Ground-Loop Hum

[roburado]

Okay, electronics gurus, got a question for you.

Let's say I have a two-amp set-up. For example, I have a JP6 with piezo, stereo cord, splitter box, one amp for piezo, one amp for magnetics. Let's say I plug both amps into a power strip or a Furman power conditioner. So, here's the question. If I do that, there should be no ground-loop hum, right?

 

[beej]

No, you'll still get a ground loop. There's going to be multiple paths to ground due to the fact that you're connecting the grounds of both amps together via your cable.

Same deal if you share a single non-isolated power supply to power some pedals that go in front of your amp and some that go in the loop. Same power source but separate circuits and when you have multiple paths to ground like that you get the dreaded hum.

 

[roburado]

Okay. Just wondering if I could avoid the DI and another cord. I mean, I have the DI, and it's just sitting waiting to go once I get my JP/piezo. Thanks, beej.

 

[Jimmyb]

Yup, +1 to what Beej has said.

The easiest way around it is to pick up a DI box. Behringer have one that costs peanuts.

 

[Jimmyb]

Ok, you replied before me.

Just use a small, high quality, patch lead to go from the splitter to the DI box.

 

[roburado]

Yup, +1 to what Beej has said.

The easiest way around it is to pick up a DI box. Behringer have one that costs peanuts.

Yeah. I actually have that DI ready and waiting for the guitar to arrive. Just wondering about the theoretical aspects of the ground-loop hum issue. Thanks, guys.

 

[beej]

My pleasure buddy

Btw, after all the recent talk about DIs I just picked up one of those Behringers on eBay. I have an acoustic gig coming up and I'm going to use the piezo on my Morse

 

[Jimmyb]

What DI have you got?

You could possibly mod that by fitting a 3 pole input jack and taking either the tip or the ring (can't remember off the top of my head) straight across to an output jack. Quite a few DI boxes have a straight parallel out that doesn't go through the transformer, so you'd hook that onto the tip connection (or ring) leaving you with a signal to take to your guitar amp.

 

[roburado]

Jimmy, I don't know if you're talking to me or to beej, but I have this one.

AUDIO TECHNOLOGY - AUDIO SOLUTIONS - ULTRA-DI DI100 : Ultra-Rugged DI Box for Stage and Studio

 

[DrKev]

I have the Behringer acoustic modeller, the ADI-21 (the brown stomp box) which is a DI but does a wonderful job taking the crystal bite off piezo pickups. It goes everywhere with my mandolin. For the price it is a fantastic piece of gear and I'd recommend that everybody try it. In fact, I'd love to know how well it works with EBMM piezos.

 

[roburado]

Thanks for the recommendation, DrKev.

 

[francric]

So no way to get rid of the hum??????

 

[beej]

So no way to get rid of the hum??????

A DI box with a ground lift.

Or a buffer w/ islolated split out. I have an Axess Electronics BS-2 buffer on my board that works like a charm.