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Re: living in the walls

Subject: Re: living in the walls
From: "Raimund Specht" animalsounds
Date: Sun May 17, 2009 1:15 pm ((PDT))
m u r m e r wrote:

> what's a 0 volt wire?



> this is a very simple pair of self-built contact mics, which i wired to 
> the xlr connectors based on some recommendations from rob at aquarian 
> audio.  the ceramic and outer rings of the piezos are wired to pins 1 & 
> 2 resectively, and pin 3 is wired to a foil shield which surrounds the 
> piezo.  then the whole shebang is plasti-dipped.  does something in 
> there equate to a 0 volt wire?

Hi Patrick,

The 0 volt wire (ground) corresponds to the XLR pin 1.

The problem in your set-up is probably that the piezo is a high-impedance 
element (other microphones have a much lower output impedance). This means that 
the piezo foil shield and the wire connected to it (XLR pin 3) can act as an 
antenna, which obviously picks up the LED noise. 

You might therefore try to electromagnetically shield the entire piezo element. 
This could be done for instance by covering it with an (isolated) aluminum foil 
or something similiar. As Greg recommended, you might also disconnect XLR pin 1 
from the piezo and instead connect it to the additional shield.

Regards,
Raimund












"While a picture is worth a thousand words, a 
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause


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