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Author Topic: MXL 990, 991 and Oktava 319 Mods  (Read 62144 times)

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kirk97132

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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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

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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

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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

 

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