20 dB pad for 1 channel of a binaural microphone 1

[telharmonium]

I just built a binaural microphone for recording sound. Basically it is
two electret mics wired to a stereo minipl jack. However, I put a 1 kilohm shunt resistor between the positive lead and ground leads of the left channel microphone. I did this so as to attenuate one microphone by 20dB. (I arrived at the resistor value by experimenting with the Minidisc recorder I plan to plug the mic into). I did this because I wanted to record 2 mono versions of a sound, with one version 20 dB softer than the other, for safety. It seems to work, but is this safe? Am I overloading/risking anything in the Minidisc, eg the mic preamp? Thanks!

 

[itsmoked]

Adding a resistor should not harm anything. Have at it!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[itsmoked]

On further thought I would probably get a jack and another plug and put your resistor in a little extension/adapter cable, then you can replace the mic without having to hack and cut. Same with value changes. Just keep all the wires intact thru your little 'adapter'.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[telharmonium]

Thanks for the advice. I was a bit worried because the rec-level on the Minidisc is menu driven ---was wondering if some component might go crazy trying to match the levels or if i screwed the impedance or something. Already installed a little switch to cut the resistor in and out of the circuit, but I'm thinking your idea of the plug might have been a better idea--- I might want to use the mic with a video camera and I realize now that diff equipment might need different values....oh well. Thanks again!

 

[itsmoked]

Sure.

Hey why the two different levels? Sounds like an unusual application.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[IRstuff]

Such configurations are often used when larger dynamic ranges are desired. However, you'd need to make sure that it doesn't come with added noise.

TTFN

 

[telharmonium]

Yeah, it"s a trick sound recordists use, because actors and environments are unpredictable. You set one channel to record say, a conversation. But then somebody walks into the room, slamming the door, or an actor starts to yell. the original channel overloads, recording distortion, but the second channel carries the signal at a good level. You load up the wave files into your editor, cut and crossfade, and you have everything at a nice level. ;-)

 

[telharmonium]

PS Why would inserting a resistor add noise? Also; any tips on how to make sure I avoid added noise?

 

[itsmoked]

Resistors are nasty noise sources. As the resistance goes up the noise does too.


Here's a nice discussion:

http://www.aikenamps.com/ResistorNoise.htm

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com