Piezo tabs

[radii]

I am working on a pickup system that uses a bunch of 3/8" X 1" piezo tabs.

I was wondering if it is possible to let each one run through a potentiometer before they all get summed in parallel and hit the preamp.
If so, what would be the best (available) value of these pots.

Thank you.

Edit:
Of course, I have no idea what the impedance is of these tabs. I know that is is really, really high :-)
How would one measure this anyway ?

Edit again:
According to David Schwab, piezos have no resistance, but a high capacitance.
Sorry for being soo clueless ... :-(

[Mark Hammer]

I suspect you'd be wise to buffer each piezo tab before attempting to blend/mix them. A simple single-JFET buffer is good enough. Try Don Tillman's circuits.

[radii]

I did think of that option, but felt that I might end up with quite a lot of cummulative noise from all of these buffers/preamps.
Fact is, that I have to boost the signal at some point. The output of those tabs is just too low.
I guess I could buffer each tab with no gain applied, then have a volume trimpot after each one before they all get to the onboard-preamp. Or should the actual gain-boosting be done by the external guitar-amp preamp / mixing console input preamp ?
There is a lot of room inside the instrument to mount a fairly good sized circuit ( about 4-5 buffers ). What about batteries however ? Mounting 4-5 batteries seems a little excessive. Would one to power them all work for a reasonable amount of time ?

[David King]

Why reinvent the wheel? Just measure the output and match the tabs that are within 1-2dB. You could probably grind down the hot ones to make them a bit smaller and hopefully less potent. If you can't do that, then check with Highlander pickups, they were selling an adjustable, 6 channel buffer that Rick Turner designed a decade or two ago.
You'll pickup a lot of carbon noise from a 5-10 meg pots that might be appropriate as passive volumes. Buffering first makes more sense to me. Keep in mind that piezos suck. I don't know why people bother with them. If you are committed to using them then consider a respectable, off-the shelf solution like RMC or graphtech that's not a science project and that has a chance of being listenable.

[radii]

I am using piezo film tabs, so grinding is not really an option. If I had ceramic elements, which is what I really want, then I could do it that way. Do you have a source for these ceramic piezos, that don't have a 1000 pcs. minimum-order ?
That would make my day !

Rick Turner's piezo products are now sold here:

http://www.d-tar.com/

Couldn't find a 6-channel buffer.

I would of course disagree, that piezos suck Used on the right instrument, they are magic !
What I'm trying to pickup and amplify, is an electric upright bass.
Here's the current Talkbass thread:

http://www.talkbass.com/forum/showthread.php?t=413856

Putting magnetic pickups on that thing, would make it sound more like a fretless BG then an EUB.

I have used RMC saddles in the past, and even have six of them in a bass that I have not played in 10 years ( I might just try to repurpose them at some point ), and there are 500 $ + systems I could buy ( Barbera and others ), but I'm trying to see how far I can get on my own. My way of sticking it to the man

The best, meaning smallest, buffer/preamp circuit I have found so far, seems to be the Alembic stratoblaster, courtesy of David Schwab.
Would it be crazy to have 5 of them on board, running of a single or 2 9V battery(ies) ?

[David King]

If you wanted to go simple then perhaps an emg acoustic under-saddle piezo inlayed into the top of your bridge so that you only have one source instead of six. Getting the balance right on those hasn't been a problem on the guitars I've installed them in. The EMG piezo buffer is quite acceptable for the price.

I'd also seriously consider the David Gage / Ned Steinberger Realist pickup. Those sound seriously authentic to my ears and don't cost a fortune.

The piezo xtal material is available from scientific supply houses on the net, you just need a small diamond saw like the 1" disks from Harbor freight to cut it with your Dremel tool. Grain direction is important here.

D-Tar is a division of Seymour Duncan, they have nothing to do with Highlander pickups which is in Northern California. You need to talk to Highlander or to Rick Turner, the man, directly.

Don't sell magnetic pickups short here. They can do what you want provided you have steel core strings and some time to wind your own to get the tone characteristics you want.

Oh, and if you are using film tab, can't you just cut them down to the appropriate size with scissors?

[radii]

The undersaddle Piezo-cable was actually my first approach. It's a coax piezo cable that i got from trout cove lutherie. It would have been the most elegant solution, because no cables would have been visible.
But it was next to impossible to get even pressure from all strings onto the cable, mainly due to, again, the strong forward pull of the strings. The saddle was being pushed more against the side walls then onto the coax cable, except for the high G string, which sounded fine. Another issue with an 1/8' thin saddle, was that the strings did not have a lot of material to gracefully "make the turn". I feared that the windings on the strings would actually come loose.

D-Tar has nothing to do with Highlander. That's true. But a lot with Rick Turner, who is the man !!

I don't think that i would get the "acousticness" out of magnetitc pup's that I'm after. Also, I would like to keep the appearance of the instrument as clean as possible. No matter how, mag pup's would be quite visible.

The size of the tabs is OK for my purpose. I suppose cutting one down to a smaller size would lower it's output, if I could cut it succesfully without shattering the crystal film ...

Thanks for the tip about the scientific supply houses. I'll look into that.
If I would only know how to actually hook those puppies up

[David King]

All the ones I've seen had a gold or copper flash coating that you could solder onto if you were careful. RMC uses a conductive glue such as chomerics conductive epoxy and that might be easier for you but I've never had a problem with the soldering approach (though it might change the sound).

That cheap coax piezo cable that comes from DIY home security is really awful sounding, try the 3/32" stuff that Highlander or EMG sells next time.

Rick T. has had so many associations with so many enterprises through the years that your head would spin to keep track of them all. I wouldn't count of his answering the phone at D-Tar but he probably will at Renaissance. Then again he might not even remember that hexaphonic buffer..

If I were you I'd order the crystals from RMC and the buffer from Graphtech, the whole kit would be under $200 assuming you're a business.

[radii]

Well, my only remaining question then would be, how do I become a business ? ...

[David Schwab]

D-Tar is a division of Seymour Duncan, they have nothing to do with Highlander pickups which is in Northern California. You need to talk to Highlander or to Rick Turner, the man, directly.

Funny thing is I seem to remember that Turner's not even using Highlander pickups any more because he found a cheaper source for piezo wire!

He did form D-Tar with Seymour. Duncan-Turner Acoustic Research.

[David King]

Rick was already doing his own piezo crystals 10 or 15 years ago.

Radii, go to your local town hall and get a business license, it will pay for itself very quickly. It helps if you live in a state that doesn't collect sales tax.