Condensor microphone resistor upgrade to 1g ohm, results ?

[ohhey]

Has anyone done one of these ? I've got some Oktava mics I would like to mod and some 1g ohm resistors but before I start soldering can anyone give me some tips on what the upgrade does for the mic ? Any other parts that need to be changed when I do this ?

I have one 219 and two MKL2500s to work with.

 

[rodabod]

Have you read the Tape-Op article on modding the circuits?

It is available here and explains what you need to know.

 

[ohhey]

[quote author="rodabod"]Have you read the Tape-Op article on modding the circuits?

It is available here and explains what you need to know.[/quote]

No, I have not seen that one, how do I get to it ?

 

[rodabod]

Here you go:

http://homepage.mac.com/stevenjensen/micmod/mic%20mod.html

Use the bloody search engine!

(only kidding :razz: )

 

[ohhey]

[quote author="rodabod"]Here you go:

http://homepage.mac.com/stevenjensen/micmod/mic%20mod.html

Use the bloody search engine!

(only kidding :razz: )[/quote]

Doh ! I have that in hard copy, I think it's in EQ mag the Scott Dorsey stuff. Nevermind... :?

 

[rodabod]

Read it!

1Gig resistors are not "better" then say 400Meg resistors - it depends on the circuit.

 

[dale116dot7]

If you're talking about the Oktava MC012 mod, it allows a slightly lower low frequency response, and slightly less low frequency rumble. I found that part of the mod not even noticeable.
But it depends on the circuit. On a U47, for example, the input resistors are somewhere around 160 meg. With an 80pF capsule, that sounds like it should really hurt the low frequencies. But on the U47, the very high gain of the tube and the tube's Miller capacitance make this resistance value a non-issue - the equivalent source capacitance is the capsule (around 80pF) in parallel with the Miller capacitance (somewhere between 300 and 2000pF). That capacitance is actually an effective feedback path in a condensor microphone amplifier circuit.