I didn't realize you Tapers are such crafty DIY'ers!
[/quote

I'm glad the adjective you used was crafty and not crappy. :)

Offline michaeljoly

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 6
  • Microphone Modification Design & Engineering
    • OktavaMod - Boutique Mics
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #11 on: October 03, 2009, 12:19:45 PM »

I left the screens on the 990's because I change the caps, depending on the purpose, from omni to card and it can help protect it from foreign objects and fat fingers...

Great idea! Its great to see recordists get under the hood like this. Its really old-school and really how the legends approached their gear.

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #12 on: October 03, 2009, 09:43:09 PM »
Mike,

Does this look like the caps you were talking about? They were used in the 990's but not the 991's, due to a limited supply. Or, take a closer look at the 990's above, since this picture is so bad.
« Last Edit: October 03, 2009, 09:45:18 PM by raymonda »

Offline michaeljoly

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 6
  • Microphone Modification Design & Engineering
    • OktavaMod - Boutique Mics
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #13 on: October 04, 2009, 11:54:36 AM »
I can't tell from that pic, but all these mics have two .22 uF caps, usually polypro, near the output transistors. Those should be replaced with 1 uF polypro to extend the bass response.

Offline Javier Cinakowski

  • !! Downhill From Here !!
  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 4325
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #14 on: October 04, 2009, 12:30:34 PM »
I was looking over your webiste Michael, those Oktava kits look like a really nice value. 

Off topic, but have you looked at doing anything to the Rode NT5 (NT55, Nt6 etc)  ?  I've got a pair of Rode NT6's here that would like to be experiemented with!  :-) 
Neumann KM185mp OR DPA ST2015-> Grace Design Lunatec V2-> Tascam DR-100mkIII

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #15 on: October 04, 2009, 06:42:03 PM »
I can't tell from that pic, but all these mics have two .22 uF caps, usually polypro, near the output transistors. Those should be replaced with 1 uF polypro to extend the bass response.

That is a polystyrene cap, which was choosen over Polypro for the 990's. Lot's of excellent reports regarding this cap in this application. I assumed that is what you might be using, too.

Offline michaeljoly

  • Trade Count: (0)
  • Taperssection Newbie
  • *
  • Posts: 6
  • Microphone Modification Design & Engineering
    • OktavaMod - Boutique Mics
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #16 on: October 06, 2009, 09:15:58 AM »
Right, many folks use a 1000 pF polystyrene cap between the capsule and FET input. I'm using something different that is part of the Premium Electronics package in my mods.

There are two .22 uF caps near output transistors. In the 990 there's enough space to get 1uF polypros in there. Its really tight on the 603 etc mic though.

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #17 on: October 12, 2009, 11:32:22 AM »
Quote
Its also possible to squeeze 1 uF coupling caps into the 603 bodies for better bass extension.

I just tried this on an MXL 991. The 1 uF's are too thick and you can't get two of them in and get the body back on. I assume the 603/604 bodies won't accomodate them either. I was using Panasonic ECQ-V1H105JL from Mouser.

.47's will fit easily with room to spare. You might be able to get .56's in there but I haven't tried it.

The .47's are ECQ-V1H474JL.

The .56's are ECQ-V1H564JL.

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #18 on: October 13, 2009, 11:44:30 AM »
Chris,

Can you post a picture?


Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #19 on: October 14, 2009, 06:29:29 AM »
Raymond -

It looks just like the pictures you posted.

After Monday night's session I'm not so bullish on these MXLs any more. My preference has shifted to the CAD e70 which is about $100 and the capsule-to-FET capacitor can be replaced on them, too.

I'ts a close race but I think the AKG Perception 150/170 comes in at a very close second.
« Last Edit: October 14, 2009, 06:31:37 AM by chris319 »

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #20 on: October 14, 2009, 05:17:49 PM »
Chris,

Did you modify the cap and the body? If not, I would suggest that you try this before giving up on the 991.

Also, the 990, which are side address 991, has more space to play with. You might try a pair of them for moding.

Ray

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #21 on: October 14, 2009, 06:44:53 PM »
Raymond -

It looks just like the pictures you posted.

After Monday night's session I'm not so bullish on these MXLs any more. My preference has shifted to the CAD e70 which is about $100 and the capsule-to-FET capacitor can be replaced on them, too.

I'ts a close race but I think the AKG Perception 150/170 comes in at a very close second.
The AKG might be a good bet, if nothing else I would expect better quality control on the manufacture.

Are they made by 797?  If you get a pair, would you mind posting some pics.

Thanks,
  Richard
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #22 on: October 14, 2009, 07:26:40 PM »
Quote
Did you modify the cap and the body? If not, I would suggest that you try this before giving up on the 991.

"Cap" meaning "capsule" or "capacitor"? I only replaced the capacitors. What is the body modification you refer to? A capsule mod for the 991 is going to put the cost of this mic well above the cost of the CAD e70.

I have already modded two 990s but had a hard time removing the inner mesh.

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #23 on: October 14, 2009, 11:40:35 PM »
Capsule and mic body. I posted the pictures here when I started the thread along with the electronic mods, caps, resistors etc.

If you are handy with a dremmel it takes around 30 minutes per mic, or less, and won't cost you a penny. By machining down the capsule you can place the diaphram closer to the sound source, effectively removing a source of reflective coloring. Again, take a look at the picrures posted above or visit Joly's web site.

IMO, this mod is extremely important in order to get the most from this KM84 clone capsule. I think you will enjoy the results.

Offline notlance

  • Trade Count: (6)
  • Taperssection Member
  • ***
  • Posts: 695
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #24 on: October 15, 2009, 10:16:00 AM »
"If you are handy with a dremmel it takes around 30 minutes per mic, or less, and won't cost you a penny. By machining down the capsule you can place the diaphram closer to the sound source, effectively removing a source of reflective coloring."

So when you machined the capsule with a Dremel, did you disassemble the capsule first to remove the diaphragm?  I would be concerned about those brass filings flying around the diaphragm, but on the other hand I would not want to mess up the capsule by disassembling it.

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #25 on: October 15, 2009, 12:02:31 PM »
Yes, if you don't the cap will be ruined. You need a spanner pin to remove the back thread that holds the cap in place.

I recommend that after you remove the retainer you place your finger on the backplate connection pin to hold the cap in place, while you carefully set the pin on a sold and firm surface. Then slowly lift the cap machined body off. The actual cap will should be balancing on the pin.

Make sure it is a clean and stable surface so the the cap element does not fall over. If it does you will have to re-esemble the cap. Which isn't difficult but can cause dust and other particle to get into it, thus funking up things. If that happens, which you can tell by viewing impression in the diaphram when you re-esemble it, you'll have to use a de-static brush to remove them and re-esemble. There are also two thin mylar spacers that seperate the diaphram from the cap element and can be a bit troublesome but must be used and account for. So, just be careful and don't knock the cap over!!!!!!

Truth be told, once you've done this a few times it is no big deal but keeping things together and away from dust can save you some frustration.

Carefully punch the screens out of the body using your finger. The retaining ring will pop out along with the screens. Place them to the side. You will be using one screen after you have finished with the body.

Then take the cap body out to your shop and go to work on it.

Here how I machine it down.

1) Take a screw driver and place the body on it with the flange side pointing up.
2) Use a metal sanding belt type dremmel attachment.
3) Begin sanding the body, while it is sitting on the screw driver. (when you do so, you will notice that the body spins as it is being sanded. This is what you want it to do because it will uniformly sand the body down)
4) After you get down to a down to 1-1.5 mil stop. You can now round off the edges using the same technique.
5) Finish the job using scotch bright to remove any roughness.
6) Clean with 90% alcohol to remove any particles. Make sure it is totally dry before re-esembling. Any alcohol left in the body will ruin the diaphram.

Re-esemble the cap.

1) Take one layer of screen and place it over the cap, making sure it is in alignment.
2) Slowly slide the the body back over the cap.
3) Carefully lift one side of the body up and slide a thin stiff object under the cap pin. If you have small finger they will work if not use a thin stiff putty knife.
4) Apply enough pressure so you can flip the cap over and the pin side is facing up.
5) Screw the retaining ring back on. Make sure it is firm but not overtightened. You can feel the tolerence by removing the play in the cap. Just wiggle the back pin until there is no play.
6) Look at the diaphram in the light to ensure there are no impressions. If there is, most likely dust got between the diaphram and the element and you'll have to take the cap apart and remove it. (One speck of dust can cause problems, however, if you were able to keep the cap together after disesembling it you will most likely avoid any problems here.

For the side vents on the mic body, simply score the fins with a dremmel cutter. You do not have to cut them off. Then take a flat head screw driver and place pressure by prying on them. The fin should easily snap. Take some needle nose pliers and remove the rest off the fin.

You can use a file to clean up the remaining fin.

I hope this doesn't seem too complicated because once you do it, it is fairly easy.

I can do a two mic bodies and two cap bodies in about an hour's time. Your first time it may take longer.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #26 on: October 25, 2010, 09:53:32 AM »
Old thread, I know...

I've been working on modifying a couple of CAD GXL1200's. Those small yellow ceramic caps are all screwed up on them. The values don't match at all. I'm going to have to re-cap both of them. It looks like the person that assembled them just used any yellow capacitor they could find in each microphone.

C3 and C4 on one mic are .22uf and .47uf. On the other they are both .047uf!
It is good that they put the larger values, but...

The caps at C1 and C2 are screwy too. But, all the resistors are right.

QC is not too good on these mics.



edit to add:
I thought my electronics moding days were over, since my eyes have been failing me lately. I picked up a pair of +3.00 glasses at Walmart and now I'm back in business.  :coolguy:
« Last Edit: October 25, 2010, 10:01:39 AM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #27 on: October 25, 2010, 12:05:53 PM »
Chuck,

I've been stalking your progress. Post some pics and give us your thoughts when finished.

