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Patchbay noise!

Discussion in 'Recording Gear and Equipment [BG]' started by Benjamin Strange, Mar 29, 2014.

  1. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    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!
  2. GrumpiusMaximus

    GrumpiusMaximus I've Seen Things You People Wouldn't Believe

    Mar 11, 2013
    Kent, United Kingdom
    Have you tried grounding the chassis of the patchbay?
  3. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    Yup. No change.
  4. 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.