Realistic (Radio Shack) PZM, cheap and easy preamp using OPA1678?

[z11111]

Looking at some datasheets for some parts and the OPA167x specifically has an application note for "Phantom-Powered Preamplifier for Piezo Contact Microphones"



That got me thinking; this looks like it could be great to entirely replace the battery box + transformer on the Realistic (Tandy, Radio Shack, etc) PZM mics. I have about four of them in various degrees of functionality and use at least two very frequently.

Also attached is an example of someone else's discrete design to accomplish the same purpose. I'll have to do some more research on how the Realistic PZM is actually working, just because the only "mods" I've done on mine are splice a balanced XLR in place of the stock unbalanced 1/4" jack.

EDIT: Aware of the pzm having a jfet at the electret capsule / not a piezo element. Was just curious about implementing something like this instead of a modded preamp/power supply.

 

[Tubetec]

PZM stands for pressure zone microphone ,
its most likely not a piezo element ,
my guess is its an electret .

 

[ccaudle]

my guess is its an electret

Correct, electret capsule with JFET in/on the capsule.

 

[z11111]

Aware of the pzm having a jfet at the electret capsule / not a piezo element. Was just curious about implementing something like this instead of a modded discrete preamp/power supply.

 

[ccaudle]

You could certainly do that. The OPA164x parts are the current go-to parts, they are very low current and high performance.
That circuit shown for piezo pickups is probably not optimal for buffering a JFET common-source output, but should work.

 

[Whoops]

That got me thinking; this looks like it could be great to entirely replace the battery box + transformer on the Realistic (Tandy, Radio Shack, etc) PZM mics. I have about four of them in various degrees of functionality and use at least two very frequently.

Here is what you need for what you want to achieve:

http://www.uneeda-audio.com/pzm/#pcb

http://www.uneeda-audio.com/pzm/pzm_kit2020.pdf