Great DIY Buffer/Preamp for Piezo Pickup Equipped Instruments

[Paul Marossy]

I built this little gizmo to try out with my acoustic-electrics and my Parker Mojo Nitefly. It really works pretty well and is very easy to build. It should work well with any instrument that has a piezo - from bass to violin.

http://www.diyguitarist.com/Guitars/PiezoBuffer.htm

It won't substitute for an amplifier that is designed specifically for acoustic guitars, but it does make one sound a whole lot better when plugged into a regular guitar amp.

I used it this morning for about an hour and I must say that it makes a huge difference with my Parker Mojo Nitefly's piezo pickups. It actually sounds like an acoustic guitar when plugged into something designed for conventional magnetic pickups. Piezos need to see a very high input impedance, so the FET satisifies this requirement and the output impedance is more along the lines of a stompbox, so it drives things made for electric guitar pretty well.

Now I have an idea to combine this buffer circuit with my stereo splitter box for an all in one unit. Could be pretty handy for Parker Fly owners...

I thought this might help someone here at the forum, so I thought I'd share it with y'all. 

[Dave_B]

Thanks, Paul!  I taped a Mouser peizo taped under my bridge on Christmas Eve, so pretty good timing on this one.   

I don't know what the input impedance is on my m-audio soundcard, but I had to do a pretty severe mid-scoop to get a reasonable sound out of it (along with a 20db boost).  I'm still not sure I'm mounting this thing correctly. 

[Transmogrifox]

Sorry about the off topic to the post, but...
Dave, I just checked out your page.  What is it that you're working on for the PIC project that is currently 20 pages of code?  The reason it strikes interest with me is that I have just gotten back into PICs.  I just completed an RS-232 I/O device with 7 pages of code (it just formats an ASCII message and inserts "titles" to data).  Anyway, it just made me interested as I'm now basking the awe of how many doors are opened in the guitar FX world by having the ability to PIC.  It's inspiring to see somebody a couple steps ahead of me...

[Paul Marossy]

I hope it works out well for you bellyflop. Please let me know how well it works. 

[birt]

hey i've got some questions about this lmittle circuit. did you try to replace the gain switch with a pot? or a pot womewhere else in the circuit?

this is really stupid but i've got this little old enclosure that's just PERFECT for this cicruit. really you should see it...
but it has a pot and i don't like holes in my enclosures. so i could leave the pot unused or do something with it.

[Paul Marossy]

Naw, I just used a switch. A pot isn't a bad idea, though! 

[birt]

yeah but the value of the pot would be really big right?
i could also leave the switch there and make the source resistor a pot. wouldn't that change the gain of the jfet?

[Paul Marossy]

Yeah, it would have to be a large value pot. Someone probably makes one that would fit the bill. The pot on the source resistor would change the gain, but I don't think it would have the same effect to the circuit - the resistor on the input is messin' with the imput impedance, not the gain of the circuit.

[birt]

Yeah, it would have to be a large value pot. Someone probably makes one that would fit the bill. The pot on the source resistor would change the gain, but I don't think it would have the same effect to the circuit - the resistor on the input is messin' with the imput impedance, not the gain of the circuit.

i know. but i think i should keep the switch in place there. i want to add the pot elsewhere. i'm gonna try some stuff and see what i can do.

[Paul Marossy]

OK, I see. Well, let us know if it works to your liking. 

[donald stringer]

My guitar is an sg copy Aria equipped with emg and active tone controls throughout. I have been curious about this piezo mic available from radioshack. Maybe this  would be a quick fix for some pseudo acoustic type tones. I was thinking maybe tape it under the bridge[gibson type] run a wire to an 25k pot and an separate output. Never would be a parker but maybe could get some interesting tones with some mid band filtering. I have read some interesting things about this process and was wondering if anybody here has done this. I am going to try it this weekend.

[Paul Marossy]

Sounds like an interesting idea, but I think you might have problems with feedback. Let us know how it goes...

[Gilles C]

I tried that for my acoustic guitar.

