Piezo + PreAmp Build


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05-05-2008, 02:14 PM
Alright. I saw the Piezo buzzer thread here (http://www.ultimate-guitar.com/forum/showthread.php?t=748459) and was inspired to throw a little something together. After I got the piezo put together (about 5 minutes), I decided to go ahead and make a preamp based on Invader Jim's schematic in the thread mentioned above.

Sound clips of the pickup run through my M-Audio Fast Track Pro are available in my profile. For the recording I used a 1997 Washburn Limited Edition dreadnought with the pickup attached using silly putty just behind the bridge.

I plan on going with a "Brown Box" theme on the preamp enclosure. Loosely based on The Orange Box. It will be attached to my guitar strap via a clip of some sort. I also plan on making a round wooden cover for the piezo pickup and staining it to match, because its ugly as sin, and this will eventually be put to alot of use.


Build Pics (sorry for quality of the bottom shot)


Board Layout

Enclosure Design

05-05-2008, 05:29 PM
I found that R1 and R2 were swapped. I guess I didn't triple check my component placement before I hit the solder.

I'll test tonight.

05-05-2008, 05:50 PM
my circuit was similar to yoursl. concept and functionality the same but with different values though. I found the output to be really high, I'm turning it into a booster pedal when I get the cash to buy the enclosure. Have fun.

Invader Jim
05-05-2008, 05:50 PM
Did that volume/tone mod work? I just kinda winged it when I drew it.

05-05-2008, 06:16 PM
I got it working, it was the R1 and R2 being swapped! I haven't been able to experiment alot, but I know the volume works. It actually sound pretty good from what I have played so far. I'll hook it up later when the kids are done with their homework and maybe grab some sound clips.

So how do eliminate the pop when I turn it on?
Besides a sound hole plug how do I get rid of this feed back on the acoustic?

05-05-2008, 06:53 PM
-Volume works backwards
Easy fix

-The tone pot doesn't seem to actually do anything
Could be wired backwards or wrong value.

-Volume with preamp vs without is about the same, no real boost
Could lowering R1 to say 1-3M increase the gain?

Invader Jim
05-07-2008, 05:12 PM
Well, I told you I kinda winged it when I did the vol/tone mod. You may be right about the resistor, though I'd try 7 or 8 meg first. 1-3 is too low a value.

05-08-2008, 01:22 PM
what is your transistor your using? MPF102, J201, ect.

05-08-2008, 02:50 PM
Ah, sorry.
Q1 = 2N5457

I think a J201 will work though.

Invader Jim
05-08-2008, 06:04 PM
Yeah, any N-channel FET works with similar results. You could change Q1 to a different type, since some types (and even transistors of the same type) yeild more gain than others.

The thing about FETs is the terrible consistency from unit to unit, i.e. one J201 may sound much better or worse than another J201, as is the case with my GraceDaddy...

05-08-2008, 08:13 PM
Hi, I spent yesterday wading through the entire diy piezo thread.

I still need to know one thing, can anybody please tell me if wiring two piezo's in SERIES or PARALLEL will yield greater output? I'm doing this mod for my electric and fixing both of the piezo's to my guitar bridge. Do you think it would be worth it to stick one to the bridge and one to the body? I was even contemplating on mixing the piezo pickups with my middle single coil to boost the output a bit, how would i wire that - series or parallel?

Sorry for the elementary questions. I generally know the basic difference between series and parallel but in guitar land I'm having trouble applying my knowledge.

Sorry I had to post in this thread, just needed a quick answer and the other thread is so bloated.

05-08-2008, 09:20 PM
you'll get higher output from wiring them in series, but i dont know if you necessarily need that... i'll let someone else answer who knows for sure.

05-08-2008, 10:15 PM
I'm not sure where you would put two of these things on an acoustic. From what I've experimented with mine, it likes a very specific spot on the guitar. This sweet spot eliminates finger noise from the wound string and doesn't pick up too much high so as to sound shrill. So even though you have more output it may still sound like crap.

I haven't experimented under the bridge but I would guess that by the way the acoustic built the effect of bad tones would be more pronounced. You always have room to experiment with the way you attach the piezo though, so that may help.

I've been pretty busy lately but I plan on experimenting more with different transistor types. I picked up a boat load of transistors out of the bargain bin at Radio Joke the other day for like 99 cents.

I also still need to experiment with getting any gain from the circuit and bringing down the noise a little bit. Then I have an enclosure to make... :)


EDIT: lol for unintentional RHCP reference

Invader Jim
05-08-2008, 10:36 PM
I saw on Instructables that hooking several piezos in series upped the input impedance and, as a result, made it sound much better than with a single piezo.

And Death, I like the new sig. Very true, though you forgot about the ego-stroking self-praise quote (see my sig :p: ).

05-08-2008, 10:49 PM
I may try that then. I'll have time to experiment some next week I think so I'll keep everyone posted on that.

yeah, there's no more room in my sig. There was other stuff I had to remove and shorton just so I could fit it all in there. I wanted to do things like

-random symbol or smile next to my favorite piece of kit
-break in train of thought (colored the same as the background color)
-something about the quotes you mentioned
-% of teens the like something that you do not, take random action
-uninspired or fanboy quote about your favorite band or musician


Alas, the quote system of UG can't accommodate my sarcasm...

DS :)

Invader Jim
05-08-2008, 11:04 PM
Yeah, that 250 (or 500 or w/e it is) character limit is a pain. You should post you sargasms on your profile for all to see :D.