Ground Loops

[TheColonel]

So I was in the recording studio on saturday, testing out the new configuration on my pedalboard. I have a Morley George Lynch Tripler pedal which switches between 3 amps. Great little pedal - highly recommended! But when I hooked up my Marshall AND a VibroVerb to 2 outputs of the Tripler, I had nothing but HUGE hum. After hours of research, I've discovered that this is because of a phenomenon called 'Ground Loops', but there is so much contrasting information about how to solve this...

So, my question is, has anyone had any experience with Ground Loops, and have you been able to solve the problem? One solution I seemed to have found is to run ALL amps and my pedalboard off the same power-board, but this could be risky with overloading the outlet. And I'm not really up for chopping off the ground pin on the plugs.

It's a pain in the ass... :angry: Any suggestions?

[damo0945]

Maybe don't run the pedal on mains power if possible... Actually if it's just a switch does it even have power?
Or I think running different things (amps) on different circuits works if that's possible...
I really don't know much about it, just some ideas. I know you're meant to run lights and sound on different circuits because lights create earth hum, I presume it's a similar thing.
Also my first idea is just a guess.

[TheColonel]

Yeah, it does need power coz it has a inbuilt booster...

[Tle89]

buy a DI box and use the ground lift switch. Basically you'll go from your guitars in to the pedals and then into the DI Box then in to the Amp. hope this helps

[Fritz]

yaeh first thing i thought of was a DI's ground lift.

By the way LOL @ george lynch - that guys' fuckin terrible!! haha

[Sammas II]

So I was in the recording studio on saturday, testing out the new configuration on my pedalboard. I have a Morley George Lynch Tripler pedal which switches between 3 amps. Great little pedal - highly recommended! But when I hooked up my Marshall AND a VibroVerb to 2 outputs of the Tripler, I had nothing but HUGE hum. After hours of research, I've discovered that this is because of a phenomenon called 'Ground Loops', but there is so much contrasting information about how to solve this...

So, my question is, has anyone had any experience with Ground Loops, and have you been able to solve the problem? One solution I seemed to have found is to run ALL amps and my pedalboard off the same power-board, but this could be risky with overloading the outlet. And I'm not really up for chopping off the ground pin on the plugs.

It's a pain in the ass... :angry: Any suggestions?


I have plenty experience with ground loops. A few years back I wired up a 36 bus audio console which is a task when it comes to avoiding ground loops.

A ground loop is caused when you have more than one pathway to ground. If the resistance differs between these pathways you will get noise in the signal.

Plugging everything into one outlet via a powerboard forces everything down one ground path. If you look at the power rating* of your amplifiers and add them up, you can probably do this just fine.

*note, this isn't the output wattage but the power draw. If you look next to the mains cable of your amplifier it should have a bunch of information printed on it, included operation voltage (110v, 240v, etc) and the number of watts it consumers (maybe 300 to 600watts depending on the amp). Add up the watts, in Australia we have 10 amp outlets (10 amps times 240volt equals 2400watts). As long as you come in under 2400 watts you are sweet.


Don't cut any pins off power plugs. If you are going to lift the ground on anything, do it in the lowest voltage/current spots in your signal chain. The reason you have a loop is because of the following:

- Even though your amps are plugged into separate outlets, they are all chained together via the ground/earth cable in the wall. This isn't a ground loop itself.

- When you plug all three guitar cables into your amplifiers then connect them to one box, you get your ground loop. Amplifier 1 can access ground through the mains cable, or through the guitar cable going back through amplifier 2 or 3.


Does it hum with just one amplifier plugged into it or only when both amplifiers are plugged in? You need to modify your guitar cables that go between the switcher and amps. Unscrew one end of the cable and snip the ground/shield (it is usually braided). Isolate it with electrical tape so that it won't touch. Try doing it with just one cable first... if that doesn't work, try it with both. It is this shield that completes the ground loop on more than one occasion. Unlike the mains earth (potentially high voltage), a guitar cable shield only drains off RF and interference. By snipping one end, the shield will still function. I'd personally mark the end that has been snipped with some electrical tape around the end of the cable. I would plug the snipped end into the switcher and always put the grounded end into the amplifier. It isn't a huge deal, but your guitar amplifier will have better grounding to drain the shield than your pedals.


Comprende?

[WHITE FALCON]

fuck you are the knowledge base here!
so glad somone with experience like you can post here!

[Ben reed]

yeah, what arin said.
this forum has more knowledge about any topic including all the random stuff in off topic, not to be mention tle and musicianship stuff.
you look at forums with thousands of members and its nothing but shit
sammas knows what he's talking about!

[TheColonel]

Comprende?

Sort of... It's a little confusing, but it kinda makes sense.

I'd only be looking at powering 3 amps at the most, and they all fall way under the 2400W mark. So that is no problem.

I have only had problems with serious hum when I use more than one amp. When I plug into only one amp there are no problems whatsoever.

[Sammas II]

Sort of... It's a little confusing, but it kinda makes sense.

I'd only be looking at powering 3 amps at the most, and they all fall way under the 2400W mark. So that is no problem.

I have only had problems with serious hum when I use more than one amp. When I plug into only one amp there are no problems whatsoever.

What bits are you confused about?

[TheColonel]

I understand it now! :happy: It was a bit of an information overload last night...

So basically, if the power usage rating of all amps and pedals is less than 2400W, I can power them all off 1 powerboard, and that should reduce hum. And I should also remove the meshed ground off the leads going from the pedalboard to the amps (at the end that is closest to the pedalboard). Is that about right?

And I'm running 2 channel switchers on the pedalboard as well, so I need to make sure that those grounds are isolated too, correct?


Also, something a little off topic... What impedance do the vintage Fender Bassman's run their cabs at? I'm looking at buying one, and I'm wondering whether I need to rewire one of my cabs from 16Ω to 4Ω. I'm either going to get that, or maybe one of these:

http://store.marshamps.com/product_info.php?cPath=49&products_id=465

[Sammas II]

I understand it now! :happy: It was a bit of an information overload last night...

So basically, if the power usage rating of all amps and pedals is less than 2400W, I can power them all off 1 powerboard, and that should reduce hum.

Should? It could... ground loops can still exist but it maybe usable. Try it and see. As far as power usage, if you draw to much your house will melt down and your parents will get mad! :wacko:


...just kidding. It will trip the circuit breaker. Not a big deal if it happens. If you are well below the 2400watt limit you are right as rain ;) Just a tip in case you lose power and wonder what happened.


And I should also remove the meshed ground off the leads going from the pedalboard to the amps (at the end that is closest to the pedalboard). Is that about right?

This is a more permanent solution. If you do this, you should be able to plug your amplifiers into any power point in the house.



And I'm running 2 channel switchers on the pedalboard as well, so I need to make sure that those grounds are isolated too, correct?

try it as is and see. If it hums, get back to me with the specifics. You may not need to cut any cables.

[TheColonel]

try it as is and see. If it hums, get back to me with the specifics. You may not need to cut any cables.

I did have some problems with the footswitch, but only when the jack was touching another jack from a pedal. I fixed the problem by isolating the 2 with electrical tape. All fixded now. ;)

To make a bit more sense of the way my board is set up... I have 2 rows of LoopMaster bypass strips, one with 5 loops and a tuner switch, the other customised to 5 loops and a channel switch. So when I hooked up all the jacks, some of them were touching. I got awful hum. But as soon as I isolated the channel switch jack from the other jacks, it was gone...