Sever buzz when running 2 amps w/ stereo pedal

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by matei, Jan 21, 2005.

  1. matei

    matei Guest

    Hello!

    I am trying to run two amps off of a stereo Chorus pedal (Boss CE-2). However, as soon as I connect one of the amps I get a horrible buzz - like bad grounding.

    I've tried switching cables, amps, running the pedal off battery instead of mains, even changing the pedal for a different one - still the buzz persists.

    By themselves the amps are quiet. By itself, the pedal is quiet. Together they are buzz city!

    Any ideas what this could be?
     
  2. Jimmy Somma

    Jimmy Somma Member

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    The problem doesn't lie with the pedal, It's with your amps. You're creating what's called a ground loop. Whenever you run multiple amps, only one of them needs to be grounded at the outlet. To fix this, use a three prong to two prong adaptor on the power cord of one of the amps. This should eliminate your hum problem.

    www.sommatone.com
     
  3. Randy

    Randy Member

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    An even better solution is to use a splitter with transformer isolated outputs, thereby eliminating the danger of lifting the ground on one of your amps.

    I use the Axess BS-2 which has the added benefits of a buffered output and a phase reversal switch. Highly reccomended.
     
  4. Jimmy Somma

    Jimmy Somma Member

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    Technically you're not lifting the ground because the amp is getting grounded through the guitar cable.

    www.sommatone.com
     
  5. hipfan

    hipfan Member

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    One of THESE should take care of your problem. I use one to cure ground looping at my rehearsal space. Works like a charm.
     
  6. TonyV

    TonyV Member

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  7. Shawn S.

    Shawn S. Member

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    I just experienced running amps in stereo for the first time, along with the ground loop I noticed that my volume pedals pot sounded scratchy like it was bad, but with an amp out of the loop the scratch goes away. The same thing happens on my guitar's volume knob too - disappearing when an amp is out of the loop (switched off).

    Will something like the Hum-X fix both the ground loop hum and also the scratchy pots?
     
  8. walterw

    walterw Gold Supporting Member

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    that scratchy sound indicates some dc voltage on the pot. a cheap fix for the ground loop issue that sometimes works is to get or make a ground-lift signal cable, with the ground connection snipped on one end, and use that on one of the amps.
     
  9. Shawn S.

    Shawn S. Member

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    When you remove the ground loop through any means (Hum X, snipped cable, A/B selector) does it also remove the scratch?
     

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