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Permalink Reply by White Raven on February 20, 2019 at 8:02am

Well, I made up a couple of piezo's direct wired to a jack and soldered a. 022 cap from the positive to the negative lugs. Good news is, there is absolutely no hum, buzz or feedback. Bad news is there is absolutely no sound. I tried both my electronic amp and my tube amp. all the way to full volume, nothing. 

cut the cap off and I have all the regular characteristics of a piezo. I haven't decided whether to try a .01, or just use hot glue and a bottle cap. 

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Permalink Reply by Jerry Jordan on February 20, 2019 at 10:12am

Sounds like you had a bad cap. It was acting like a short circuit. I would try several other caps. A multimeter should help troubleshoot the problem.

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Permalink Reply by White Raven on February 21, 2019 at 4:22am

definitely possible. i will have to pick up a heat sink and a multimeter. then learn how to use it.

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Permalink Reply by François on February 21, 2019 at 9:19am

For the heat sink, just use a pair of needle nose pliers with a rubber band wrapped around the handle.

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Permalink Reply by Taffy Evans on February 20, 2019 at 4:21pm

Hi WR, if you want to keep it simple, I recon use the tone control on the amp as you suggested, that way you have variable control of treble frequencies.

Mounting the piezo element as suggested on here by others will give a more pleasing sound from the guitar. I'd be asking myself how many capacitors have I got to fit till I find the one that works, and then its fixed at that one frequency.

A capacitor shunts much of the high frequencies to earth and lets the low ones pass. 

Talking about feed back. I find that the bass [low] frequencies are more likely to drive my guitar into feedback than the treble [high] frequencies, at the same volume setting.

In an acoustic guitar there are two sources of feed back, one is soundwaves from the amp/speaker matching the fundamental soundwaves of the guitars timber vibrations, and/or speaker soundwaves acting with the fundamental air resonance in the box to do the same thing. I think one source feeds the other. You can dampen the strings and the air/body effects will still cause feed back to continue.

Tip: put a heat sink on the legs of the capacitor being soldered so as not to damage it.

Taff

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Permalink Reply by White Raven on February 21, 2019 at 4:21am

great advice. thanks.

they might have been crap capacitors, I dont have a multimeter or know how to use one, so checking them might be a challenge. As for damaging them when soldering, I never thought of that. I didn't use a heat sink.

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Permalink Reply by François on February 21, 2019 at 5:01am

Most multimeters don't verify for capacitance, just resistance, continuity, power and amps.

For the price of a capacitor, just change it and see.

There will be a difference between a capacitor that is mounted in parallel (as in on the jack) and in series like on most guitars. You might want to just change it up and see what happens.

Thing is, on guitars, the volume is changed by adding a resistance from the tip to the ground. The greater the resistance, the greater the volume. By putting a capacitor in the same way, you probably are shorting the jack (capacitor has too little resistance) and thus killing the sound.

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Permalink Reply by White Raven on February 22, 2019 at 4:19am

I wondered about whether it would short the jack, electricity follows the path of least resistance. I'm not very patient as an experimenter, but I might still go down this road a bit further. It would be easy to just pot the hell out of the piezo and accept whatever it gives me. 

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Permalink Reply by Paul Craig on February 21, 2019 at 6:05am

Ted Crocker came up with this scheme for piezo's. I've been interested in trying it, but haven't done so yet.

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Permalink Reply by Taffy Evans on February 21, 2019 at 1:42pm

Hi yes I use that set up. I'm not an electronics person, but I suspect that is a treble bypass system on the volume pot. It allows the high frequencies to be heard at low volumes. The resister allows some of the other lower frequencies through for a bit more body to the tone. I solder the resistor to the same lugs as the cap. 

Taff

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