Ray

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #28 on: October 25, 2010, 12:22:28 PM »
Chuck,

I've been stalking your progress. Post some pics and give us your thoughts when finished.

Ray

Will do.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #29 on: October 25, 2010, 05:33:53 PM »
I did get the capsules modified. I touched them up with some Nickel Metallic (Krylon) spray paint.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #30 on: October 25, 2010, 05:37:44 PM »
They looked like this before the mod:
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline jbell

  • TDS
  • Trade Count: (149)
  • Needs to get out more...
  • *****
  • Posts: 4582
  • Gender: Male
  • Spreadicated
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #31 on: October 25, 2010, 07:13:27 PM »
These look similar to the Avantone CK1.  Are they the same mic?

They looked like this before the mod:
Mics: DPA ST4011ER & 4018ER | Neumann kk 184 (matched)> Nbob/PFA
Preamps: DPA MMA 6000 | Audioroot Femto
Recorders: Sound Devices Mixpre-10 II | Sony PCM A10

-20        -12         -6        TDS   (32/48)     
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]][}   
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]][} 
__________________________
|Record|  Runtime: 4:19.99  {|||] 75%

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #32 on: October 25, 2010, 07:55:53 PM »
They all start out as the same microphone, using basically the same circuit and the same capsule. Avantone may have better parts or QC. I have not opened up an Avantone.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #33 on: October 25, 2010, 11:04:10 PM »
I did get the capsules modified. I touched them up with some Nickel Metallic (Krylon) spray paint.

What method did you use to sand them down?

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #34 on: October 26, 2010, 09:18:44 AM »
I hand sanded the front chamber off with 80 - 220 grit sand paper.
Then, I wound some gaffers tape around the sanding attachment on my dremel. I wound enough so that I could slip the capsule housing over it with the capsule being tightly secured. Then I checked and adjusted the run-out until it was pretty even all around.

I turned on the dremel and ran it against increasingly finer sand paper until I got the thickness and chamfer that I wanted. I finished by running it against some ScotchBrite. I measured everything and proceeded with the next one. It took 3 hours total.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #35 on: October 26, 2010, 09:24:08 AM »
Hey Ray, do you know if these caps with fit on the MXL603/CAD GXL1200 bodies? Do they use the same diaphragm?

http://cgi.ebay.com/New-Mic-Hypercardioid-Capsules-MXL-CAD-Apex-45-/290467075180?pt=LH_DefaultDomain_0&hash=item43a12fd46c#ht_2088wt_906

http://cgi.ebay.com/New-Condenser-Mic-Omni-Capsules-MXL-CAD-Apex-43-/290467075171?pt=LH_DefaultDomain_0&hash=item43a12fd463#ht_2088wt_906

http://cgi.ebay.com/Condenser-Mic-Cardioid-Capsules-MXL-CAD-Apex-44-/290467075164?pt=LH_DefaultDomain_0&hash=item43a12fd45c#ht_2088wt_906

They are different than the typical capsule that came with these mics, as the vents are actually on the capsules. They're cheap too!



edit to add:
So far, his is one of the more satisfying recording gear mods I've done. It's so cool to be able to take the capsules apart and see exactly what the components are. If those eBay capsules will work, I'll have a pretty good pair of microphones with omni, cardioid and hyper-cardioid capsules for well under $200!

I've read everything I can get my hands on about these mics and have come to the conclusion that that are worth the work to mod.
« Last Edit: October 26, 2010, 09:36:08 AM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #36 on: October 26, 2010, 08:59:29 PM »
These don't look to be the right match for the MXL's and are not the same ones I bought off e-bay a while back. Wait until the others come back up on ebay.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #37 on: October 30, 2010, 06:39:34 PM »
I finished moding my CAD GXL1200 microphones today.
I took some pictures.
The first picture is the stock internals. The rest of the pictures are of the finished mics.

The next thing is to take them out and use them.



Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline jbell

  • TDS
  • Trade Count: (149)
  • Needs to get out more...
  • *****
  • Posts: 4582
  • Gender: Male
  • Spreadicated
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #38 on: October 30, 2010, 06:41:31 PM »
Nice!  They look good
Mics: DPA ST4011ER & 4018ER | Neumann kk 184 (matched)> Nbob/PFA
Preamps: DPA MMA 6000 | Audioroot Femto
Recorders: Sound Devices Mixpre-10 II | Sony PCM A10

-20        -12         -6        TDS   (32/48)     
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]][}   
]]]]]]]]]]]]]]]]]]]]]]]]]]]]]]][} 
__________________________
|Record|  Runtime: 4:19.99  {|||] 75%

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #39 on: October 30, 2010, 07:35:35 PM »
^^ nice work.


Any benefit to replacing the 1G resistors?  I don't know if they introduce noise or not, but I'm curious.


Also, can you tell me something about the capsule?  Electret or externally polarized?  Does it have the Neumann-look front, a brass plate with regular pattern of holes in front of the capsule?


  Richard

Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #40 on: October 30, 2010, 10:12:31 PM »
Richard, I have taken apart the capsule. It's a gold sputtered diaphragm, a couple of spacers then the back-plate, venting holes and the center connector. The front does not have a plate with holes in front like the Neumanns. There was an elaborate grill on the front of the mic, but it's recommended to remove that, so I did. I put a 3/4" stainless steel screen in front to replace it.

Here's a little bit about it:

http://recordinghacks.com/microphones/MXL/603S

There are photos on line showing the disassembled capsules, but I'm having trouble find them online now. It's my understanding that it's a true condenser.

The capsule gets a lot of praise, that's why I started messing around with this mic. I haven't recorded anything loud with it yet.

I do not have a source for 1G or bigger resistors, so I didn't change them or the stock transistors.


Edit to add photo of dissected capsule.
« Last Edit: October 30, 2010, 10:24:07 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline raymonda

  • Trade Count: (10)
  • Taperssection All-Star
  • ****
  • Posts: 1631
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #41 on: October 30, 2010, 11:12:00 PM »
Nice work!!!!!!!!!!

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #42 on: October 30, 2010, 11:23:36 PM »
^^^ Nice!  Thanks for the tech details.


  Richard
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #43 on: October 31, 2010, 03:53:53 PM »
Chuck...first off, nice work!  So I see you had replaced a lot of stuff.  And I am wondering about a lot of things.  Should I ask here or would you rather take it to PM's or e-mail?  Thanks, Kirk

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #44 on: October 31, 2010, 04:20:38 PM »
Chuck...first off, nice work!  So I see you had replaced a lot of stuff.  And I am wondering about a lot of things.  Should I ask here or would you rather take it to PM's or e-mail?  Thanks, Kirk

Either way. But, keep in mind, I just followed instructions others have posted in various DIY forums. I didn't re-design anything. I can follow a schematic to stuff a circuit board, but I really can't design/re-design a circuit.

I started testing the moded mics this morning, while watching the Broncos lose to SF. :(

One of the bodies has 4-6dB less gain than the other and has a slightly different self noise sound. There is a 4v difference in the voltage getting to the capsules from the bodies. I have to admit that I don't have much experience working on transistor circuits. Op-amps I know pretty well, but transistors and biasing is not something I have done before. If biasing is even the problem ???

I replaced most of the resistors (hand matched values between mics) and capacitors, but left the main transistor 2SK170BL biasing resistors alone. I also didn't change any of the transistors.

Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #45 on: October 31, 2010, 05:49:09 PM »
Right on.  I've been reading this stuff too.  And it seems you took everything out that you could replace.   What did you replace C1, C2, C3 & C4 with?  Are they ceramic?  It also looks like you changed the values of D4 & D5?  And did you just cahnge them out from ceramic to metal film or did you change values too IE: C12.    Thanks for sharing your work, Kirk

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #46 on: October 31, 2010, 06:17:18 PM »
Right on.  I've been reading this stuff too.  And it seems you took everything out that you could replace.   What did you replace C1, C2, C3 & C4 with?
C1    WIMA FKP2 - .01uF /63v (Polyester film)
C2    WIMA FKP2 - .01uF /63v (Polyester film)
I chose those capacitors because Marik had recommended that value for those, and they fit well.

C3   WIMA MKS2 - .47uF /63v (Polyester film)
C4   WIMA MKS2 - .47uF /63v (Polyester film)
Because that's what was available and they fit. I may try different values, if I can find bigger ones that fit.

C11   Panasonic - .033uF/ 100v (Metal film)
C12   Panasonic - .033uF/ 100v (Metal film)
I chose those, because I already had them and again, they physically fit.

It also looks like you changed the values of D4 & D5?
I didn't change those.

And did you just cahnge them out from ceramic to metal film or did you change values too IE: C12.
The resistors I used are good metal films. When I was first testing the mics, I noticed pretty wide tolerances for some of the stock resistors. So, I decided to replace most of them. Then I hand matched everyone, so that the values were (nearly) identical in each mic. I hoped that would make the mics exactly the same in every respect, but that didn't work, since one mic has more gain than the other now.  :-[
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #47 on: November 02, 2010, 03:26:59 PM »
I'm wondering if someone would be willing to provide some circuit design help?
I have attached a schematic for the circuit for the mic. It's not very accurate. But the section of the circuit around the 2SK170BL is what I am concerned with now.

The stock values for the 2SK170BL biasing resistors in my mics are:

R13   91K ohms
R14 470K ohms

Another circuit that uses the same transistor has the values at:

R13 240K ohms
R14 270K ohms

I'm wondering what the difference is and if either set of values is better than the other. For kicks, I changed the values in one mic to 240k and 270K and didn't notice any big difference. It didn't change the noise or output level by much. I'm hoping someone can give some guidance on what the best values would be.


edit to add schmatic for another mic that uses the 2SK170BL transistor (GenChinaMic.pdf).
« Last Edit: November 02, 2010, 03:34:08 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #48 on: November 02, 2010, 03:33:55 PM »
^^^ Thanks for the schematic!


