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DIY passive mic attenuator - will this work?
Old 6th January 2007
  #1
Here for the gear
 

DIY passive mic attenuator - will this work?

Hi,
I'm trying to build a passive mic dim pedal for a bluegrass band similar to one that I've built as a guitar pedal. The pedal should provide a variable dim (I'm guessing that the 'usual' setting would be about 6db drop) that can be switched in and out for solos. There is also a treble bleed capacitor in the circuit for when the volume is turned down, though I'm not sure what the value should be (in the guitar circuit its 0.001uf).

Will this circuit work? Will it work with phantom power engaged? What value should the capacitor be?



Do I need a dual gang pot dimming the signal from both pin 2 and pin 3?

thanks for our help.

J
Old 6th January 2007
  #2
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Quote:
Originally Posted by j mobot View Post
Hi,
I'm trying to build a passive mic dim pedal for a bluegrass band similar to one that I've built as a guitar pedal. The pedal should provide a variable dim (I'm guessing that the 'usual' setting would be about 6db drop) that can be switched in and out for solos. There is also a treble bleed capacitor in the circuit for when the volume is turned down, though I'm not sure what the value should be (in the guitar circuit its 0.001uf).

Will this circuit work? Will it work with phantom power engaged? What value should the capacitor be?



Do I need a dual gang pot dimming the signal from both pin 2 and pin 3?

thanks for our help.

J
There is a very good circuit at this link, which might give you a few pointers on how to easily optimize your idea, while retaining the original signal integrity. Scroll down to 'Figure 2 - Mic / Line Inputs And Switching'. This schematic contains a 20dB pad section, as well as phantom power, phase switching, 'thump' protection, etc... The comments are perhaps the most helpful though. The author provides a very good description of the circuit operation and suggests a few mods. You should be able to pick & choose whatever you want to build. Cheers!

http://sound.westhost.com/project30a.htm
Old 9th January 2007
  #3


Your circuit is going to cause the mic signal to be unbalanced - a lot! You should use a dual ganged pot on both signal wires at the very least.

While it may work fine, your unbalanced dimmer will pick up a lot more noise when you are in a hostile environment (light dimmers, motors, flourecent lights, etc).



-tINY

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