Again trying wiring based on a humbucker pickup. This time with results. Instead of stacking the two piezo they are side by side. One facing up the other down. Wired as shown below and directly to an output jack.
Placed between two pieces of corrugated cardboard and pressed inside a cbg. Exposed and at 12 inches from a small amp speaker. Amp set at 1/4 volume. The hum level was no different from what the amp normally has. There was no squall. Not even when strumming the guitar.
Control. The open guitar nor the amp was moved. Nor was any of the setting different.
A single piezo sandwiched in the same corrugated cardboard. Wired directly to an output jack. Placed inside the very same cbg. Squalled uncontrollably. Was not able to hear when I strummed the guitar. Squalling didn't change.
The wiring is as the gif below. One hot running to ground. The other to the hot side. The two black ground wires are soldered together and go nowhere.
Hoping other builders would try this to see what results you folks can get.
Going to try this again tomorrow ( when it's not 3:00 in the morning ) Going to try with both piezo facing the same direction. To see if there is any difference in sound or effect.
Great stuff CTBR .,.,love to see this experimentation.,.,piezo's and coils are definitely different animals.,.,like comparing rocks to marshmallows.,.,I have a few builds using piezo's that don't mind distortion..,most do howl if you turn it up.,.,i'll give this a try.,.,keep up the good work!!
Piezo crystals do have an 'orientation' (first pic). compression drives a charge one way, tension (stretching) drives the charge the other way.
by flipping a second piezo one gets compression while the other gets tension, they throw opposite charges (one gives off the red line, the other gives off the blue line. +1 and -1 at the same time result in the green line compared to ground.
It won't cure feedback, but then neither does a hummbucker.
A hummbucker kills outside RF noise that the coils pick up as though they were the UHF antennas on an old analog TV set. Because one coil is wound backwards from the other, the RF antenna effect of one is opposite the other and they cancel. the magnets don't have any effect on the coil acting as an antenna to outside RF noise.
but by flipping the magnet in the reverse wound coil, they add together when responding to the sting vibration. one sees the string coming at the N pole and generates a clockwise charge, the other one see the string coming at the S pole and generates a counterclockwise charge. so you chain the second coil backwards to the first to catch that backwards charge from the backwards side at the same time the other is getting a forwards charge, and they add up.
Yep, that all makes sense, I didn't know about the piezo orientation part though.
Thanks JL. Totally dig the piezo info. So I was on to something by turning one upside down.
I really haven't stopped experimenting. Did something really stupid. Didn't realize just how dumb till I plugged it in. Wired two piezo in parallel to a volume pot. Wired a third piezo in backward, Sending it's hot to ground and black to the input. What I did was have a volume pot that was always on......: ) A piezo blend pot if you will.