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

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Offline raymonda

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

 

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