Patchbay noise!

[Benjamin Strange]

Hi all - I've got a gremlin in my signal chain that just won't quit, and I cannot figure out how to fix it. Here's the scoop:

I've got three Mesa Boogie guitar preamps, each wired through a DBX DB48 Patchbay. My typical signal flow is:

guitar>DI thru>patchbay>preamp>patchbay>speaker sim>patchbay>interface

This isn't too complicated of a wiring scheme, and it allows me to switch between three preamps with moving just two cables. However, I'm getting some low 60 cycle hum anytime the patchbay comes between the guitar and the preamp. I've isolated the problem to the patchbay itself - even with nothing else going through the patchbay, if I wire it between the guitar and a preamp, I get noise. I've tried both balanced and unbalanced connectors, I've denormalled the patchbay, tried different bays - hell, I even pulled out my old Behringer patchbay, and it does the exact same thing. What gives? Should I not be running a guitar directly into a patchbay? Or is it that I should never run a patchbay before a guitar amp?

I would really like to have a good solution for switching between three different preamps without the noise, and I had thought a patchbay would be the simple, cheap solution. I don't think I should need to buy a Voodoo Lab GCX just so I don't have to reach behind my rack everytime I want to use a different preamp. Surely there's a solution. Any advice would be greatly appreciated. Thanks!

 

[GrumpiusMaximus]

Have you tried grounding the chassis of the patchbay?

 

[Benjamin Strange]

Yup. No change.

 

[Hellbastard]

I suspect a graound Loop of some sort. Do you have a Line Isolator? something like an ART CleanBox or even Better a Lehle P-Split.

For your three Preamp setup I really recommend you get Lehle Dual, best Routing units out there.

 

[Samitch04]

edit: [Just now seeing how old this thread is, did you ever figure it out?]

I've been looking into running a patchbay in my system, i hope you get this figured out, I've been thinking of trying the berhinger.

So I wonder, are you running a power conditioner? if not are all of your power cables at least plugged into the same power strip? after plugging them all up i would try and separate any crossings between power cables and signal cables. If they must cross try to minimize the crossing to a set of perpendicular lines (like a 4 way stop intersection, shape of a plus sign + type of thing) avoid running the power and signal cables parallel of each other; the less contact the better.

These are all some basic housekeeping things, but sometimes I've still had the ground loop(s) occur.

Consider moving your patch-bay away from any power amps/power sources. Inside a patch-bay would, I hypothesize, would invite a lot of opportunities for interference, especially if not shielded properly. So i think getting any transformer further away from your signal cables and patch bay can not hurt.

Sometimes weird things happen like (as mentioned above) the need to ground the chassis.

I have a wireless unit (line 6 something or another) which let me split my signal 2 or 3 ways at a time; when i ran one signal to my pre-amp to my PA no hum or anything like that. when i ran another signal to my regular bass amp again no hum or anything. But when i ran both setups at the same time PA + bass rig i got a hum through my bass amp or the PA. After isolating the area the hum was in (in your case it is the patch bay) mine happen to be in the pre-amp region; i started playing around with the cables. what ended up fixing it was draping the excess cable i had off one side of the amp as opposed to letting it sit on top. something stupid like that that i basically lucked into by just moving the cables around.

One other thing to maybe try would be partially plugging in the TS cables into the TRS jacks to just use the RS sections of the jacks. (this has worked for me in many hodge podge setups in the past)

With all this being said, I hope it works out for you. Please let us know if it does as I would like to start using a patchbay in the near future.

Good luck and happy hunting!

 

[ZenG]

I suspect a graound Loop of some sort. Do you have a Line Isolator? something like an ART CleanBox or even Better a Lehle P-Split.

For your three Preamp setup I really recommend you get Lehle Dual, best Routing units out there.

This.

You might also try a Hum-X hum destroyer. Pricey but they work. At least mine does.

 

[seamonkey]

Try lifting some grounds