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sd vs. unbalanced contact mic

Subject: sd vs. unbalanced contact mic
From: "tempjez" tempjez
Date: Mon Jul 7, 2008 4:44 am ((PDT))
> 
> I've built many contact pickups over the years from inexpensive 
piezo  
> buzzers from Radio Shack. It's a very simple matter of soldering a  
> 1/4" lead onto the piezo element, & it is an unbalanced connection. 
I  
> use the instrument DI input on a Sound Devices USBPre to get into 
the  
> laptop. Any sort of balancing device will get you into a suitable 
mic  
> pre input. A passive transformer, such as the inline Shure or 
Sescom  
> units will do, however there is usually an insertion loss with any  
> transformer, a drop in volume which the mic pre must make up. An  
> active DI will properly bridge the high impedance unbalanced 
output  
> of a piezo element. Before doing any of that, though, I would  
> recommend trying an XLR connector on one of your pickups, wired 
hot  
> (tip) to pin 2, & shield (ground) to pins 1 & 3. You should also 
try  
> it with no connection to pin 3 on the XLR, since, with some 
circuits,  
> this will give a perfectly fine noise-free unbalanced to balanced  
> connection, without the several db signal drop caused by tying pin 
3  
> to ground.
> 
> Scott Fraser
> 
thanks Scott, although I actually have been making my own for years 
too (contact & hydrophones). I was actually asking about the 
specifics of the SD inputs given that they state that they accept 
unbalanced inputs, combined with the Cold Gold mics. I got these to 
research for elements of the 'in place' project that involves 
establishing supply routes for establishements & interested 
individuals here in the UK. 
> 
> 
>





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