HELP, buzzing problem when splitting signal, not so straightforward though

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these_go211

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hopefully someone can help me here. this has been driving me crazy the last few days. i've found when i split my signal b/w my amp (which is not connected into my mixer) and one of my preamp/pedals which is connected to my mixer i get an annoying buzz. the pedals i'm going into are either a vstack preamp/overdrive or a boss HM3. both are battery powered. i've also gone into my sansamp bass driver di and the buzz is pretty low in volume. not so bad to the point that a track could still be usable, but i still hear a faint buzz.

now, if my guitar is going straight to my amp, NO buzzing. if guitar is going straight into a preamp/pedal which is connected into my mackie mixer, NO buzzing. to split my signal i'm using either a startouch a/b/y splitter or my boss stereo digital delay (dd6). problem exists equally when using either the startouch or the boss. my cables are high end mogami gold cables. the problem appears with either my les paul studio or my sg. i've tried different combinations of cables. one thing that could be important is that when i had had my guitar connected into the splitter, with 1 cable out to the amp and the other out to one of the pedals, if i unplugged my amp the problem went away. with the amp unplugged there was no buzzing. but as soon as i even started to plug the amps power prong into either a power strip or directly to the wall the buzzing came back. so it seems like when my setup is "bridged" between the amp and the mixer that's when the setup buzzes. what could this mean?

to summarize, the problem only exists when i'm simutaneously connected (thru some kind of splitter) to both the mixer and the amp. could both my guitars have shielding issues with the pickups? my mackie mixer is connected to a power strip on one wall and the amp is connected to a power strip on the other wall. but they are probably the same circuit. does this matter? i've switched out using different cables and different power strips as well. this really sucks as i was looking forward to being able to split my signal to 2 different places. thanks a ton for any help. sorry for this long post!
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

Welcome to ground loop hell.

For some crazy reason, connecting devices that are also connected to the same ground creates a loop. The result is a loud hum. There's no device that fixes this, like a noise gate or anything. You might try using a groundless plug on one of the devices, and see if that helps. That way, all the grounding is done through one piece of gear. However, you might get a heck of a shock on your lips from a microphone that's grounded.

I used to run multi-amp setups, and it was always a huge headache to deal with possible grounding issues. I finally sold all those amps, and ponied up the dough for a great sounding 3 channel head. Now, one amp does it all.
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

the problem is a ground loop between the mixer and the amp. lift the ground on one of those and the hum will go away
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

beat me to it joe
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

Those ground gremlins have made me so angry in the past.

One time our band was rehearsing in a dark room, and I'd tried some ground-lift plug or something, and when we were playing, my mouth touched the mic and a huge spark lit up the room. I think I still have a tiny spot on my lip from that incident!

I used to use a Marshall Superbass and a Blues Pearl Texas Tornado as my dirty/clean setup, and always had humming problems, even after buying a Lehle A/B box.
I finally got fed up and bought the Bogner Ecstasy head. No more stereo rigs for me....it's just a hassle.
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

i always use a blue fuzzy spit catcher on my vocal mics just incase. i used to use a twin for clean and marshall for dirty but just got tired of hauling all that around
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

jeremy said:
the problem is a ground loop between the mixer and the amp. lift the ground on one of those and the hum will go away
Click to expand...

Easy to say, harder to do. By "lift the ground", Jeremy means remove a ground connection that will break the loop. In this case the "loop" runs thus:

amp -> cable shield -> splitter -> cable shield -> mixer -> mixer power cord ground -> wall outlet -> house wiring ground -> other wall outlet -> amp power cord ground -> amp

The easiet way to break the loop is to stick one of those old 3-pring-to-2-prong adapters on one of the power cords and not hook up the little green ground tab. BAD IDEA. It leaves the equipment without its safety ground, which is there for a purpose - safety.

Another easy way is to modify a guitar cord by clipping and insulating the shield conductor in one connector. Then use that cord to make one of the connections out of the splitter. I'd put it between the splitter and mixer, with the modified "ground lift" connector at the splitter end. Mark this connector with colored tape or something, so you remember it's a special cable, and which end is which.

A third method is to make a little ground lift box, Buy a small plastic project enclosure from Radio Shack, and install two 1/4" jacks and an SPST mini-toggle. Wire the centers of the jacks to each other, but wire the shields through the switch. Opening the switch opens the loop, and you can just use two guitar cords to insert this doohickey between the splitter and the mixer.

Better yet, if your mixer has lo-impedance XLR mic inputs, buy a direct box. Put it between the splitter and the mixer using a guitar cord in and a mic cable out. All direct boxes have ground lift switches on them. However, the work between the 1/4" hi-z input & thru jacks and the lo-z XLR. They ground lift won't work if you simply jumper through the 1/4" jacks and run into a 1/4" mixer input. Gotta use the XLR.

I like this last suggestion best.
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

thanks a bunch guys for the quick response. wow do i LOVE this forum :) ground loops, not cool! rich, i do have xlr inputs on my mixer and i happen to have a countryman 85 direct box i bought for bass a while back. i guess what you are saying is that instead of coming out of the splitter and going into my vstack pedal and then the mixer (using all 1/4" connections), what i would do is run from the splitter into the vstack pedal and *then into the countryman di box* so i can xlr out of that into the mixer. i'll give that a try. that also explains why when i split my signal to the amp and then to the sansamp bddi the hum is hardly noticeable as the sansamp bddi has xlr out. it also has a ground connect switch on it i see. i'll have to play around with that.

thanks so much again for all your responses. i'll let you know how it goes!
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

IT WORKS!!!! you guys are the coolest. i owe you all beers......well for now, i guess a virtual beer will have to do! but if any of you make it to san jose a real beer(s) is in order. there is still actually a slight very low volume hum but it's a marked improvement over the hornet's next that was previous.

i did it the way i outlined in my last email. splitter-->vstack-->countryman di with xlr out and ground lift engaged, uh, or disengaged, whichever one cancels the hum :) it's cool that i have now found another use for this di as it's been retired since i bought the sansamp. many many thanks again!
 
Re: HELP, buzzing problem when splitting signal, not so straightforward though

Glad to help, and glad it worked out.

Note that this method will not fix ground loops in multi-amp setups because they both require 1/4" Hi-z inputs. Transformer-isolated splitters for multiple guitar amps are not nearly as common as direct boxes. I don't really stay up on amp splitters because I can only afford one amp. I know Framptone makes a high end one.

Those in the know: Who else makes isolated multi-amp splitters?
 
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