Stereo cable/JPM/Piezo-Hum

[tritheory]

Hello,

I plugged my JPM in for band practice tonight with a stereo cable to that tip went to my electric rig and ring went to LR baggs acoustic preamp and into channel on the p.a. However...I has terrible ground loop/hum form the p.a and electric rig being hooked together...

Was wanting to get advice on this....

Thanks,

Steve

 

[roburado]

Try what's here in this thread. http://www.ernieball.com/forums/music-man-guitars/21155-help-pretty-please-problem-my-new-john-petrucci.html Use DI box with ground lift for the piezo signal. This sounds like the same problem that people come here to ask about every so often.

I'm not really an authority, or anything. It just sounds like the same problem. Maybe, someone who knows better can give you a better answer.

 

[SteveB]

What Roburado said. It's a problem of different grounds. Use a DI box with ground lift on your piezo signal.

 

[CudBucket]

I've had my Piezo equipped JP for a while yet and haven't even plugged it in. I know, I know. It's a wierd thing with me and new guitars. Sometimes, I get'em, and play them without ever plugging them in for weeks or months. Whatever.

Anyway, I've put together a mini PA in my music room and have seen enough of these posts to know I need a DI box with a ground lift. Thanks guys.

 

[the24thfret]

Call me stupid, what's a ground lift?

 

[beej]

Normally you want a single electrical path to ground (e.g. through your Amp). When you have two different paths to ground, you can get what's called a "ground loop". This usually happens when you've got two different amplifiers and by way of your cable, their grounds are connected to one another. The voltage difference causes an audible hum - the terrible noise in question.

A "ground lift" will isolate the ground on one cable from the ground on the others, thus breaking the ground loop - e.g. the grounds on both amps won't be connected anymore.

 

[SteveB]

Call me stupid, what's a ground lift?

Beej didi a great job with the details. I'll chime in and add that the ground lift on the DI box will simply be a switch that you can throw one way or the other. One of the two positions (when the lift is engaged) ought to resolve the type of hum problem mentioned in this thread.