Dual amp setup: ground loop and electric shock issues

brmusician

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Hello. I'd like to play with my new Boss Dimension C Waza Craft (DC2w) in a dual amp setup, since it's a stereo pedal. However, I'm seeing in forums a lot of people concerned about safety when using two amps, since their grounds can form loops which will eventually leak to the player as electric shocks. As a solution, they recommend ABY boxes with special isolation transformers.

My question is: do buffered pedals like stereo modulation ones (Boss DC2w included) will do the job or do I need a specific pedal like these ABY boxes with transformers?
 

rze99

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Crobbins

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An ABY pedal like this is what I Use.

BON1442.jpg
 

randym

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I use a splitter when not using a stereo pedal/effects unit. I think when using a stereo pedal/effects unit to two amps (or to any two destinations) you won't be in danger of shock or ground loop (probably). Have you tried it yet?
 

schmee

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I have not experienced shock issues combining factory built amps. But many noise issues. So much trouble I quit trying to use 2 amps long ago.

The Tonebone stuff is good and eliminates much of these problems. I had one just before I quit using 2 amps.
Furman power strips only eliminate this stuff above about $350 cost last I looked.
 

brmusician

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I use a splitter when not using a stereo pedal/effects unit. I think when using a stereo pedal/effects unit to two amps (or to any two destinations) you won't be in danger of shock or ground loop (probably). Have you tried it yet?
I haven't tried because of these warnings on forums. I live on a pretty old building (~60 years old), and although wall sockets have three holes, I don't know if ground works properly.
 

'64 Tele

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I've used A/B/Y pedals and currently, the stereo out from last pedal in chain to two amps.
They are both on the same circuit (plugged into same multi strip along with pedal board in same circuit/strip).
No issues with phase, hum, shock.
You'll love it....sounds huge and you'll be spoiled for one amp ever again.
 
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Ben Harmless

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Just keep your amps on same circuit. Imho

This is 90% of it.

Ground loops and getting shocked by your amp are two different problems.

This is true - they're almost opposite problems, in fact.

I live on a pretty old building (~60 years old), and although wall sockets have three holes, I don't know if ground works properly.

For that, my friend, we have outlet testers, which are pretty cheap (compared to their usefulness in situations like this). Pick one up at virtually any hardware store. A lot of people have one in their gear back, just under the broken cables that they intend to fix some day.

The safety issue isn't inherent in running two amps. It arose decades ago when the popular wisdom was to eliminate ground loops by prying the ground prong off the plug of one of the amps, thereby assuring that there was only one path to ground. Of course, if the ungrounded amp developed the wrong kind of fault, all of a sudden your cable has lethal current in it... If both amps are properly grounded, the shortest route to ground wouldn't ever be through the player.

Hum is another matter, and for that you can pick up one of the Radial boxes which provides transformer isolation. I wish I'd done this years before I finally figured it all out. Seriously. I pinched pennies when I should have just bought the thing once and moved on.

That said, plug both amps into the same circuit, and see if you even have a problem. If you don't, then don't worry about it. If you end up using a stereo rig in a live setting, you can't necessarily control the power, and you might want to pick up the splitter, but otherwise don't sweat it. Oh, and remember that despite what a lot of internet-pro dudes tell you, stereo guitar is often wasted in a live setting because many PAs are run in mono, or engineers are reluctant to hard pan things in stereo because then 10,000 out of your 20,000 screaming fans will only hear half of your guitar tone. It's fun as heck though, and if you play little clubs and spread the amps out, you can get some great effects.
 

JuneauMike

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An ABY pedal like this is what I Use.