Looks pretty standard for modern mics, in particular, transistor at the upper left to generate the 60V or so polarization voltage.  There is a similar circuit in the Studio Projects C4 and many others.


  Richard

Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #49 on: November 02, 2010, 03:45:56 PM »
No sweat Richard.

I wonder if the lower gain from one of my mics is because there is a 4v difference getting to the capsules of each mic? I don't think either is getting 60 volts. Off the top of my head, I thought it was more like 40v for one and 36v for the other. I don't know how to tweak the circuit to make sure both mic capsules get the same voltage.
« Last Edit: November 02, 2010, 03:49:17 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #50 on: November 02, 2010, 04:50:15 PM »
Jon, thanks for the reply. Is that something I could, or should do? Replace the resistors with a 500k or 1 megohm cermet trimpot?
But, I don't have a scope to view distortion with and how do you feed signal to the mic to even measure it?

Also, why does one circuit use completely different values for those resistors? Is there an ideal range? It's always been my understanding that high value resistors contribute more noise than lower values. Again, I'm a neophyte here just looking to learn and make these mics as good as I can with limited equipment.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #51 on: November 02, 2010, 05:45:43 PM »
I use my DAW and converters to generate/analyze test signals.

I'd love to read the details of how to do that if you don't mind sharing. Even a link to a source I could read about doing that would be great.

I can generate signals, I just don't know how to send them to the transistor then monitor it for distortion. If I used a pot to figure out what the values should be, I could then find fixed value resistors to permanently install.

How close of a tolerance does the resistor ratio need to be? Also, if I get one 2SK170 done would I have to do the same thing for the other mic? Is there a big difference between individual transistors? If not, I'd think the best values would be posted somewhere.

Edit to add:
I just measured the voltage at R9 on the GenChinaMic.pdf circuit. I got 20.1v on one mic and 24.3v DC on the other.

« Last Edit: November 02, 2010, 06:01:01 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #52 on: November 02, 2010, 06:38:41 PM »
So as I follow this thread with EXTREME interest.......ANd if you could see this, I now have 4 mics sitting apart on my desk >:D....I want to piggyback in on Chucks questions.  General question (to Jon?  Thanks in advance who ever answers)  Is there a big difference if I sub a .047uf capacitor for a 0.033 one in the generic C3 position of a mic?  What will the difference do?   Then is there a big sound difference between a Wima polyester style and a metal film style?  Thanks everybody...and a BIG BIG thanks to Chuck for posting this and sharing his work.   
« Last Edit: November 02, 2010, 06:44:28 PM by kirkd »

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #53 on: November 02, 2010, 07:13:08 PM »
That's odd.  Why bother with a step-up circuit when ~34V is available straight off the XLR pins  ???

I thought the same thing. Maybe it would be possible to just bypass the step-up circuit. It might make the mic less noisy that way too.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #54 on: November 02, 2010, 08:29:31 PM »
That's odd.  Why bother with a step-up circuit when ~34V is available straight off the XLR pins  ???

I thought the same thing. Maybe it would be possible to just bypass the step-up circuit. It might make the mic less noisy that way too.

If the polarization voltage is really 20V, then an increase to 34V will certainly increase sensitivity (5dB or so), which will also lower relative noise as a hotter signal will hit the FET.  That, however, will decrease max SPL correspondingly.

The advantage of the step-up is for low-voltage phantom; it will tolerate some degree of low supply voltage before dropping out of spec.  That's why it might be good to revise the step-up circuit instead.  But if you don't need that, then yeah, trying bypassing the step-up (just remove R9, and route new 1M resistors from pins 2 and 3 to C9).

Really?
So, I could just tie XLR pins 2 + 3 to the positive side of C9 and that will bypass the step up circuit? I've read that Marik advocates bypassing the step-up circuit. I will try it. But, just to make sure, I can remove R9 (1M), tie that to PIN 2 and C9, tie another 1M resistor from XLR PIN 3 to the positive side of C9?

That can't be right, it would combine the in phase and out of phase signals. ???

I just want to make sure I have it right, as I don't want to blow the thing up :) Can I also remove R12 (1.5k)? That resistor is also tied to the step up circuit.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #55 on: November 02, 2010, 08:30:45 PM »
Jon, Thanks for the reply.  Thanks for sharing your knowledge.  I should have known better than to say something is generic when all these mics are just slightly different between manufacturers.  But I believed you answered my question.  I'm reading the article and working on digesting that.   At this point I'm thinking I am almost ready to try and work on my mics.  The SDC's are first.  Then we'll see about the LDC's.  Based on Michael Jolly's observations he states that most of these SDC's have a HF bump due to the vent configuration.  While I am not ready to start cutting the vent area to open it up the Samson CO2's had a very tightly meshed screen behind the open.  So first I removed that and I removed the small foam piece above the mic capsule.  There was no easy way to get the capsule more forward in the housing due to it's design.  And there was no easy way to remove the screen with out really tearing things apart.  So I left it alone.  But it does look like the vents are a lot more opened up now.  Here are some before and after pix.  Next will be the actual soldering ;D

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #56 on: November 02, 2010, 08:49:28 PM »
Hmmm... that cap isn't the same cap I have on mine.
The GXL1200's and MXL 603's have the shorter capsules. They don't have the vents like your's. The vents are on the mic body. I've inquired about the capsules you have pictured and have been told by several sources that those capsules are not interchangeable with the GXL1200/ MXL603 bodies.

Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #57 on: November 02, 2010, 09:38:00 PM »
Jon, Thanks for the reply.  Thanks for sharing your knowledge.  I should have known better than to say something is generic when all these mics are just slightly different between manufacturers.  But I believed you answered my question.  I'm reading the article and working on digesting that.   At this point I'm thinking I am almost ready to try and work on my mics.  The SDC's are first.  Then we'll see about the LDC's.  Based on Michael Jolly's observations he states that most of these SDC's have a HF bump due to the vent configuration.  While I am not ready to start cutting the vent area to open it up the Samson CO2's had a very tightly meshed screen behind the open.  So first I removed that and I removed the small foam piece above the mic capsule.  There was no easy way to get the capsule more forward in the housing due to it's design.  And there was no easy way to remove the screen with out really tearing things apart.  So I left it alone.  But it does look like the vents are a lot more opened up now.  Here are some before and after pix.  Next will be the actual soldering ;D
Hey now.  That Samson C02 is a Transsound brand, electret capsule.  It is similar to those found in AT2020/21 and Behringer C2.  (Note: The Behringer B5 is an externally polarized cap).


There is nothing wrong with electrets -- some great mics use them.  The problem is Transsound are pretty much middle of the road.  You'll get much nicer/smoother and more detailed sound out of some of the other electrets, including: Sennheiser MK40 (KA10 capsule), AT822/825, AT3031/4021, etc.


As for externally polarized capsules, there seem to be lots of options, MXL, APEX, CAD, SP, AKG, etc.  Too many to mention, but they all have a decent chance... provided the quality control is there.

Nothing wrong with modding.  I might just wait until you have a better capsule in there first.  And, in the meantime, please keep the pictures coming!

  Richard

« Last Edit: November 02, 2010, 09:42:11 PM by illconditioned »
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #58 on: November 02, 2010, 10:42:18 PM »
Jon, is this what you have suggested?
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #59 on: November 03, 2010, 09:01:22 AM »
Cool. Thanks Jon. I'll try that.
I bought another mic over the weekend. I'm going to keep one mic that I can experiment on.


edit to add:
I revised the drawing and attached it here.
« Last Edit: November 03, 2010, 01:39:49 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #60 on: November 03, 2010, 11:54:02 AM »

Hey now.  That Samson C02 is a Transsound brand, electret capsule.  It is similar to those found in AT2020/21 and Behringer C2.  (Note: The Behringer B5 is an externally polarized cap).


Nothing wrong with modding.  I might just wait until you have a better capsule in there first.  And, in the meantime, please keep the pictures coming!

  Richard

Richard,
  Any direct replacement ideas?  Or, any replacement ideas that won't require a lot of work to make then fit?  I'm not gonna buy different mics to mod right now.  But I'm willing to put some time into these.  Will the KA10 capsule fit? 

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #61 on: November 03, 2010, 01:20:49 PM »

Hey now.  That Samson C02 is a Transsound brand, electret capsule.  It is similar to those found in AT2020/21 and Behringer C2.  (Note: The Behringer B5 is an externally polarized cap).


Nothing wrong with modding.  I might just wait until you have a better capsule in there first.  And, in the meantime, please keep the pictures coming!

  Richard

Richard,
  Any direct replacement ideas?  Or, any replacement ideas that won't require a lot of work to make then fit?  I'm not gonna buy different mics to mod right now.  But I'm willing to put some time into these.  Will the KA10 capsule fit?
I cannot suggest a replacement.  The KA10 capsule is smaller, 10mm diameter.  This is in many Sennheiser products, like gooseneck and lav mics.  I have not (yet) found a good source, but you can find this capsule in the "sennheiser driven" cardioid capsules from microphone madness.  This capsule sounds great, and will beat most mini cardioid electrets (AT853, CA-11, Audix micros).  This is my opinion anyway.


Honestly, these mics are not worth modding unless you can get a better capsule in there.  If you're looking for a cheap DIY project, I can think of two options.  One is getting an old AT822 stereo mic and ripping the capsules out, and running on plug in power.  The other is getting something like AT3031, AT3035 or similar, and using the capsule from these.  These are all electrets, although different size then the Samson mics.


