Hey guys. Still pulling my hair out here with getting the piezo rod pickups grounded.
I had a completed build that worked fine and sounded great... when you were touching the jack or the volume pot. Otherwise, bad hum. Grounding problem! I traced everything with a multimeter and it was fine, could not pin down a faulty component. So I ripped out everything and started with new parts and new wires. Guess what, same issue. I wouldn't be half as frustrated if I had not wired up a twin CBG with the exact same parts and NO ISSUES the first time out.
Any advice appreciated. I'm using a piezo rod with volume pot, wiring with this diagram...
If everything checks out with a multimeter, there must be other issues that "don't show up" with a multimeter. Any leads on what that might be. I can't ground the jack to the bridge because there is no metal. (Bone nut on piezo rod in wood housing. )
can you add a piece of metal at the string anchor to wire to, even a small strip under the ball ends is enough to link all the strings, post a pic of it, and someone may have an idea for you
Piezos you don't normally need to ground... this sounds like a bad instrument cable to me...
Ditto John Sawyer
troubleshooting 101, swap out major components to isolate where the problem is
It seems that the more components in the circuit, the more likely to pick up hum.
You might want to try wiring the pickup directly to the audio jack and see how it sounds. If you still have hum, then either the audio cord is bad or you have a bad pickup. I have ran across piezos that are very noisy even when wired directly to the jack. Swap out the piezo and the noise is gone. They are pretty cheap devices so QC can't be that good.
The other thing to consider is where you are playing. If you are around florescent lights, they can cause audio noise. Also, if you are using an amp that plugs into AC try an amp on battery power only to see if it is some kind of AC line noise.
Give some things a try and you will find it.
I think Tom T's advice is a good way to start, by pass the pot, go straight from piezo to jack and see if that works, if so the problem is either the actual pot, or the wiring, another thing i'll just add and i might be being obvious, is the outer sheath of the piezo cable grounded?
Darryl and Tom, yes that is great advice. I had done that on the first harness with no change. I did it again tonight on the second harness. A little better but still there.
I decided to try a different amp all together on this direct connection and it sounded FINE through my big keyboard amp. I wired up the full harness with volume pot again, still fine through the keyboard amp!
So there seems to be something with the little practice amp I was using, not grounded. What I STILL cannot explain is why by clone build of this one was fine and why a disc piezo build is just fine as well. For another day.
For now, I am happy to have this build done for a customer who has been waiting on it. And mentally I am VERY ready to move on from this one.
Thanks all for the discussions!
Like others here i'm sure, i've had some piezo builds that for some reason, just will not play well with some amps, but ok with others, but that is usually an impedence issue, some amp-s just don't like piezo's without a pre amp