Piezo pickups for Ecoplate plate reverb

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hiverdude

Member
Joined
Jan 3, 2009
Messages
10
Hi Everyone!

I have an Ecoplate 1 and and Ecoplate 2.

Last year I ordered the new piezo pickups from Jim Cunningham at JCC & Associates. I got them, and they sat on my shelf for about 9 months.

When we finally got around to installing them, we found that one of the pickups wasn't working. Not a big deal, that stuff happens.

But JCC has vanished! The site is up, but they no longer have a working email address.

So, my question is this. Given that my plates use the circuit found here:

http://platereverb.com/manuals/Plate%20Construction.pdf

What kind of piezo pickup should I get? What kind of impedance, etc? Any help would be really appreciated.

Thanks,

Colin
 
Oh!  Interesting!

Thanks for this!

I was going to ask (and this shows how little I know) whether it was possible to use a piezo speaker as a pickup.  I had thought it would be possible!
 
Some more piezo info:
Piezos come in two polarities, depending how the machine has dropped them onto the copper baseplate.
Easy to measure with a multimeter, 200mv DC.
Rest the piezo on a big O-ring, rubber band, or tap washer, so it can flex. Ceramic side up.
Black lead to brass. Now gently and slowly apply pressure with the red lead to the centre of the ceramic.
The readout will go +, when depressed, and - when released.
Or the other way.

No experience in plate reverbs, but I would start with measuring the capacitance and size of the piezo you have got (ceramic and brass size).
Match size / capacitance / resonance, so you won't have to re-design your preamp.
Leo..


 
Hahaha, I'm sorry, but one more thing:

How does one find the resonance of a piezo?  Do you just play some tones through it and listen for where it gets louder?

All the other measurements seem totally simple!
 
There's a more scientific way to do it.
Feed the piezo through a 100k series resistor. Measure the voltage (with a high-Z instrument) across the piezo. The response (which is that of a first-order low-pass) will show a hump at the resonant frequency.
 
abbey road d enfer said:
There's a more scientific way to do it.
Feed the piezo through a 100k series resistor. Measure the voltage (with a high-Z instrument) across the piezo. The response (which is that of a first-order low-pass) will show a hump at the resonant frequency.

Would there be a difference in frequency (and Q) if the piezo is glued to the plate, or in free air?
Leo..
 
You could try a ballanced pickup by selecting a positive going, and a negative going piezo.
Glue them close together on the plate.
Connect shield to ground, + to one piezo, and - to the other.
:-\
Or same gender piezos on opposite sides (back to back) of the plate.
:-\
 

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