  Richard
« Last Edit: November 03, 2010, 01:23:23 PM by illconditioned »
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #62 on: November 03, 2010, 01:50:25 PM »
I have to say that I'm really learning a lot about microphones and microphone design by moding the CAD GXL1200's.
I got to take-a-part a condenser capsule and see what the components are. I'm learning about the best circuits to power capsules and it's pretty cheap to buy the MXL603 clones. I guess the proof will be how they sound after I'm done.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #63 on: November 03, 2010, 04:03:24 PM »
Jon, I took a look at Zapnspark's BiasingFETScopeMethod.pdf http://tech.groups.yahoo.com/group/micbuilders/files/Zapnspark/

I'm wondering if I can test the JFET in the circuit, or should I build a bread board circuit to bias it? He has a 10k resistor at the gate. Would it work OK with the stock 1G that's there now? I figure I can make a 1k sine wav CD run that signal through a passive pot, hook it up between C2 and ground. Then monitor on my DAW between R4 2.2k and ground. The ideal setting is when both the positive and negative peaks distort at the same point, right?

Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #64 on: November 03, 2010, 05:24:29 PM »
Can anybody tell me what these are?

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #65 on: November 03, 2010, 05:42:55 PM »
And while I had the camera out, I took these.  But I really doubt if I want to touch them.  Thought y'all might wanna see.  Mics are Toa KY's and these are the guts part.  The mic capsule is a separate piece.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #66 on: November 03, 2010, 06:20:58 PM »
Can anybody tell me what these are?

Looks like one 1nF ceramic & 1.5nF (Maybe Mylar) capacitors. One is 63v the other 100v.
« Last Edit: November 03, 2010, 06:23:46 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #67 on: November 03, 2010, 08:01:34 PM »
Do the voltage ratings matter or is it just that they must be able to handle that much voltage?  IE: if I used a 1K  250v metal film would it do anything different than a  1K 100v  polyester?

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #68 on: November 04, 2010, 02:43:02 AM »
any jfet replacement suggestions?  since we are closer to being able to bias our existing fet for ourselves, is their any room for real world improvement?

BTW, thanks to Jon for the expertise and Chuck for the motivation to mod the remaining Apex 185's I have... Thanks to Raymonda for the housing mod motivation...

Joe

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #69 on: November 04, 2010, 08:04:58 AM »
Some say the J305 is a good one. I have attached Zapnspark's schematic for that FET.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #70 on: November 04, 2010, 11:47:31 AM »
Jon, on that circuit, how do you increase the polarizing voltage? Or make it exactly the same in two different mics?
After reading more, I think it may not be such a good idea to bypass the DC up converter, because there is no regulation if the phantom power source dips. When the phantom power voltage dips, it lowers the output of that FET. I'm convinced that there is something wrong with the DC converters in one of my mics. I read about someone else who had the same problem, 4 db less output from one mic. He bypassed the DC converter, and that fixed the problem, but he said the microphones output would ride up and down with the phantom power voltage.

One more thing...
I've read that 20-30v DC is normal for the polarizing voltage in the 603 circuit. I wonder if just matching the zeners between a stereo pair would be a good way to get equal voltage going to each mic? I hope that makes sense.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #71 on: November 04, 2010, 02:08:52 PM »
Can anybody tell me what these are?

Looks like one 1nF ceramic & 1.5nF (Maybe Mylar) capacitors. One is 63v the other 100v.

OK since there is room I'm gonna swap out the 1nF 100v for a 1K 250v metal film. 

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #72 on: November 04, 2010, 02:26:38 PM »
Can anybody tell me what these are?

Looks like one 1nF ceramic & 1.5nF (Maybe Mylar) capacitors. One is 63v the other 100v.

OK since there is room I'm gonna swap out the 1nF 100v for a 1K 250v metal film.

I know that lots of guys say that it's best to have capacitors just slightly over the working DC voltage in circuits. In microphones that applies, because higher voltage caps are bigger, so there may not be room for them to fit. I may do another Mouser order soon. If you can wait, I would send you some of the Xicon 1000pf 50v Styrene capacitors that everybody seems to like. I also raided my local electronics supply warehouse last week and picked up a bunch of different mylar & polyprop caps to try when I have the time.

edit to add Mouser link: http://www.mouser.com/search/Refine.aspx?Ntt=Xicon%20Polystyrene%20Film%20Capacitors
« Last Edit: November 04, 2010, 02:32:13 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #73 on: November 04, 2010, 06:53:21 PM »
Seems there has been a discussion about the oscillator circuit at Micbuilders, they say it outputs 60V.  Curious.  I don't have time to breadboard it myself anytime soon, I am quite backlogged on development projects . . .

OK. Like you said a couple of pages ago. It's hard to measure the DC, because of the high resistance at the capsule position. I measure it again and found that the DC voltage before it hits the 1G resistor in one mic is 44v. It's 38v on the other. Not sure why it measured 20v and 24v previously. I measured the voltage inside the mics using three of my P48 mic pre-amps and got the same result, 44v on one and 38v on the other.

Also, as soon as the 48v hits the mic load it gets knocked down to 32v across XLR pins 1 & 2. So, the up-converter is working to bring it back up on both. But it's not getting the voltage up to 60v on either mic. I know that Michael Joly advocates higher voltage on those mics. The posts I find from Marik advocate bypassing the DC converter and running the mics at lower voltage.

Can you provide a link to the discussion on Micbuilders?

Edit to add discussion on micbuilders here:
http://tech.groups.yahoo.com/group/micbuilders/message/14006
« Last Edit: November 04, 2010, 07:26:01 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #74 on: November 05, 2010, 12:26:02 PM »
Now, I'm cOnFUseD  by the discussion at micbuilders ???

It sounds like there is no real consensus on how to measure voltage reaching the microphone capsule with a typical DVM.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #75 on: November 05, 2010, 01:00:28 PM »
So, when I measure 44v before the resistor, that is really only 90.1% of the actual voltage that the capsule gets? The reason for this is the very high resistance in the circuit negatively affects my DVM? Thank you very much for explaining that.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #76 on: November 05, 2010, 02:40:37 PM »
Jon, I guess that's why you design such good circuits. You've got all the formulas and math behind you.

I had no idea it was that complicated to just figure out how much voltage is getting to the mic capsules.

Since the only components I haven't swapped out of the circuit are the DC converter components, I guess that's going to be the next thing for me to look at.

My local electronics warehouse has a have a good supply of the 6.8pF and 27pF capacitors that are in that circuit. Maybe even inductors (are they RF inductors?) that are close in value. It sounds like small variations in those components may be responsible for the different DC output voltage between the mics. If I can match up those components more closely in both mics hopefully the capsules will each get the same voltage, so they will be matched more closely.

I really appreciate your input.
« Last Edit: November 05, 2010, 02:45:11 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #77 on: November 07, 2010, 07:32:01 AM »
I am now set up to measure mic frequency response, which I have done with the MXL 991. Below are links to curves of an unmodified 991 and a (different) modified 991:

Unmodified:

http://groups.yahoo.com/group/micbuilders/photos/album/1663506385/pic/417612400/view?picmode=original&mode=tn&order=ordinal&start=1&dir=asc

Modified:

http://groups.yahoo.com/group/micbuilders/photos/album/1663506385/pic/953648042/view?picmode=original&mode=tn&order=ordinal&start=1&dir=asc

The output of the unmodified mic is significantly lower than the modified mic. The only components modified were capacitors. Both mics exhibit a 3 - 4 dB dip around 6 kHz.
« Last Edit: November 07, 2010, 08:46:42 AM by chris319 »

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #78 on: November 08, 2010, 09:31:40 AM »
Cool. Thanks for that Chris.

Well, I have the answers to some of the issues I had.
One of my DVM's must have a lower impedance than the other, because I still get 24 ~volts when measuring the voltage before the 1G resistor with that meter.
My other DVM measures closer to 50v. I looked up the specs on that meter and it has 10M input impedance.

I was able to regulate the voltage between the two moded mics by using different values for the 27pF capacitor in the DC converter section. I found that if I lowered the capacitor value, for the lower voltage mic it brought the voltage up enough to closely match the other mics voltage. I couldn't find the exact right ratio in the 27pf caps I had, so I paralleled two 6.8pf caps together for each mic. This brought the voltage up around 8v in each mic. Now they are both within +/- 1v of each other. The mics are much quieter now too. They seem to like the higher voltage.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Roger Gustavsson

  • Trade Count: (1)
  • Taperssection Member
  • ***
  • Posts: 423
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #79 on: November 08, 2010, 11:43:25 AM »
I am now set up to measure mic frequency response, which I have done with the MXL 991. Below are links to curves of an unmodified 991 and a (different) modified 991:

Unmodified:

http://groups.yahoo.com/group/micbuilders/photos/album/1663506385/pic/417612400/view?picmode=original&mode=tn&order=ordinal&start=1&dir=asc

Modified:

http://groups.yahoo.com/group/micbuilders/photos/album/1663506385/pic/953648042/view?picmode=original&mode=tn&order=ordinal&start=1&dir=asc

The output of the unmodified mic is significantly lower than the modified mic. The only components modified were capacitors. Both mics exhibit a 3 - 4 dB dip around 6 kHz.

How did you measure them? Cardiod microphones need to be measured at exactly the same distance, the response varies a lot with distance. I think you will have to be registrated at micbuilders to see the pictures.

Roger


Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #80 on: November 08, 2010, 12:59:12 PM »
How do I attach a jpg in this forum? I can't seem to find a way to.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #81 on: November 08, 2010, 01:15:46 PM »
Use the Additional Options button when replying.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #82 on: November 09, 2010, 06:04:05 PM »
Quote
How did you measure them? Cardiod microphones need to be measured at exactly the same distance, the response varies a lot with distance.

I came across a paper from Neumann discussing this. The short story is that 60 cm (24") is considered a sufficient distance to overcome proximity effect.
« Last Edit: November 09, 2010, 06:33:05 PM by chris319 »

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #83 on: November 11, 2010, 01:25:19 PM »
any jfet replacement suggestions?  since we are closer to being able to bias our existing fet for ourselves, is their any room for real world improvement?

BTW, thanks to Jon for the expertise and Chuck for the motivation to mod the remaining Apex 185's I have... Thanks to Raymonda for the housing mod motivation...

