Stereo FX in the loop of 2 amps - ground loops?

Me

Me

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Hi all. I’ve got 2 amps (Diezel Hagen and Bogner XTC) and was planning on using both of them live, normally I’m one or the other. If I run both at once I have to put an iso transformer in the input of one, else get horrible ground loop hum. So that’s sorted. But if I run out one amps mono fx send into the left side of a Strymon timeline+bigsky, and the other amps mono send to the right, then return both sides back to their respective returns, can I get a second ground loop?

I’ve tried this at home and it seems ok. But I don’t want to take this out somewhere then find it gets noisy and I can’t use one of them. Anyone do this a lot and sometimes have problems, or you’ve done it loads and never had a problem?

Also do you know if there’s a standard way of fx sends to ground or float sends or returns of loops, or is that down to the individual amp manufacturer and varies?

Or do you know if strymon only ground the left/mono in or out, or if the grounds are all commoned together inside their stereo pedals (I tried to ask strymon and their tech support didn’t seem to know, just said try it)?

As I say, it *seems* ok at home, but my rig is enough of a pain to move, so don’t really fancy taking an extra head and 4x12 to a gig, looking like Mr fancy 2-amps tw@t, then not actually being able to run the big sound in stereo would be less than fun. So any advice appreciated.
 
I use a Lehle ABY and it allows ground lift if/when required. Pricey but fixes all issues. Used to run 3 amps and never had a problem
 
alund said:
I use a Lehle ABY and it allows ground lift if/when required. Pricey but fixes all issues. Used to run 3 amps and never had a problem
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That’d work in front (which I already fixed with an RJM PBC), but won’t take 2 different amps fx sends to 2 pedal inputs (or the returns) will it?
 
Me said:
That’d work in front (which I already fixed with an RJM PBC), but won’t take 2 different amps fx sends to 2 pedal inputs (or the returns) will it?
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Ah. So I never used fx in both amps. Always kept one dry. So not sure.
 
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You might use some isolation transformers. You can buy those little hum eliminator boxes, like from EB Tech and such. I think there is a cheap Pyle one on Amazon that is popular.
 
You can make your own ground lift cables for effects in the loop. That is what I plan to do. Make custom cables grounded only at one end and connect that part to the amp. Run the ungrounded end at the effects pedal. Shouldn’t have any problems with noise and no need for iso transformers which lift the ground and also isolate the hot. Of course always have the amps grounded at gigs. Since you’re at instrument level there’s no other real concern here. You most definitely should also run an iso box for your guitar not only for safety at gigs but also for ground loops which you’re aware of.

I’ll also say you should only do what you need to remove ground loops - if they work without needing iso transformers or custom cables then you’re fine to use them without. It will be obvious in noise and functionality whether there’s ground loop hum or not.
 
glpg80 said:
You can make your own ground lift cables for effects in the loop. That is what I plan to do. Make custom cables grounded only at one end and connect that part to the amp. Run the ungrounded end at the effects pedal. Shouldn’t have any problems with noise and no need for iso transformers which lift the ground and also isolate the hot. Of course always have the amps grounded at gigs. Since you’re at instrument level there’s no other real concern here. You most definitely should also run an iso box for your guitar not only for safety at gigs but also for ground loops which you’re aware of.

I’ll also say you should only do what you need to remove ground loops - if they work without needing iso transformers or custom cables then you’re fine to use them without. It will be obvious in noise and functionality whether there’s ground loop hum or not.
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I'll take two please.....put me on the pre-order....probably need a couple more actually.....
 
I’ve done this at home and experienced a ground loop. To fix it, I made sure both amps and the effects were all plugged into the same power source. When I had them on different outlets I had a ground loop, plugging them into the same outlet (via a power conditioner) it cleared. Maybe not scientific and probably says my house isn’t wired the best, but getting a common ground between them all fixed it. Not sure that gives enough info to lug all that gear, but may help.
 
Yeah. I just had another idea. Got a multimeter and there’s basically no isolation between the jack grounds on the strymon. So definitely a possibility of a ground loop. I might make up some cables with a floating ground for the right hand amp and see how that works. If not, then look at some iso transformers. (I’m also now pondering maybe I should get the multimeter out again and see how/if both amps fx sends/returns are connected to mains voltage ground too 😝)
 
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