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PostPosted: Fri Jun 07, 2013 11:01 pm 
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Cocobolo
Cocobolo

Joined: Tue Nov 01, 2011 10:17 pm
Posts: 190
First name: Raymond
Last Name: Pipkin
Focus: Build
Status: Amateur
I was wondering if the properties of the various components of the guitar body have a big impact on piezo pickups. Obviously wherever it's mounted, like under the bridge plate. But, does the back, cavity and sound board tuning matter? Would wolf tones and exaggerated harmonics come through in a pickup like a K&K or LR Bags under saddle or bridge plate mounted pickup? Do the regular tone concerns apply?


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PostPosted: Sat Jun 08, 2013 1:15 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 3933
Location: United States
A piezo unit basically converts force into charge: it's a small capacitor (usually a few picoFarads or less) that produces more charge the harder you squeeze it due to the nature of the dielectric. When it's used as a UST it sees the force of the strings on the saddle top. Top mounted units generally work as accelerometers, with a thin piece of piezo material that gets squeezed between the top and a mass that's stuck to it. I suppose there could be units out there that work in 'bending' or 'stretching' modes too, but that seems less likely.

All of these pickups are definitely affected by the response of the rest of the guitar, wherever they're mounted. We know, for example, that movement of the back can cause pressure changes in the air in the box, which will push on the top, so a top mounted transducer will 'see' at least some of the back response. Of course, it mostly sees the top response, and can be more or less sensitive to specific top modes depending on where you put it. That's why you have to experiment a bit with placement: different guitars move differently. The output of a UST will vary from one guitar to another depending on the resonant structure of the instrument: it's not just sensing the strings, but rather the relationship of the strings to the top. This gets complicated, but that's what makes the guitar interesting.


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PostPosted: Sat Jun 08, 2013 8:02 pm 
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Cocobolo
Cocobolo

Joined: Tue Nov 01, 2011 10:17 pm
Posts: 190
First name: Raymond
Last Name: Pipkin
Focus: Build
Status: Amateur
Thanks for the information Alan. This is very helpful.


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