Why does my piezo hum?

[Kenton Kelley]

I have been playing my CBG and enjoy getting some really cool tones through a amp modeler. I notice today that I get hum through some of the higher gain mods but I wrote it off to that's what that takes to get that sound. Then I found that if I touch the housing of the 1/4" plug that the hum is greatly reduced.


How do I get rid of the hum and please explain why it occurs? Thank you.

[Ted Crocker]

Piezos don't play nice with Gain. You can live with it or dial it down.

What you describe sounds like a grounding problem. Is there a volume & tone control in the piezo circuit? My first suggestion would be to look for a bad solder connection, or just redo all the solder points. What happens when you use a different guitar cable or plug in the amp in another room?

[Kenton Kelley]

No volume or tone control, just piezo pair wires twisted straight to the the guitar jack with heat shrink from end to end. I 'll have to unstring and open the box to check my solder points. The only better thing I can think of doing is to change the wire using a shielded conductor and connect the shield to the sleeve of the guitar jack. Any opinions?

It just seems that something can be done if I can greatly reduce the hum by touching the shield. I just don't understand why this happens with a piezo for a pick up.

[Johnny Lowebow]

Can't remember the lyrics ?

[Joe Thomas]

Besides piezos being very disagreeable with gain I do agree with Ted, sounds like a grounding problem. If the problem has just started (or gotten worse) then I would be inclined to think you may have a faulted ground. When I wire for a piezo I tend to use a larger gauge wire (or braided strap) on the ground part of the circuit to keep the resistance to ground as low as possible. This helps alot when wiring for piezo. Since you state that no volume or tone control is used then check your bond for the bridge/tailpiece.

P.S. Why is it every time I see one of Randy's products I get visuals of Randy with a shovel in the graveyard after midnight whistling "Dem Bones, Dem Bones"? LMAO!!!

[smojo]

Wow Randy - love the pickup
Randy S. Bretz said:

The string saddle is carved right into the bone- all one piece.

Randy S. Bretz said:

This is my new bone piezo bridge the underside is covered with hot glue. There is no feedback whats so ever!!

Kenton Kelley said:

No volume or tone control, just piezo pair wires twisted straight to the the guitar jack with heat shrink from end to end. I 'll have to unstring and open the box to check my solder points. The only better thing I can think of doing is to change the wire using a shielded conductor and connect the shield to the sleeve of the guitar jack. Any opinions?


It just seems that something can be done if I can greatly reduce the hum by touching the shield. I just don't understand why this happens with a piezo for a pick up.

[Larry Q. Chapin]

On just about every piezo pup that I had made/used there is some humm (And yes it goes away when I touch the 1/4 input jack) it seems to be just the nature of the piezo... Ted's right, piezo's do not play nice with gain, these take a little tweaking on the amp to get them to be dialed in just right. Unless it's unbearably bad (in which case it probably is a bad solder joint) then I'd say just live with it and don't bother trying to take it all apart.

[legnahkra]

hi, just clear something for me... are you using the piezo with the white film facing the wood..? i used to do that in the beginning and got a lot of issues with humming and noises. i turned the piezo the other side, hot glued it... and viola..! maybe you should try that.
guess nothing can touch the soldering spots on the piezo...

[Gene]

it hums cause it dont no the words

[Mark Werner]

The very first article I ever saw about using typical RS piezos recommended tossing the thin twisted wires that come on the things and replacing that with grounded audio cable.
I have done that with every one I used, and.... No hum.
This cable is the stuff that comes with most audio connectors; I have dozens of old ones around the house and just cannibalize 'em. The outer wire segment, twisted under the outer covering, is just pulled to one side and "tinned" for the ground connection, then the center wire can be stripped to expose enough to solder to the hot part of the piezo.

[jim]

shielded wire has nothing to do with piezo humm, most cases are caused by cold solder connections or bad cables.

Mark Werner said:

The very first article I ever saw about using typical RS piezos recommended tossing the thin twisted wires that come on the things and replacing that with grounded audio cable.
I have done that with every one I used, and.... No hum.
This cable is the stuff that comes with most audio connectors; I have dozens of old ones around the house and just cannibalize 'em. The outer wire segment, twisted under the outer covering, is just pulled to one side and "tinned" for the ground connection, then the center wire can be stripped to expose enough to solder to the hot part of the piezo.

[Mark Werner]

May well be the case; I never tried any other way since these builds have been so successful. At any rate, it's easy enough.
The other thing I've been doing is to mount the piezo in 3M silicone. Seems to reduce the tendency to be "microphonic" and pick up every little sound from handling the guitar.

[Wichita Sam]

don't need to shield piezos.... believe ted.... almost always bad solder joints (stray piece of stranded wire?)....

Kenton Kelley said:

No volume or tone control, just piezo pair wires twisted straight to the the guitar jack with heat shrink from end to end. I 'll have to unstring and open the box to check my solder points. The only better thing I can think of doing is to change the wire using a shielded conductor and connect the shield to the sleeve of the guitar jack. Any opinions?

It just seems that something can be done if I can greatly reduce the hum by touching the shield. I just don't understand why this happens with a piezo for a pick up.