BON1442.jpg
I use a simple active AB/Y pedal similar to the one above (It's a Twin City). It's got reverse polarity, ground lift and a drag feature. I've needed all of those at one time or another. Running two amps will not necessarily cause ground loops or out of phase problems with the speakers every time, but you need to have a plan in case they do crop up. And these active AB/Y boxes seem to be the easiest way to deal with the inevitable.
 

brmusician

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I've used A/B/Y pedals and currently, the stereo out from last pedal in chain to two amps.
They are both on the same circuit (plugged into same multi strip (along with pedal board in same circuit/strip).
No issues with phase, hum, shock.
You'll love it....sounds huge and you'll be spoiled for one amp ever again.
Just tested it with a Fender Super Champ XD together with a Blackstar HT1 (with an external 1x12 alnico blue cab) plus the Dimension C. Everything connected to the same outlet. No difference in noise floor between single and dual amp, no perceptible electric shock. Tone is really great... this pedal is an 80's box, and mixing clean and overdriven amps makes it even better. I also just ordered a single ended 12W amp, but didn't receive it yet. Don't know if I would be lucky in a gig... for the moment, I'll only play in stereo at home.
 

brmusician

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I use a simple active AB/Y pedal similar to the one above (It's a Twin City). It's got reverse polarity, ground lift and a drag feature. I've needed all of those at one time or another. Running two amps will not necessarily cause ground loops or out of phase problems with the speakers every time, but you need to have a plan in case they do crop up. And these active AB/Y boxes seem to be the easiest way to deal with the inevitable.
Pretty expensive here in Brazil, though. The most affordable one here is the Orange Amp Detonator for around $300. Fulltone True-Path costs around $400.
 

brmusician

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This is 90% of it.



This is true - they're almost opposite problems, in fact.



For that, my friend, we have outlet testers, which are pretty cheap (compared to their usefulness in situations like this). Pick one up at virtually any hardware store. A lot of people have one in their gear back, just under the broken cables that they intend to fix some day.
What should I do in case of an outlet with just the classic two pins instead of three?


The safety issue isn't inherent in running two amps. It arose decades ago when the popular wisdom was to eliminate ground loops by prying the ground prong off the plug of one of the amps, thereby assuring that there was only one path to ground. Of course, if the ungrounded amp developed the wrong kind of fault, all of a sudden your cable has lethal current in it... If both amps are properly grounded, the shortest route to ground wouldn't ever be through the player.
The problem here is that most venues are located nearby the historic center, so although outlet sockets are new, electric installation can be pretty old. However, I presume the electric shock is already an issue with players who also sing, which is my case for decades.

Hum is another matter, and for that you can pick up one of the Radial boxes which provides transformer isolation. I wish I'd done this years before I finally figured it all out. Seriously. I pinched pennies when I should have just bought the thing once and moved on.
Will they provide an additional protection against electric shocks?



That said, plug both amps into the same circuit, and see if you even have a problem. If you don't, then don't worry about it. If you end up using a stereo rig in a live setting, you can't necessarily control the power, and you might want to pick up the splitter, but otherwise don't sweat it. Oh, and remember that despite what a lot of internet-pro dudes tell you, stereo guitar is often wasted in a live setting because many PAs are run in mono, or engineers are reluctant to hard pan things in stereo because then 10,000 out of your 20,000 screaming fans will only hear half of your guitar tone. It's fun as heck though, and if you play little clubs and spread the amps out, you can get some great effects.

I play on small venues where a small 15W tube amp is enough. I presume a dual amp setup would be easy to adjust. I'll certainly buy one of those ABY boxes with transformers if I do it in a live setting. Luckily at home it worked without any hack.
 

JuneauMike

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You keep using the term "electric shock." I'm not aware that modern amplifiers (with three prong chords) when run dual mono pose a risk of electrocution.

The actual risk they all pose are basically ground loops (hum and assorted noises) and polarity problems (out of phase speakers).

If power in the historic district where you play is sketchy then electrocution may be less of a danger to you than dirty power that can harm modern electronics. If you are worried about the mains voltages going in to your amps maybe a thing to look into would be a power conditioner. But it sounds like maybe you are on a budget.
 

drmmrr55

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Hello. I'd like to play with my new Boss Dimension C Waza Craft (DC2w) in a dual amp setup, since it's a stereo pedal. However, I'm seeing in forums a lot of people concerned about safety when using two amps, since their grounds can form loops which will eventually leak to the player as electric shocks. As a solution, they recommend ABY boxes with special isolation transformers.

My question is: do buffered pedals like stereo modulation ones (Boss DC2w included) will do the job or do I need a specific pedal like these ABY boxes with transformers?
BigShot.jpg
 




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