Still looking for ideas. Found this link. Was wondering if anyone has tried this in a CBG?
Balanced Piezo contact microphones
Sorry folks. I put this in the wrong section of this forum. So I posted it here and deleted the original.
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OK so here's what happened and a good explanation.
After turning the amp up loud I got the wobble. That nasty phase sound that will not work. I tried with with both hots wired together as well. Still with the piezo back to back. I also re did the first one. Using electrical tape to make sure the solder joints wouldn't hit the other piezo. This is a bust. I added 'dead in the water' to the post tittle.
this worked for the scientists because they were using an XLR jack. With a positive, negative and shield. Just not going to work with a 1/4 jack.
I;m still hunting for answers......
It would work with a 1/4 inch TRS jack but you would have to have a balanced TRS input on the amp. Or use the XLR with an acoustic amp.
Though if you have to buy a new amp you're probably better off buying a preamp to install in the guitar (or externally in a small box) and using your regular amp.
Yap, my thoughts were "Stereo Jack!!!" Not going to work with an amp.
I've had active pickups in a guitar before. Have a bad habit of leaving my guitar plugged in and turning off the amp. Afraid I'd do the same thing with a preamp. Be constantly changing batteries. They'er nice. Plenty of folks swear by them. Just not something I want to mess with.
'Balanced' signals send a + (PIN 2) to ground signal on one wire and a matching - (pin3) to ground signal on the other wire. This lets you use a much longer mic cable since the mixing board can read the delta between them.
If you don't connect the piezo sandwich to an XLR plug (or balanced TRS 1/4") and then plug it into a MIC or BALANCED LINE IN socket on a mixing board, you are missing the purpose of the balanced signal, sort of like putting a bag over the left side-view mirror on your car.
this is almost the same way a humbucker pickup is wired. One bobbin is wrapped in reverse with it's polls opposite of the other. This negative wave cancels out electrical hum and noise. So in theory the upside down piezo side would have a reverse wave.
So i tried it. WORKS! The hot side of the piezo presses against the CBG top gave a good sound. The cold or 'wired to ground' done the same was about half the volume. Not sure why. Not exactly noise proof. But should help when sandwiching or incasing the piezo.
I'll try to get a vid up with sound samples. Going to have to try to balance the camera with the amp and what I'm doing. All without getting the sound form the body of the CBG itself.
I need to wire up a single to hear the timber and volume difference. Perhaps add that to the vid as well. My also try with both positives wired together with only the ground going to ground. I've got the parts. And i'm having to much fun. : )
Looks like to do this with a 1/4 jack you would have to take the hot from the string facing piezo and go to the hot of the jack. Then take the combined ground plus the hot from the bottom piezo and go to the ground of the jack.
the above is a gif showing the conversion of an X:R to 1/4 jack. Pin 2 is positive, 3 is negative and one is ground.
I'm no electronics expert but it seems to me that if one of the piezos has both leads going to ground then it's not going to to anything, so you no longer have a balanced signal.
Looking at the wiring from the web site it makes more sense.
You would have to have some kind of thin shield between the two. However the thinner the better.