School me on ground loops, please

[eudaimonia02912]

Can you guys school me on ground loops?

Right now my amplifier and all of my effects are plugged into Monster Cable Pro 1000 power strip (which includes some power conditioning). Some of my effects are plugged into this strip directly. (Disconnecting these has no effect on the amount of what I take to be ground loop noise.) Others are powered by a Voodoo Labs Power Plus 2, also plugged into this strip.

I'm hearing what sounds like 60 cycle hum when I have my guitar plugged in and the volume is on on the the guitar. (My guitars all have humbuckers.) Some days it's worse than others. Whenever I do hear it, I can make it disappear by touching metal on my guitar cables. The sound gets worse if I turn the gain up, either by switching to a high gain channel or by turning on a distortion pedal.

I don't think it's the amp or my pre-amp tubes. I've had this problem with other amps before, changing pre-amp tubes doesn't make a difference, and it seems to occur anywhere in my house.

It sounds to me like it's a ground loop or 60 cycle hum, but I don't know much about these things, and I figured with all of my power supply care, I shouldn't have a ground loop.

What's the best way to make it go away? Should I try one of those ground loop breakers from EbTech?

 

[eudaimonia02912]

Oh, look:
http://www.ebtechaudio.com/findloop.pdf

 

[ESP123]

It could be interference from your outlets. If you've heard this in multiple places when using your amp it might be something else too. I would try one of these first in your main place where you mostly play and hear this noise. Here is a product you might want to try first,

http://www.amazon.com/Ebtech-Hum-Voltage-Filter/dp/B0002E4YI8

 

[phyrexia]

Whenever I do hear it, I can make it disappear by touching metal on my guitar cables.

Is this problem with just one guitar?

If you can touch the metal on the jack and it stops, then you should be able to touch the strings or the tuners or the pickups and it'll stop.

It sounds like you are missing your bridge ground on your guitar, to me.

Stupid Question: You are certain you're using only instrument (shielded) cables, right?

 

[kiff]

If you disconnect all of your effects and run just your amp, does it still happen?

If that fixes it then add one effect back into the chain, one at a time. Do this with the effects using independent transformers (wall warts). If any share the power off of a single transformer/WW, that could be a suspect. WW's are ground isolated since the transformer doesn't make a "physical" connection to AC power lines.

If you have a rack effect that has a 3-prong plug (the 3rd prong is a physical ground connection) , just running it and the amp can create a ground loop.

 

[eudaimonia02912]

Hi everyone,

Thanks for your responses.

Some answers to questions:
1. It happens with all three of my guitars, though some are worse than others.
2. It happens even when I have the guitar plugged straight into the amp, with no effects. It gets worse with gain or when effects are added. My noise gate kills it except when a new pedal I got is turned on. But the pedal isn't causing the problem--it just amplifies it.
3. I've had this problem with other amps in my house; it's not as bad on the Mark as with, e.g., a 5150 I had.
4. Yes, the cables are shielded instrument cables.

Perhaps the problem is that everything is being run off of the same strip. I have a power conditioning power strip plugged into the wall, and everything else is plugged into that strip.

 

[phyrexia]

1. It happens with all three of my guitars, though some are worse than others.
2. It happens even when I have the guitar plugged straight into the amp, with no effects. It gets worse with gain or when effects are added. My noise gate kills it except when a new pedal I got is turned on. But the pedal isn't causing the problem--it just amplifies it.
3. I've had this problem with other amps in my house; it's not as bad on the Mark as with, e.g., a 5150 I had.
4. Yes, the cables are shielded instrument cables.

I still think if the hum stops when you touch metal on the cable, it's a grounding issue with your guitar(s).

With my setup, with any of my electrics, there is a buzz when I am not touching any metal attached to the amp's input. When I touch the strings, metal cable ends, or metal toggle switches on the amp, the instrument becomes grounded and the ground hum or buzz goes away. That's how it's supposed to work. Is this the case with your rig?

Are your instruments stock or have they been modified? I would still suggest to check the wiring in them. On strat style instruments, a wire travels from ground through the body and is soldered to the tremolo claw. On fixed bridge guitars, like a Les Paul, there is usually a hole drilled from the control cavity to one of the studs for either the bridge or tailpiece, and a wire is soldered from ground and usually just pressed into an electrical connection by the stud.

On the bright side, without the bridge ground, it's harder to get zapped by a microphone when you're playing and singing. But the downside is the eternal buzz.

Victor

 

[madryan]

What exactly are you running and how are you running it? I found that if you're running a patch box at your pedalboard with a common ground and using the loop and the tuner out it'll create a ground loop.

If you bypass the effects loop and plug straight in with a guitar with no known issues and the noise is still there it's your power.

unfortunately the Monster power unit you have does absolutely nothing to correct bad power. To really get the benefit of true conditioning and filtering you need a unit such as the Furman AR series which have a transformer built in. Tripp-Lite makes a line of computer and server power supplies that do the same thing but are somewhat cheaper.

If you want the absolute best (but they're not actually that expensive) get a basic unit from these guys...

http://www.equitech.com/

Makes the Monster and Furman stuff look like a toy for about the same kind of money. They're also just up the road from me.

 

[eudaimonia02912]

I've been messing around more, and now I think my initial description wasn't quite right. I think that perhaps one of my guitars isn't properly grounded.