Piezo Pickup Experiment

[tinitus]

some info

How to make a Piezo Pickup
Double Bass Guide | by Jonas Lohse
Amps + Preamps | Double Bass Guide
http://www.bestbassgear.com/wiring-d...918-buffer.pdf
http://www.till.com/articles/PreampCable/index.html

[wazupwiop]

Thanks for the literature. I don't think I want my preamp to require phantom power, lol. That is a little "over the top" for me. I did learn quite a bit though.

I am gonna order a J201 and once everything arrives, I'll be set and ready to go.

[wazupwiop]

I talked to Peter Sesselman again, and I specifically asked about impedance issues. He sent me a 3-resistor attenuator circuit, and said that it would fix any issues I have with impedance.

I am not going to build the JFET buffer just yet. I am going to build Mr. Sesselman's circuit, and then, if that doesn't work, build the JFET buffer.

Thanks for all the comments on the thread. You guys have been a HUGE help so far.

[TheGimp]

CBGs often times use a Radio Shack 273-064 piezo buzzer as a pickup. The piezo element is removed from teh plastic housing, and the bare piezo element is mounted inside the guitar.

I have not heard of any complaints about drive level, and have tested one such setup with a tube guitar amp (1M input resistor).

The caviat is that there may be guitar amps with much lower Zin than the traditional 1M or 470K. The Gibson Falcon uses 150K for the input resistor to ground. Some SS amps may be lower. If the Zin is too low it will start loading the pickup and change the tone so most amps stay with 1M Zin.

[wazupwiop]

Originally Posted by TheGimp

CBGs often times use a Radio Shack 273-064 piezo buzzer as a pickup. The piezo element is removed from teh plastic housing, and the bare piezo element is mounted inside the guitar.

I have not heard of any complaints about drive level, and have tested one such setup with a tube guitar amp (1M input resistor).

The caviat is that there may be guitar amps with much lower Zin than the traditional 1M or 470K. The Gibson Falcon uses 150K for the input resistor to ground. Some SS amps may be lower. If the Zin is too low it will start loading the pickup and change the tone so most amps stay with 1M Zin.

I ordered piezo elements from futurlec.com. I don't have to pry them out of a casing. The attenuator circuit is supposed to help with all of the piezo to amp stuff.

The attenuator basically lowers the impedance by using resistors to take some of the load off the signal. I hope I phrased that correctly, lol. I am newer to this electronics stuff.

[TheGimp]

Good data here:

http://www.media.mit.edu/resenv/clas...SI-techman.pdf

[Nigel Goodwin]

Originally Posted by wazupwiop

I talked to Peter Sesselman again, and I specifically asked about impedance issues. He sent me a 3-resistor attenuator circuit, and said that it would fix any issues I have with impedance.

Can you post it here?, a three resistor attenuator sounds a bit strange (PI and T attenuators are usually used for impedance matched RF circuits).

What values does it use?.

To be honest a single resistor in series with the PU would give you a high input impedance (no need for two or three). and would minimise the loses.

But any attenuator solution relies on having plenty of extra gain available in the amplifier.

[wazupwiop]

Basically it is a 100k resistor that jumps from hot to ground on the output jack. There is another resistor between 100k and 250k that is linked between the hot output of the piezo and the hot of the jack. Here is a little diagram:
http://us.f1146.mail.yahoo.com/ya/do...Inbox&inline=1

Keep in mind that this is a dual-piezo design and I will be altering it slightly.

[Nigel Goodwin]

Originally Posted by wazupwiop

Basically it is a 100k resistor that jumps from hot to ground on the output jack. There is another resistor between 100k and 250k that is linked between the hot output of the piezo and the hot of the jack. Here is a little diagram:
http://us.f1146.mail.yahoo.com/ya/do...Inbox&inline=1

The picture doesn't display.

But sticking a 100K(250K) and 100K as an attenuator is simply presenting a pretty low load impedance across the piezo, worse than it not been there (a guitar amp is probably as high or higher impedance than that).

I would suggest for a piezo you should be looking at loading in the megaohms 2M2, 4M7, perhaps even 10M. Piezo's really need high impedance loading.

[tinitus]

Originally Posted by Nigel Goodwin

I would suggest for a piezo you should be looking at loading in the megaohms 2M2, 4M7, perhaps even 10M. Piezo's really need high impedance loading.

and what would be the result of lower impendance load ?