Joe
Joe, Any chance of posting pix of the 185 guts?  I'm wondering how different the layout is compared to the 180's. 

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #84 on: November 11, 2010, 02:22:48 PM »
sure, i'll post this afternoon. btw, 185= 603 clone w/ rolloff and pad, 180 = 603 Clone, 190 and 195 are electret ala your c02 more than likely.

frontend audio carries the 185 stereo kit ( shocks, omni, card, body all in pairs, case ) for $110 shipped.

wonder how much busman wants for hyper caps....

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #85 on: November 11, 2010, 02:29:22 PM »
Saw hypers on ebay for $8 Dunno how good they are.  Thanks for info, I'm think bout some 180's to play with.  without changing the capsules on the CO2's there is probably a limit on the quality I can get out of them.   I thought with the switches they revert to surface mount parts to make room for things.  for me that equates to harder to work on.  I'm already wearing glasses to see this stuff and even have a "special" set that are about 5X for real small stuff. 

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #86 on: November 11, 2010, 03:53:16 PM »
   I thought with the switches they revert to surface mount parts to make room for things.

Nope still all through hole construction.... Same part to mod, same part numbers....

 Having a hard time finding previous photos after a os reinstall.... may have to shoot more for you! 

Electret capsules or externally biased? 

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #87 on: November 11, 2010, 04:08:47 PM »
Chinese SD microphones with the transformerless Schoeps style circuit
All use the same capsule(s)

797 Audio CR1-4
ADK SC-1
ADK SC-2 *
ADK SC-T
Advanced Audio CM-54 *
AMT 404
Apex 180
Apex 185 *
Audio 2000 ACM1901 *
Busman BSC-1
CAD GXL 1200
Carillon AXIS 1
Cascade M37
Cascade M39 (available in all silver & all black) *
Felio CR1-11
Feilo CR1-14 *
KAM i2 (all black) *
Marshall MXL 600
Marshall MXL 603
Marshall MXL 603S (super cardioid capsule)
Marshall MXL 604 *
Marshall MXL 991 *
Nady CM-90
Nady CM-95 *
Peluso CEMC-6 *
SE Electronics SE1
SE Electronics SE1A
SE Electronics SE2A

__________________________________________

* These microphones have the pad and high pass switches
« Last Edit: November 11, 2010, 04:20:03 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #88 on: November 11, 2010, 04:13:30 PM »
This search: http://shop.ebay.com/?_from=R40&_trksid=m570&_nkw=MXL+capsules
brings up a Hong Kong vendor selling $7.49 capsules on eBay. But it's my understanding that the center pin connector does not make contact with the center pin on the 603 style mics. Also, the cardioid version and hyper-cardioid version have the venting on the capsule, if you look closely.

Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #89 on: November 11, 2010, 04:20:45 PM »
all the above is correct, leading back to busman being the friendly dealer of hyper caps KNOWN to work....

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #90 on: November 11, 2010, 04:27:24 PM »
Those cheap capsules on eBay are meant for this style mic:

http://www.mxlmics.com/products/900_series/993/993%20.html

I have not done much research on these.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #91 on: November 11, 2010, 05:12:12 PM »
Electret capsules, I looked at mouser and digikey  options but I don't think that there is a drop in replacement.  I don't know if I want to get into retro fitting one into the head assembly. 

I do know that the ADK SC bodies will fit their own Zigma capsules but those capsules will not fit the MXL mic bodies.  And I guess not all of the capsules interchange due to center pin lengths head mounting styles and thread pitch. 


797 makes a crap load of stuff for a crap load of manufacturers.  From what I have gather some of the products them make have better QC due to the manufacturers requiring it from them.  At one point I had contacted them regarding buying a 414 clone but they will not sell some of there stuff in the US...imagine that >:D 

I am assuming that list of mics are all true condensers?  And then there would be a list of Electret capsule mics?

Here is a a question, what about the Karma K-10? 

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #92 on: November 11, 2010, 05:21:04 PM »

797 makes a crap load of stuff for a crap load of manufacturers.  From what I have gather some of the products them make have better QC due to the manufacturers requiring it from them. 


That is exactly it.  I've heard bad things about Apex mics, for example.  And I tried one (a stereo USB mic) and it had all kinds of hissing/popping noises in it.  I'm guessing a MXL or similar mic is the place to start.  Those will have decent QC.  Oh yeah, I'm guessing a lot of the QC is in the capsules themselves.


  Richard

Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #93 on: November 11, 2010, 06:00:24 PM »
I am assuming that list of mics are all true condensers?  And then there would be a list of Electret capsule mics?
Here is a a question, what about the Karma K-10?

I've been doing some research on this. That list is all condensers that start out as the basic China 797 Schoeps circuit mic. There are some differences. Some of the capsules have that heavy metal front grill. Some of the bodies have more or different vent openings. Some of the circuits have different component values. Some use better quality components, etc...

Like Richard, I've investigated most of the low cost electrets, but they don't appeal to me as much as the gold sputtered condensers mentioned here.

As far as the Karma mic... I excluded it from the list, even though it uses the same capsules, because it's got a transformer in it and the others do not. It also has surface mount components, which are not user friendly for typical mic moders.

I'm getting to the point where I can hardly work on through-hole circuits anymore because of my eyes and arthritis. So, SMT is definitely not for me.  ;)
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #94 on: November 11, 2010, 06:25:07 PM »
the apex 185 card caps have the grill with screen behind. the omnis are a screen front style cap. the busman caps are all screen front as far as i can tell.

i wouldn't be suprised that one of these low cost usb mics sucked, but i don't feel tbat either of my pair of apex 185s suffer for lack of qc. ( or at least any more than any of the others in this class!)

the 993 mxl's are the same topology as the 603 clones but different case.... the question becomes whether the pins meet for electrical contact and how the extra vents would affect performance.

$8 is  certainly cheap enough to experiment with if they do contact.... maybe micheal will chime in soon about the 993 caps soon!

Joe
« Last Edit: November 11, 2010, 06:26:51 PM by bugg100 »

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #95 on: November 11, 2010, 07:26:58 PM »
I cross posted over at GearSlutz

http://www.gearslutz.com/board/low-end-theory/395643-best-budget-mics-my-recommendations-19.html#post5993278

and Michael responded with this:

The 993 has the same pronounced HF peak (8dB@8khz or so) as the 603, CM-90, 1200 etc mics due to a combination of the capsule diaphragm tension, backplate design and acoustic chambers in front and behind the diaphragm. It takes a comprehensive modification of the capsule system to remove the narrow-band HF peak from these mics without attenuating the 16kHz air.

It's seems strange to me that they made the bodies longer, and they added vents to the capsules, but the same capsule frequency anomalies persist  ??? Why didn't they address some of the frequency issues of the earlier production runs and improve them in the next runs?

One good thing is that there is plenty of information to be found online for this type of microphone for moders.
I didn't have a good understanding of the issues involved in making quality microphones when I first started digging into these. Now, I'm starting to realize that it's just not that easy to make great sounding mics.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #96 on: November 13, 2010, 08:00:56 AM »
Here is my DIY frequency response curve for an MXL 991 with a cardioid capsule, after having replaced the stock ceramic capacitors.
« Last Edit: November 13, 2010, 10:24:26 AM by chris319 »

Offline OOK

  • Trade Count: (17)
  • Needs to get out more...
  • *****
  • Posts: 2727
  • Gender: Male
  • formerly OtherOneK
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #97 on: November 13, 2010, 11:18:41 AM »
Here is the stock curve for the 991 from the MXL site for comparison...........The card pattern is more wide card than card...



 
DPA/HEB 4060's > R09HR
MBHO648/KA100Lk/KA200/KA300/KA500 > SD702

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #98 on: November 13, 2010, 12:46:52 PM »
I know you said it is a DIY graph.  But wow, that seems like a sharp valley at ~6.3K and quite the hump between 9K & 16K.  Does the 2dB or so opposites give a flat type of sound?  After reading that back to myself it doesn't make a lot of sense so I guess what I'm wondering is how different does it sound?   How accurate do you think your readings are? 
« Last Edit: November 14, 2010, 04:18:03 PM by kirkd »

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #99 on: November 13, 2010, 11:59:53 PM »
There is one caveat in the fine print of my curve: it is a 1/12 octave curve. Generally in mic measurement 1/3 octave curves are used. My curve has less smoothing because measurements are taken at a narrower spacing of frequencies than a 1/3-octave curve (assuming the manufacturer has put out an honest curve which hasn't been "embellished").

I do not have an anechoic chamber, but reflections can be neutralized in today's software using a Fast Fourier Transform -- you just have to know how to manage them. I am pretty certain about that 6 kHz notch. Other mics I have tested do not exhibit this notch, so I have ruled out the room, the setup, etc. I have a pair of AKG Perception 150s which I have measured; one has a notch just before the presence peak and the other doesn't. This makes me think that the reason a $100 mic sells for $100 is that the manufacturer does not do much in the way of quality control, such as discarding capsules that are way out of spec.

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #100 on: November 14, 2010, 01:54:37 AM »
You're making a lot of assumptions about my setup without first having it explained to you.

I use an omnidirectional (no proximity effect) reference mic which has been calibrated by an acoustical laboratory. The distance from sound source to mic is kept constant at 24". When mics are changed they are moved to maintain this distance. The FFT resolution is on the order of 3 Hz. I have measured several dynamic mics and some of them have a great deal of low-end roll-off, so if a mic doesn't have low-end response it will show up in the curve.

I actually own two calibrated omnidirectional reference mics. When measured one against the other the frequency response curves cancel at 0 dB plus or minus one dB or so from 20 Hz to 20 kHz, close enough for me.