There was too many mechanical noises, like when I was hitting the guitar with my fingers.

Gilles

[slacker]

I've got a little stick on piezo pickup designed for acoustic guitars. I've tried that wedged between the tremblock and the cavity on my strat and it sounds like a very bad, very thin acoustic. Got much more interesting results wedging the pickup between the trem springs 

[John Lyons]

There are few nice sounds to be had from piezo elements placed on a guitar/piano/anything that resonates.
I have had good results from using a small hobby clamp or clothespin type holder and placing the piezo on the head stock.
The better the contact between the piezo and the guitar the more lower freiquencies. The head stock sounds best to me but if you can jamb a  piezo under the pick guard or use a small hobby clamp near the horn or sides of a guitar you will get better resuslts. Then using pauls preamp and some sort of EQ you will be set.

Radio shack sells a black piezo buzzer that can be carefully dismantled and used as a pickup.
Here's how I found a way to use it and get some ruggedness out of them:

Take apart the Piezo carefully with a pair of angle cutter/wire cutters and extract the Piezo disk.

There is an outer ring and an inner ring (two connections, tip and sleeve) use the inner for tip. If you find other piezos I have found that the smaller ones work bette. About the size of a dime up to a quarter. I have some larger ones that didn't sound as good.

Solder on a thin flexable sheilded cable. The more flexable and maliable the better. As noted above, any vibration or noise will be picked up by the cable movement and scuffing of it... Solder the connections as flat as you can. Try to get the insulation part way onto the disk as well.

Get some 5 minute epoxy and put as much on to cover the whole top of the disk, it can be domed up a bit. This protects and seals in the wires and connections to the thin wafer of the piezo. I have ruined a few before I did this step. It's super fragile. Make sure to enclose the edge where the wires meet the disk as a straing relief. Keep the botton of the disk free of epoxy. you want it to be flat as possible. I used about a 3-4 foot section of cable and for the jack end I used a barrel connector (female 1/4" ) so I can connect it to a longer cable if I need to.

If you hold the piezo and place it on with only your fingers you can get some wild phase type sounds if you rock it a little and change finger pressure, It helps to have someone else do this as you play. Try putting the disk inbetween the strings like with a pick. Instant Sonic Youth!

Start with the amp turned down and set clean as there are wild pops and noises you need to learn to control. Anything that makes noise will get picked up. If you can shock mount the cable a bit by tucking it in somewhere so you aren't dragging it around you will pick up less noises. This is why the more flexable cable works best. Less stiff  = less noise since the cable is attached to the disk itself.

I've spent way too much time experimenting with these.

John

[aron]

Paul,

Why does this make a guitar that already has a built-in buffer sound better? AFAIK, almost every guitar with a Piezo pickup already has a buffer built in right?

I'm just wondering why would it make it sound better when (I think) the guitar already has a low impedance output.

Aron

[Paul Marossy]

Why does this make a guitar that already has a built-in buffer sound better? AFAIK, almost every guitar with a Piezo pickup already has a buffer built in right?

It seems to help when you are running long cables, cuts down on treble loss. Piezo pickups are very high impedance. I think this circuit is mainly designed for something like a passive piezo type system, vs. a well designed preamp/buffer system. I think a lot of the lower end guitars have a rather poor onboard preamp, or at least they used to. Just because a guitar has a preamp doesn't mean it's well buffered...

[aron]

Just because a guitar has a preamp doesn't mean it's well buffered...

I'm not doubting that it makes your guitar sound better. I'm just wondering why. How would an onboard preamp be poorly buffered? I would imagine your Parker would have a very decent preamp in there. At least have a low impedance output. Hmmm.....

[Paul Marossy]

I'm not doubting that it makes your guitar sound better. I'm just wondering why. How would an onboard preamp be poorly buffered? I would imagine your Parker would have a very decent preamp in there. At least have a low impedance output. Hmmm.....

No worries, I know where you're coming from. My Parker has a nice Fishman preamp in it. I have an Epiphone acoustic that I bought the 13 years ago that doesn't even come close!