JP plugged into two amps: eliminating buzz

[Hiza22]

Hello,

The JP7 from my signature has a piezo, and recently I've been trying to make myself a nice tone with the guitar plugged into two amps (using only mono cables):

- the lower jack sends the magnetic pickups' sound to all my pedals and a tube amp (Laboga Beast),
- the upper jack sends the piezo's sound directly to a solid state amp (Crate G160XL).

My problem is that, in this configuration, I get a low buzz from the Laboga. My guess is that it's some sort of ground loop between the amps. The rest of the time, when the guitar is plugged into one amp only, I have perfect silence, no buzz.

All my pedals are powered by a Voodoo Lab 4x4 (isolated outputs). The amps are plugged into different electrical outlets, but those outlets are on the same wall and part of the same circuit.

How can I eliminate that buzz? If it's indeed a ground loop problem, is there a way to isolate the amps from each other? Thanks for any advice.

 

[wolfbone07]

I solve that problem with a Lehle switcher : Littel Dual : it has isolating transformers in it = no hum.

 

[DrKev]

My problem is that, in this configuration, I get a low buzz from the Laboga. My guess is that it's some sort of ground loop between the amps. The rest of the time, when the guitar is plugged into one amp only, I have perfect silence, no buzz.

Yes, ground lopp is absolutely the first thought too.

All my pedals are powered by a Voodoo Lab 4x4 (isolated outputs). The amps are plugged into different electrical outlets, but those outlets are on the same wall and part of the same circuit.

But your buzz suggests otherwise. Try powering the amps and pedals from an extension board (power strip) plugged into one socket on the wall. A standard wall socket can happily supply more power than 6 guitar amplifiers will ever need so it's perfecty safe to do so. Going through the extension board guarantees that everything is on the same circuit and sharing the same ground. If then you still have a buzz, ground loop is not the problem and we're possibly looking at an issue in one of the amps.

Kev.

 

[Hiza22]

DrKev, thanks for your answer. I moved my Crate amp so that I could plug it on the same extension board as the Laboga, and sure enough, the buzz disappeared. So I checked the map of my electrical installation (I had the whole house redone two years ago, so it's accurately mapped), and those two outlets weren't directly linked as I thought. You were right.

Wolfbone07, even though I won't need to buy such a device this time, thanks for the pointer. I wasn't really familiar with that kind of thing before, and guitar splitters like the Little Dual, able to work with a dual-output guitar AND two amps don't seem too common.

 

[QuietSpike]

We don't call him "Doctor" for nothin!!

 

[DrKev]

It's not rocket science.

I'm happy there is no electrical fault in one of the amps.