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #101 on: November 14, 2010, 02:10:24 AM »
Attached is a curve for an omnidirectional E-V RE85 showing very little low-end response. All you have to do is listen to this mic to hear the lack of low end. Also attached is a curve for a cardioid E-V N/D 367s measured at 24". If proximity effect were an issue it would likely show up in this curve.


Offline dogmusic

  • Trade Count: (0)
  • Taperssection Member
  • ***
  • Posts: 850
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #102 on: November 14, 2010, 07:55:16 AM »
This search: http://shop.ebay.com/?_from=R40&_trksid=m570&_nkw=MXL+capsules
brings up a Hong Kong vendor selling $7.49 capsules on eBay. But it's my understanding that the center pin connector does not make contact with the center pin on the 603 style mics. Also, the cardioid version and hyper-cardioid version have the venting on the capsule, if you look closely.

I was looking at buying the omni version of those capsules for my 603's. Where did you learn that the center pin connector does not make contact with the center pin on the 603 style mics?

Phillip
"The ear is much more than a mere appendage on the side of the head." - Catherine Parker Anthony, Structure and Function of the Human Body (1972)

"That's metaphysically absurd, man! How can I know what you hear?" - Firesign Theatre

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #103 on: November 14, 2010, 10:42:13 AM »
This search: http://shop.ebay.com/?_from=R40&_trksid=m570&_nkw=MXL+capsules
brings up a Hong Kong vendor selling $7.49 capsules on eBay. But it's my understanding that the center pin connector does not make contact with the center pin on the 603 style mics. Also, the cardioid version and hyper-cardioid version have the venting on the capsule, if you look closely.

I was looking at buying the omni version of those capsules for my 603's. Where did you learn that the center pin connector does not make contact with the center pin on the 603 style mics?

Phillip

Through reading various threads on the Gearslutz and Prodigy-pro message boards.
I have not tried putting those caps on my mics. So, I do not have first hand knowledge.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #104 on: November 14, 2010, 11:37:21 AM »
jim jacobsen responeded as such on gearslutz recently.... 

frontendaudio sells them seperate and in the past they have been on ebay. chris busman, a member here sells them also. and he is one of the few with hypers.....

joe

Offline Javier Cinakowski

  • !! Downhill From Here !!
  • Trade Count: (11)
  • Needs to get out more...
  • *****
  • Posts: 4325
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #105 on: November 14, 2010, 01:51:50 PM »
I need to dig up some old posts/emails, but the k10 does not share the same capsule lineage as the 797 mics. Karma has something to do with the seelectronics/felio split.

The list earlier in this thread has mics that are made in-house, not rebranded.  797 and Felio arn't the only manufactures in hk/shanghai.    seelectronics has its own factory now, I would imagine they are similar to Rode, making their own mics from evolved 797 designs.  Just cause the threads are the same doesn't mean the actual capsule was made in the same plant.
« Last Edit: November 24, 2010, 09:44:53 PM by Javier Cinakowski »
Neumann KM185mp OR DPA ST2015-> Grace Design Lunatec V2-> Tascam DR-100mkIII

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #106 on: November 14, 2010, 06:39:43 PM »
Quote
earlier you said that your measurements were in reference to the manufacturer's curve, which I took to mean MXL's curves

I looked over my posts in this thread and didn't find myself saying that. I said my curves are 1/12 octave compared to other curves which are generally 1/3 octave.

Quote
Still, you have a cardioid, albeit a very wide cardioid, with -3dB at 20Hz.  That is unusual.  It's actually more typical of a small diaphragm omni.

Maybe so, but it's still a pressure gradient transducer owing to the existence of vent holes behind the diaphragm. If the bass response were deficient in this mic I'm sure it would show up just as it did with the E-V mics.

Quote
Joly's observed +8dB 8kHz peak is gone missing.

With all due respect to Michael, maybe that peak is in his ears rather than derived through actual measurement. The whole point of my setting up a measurement station is to bring some objective data to the discussion which has not been embellished by a manufacturer. The other option is to send these mics out for testing but that costs $$$.

BTW I did some proximity effect tests. It starts to become noticeable around 18" from the sound source, up about 1 dB at 50 Hz. At 24" it is so tiny as to be considered negligible.

Offline goodcooker

  • Trade Count: (43)
  • Needs to get out more...
  • *****
  • Posts: 4731
  • Gender: Male
  • goes to 11
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #107 on: November 14, 2010, 10:13:32 PM »
Awesome...now I'll have something to do when it starts snowing  ;D
Line Audio CM3/OM1 || MBHO KA500 hyper>PFA|| ADK A51 type IV || AKG C522XY
Oade Warm Mod and Presence+ Mod UA5s || Aerco MP2(needs help) || Neve Portico 5012 || Apogee MMP
SD Mixpre6 || Oade Concert Mod DR100mkii

pocket sized - CA11 cards > SP SB10 > Sony PCM A10

http://www.archive.org/bookmarks/goodcooker

"Are you the Zman?" - fan at Panic 10-08-10 Kansas City
"I don't know who left this perfectly good inflatable wook doll here, but if I'm blowing her up, I'm keeping her." -  hoppedup

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #108 on: November 15, 2010, 01:04:42 AM »
I should elucidate on my proximity effect measurements. Going from 24" to 18", a small increase in proximity effect is observed on the order of 1 dB. Going from 24" to 30", the increase in bass due to proximity effect is tiny -- a small fraction of a dB. The measurements were made with a Shure SM57. The E-V N/D 367s, a cardioid, demonstrates that proximity effect is not a major factor in my measurements with a mic having such poor bass response.

I prefer to go by objective measurements rather than subjective guesstimates of what people think they hear, particularly when we don't know the characteristics of the device they are using to listen.

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #109 on: November 15, 2010, 01:04:57 PM »
Yes clearly Mr. Fouxman and I are dilettantes who are incapable of making an objective measurement.

Good day to you.

What did I say to warrant such sarcasm? I never intimated that you are dilettantes. You are either set up to make measurements, in which case you have hard data as the basis for discussion, or not.

Good day to you, too.

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #110 on: November 15, 2010, 04:25:20 PM »
Hey,  fwiw...Jon I really don't think there was any kind of put down or derogatory intent.   At least that is how I see it. 

This thread has been a wealth of knowledge and sharing and I for one would hate to see it go south like so many other mic mod threads have done...mostly over at GS.   

I have tons of respect to the guys who are building and/or modding mics.  Me, I'm just a wanna be electrical genius.  Lots and lots of want and very very very little traces of anything remotely resembling genius.   Of all the people who do this Jon is always the guy who is up front and willing to share.  Joly can get to be more salesman and when others enter into it  with Michael devolves quickly into off topic things. 

So before this turns into something else, I really have appreciated everyone's feedback and answers to me stupid questions.  I hope that I get to keep asking the questions here and this gets back on track to working on mics. 

The one thing I was going to post before this little hiccup......Chris do you have a stock 603 that you could test the same way as you tested the mod?  At least then we could compare the differences between before and after.  And maybe that would help to negate the method.  I cannot even begin to discuss some of this stuff on the level you guys do.  But I could see the difference between a before graph and an after graph. 

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #111 on: November 15, 2010, 05:22:38 PM »
Jim over on the gearslutz thread says those eBay capsules "will fit any 22mm pencil consenser mic 991,603 etc."
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #112 on: November 15, 2010, 05:30:09 PM »
I do have a stock 991 somewhere. I'm not saying the bass response is due to a capacitor substitution. All we know is there is very little rolloff down to 125 Hz according to MXL.

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #113 on: November 15, 2010, 05:34:17 PM »
yeah, thats what i see there. i may order a pair of the hypers to try out. i really only tape din'ish on stage withe the drum kit in the nullpoint of both cards and am curious about hypers/super in this usage. this seems certainly the cheapest option for that.

I'm just concerned about the vents on the capsule as well as on the body, any input?

Joe

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #114 on: November 15, 2010, 05:40:06 PM »
I have the same thought.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #115 on: November 15, 2010, 06:00:43 PM »
unfortunately there is no discount on combined shipping, still not unreasonable.

btw, same seller has the metal shockmounts in silver and black that come with the apex 185 stereo kit for about $15 each after shipping.

they work well for me despite being REALLY abused.  like when a rather large girl jumped on the back of a rather drunk, rather slight boy.... he held up for at least 10 seconds before going cheekbone first into the corner of the stage.... pulling my stand by the cables onto the floor in a vain attempt to save himself.... the band (gentleman jesse and his men) were so freaked out by dude being knocked cold that they stopped mid-song to check on the poor guy.  i got a great tape with an interesting interlude and he got cool scar.

These shocks work....
« Last Edit: November 15, 2010, 06:52:47 PM by bugg100 »

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #116 on: November 21, 2010, 11:18:48 AM »
The first outing with my modified CAD GXL1200's was a huge disappointment.
They both sound very, very thin. No bass at all. I haven't run a spectrum analysis yet, but I'm guessing that everything below 120Hz is gone. I ran them within inches of my C-463s into the DR-680 and the difference is huge. AKG's sound warm and round. GXL1200's extremely thin and tinny.

There must be a problem with one or more of the values of the components I swapped out.

I ran them twice yesterday. First at an acoustic in-store The Gracious Few performance and then later that night at the Black Sheep. I ran them into a Busman UA-5 at the in-store and got the same extremely thin sound. My C-481's sounded great on the same mic stand at the same event.

I'm not really sure how to proceed on figuring out what is wrong. If one of them had an issue, it would be easy enough to just examine all of the components and figure out what the difference is. But, they both sound the same, really bad.



Edit to add:

Short samples:

TGF_GXL1200.wav
http://www.filesavr.com/B4gml4FH

TGF_C-463.wav
http://www.filesavr.com/UsIL0XV0

These links don't work correctly using Google Chrome. They work OK with MS IE. Go figure  ???
« Last Edit: November 24, 2010, 01:13:16 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

kirk97132

  • Guest
  • Trade Count: (0)
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #117 on: November 21, 2010, 03:12:07 PM »
Bummer dude. 

