Ground loop hum from a PA system

[gassidy]

Hello Line 6 community,

 

I am using an HX Stomp as part of a bigger pedalboard recently and have been able to play without issue at home. However, I did my first outdoor gig with it and experienced what sounded like a ground loop noise through the PA system when I was hooked up to the PA and pedal board. I bypassed the helix, sound was gone. I used only helix, sound was gone. Both power supplies for pedals and helix were on the same power strip.

 
I believe it is ground because the noise is consistent regardless of the output of the

HX (I turned the volume all the way down)

 

 Anyone have any clues?

 

On a side note, I always get a hum when I use analog bypass. I am wondering if there may be something specifically faulty with my unit.

 

 Thanks in advance

[MusicLaw]

The only way to isolate the problem is begin with a very simple signal chain. Start with the Stomp and Pwr Supply. One by one add additional items. It will take some time and a bit of attention, but you will discover the problematic gear. Even a faulty cable or plug can be a culprit.

 

Please post your findings to share with others whom may be following this thread. 

[Schmalle]

Something like this?: 60 Hz hum

That's most likely coming from a not lifted ground to P.A. which was powered by another outlet. Push the ground lift switch on your Helix when you send a signal to P.A. or ask the sound guy to lift ground on the mixing console.

[kc99x]

I had what sounds like the same problem. I built my own analog bypass that bypassed both the hot and ground leads to completely remove the helix from the equation. (Jacks had to be isolated from the box.)

 

Plugged everything back in and the hum was gone whether the bypass was engaged or not. I was using a different cable from the guitar to the effects. The "bad" cable has no issues plugged into the helix and using headphones (or directly into an amp) which is why I thought it was fine. I think the cable was picking up interference from the power supply for other effects, but only in a way that the helix made it audible. Your issue where there is no problem with no helix or only helix sounds similar. When you tested the helix by itself, was the other power supply plugged in? If no, check that in addition to the cables.

 

Bottom line is there is something about the helix that makes it more sensitive to the weakest link in the chain than any other piece of equipment I've owned, and you can't be 100% sure any item (or combination of items) is not a problem until there is no longer a problem. It's annoying, but less annoying than a defective helix.

 

[gassidy]

Update -

The issue seems to be different than the replies, but I found a solution.

I was able to generate noise by putting basically any pedal AFTER the helix in my chain. I was able to eliminate the issue by using a DI with a send/return and putting the Stomp in the send/return by itself.

[Schmalle]

13 minutes ago, gassidy said:

Update -

The issue seems to be different than the replies, but I found a solution.

I was able to generate noise by putting basically any pedal AFTER the helix in my chain. I was able to eliminate the issue by using a DI with a send/return and putting the Stomp in the send/return by itself.

So it was a ground hum then.

[gassidy]

On 7/7/2021 at 2:09 PM, Schmalle said:

So it was a ground hum then.

Seems like it was a loop but Stomps don't have a ground lift switch and the DI I was running had a ground lift that didn't cut the hum.