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. 

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Hi CTBR, its strange to here that your piezo set up did dot drive the distortion. I have always found great overdrive tones from the piezo's, at least as good as cheaper single coils. I just tried a three stringer through a 5 watt cheapy amp and it sounded as dirty as all hell.

I wonder why yours is lacking?

Taff 

i have a theory... 

the two piezo's are out of phase because vibrations are being picked up by the front of one and the back of the other so 180 out of phase. but because there is a small distance between the two they are not picking up the exact same part of the wave. as you didnt hear any phase cancelling effect i am guessing that the phase cancellations are happening at a higher frequency. i.e. we cant hear it. piezo are and were originally designed for ultrasonic frequencies. most of the "fogger"water thingys use a piezo. but instead of picking up a signal from a vibration they are fed with a 40KHz approx sinewave to make them vibrate.

anyway the closer the two pickups are together the more phasing i bet you will get.

Taffy those low watt amps clip because they'er not designed to handle their own volume output. Try putting your CBG within a few inches of that speaker wile it's distorting. All my tests have been done 12 inches away from a 10 watt amp. 

Timothy, your correct on the phasing and how a humbucker works. The other benefit of a humbucker over a single coil is it's ability to handle higher stage volumes without feedback. The vid link is kind of grade school but explains everything. Even why a humbucker has a lower high end.

https://www.youtube.com/watch?v=jQas_BXkwBs

Most quality humbuckers have different coil windings on each side. This difference changes the over all 

Decided to make a pickup out of two pieces of 1/4 inch oak. So I hot glued both piezo in place. Glued the other piece of oak on top.  Did all my soldering and wired it up to an output jack. Held it down inside the upside down, open backed, CBG I've been playing with all along. And no sound. Hot to hot, cold to ground. Everything is in place. I can tap on the wood and barely hear it through the amp. This gives me hope. Because I never have problems with experiments like this unless they're going to work. If something isn't going to work it will blow up in my face right away.  : ) 

Like a humbucker this set up looses some of the highs and brings out more of a midrange tone. So I know I have that going for me. But every time I try something different with the pickup/volume test I get different results. The cardboard gave me the best feedback protection. Placing the piezo on the top then covering them with wood. Squalled at a lower volume. Perhaps a softer material for the back of this wiring would help. 

Sorry folks. I haven't had much time to spend on this experiment. Had to be somewhere again today. 

Another side to this is with both grounds soldered together and not going anywhere there is a lot of hum. when I touch these to the ground on the output jack the hum goes away. So i'll have to go back to soldering both grounds and one hot to ground. However because I don't have both piezo stacked I don't have the shifting phase I had with the first experiment. Even placing them where they are just about touching gives a good signal. 

what size disc's are you using?

i just got given a bag of small disc's guy at work wanted to make a fogger and didnt realise he had to build an oscillator and drive them.... these look around 10 to 12 mm so under 1/2"

might have to use 1 under each string....

Check threads on this forum for piezo size. Really don't think size matters that much. I do know I read somewhere that you can actually wire to many piezo together.  Also that parallel wiring is better for piezo. Each piezo hot running it's own line to the output, or volume if your using one. 

If you did wire one under each string this is what will happen. You will have a spread of sensors picking up a single wave at different points. Because each piezo picks up all the vibrations in your guitar top. You'll end up with a lot of phasing. 

After countless tries. With three different pairs of piezo. I can't duplicate what happened with the first set. Not even with the first set. I've even tried different wiring configurations. The only good thing that's come out of this is I'm now really good at attaching wires to piezo. But that's not helping anyone. I'm not done beating this dead horse yet. Just putting it on a back burner till I find out how I can make this work. If someone can make a silent piezo underwater mic there has to be a way to make one for a CBG.

The only thing that positive that's come out of this is knowing that a dual wired piezo in this manner comes to squall at a higher volume level than a single wired piezo in the exact same position.  

Could the first try result have been due to a bad solder joint on the 2nd piezo? 

Hi, I have just finished a cbg that will be my "Frankenstein" test bed for the testing of Piezo transducers. See, you got me started Blue Rat.

Having installed hundreds of transducers over the years, in all types of instruments, I thought it may be an educational project, as and when I find the time. 

I will not be trying to eliminate feedback when using a piezo transducer pickup, as I feel the nature of the beast does not allow this, mainly due to the way it functions in a hollow chamber. Blue Rat has demonstrated how hard this can be. 

What I will do is mount transducers into this cbg in areas already suggested by members on here, and some ideas of my own, and test the tone, output and feedback qualities by switching between them. I will also have a pre amp fitted to test the effects when its  in or out of the loop. I will start a new thread for this.

Just a few things I'd like to comment on. B R,the backless box was for easy access, was the back replaced for testing?

Piezo size....As piezo transducers react to the tops vibrations the more sensitive the top to string vibration the smaller transducer would be used, a less responsive or laminated top may require the larger disc to get a suitable/similar output.

In my quick test in eliminating feed back the best result I got was to cover the soundhole. No feedback.

Taff 

Thanks Taffy, no the box was left open. I would cover the piezo with a small piece of 1/2 ply, a chunk of foam or one or two layers of corrugated cardboard. Or leave them open and strum the strings. The CBG is in a way that allows me to have free access to the strings. This allowed me to strum them derring the testing. All with the box open and the piezo 12 inches away from the speaker. All the piezo are the same 27mm size. The idea was to create a worst case scenario for the piezo. This way the wiring setup itself would be tested. I found that it didn't matter what I covered the disks up with. Each different wiring I tried would feedback at the same volume level no matter what I covered it with, or left them uncovered. The best results are from the wiring diagram in the first post but with both black wire grounds wired to ground. 

Hi, I mentioned the back of the cbg as I thought that may have been a more of a worst case scenario with the back fitted. As is normally the case the air/soundwave pressure in the box would have been added to the top vibrations [pressure] creating a more realistic situation. I think this is why I could cancel  the feedback in my closed box with soundhole, by limiting air movement/pressure in the box, by covering the soundhole. Doing this I thing broke or limited the feedback loop between box and speaker. 

All very interesting.

Anyway here's "Frank" waiting for the transplants.....5-6 transducers, volume pot, jack and preamp. I built this in a way that allows me to remove the neck from the closed box, or remove the neck and lid as one unit [still strung up and tuned] to allow for operations inside.

Cheers Taff

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