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #118 on: November 21, 2010, 03:35:21 PM »
lol
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #119 on: November 23, 2010, 06:06:04 PM »
Chuck -

Did you make before and after recordings with these mics?

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #120 on: November 23, 2010, 06:56:28 PM »
No, I didn't.  :-[ Lots of folks say these mics are a bit thin sounding, but I can't believe they are that thin sounding. Did you listen to the WAVs? It sounds like that section of Pink Floyd's album Wish You Were Here just before the song Wish You Were here when the nice full jazz jam switched to someone tuning a radio.

I'm baffled. My next step is to start re-inserting the old parts one by one, and testing after each component is changed back to it's original value. That is, unless someone can point out something I obviously did wrong with the components I changed. I have attached the updated schematic and I put the component values I changed in blue.

The only other thing I can think of it that I fried one of the diodes or transistors or other components when soldering in the swapped components. But, I'm pretty careful and have an adjustable temp soldering station with the smallest tip there is. The strange thing is that both mics have the same exact loss of bass.  ???

I always go into doing something like this as a learning experience. I really don't have much money tied up in it and I have learned a lot so far. I've modified lots of stuff over the years, using someone else's notes and component values. My experience is that sometimes it's worth the trouble and sometimes it's not.

If anyone has any advice on what may have gone wrong, I'd appreciate hearing your opinion.
« Last Edit: November 23, 2010, 07:05:30 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #121 on: November 23, 2010, 07:29:25 PM »
Funny, that's the only portion of the schematic that I'm not sure what the values should be, because the original MXL schematic has a pot installed rather than the 250k resistors. So, in my mic I think R6 is 2.2k and the two 250k resistors are the voltage divider. I just re-drew that part of the schematic wrong. Does that make more sense? The original values for that voltage divider in the MXL circuit are 91k and 470k. But, the CAD mics I modified use the values I have in the re-draw.

edit:
I don't know the original values for the voltage divider resistors. My CAD mics used 91k and 470k.

Jon, would a problem/error with those resistor values account for the lack of bass? 

I have attached a revision: Modded GXL1200 Schematic v2.jpg
« Last Edit: November 23, 2010, 07:48:40 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #122 on: November 24, 2010, 01:38:31 AM »
Chuck -

You could do worse than to get another one of these mics and keep it unmodified as a reference. It's only a $50 mic. I would also make a reference recording with the unmodified mic with better source material under more controlled conditions, even if it's just you speaking into it. No offense intended but the source material in your wav files is pretty poor. Also, you're making a number of major changes to the mic and you're not working very methodically. Make a list of the components you swap (I don't see before and after values in your schematic, just after) and make a test recording of each modification against the reference mic with each change of components. You could also take the capsule from the unmodified mic and test it against your mics with circuit modifications. Once you take a Dremel tool to the capsule your changes are unrecoverable.

Quote
Those small yellow ceramic caps are all screwed up on them. The values don't match at all. I'm going to have to re-cap both of them. It looks like the person that assembled them just used any yellow capacitor they could find in each microphone.

C3 and C4 on one mic are .22uf and .47uf. On the other they are both .047uf!
It is good that they put the larger values, but...

The caps at C1 and C2 are screwy too. But, all the resistors are right.

QC is not too good on these mics.

It's stories like this that convince me you're better off spending more money on a mic where the manufacturer does better QC. Either that or have something like an Oktava MK012 modded by someone who basically guts the electronics and puts in all new components.

Just a suggestion.
« Last Edit: November 24, 2010, 01:44:50 AM by chris319 »

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #123 on: November 24, 2010, 09:28:46 AM »
Chuck -

You could do worse than to get another one of these mics and keep it unmodified as a reference. It's only a $50 mic. I would also make a reference recording with the unmodified mic with better source material under more controlled conditions, even if it's just you speaking into it. No offense intended but the source material in your wav files is pretty poor. Also, you're making a number of major changes to the mic and you're not working very methodically. Make a list of the components you swap (I don't see before and after values in your schematic, just after) and make a test recording of each modification against the reference mic with each change of components. You could also take the capsule from the unmodified mic and test it against your mics with circuit modifications. Once you take a Dremel tool to the capsule your changes are unrecoverable.

Quote
Those small yellow ceramic caps are all screwed up on them. The values don't match at all. I'm going to have to re-cap both of them. It looks like the person that assembled them just used any yellow capacitor they could find in each microphone.

C3 and C4 on one mic are .22uf and .47uf. On the other they are both .047uf!
It is good that they put the larger values, but...

The caps at C1 and C2 are screwy too. But, all the resistors are right.

QC is not too good on these mics.

It's stories like this that convince me you're better off spending more money on a mic where the manufacturer does better QC. Either that or have something like an Oktava MK012 modded by someone who basically guts the electronics and puts in all new components.

Just a suggestion.

Yeah, actually, I did document everything I did as I replaced components. I made a spread sheet with all the pre-mod component values and as I replaced components I added the new values to the sheet. I didn't note that on the schematic. I even tested the mics every time I changed something. But my tests consisted of listen to ambient noise & snapping my fingers in front of it, just to make sure they worked. I should have used a more full spectrum test source. I'll do that nest time.

Yeah, and I just purchased a pair of the KAM i2 mics on eBay for $68!  ;D
They are the MXL clones and come with omni and cardioid caps. I was thinking the same thing as you, that I need a reference to work from. When they arrive, I will make some controlled full spectrum recordings before opening them up. I'll be much more methodical this time. 

As I said, It's learning experience. I'll figure it out eventually.
Yeah, and on that source material. They were set up way in the back of the venue. I had my C-481's ceiling mounted FOB. I just made the recording in the back to see how the moded mics did in a loud environment against mics that I am very familiar with.

Thanks for the input.

If I get the first pair to work right I'm thinking about donating them to the venue, as they don't have a good pair of condensers for drum overheads. They treat me very well there. So, I may be able to do something good for them.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #124 on: November 24, 2010, 12:02:25 PM »
Hey Chuck, I can shhot new photos of unmodded apex 185 or just report existing values, but am out of town for the week. Let me know if you need any. The KAM i2 looks like the mxl 604 and 185 apex in that it has the roll off and pad switches in same locations....  Curious about their component selection and quality, snap photos maybe?

Your test files earlier seemed to be linked to the same file...  BTW, interesting to know that the test setup was so different...

Jon, thanks for your continued help here!

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #125 on: November 24, 2010, 12:19:57 PM »
Oh, I have plenty of photos of the guts or all the MXL 603/604 clones.  ;D
I'd be happy to zip them all into one file and put them up for anyone that wants to see them.

I just tried to download the audio clips I put up and it isn't working right. I rarely use that place. Can someone suggest a better (free) place to upload files too?
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #126 on: November 24, 2010, 12:39:51 PM »
mediafire.com works well for me.

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #127 on: November 24, 2010, 12:42:55 PM »
Thanks.
I'll re-post the WAV's there and zip up all the info and schematics I have for the MXL clones and upload that too when I have the chance after work today.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #128 on: November 24, 2010, 04:09:05 PM »
If the 2k2 was missing, the circuit would be pretty seriously impaired, but I couldn't describe exactly without building or simulating it.  But since that's not the problem, I would verify cap values at C4,C9,C13, and DC voltages at all points around C9 & C13 (you can't directly measure C4).  C7 is mislabeled BTW.

Thanks, Jon.
I'll check those capacitors and the voltages.



Edit: to add fixed schematic.
« Last Edit: November 24, 2010, 04:12:35 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #129 on: November 24, 2010, 08:06:45 PM »
Links to generic china mic photos and schematics:

China_Mic_Clones.zip
http://www.filesavr.com/34H5bzjy

CAD_GXL1200_Mod.zip
http://www.filesavr.com/TjE59uE6

Please let me know if these links do not work.
They seem to work better with MS IE and not so well with Google Chrome.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #130 on: November 25, 2010, 01:45:03 AM »
Chuck -

Make test recordings of both of your new mics by speaking or playing into them. First see if they even sound similar to each other. Hold one aside for comparison. Next I suppose would be to find out which components in your experimental mic don't conform to the schematic and replace those.

That's how I'd do it, anyway  :)

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #131 on: November 25, 2010, 11:35:50 AM »
I wonder if it's because I put 150 ohm resistors in for R4 & R5, rather than 150K ohm resistors  ???  :P
I promised my wife I won't mess with it anymore today, being Thanksgiving Day and all. But, I'm betting that's it.
I'll confirm tomorrow. I just hope I didn't fry the 2N5401's.

Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline DigiGal

  • AES Associate Member
  • Trade Count: (30)
  • Needs to get out more...
  • *****
  • Posts: 2583
  • Gender: Female
  • Stay healthy and safe!
    • DigiGal Internet Archive Recordings
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #132 on: November 25, 2010, 12:23:45 PM »
I wonder if it's because I put 150 ohm resistors in for R4 & R5, rather than 150K ohm resistors  ???  :P

doh!   Hope you got it, Happy Thanksgiving.
Mics: AKG CK91/CK94/CK98/SE300 D-330BT | DPA 4060 4061 4266 | Neumann TLM 103 | Senn ME66/K6/K6RD MKE2 MD421 MD431 | Shure VP88 SM7B SM63L SM58 Anniversary Cables: Gotham GAC-4/1 Quad w/Neutrik EMC | Gotham GAC-2pair w/AKG MK90/3 connectors | DigiGal AES>S/PDIF cable Preamp: SD MixPre-D Recorders: SD MixPre 6 | Marantz PMD 661 Edit: 2011 27" 3.4GHz Quad i7 iMac High Sierra | 2020 13" MBA Quad i7 Catalina | Wave Editor | xACT | Transmission | FCP X 

Offline illconditioned

  • Trade Count: (9)
  • Needs to get out more...
  • *****
  • Posts: 2998
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #133 on: November 25, 2010, 02:07:44 PM »
Links to generic china mic photos and schematics:

China_Mic_Clones.zip
http://www.filesavr.com/34H5bzjy

CAD_GXL1200_Mod.zip
http://www.filesavr.com/TjE59uE6

Please let me know if these links do not work.
They seem to work better with MS IE and not so well with Google Chrome.
Thanks for the info and photos.

