I have wired a disc piezo and a rod piezo in parallel through a simple active (9V) endpin Jack preamp. I tested it before installing, by tapping them on the table. The disc piezo cane through strong. The rod piezo was faint. I plugged a different rod piezo (by itself) into the preamp, and its signal was strong (as loud as the disc had been).
I thought maybe I had messed the first rod up when wiring it and the disc together. So I took the second rod piezo (the one that tested strong by itself) and soldered it and the disc in parallel, then plugged them into the preamp. This time I took extra care in wiring and soldering them. I am absolutely certain I have wired them correctly, in terms of negative and positive, with no shorts. Same result. The disc signal is loud, but the rod signal is faint.
Is there something about the different signal strengths of discs and rods that makes a rod come through quieter than a disc when wired in parallel through the same preamp?
I don’t know if these details make any difference to the question, but the disc is somewhat oversized (2 inches metal diameter), and the disc is wired with slightly thicker gauge wire than the rod (which is wired via the standard shielded wire with the woven outer shield/ground).
Any ideas?
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Rod Piezo's have less output than the round disc type which is why most people use a preamp with the rod piezo. Rod piezo's have less handling noise and less attitude that gives them better acoustic tone.
You could put the round disc piezo in the neck area of your git and the rod piezo in the bridge to give them a more equal performance. You could use a on/on/on 3-way switch to use either or both in parallel. You may also have a preamp bypass lug on your jack to wire up the disc piezo?
Bryan Pieper > Paul CraigJanuary 14, 2019 at 2:42am
That’s a great idea. I will attach the disc piezo all the way up at the neck and body junction.
Also, I didn’t really factor in the fact that rod piezos are made to function under compression, not merely vibration. When I tested them, I simply tapped the disc and rod on the table or flicked them. Perhaps that isn’t really a proper test of what signal the rod will produced when compressed under the saddle.
In any event, it sounds like a rod simply generates less signal than a disc. Next time, maybe I’ll install a blend pot between them to see how that works.
Paul Craig > Bryan PieperJanuary 14, 2019 at 2:06pm
A blend pot would be an excellent idea.
Bryan Pieper > Paul CraigJanuary 12, 2019 at 7:45pm
This is what I suspected: That discs simply have more output than rods.
Why would putting the disc piezo in the neck area give them a more equal performance? Is that because there is less vibration in the neck (where the disc would be) than in the saddle (where the rod would be)?
Paul Craig > Bryan PieperJanuary 13, 2019 at 1:16pm
Correct. The string vibration will be stronger at the bridge area and the rod needs to be under string pressure at the bridge.
So you'll be lessening the output for the disc at the neck area and giving the rod piezo the most exposure to try and equal out the output.
Disc piezo at the neck and body junction will have a more mellow/warm tone. Upper low string side of the neck for more bass, lower high string side for more treble.
Timothy Hunter > Bryan PieperJanuary 12, 2019 at 10:38pm
partly because the vibrations at the neck would be less than the bridge but mainly because these rods are supposed to be under compression, directly under the bridge piece.
sounds like the disk is shorting the rod. If you wire a 100 ohm resister in parallel with a 1 ohm resister, you get a result of 0.99 ohms. perhaps wiring them in series instead?
Replies
Rod Piezo's have less output than the round disc type which is why most people use a preamp with the rod piezo. Rod piezo's have less handling noise and less attitude that gives them better acoustic tone.
You could put the round disc piezo in the neck area of your git and the rod piezo in the bridge to give them a more equal performance. You could use a on/on/on 3-way switch to use either or both in parallel. You may also have a preamp bypass lug on your jack to wire up the disc piezo?
Also, I didn’t really factor in the fact that rod piezos are made to function under compression, not merely vibration. When I tested them, I simply tapped the disc and rod on the table or flicked them. Perhaps that isn’t really a proper test of what signal the rod will produced when compressed under the saddle.
In any event, it sounds like a rod simply generates less signal than a disc. Next time, maybe I’ll install a blend pot between them to see how that works.
A blend pot would be an excellent idea.
Why would putting the disc piezo in the neck area give them a more equal performance? Is that because there is less vibration in the neck (where the disc would be) than in the saddle (where the rod would be)?
Correct. The string vibration will be stronger at the bridge area and the rod needs to be under string pressure at the bridge.
So you'll be lessening the output for the disc at the neck area and giving the rod piezo the most exposure to try and equal out the output.
Disc piezo at the neck and body junction will have a more mellow/warm tone. Upper low string side of the neck for more bass, lower high string side for more treble.
partly because the vibrations at the neck would be less than the bridge but mainly because these rods are supposed to be under compression, directly under the bridge piece.
Could be the polarity of the disk doesn't match the wire colors? Try switching them.
sounds like the disk is shorting the rod. If you wire a 100 ohm resister in parallel with a 1 ohm resister, you get a result of 0.99 ohms. perhaps wiring them in series instead?
“I don’t see how the electrical signal generated at the end of one branch of the “Y” (the end of the ROD piezo branch). . .”
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