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.
Looks like one piezo is acting as a dummy coil. It's not wired in series, but a variation of parallel. What's the grey box that the black wires are going to?
Some guitars like the Gibson or Epiphone Blueshawk have P90 single coil pickups with a 3 pickup under the top without magnets or poles and is used as a dummy coil to buck hum while still having single coil tone.
The two black wires from the piezo are soldered together and shielded and go nowhere. I treaded those like the inside wires of a humbucker.
The two red wires I treated like the the two end wires. Making a mock humbucker out of two piezo.
I was able to turn the amp up half way today before I got squall, Squallbucker still at 12 inches away wile the strings were being strummed. Then one of my leads broke. Those little things are just not meant to be yanked around. : )
A series wiring would be signal through hot of piezo 1 - piezo 1 ground to hot of piezo 2 - piezo 2 ground to ground. That doubles the impedance and isn't good.
Parallel wiring would be both grounds to ground and both hot/signal to signal. Which half's the impedance like when using 2 8ohm speakers turns into a 4ohm load.
So your sending signal through piezo 1 into piezo 2 backwards. That's why I was mentioning that it's acting like a dummy coil. It's cutting the noise like a humbucker without doubling the impedance.
yes, just like a dummy coil on a humbucking pickup. I'm really hoping others will try this and see if they get the same results. If this works and sounds good it will be a way to use a piezo at louder volumes when playing live. It's still microphonic in nature. Still doubt you would be able to use distortion at high volumes.
The reason I turned one upside down was to try to emulate the reversed magnetic field of the dummy coil.
Hi, interesting stuff. I'm not very clever when it comes to pickup specs, and you guys seem to know your stuff in that regard.
Do piezo crystals have a magnetic quality like the north and south poles of a humbucker?
When testing my magnetic pickups one coil reads south (wound) and the other reads north (wound), and when wired together give the hum cancelling effect. When I test the piezos there is no magnetic field.
I understand the piezo crystals are sandwiched between two plates and are effected the same from either side by string vibration, so may not have the same hum cancelling properties, but you said it did, I'm intrigued. And possibly wrong in my thinking.
you are probably getting a phase cancellation effect. would be interested to hear the tone of this pickup up and down the fretboard compared to a single piezo .
like a half cocked wah pedal.. frequencies dropping out and returning as the pitch goes up and dow,..
Taffy, piezo are not magnetic. They transfer all vibrations into an electrical signal. This is why it's way to easy to get a lot of feedback and squalling when playing live at higher volumes. Didn't notice any hum cancellation. Because RMF fields (what causes the hum ) are magnetic I really don't think there is any way possible to cancel them out with a piezo. However the feedback and squalling was greatly reduced.
Timothy, The first experiment I did, stacking the two piezo, gave very noticeable phasing. This experiment I didn't notice it, Or was to excited from the lack of squalling to listen for it. : ) I'm going to make a wood sided pickup and place it in a CBG. Plan on playing this trough my 80 watt Marshall. This amp as a clearer sound to it. I'll be able to hear if there is any phase cancelation.
Thanks CTBR, sorry I miss read your account.
Yes feedback is a problem with amplified hollowbody instruments, nowadays there are "feedback busters" that block the soundhole limiting air movement, and preamps. Back in the day I would occasionally get guitars for repair that had been filled with cotton wool to limit feedback. I also had to devise ways to block the "f" holes in arch top guitars for the sams reason.
I'm thinking that adding another piezo in this way is having the 2nd piezo act like a resistor or capacitor that reduces the impedance, but I'm not sure.
Thanks CTBR, sorry I miss read your account.
Yes feedback is a problem with amplified hollowbody instruments, nowadays there are "feedback busters" that block the soundhole limiting air movement, and preamps. Back in the day I would occasionally get guitars for repair that had been filled with cotton wool to limit feedback. I also had to devise ways to block the "f" holes in arch top guitars for the same reason.
Another way to stop magnetic pickup squeal is to wrap the bottom and sides of the pickup under the top of the guitar with foam. I did this with the bridge pickup in my Strat-O-Res guitar. I just totally covered the bottom and sides with some black foam and secured it with electrical tape. It 's just like stuffing the guitar with foam/wool, but this doesn't block any acoustics in the body like the foam/wool would do inside the guitar.
Tried this experiment with both piezo facing the same direction. Did not work as well. Also tried it backwards, with the wrong side of the piezo down. This had less volume. Comparing the squallbuster with the sound of just one piezo. Same sound. Same volume. The only difference is the point when you get feedback and squall. With the squallbuster I was able to get my small amp up to 9 1/2. With the single piezo I was able to turn it up to 6. Both are still wrapped in the same cardboard. I know I'll get a better total response with wood. But possibly more feedback at a lower volume.
To answer the phase question i didn't hear anything like a coked wah or a shifting of an out of phase signal. The tone and volume between the single piezo and the squallbuster was the same no matter where I placed them in the box.
Next will be to place this in wood and do the same experiment. Moving both around in the box and comparing the tone. And bringing each to the point of squall. I want to do more experimenting before I glue one to the inside of a CBG. So far I'm very happy with the less squalling aspect of this pickup design.
For fun I did try it with the amp's built in distortion. Nope, it's a piezo pickup and this just isn't going to work with distortion.