I'm not hacking these at the moment, but I enjoyed looking at the disassembled capsule.  Hope you got it back together ok :).

  Richard
Please DO NOT mail me with tech questions.  I will try to answer in the forums when I get a chance.  Thanks.

Sample recordings at: http://www.soundmann.com.

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #134 on: November 25, 2010, 09:15:33 PM »
That is *not* how I would do it, because if there was an error unrelated to component selection it will not necessarily be fixed.  Then you'd be back to the same components you wanted to replace and still not have a functional microphone.

Man you're getting testy. The point I was making:

Quote
find out which components in your experimental mic don't conform to the schematic and replace those

is intended to overcome the "any old yellow capacitor of whatever value" syndrome described previously, but I suppose you have an issue with that. If the design or modified design calls for a 47uF cap but the assembler was given a box of undetermined-value capacitors to use, that would be a problem.

Quote
verify component values

That's what I just said, Jon!
« Last Edit: November 25, 2010, 09:20:56 PM by chris319 »

Offline Roger Gustavsson

  • Trade Count: (1)
  • Taperssection Member
  • ***
  • Posts: 423
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #135 on: November 26, 2010, 04:50:35 AM »
I wonder if it's because I put 150 ohm resistors in for R4 & R5, rather than 150K ohm resistors  ???

It would certainly result in a brutal roll-off at about 2.2 kHz! C4 and C9 could have smaller values if space is limited. Schoeps use to set their low frequency corner between 20 and 30 Hz.

Roger

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #136 on: November 26, 2010, 04:24:34 PM »
The wrong resistor values was the problem. When I removed the 150 ohm resistors and inserted the correct 150k ohm resistors the mics came to life. The modified mics sound much better now.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #137 on: November 26, 2010, 09:25:14 PM »
The wrong resistor values was the problem. When I removed the 150 ohm resistors and inserted the correct 150k ohm resistors the mics came to life. The modified mics sound much better now.

Good to hear. Do you now have a pair of $50 Schoepses?

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #138 on: November 26, 2010, 10:55:39 PM »
Chuck,

Have you recieved your KAM mics yet?

Way to go for hanging in and finding your mistake!

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #139 on: November 27, 2010, 12:03:29 AM »
I haven't gotten the KAM mics yet.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #140 on: November 30, 2010, 11:43:51 AM »
I received the KAM i2's last night.

I've attached photos of the internals.

These bodies are about a 1/2 inch longer than the CAD GXL-1200 bodies. The KAM mics have the low cut and -10db pad switches on them. Also, the ceramic capacitors are green and all of the components match perfectly between the microphones. There is what I assume to be a quality control sticker on each mic circuit board.

The circuit boards look much better and there is no residual flux on them as there was with the CAD mics.
The electrolytic capacitors are smaller in size (physically) than the caps in the CAD mics too. This will make them easier to modify.

I did do some tests on them and they match pretty well.

I bought these on eBay, as B-stock mics because of the paint job. The flat black paint is already flaking away from the holes where the switches are. I'll probably sand down the tubes, install jumpers in place of the switches, fill the switch holes and re-paint them. As I don't have any use for the switches.

Also note that one of the XLR ends is brass and the other is (pot metal?). Also, the painted markings on each mic are slightly different, which may mean that they came from different production batches.  ???

Overall, I think these will be much easier to work on than the CAD mics, because of the longer body and smaller electrolytic capacitors.

« Last Edit: December 01, 2010, 11:47:18 AM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #141 on: November 30, 2010, 05:02:56 PM »
So Chuck, what do you have in mind with the KAM i2s? Don't forget to make before and after recordings!

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #142 on: November 30, 2010, 06:09:47 PM »
I partially rationalized buying another pair of these mics to get the omni-capsules that were included with the KAM i2's. I'll probably experiment with putting different components into the new pair to see if it makes much of a difference in the way they sound compared to the pair I've modified already. If I end up liking one pair more than the other, I'll probably donate the other pair (with just the cardioid capsules) to the club I do most of my recording in.

Looking at it with hindsight, I would have made out better just getting one pair of the KAM mics that have both sets of capsules. They have a lot more room in them for larger capacitors and I got them for a good price.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #143 on: November 30, 2010, 08:33:12 PM »
Don't forget to make before and after recordings!

dude. relax.....

Offline chris319

  • Trade Count: (0)
  • Taperssection Regular
  • **
  • Posts: 142
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #144 on: November 30, 2010, 09:39:43 PM »
Don't forget to make before and after recordings!

dude. relax.....
Butt out.

Offline bugg100

  • Trade Count: (0)
  • Taperssection All-Star
  • ****
  • Posts: 1015
  • Gender: Male
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #145 on: November 30, 2010, 10:55:35 PM »
i don't think so.


Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #146 on: December 01, 2010, 12:01:52 PM »
I stumbled onto this Scott Dorsey circuit recently. It would not be too hard to adapt it to the i2 microphones. It's simpler than the stock circuit and all the transistors are the same.
It might be cool to use this circuit on the new pair to see what the differences are ???
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #147 on: December 01, 2010, 02:58:19 PM »
So, there's no reason to try that circuit unless I want less sensitivity and more noise. Thanks, Jon.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #148 on: December 03, 2010, 12:12:15 PM »
I had some time to check and document all the components in my KAM i2 microphones and revise zapnspark's schematic for the Generic China Mics with the component values and circuit board labels I found.

I'm not 100% sure that D3 is a 6v zener. zapnspark didn't have that one on his original schematic.

Also, zapnspark suggested that I add capacitors C17 & C18.

This is what he said about those capacitors:

Those 2 caps across the 150k resistors actually perform a number of functions.
Mainly, they roll off the mic. response above 20 kHz.
* This kills any 2 mHz leakage signal from the Hartley oscillator capsule polarizing supply from reaching the XLR pins 2 and 3.
* They add stability to the 2 PNP emitter follower transistors. Especially when driving capacitive/inductive loads. (e.g. long cable runs)
* They aid reducing external RF interference that might enter the body of the microphone from the outside world.
There should be no audible effects from adding these roll-off caps.


So, I figured that I'd add them.
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #149 on: December 03, 2010, 01:11:24 PM »
So, adding 47 ohm resistors will make it better, I can do that. If it's a best practice.
Do they go here? (marked in red)
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #150 on: December 03, 2010, 03:45:06 PM »
No, other side of the caps.

...like this then?


edited: to change drawing
« Last Edit: December 03, 2010, 04:42:48 PM by Chuck »
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #151 on: December 05, 2010, 07:17:42 PM »
It turns out that the removed switch holes and traces and the holes and traces for the extra capacitors makes it possible to add the the 1nF capacitor and the 47 ohm resistors without cutting any traces.  ;D
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline Chuck

  • Trade Count: (42)
  • Needs to get out more...
  • *****
  • Posts: 10812
  • Gender: Male
  • time between the notes...
    • My recordings on the LMA
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #152 on: February 07, 2011, 07:33:01 PM »
Microphone comparison:

http://www.filesavr.com/nG5waFIW

File name: mic comp.zip

Included are two less than one minute long 44.1kHz/ 16bit, stereo WAV files recorded into a DR-680.
Both pair of mics on the same mic stand, 3" apart horizontally. The files are lined up for easy A/B switching.

One file is a modified pair of CAD GXL1200 (cardioid) microphones.
The other file is a different pair of cardioid of mics.

Which recording sounds better?
Reality is merely an illusion, albeit a very persistent one.

Microphones: AKG C 480 B comb-ULS/ CK 61/ CK 63, Sennheiser MKE 2 elements,  Audix M1290-o, Micro capsule active cables w/ Naiant PFA's, Naiant MSH-1O, Naiant AKG Active cables, Church CA-11 (cardioid), (1) Nady SCM-1000 (mod)
Pre-amps: Naiant littlebox, Naiant littlekit v2.0, BM2p+ Edirol UA-5, Church STC-9000
Recorders: Sound Devices MixPre-6, iRiver iHP-120 (Rockboxed & RTC mod)

Recordings on the LMA: http://www.archive.org/bookmarks/ChuckM
Recording website & blog: http://www.timebetweenthenotes.com

Offline SmokinJoe

  • Trade Count: (63)
  • Needs to get out more...
  • *****
  • Posts: 4210
  • Gender: Male
  • "75 and sunny"... life is so much simpler.
    • uploads to archive.org
Re: MXL 990, 991 and Oktava 319 Mods
« Reply #153 on: March 16, 2011, 08:51:48 PM »
Microphone comparison:

http://www.filesavr.com/nG5waFIW

File name: mic comp.zip

Included are two less than one minute long 44.1kHz/ 16bit, stereo WAV files recorded into a DR-680.
Both pair of mics on the same mic stand, 3" apart horizontally. The files are lined up for easy A/B switching.

One file is a modified pair of CAD GXL1200 (cardioid) microphones.
The other file is a different pair of cardioid of mics.

Which recording sounds better?

I prefer sample A.  It's a lot more open and realistic.  I'm not saying the B sample is muffled, but I prefer A.
Mics: Schoeps MK4 & CMC5's / Gefell M200's & M210's / ADK-TL / DPA4061's
Pres: V3 / ST9100
Decks: Oade Concert Mod R4Pro / R09 / R05
Photo: Nikon D700's, 2.8 Zooms, and Zeiss primes
Playback: Raspberry Pi > Modi2 Uber > Magni2 > HD650

 

RSS | Mobile
Page created in 0.382 seconds with 176 queries.
© 2002-2024 Taperssection.com
Powered by SMF