Sansamp RBI Bass Pre

Discussion in 'Preamps / Channel Strips' started by ThirdBird, Oct 15, 2017.

  1. ThirdBird

    ThirdBird Active Member

    Joined:
    Dec 4, 2007
    Location:
    Toms River, NJ
    Anyone have any ground loop problems?

    I'm getting an awful hum when I'm going out (affected or not) into a small 12" bass combo.

    Any tips?
     
  2. Boswell

    Boswell Moderator Well-Known Member

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    Apr 19, 2006
    Location:
    UK
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    Which exact Sansamp model is it? Google brings up several possibilities, but not one that is definitively the model you describe.

    What's the make and model of the amplifier?

    Do you get the hum only when an instrument is plugged in?

    Do both the RBI and the amp have ground connections via their respective mains cables to the same mains outlet?
     
  3. ThirdBird

    ThirdBird Active Member

    Joined:
    Dec 4, 2007
    Location:
    Toms River, NJ
    Ah, my bad.

    It is the RPM bass pre (not RBI), and it's going into an Ampeg BA112.
    I'll check the plugged in question later.
    No, they are not on the same outlet.
     
  4. Boswell

    Boswell Moderator Well-Known Member

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    OK, I found that one, although I wasn't sure whether there were major differences between the standard and the bass models. Either way, both the BA112 and the RPM take an IEC mains plug, so I assume that the chasses on both the them is mains earth.

    With this type of dual-earthed arrangement, it becomes more important to power both units from the same mains outlet, usually by having a small mains socket board or (better) a Y-shaped dual mains lead. This ensures adequate earth bonding, assuming your wall outlets are well earthed.

    The final link is the bass guitar itself. It would be useful to know whether you get the hum (a) with no guitar plugged in, (b) with the guitar plugged in but placed in a stand, or (c) only when playing it with fingers touching the strings. If it's (a), then does the volume control on the RPM or the BA112 make any difference to the audible hum level?
     
    kmetal likes this.
  5. ThirdBird

    ThirdBird Active Member

    Joined:
    Dec 4, 2007
    Location:
    Toms River, NJ
    thanks dude. can you elaborate on this a bit more?

    "small mains socket board or (better) a Y-shaped dual mains lead."
     
  6. Boswell

    Boswell Moderator Well-Known Member

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    Here are examples from the Amazon (US) site:

    This is the mains Y-cable.

    This is the socket board.

    It took me a while to translate UK "socket board" into US "power strip".
     
    kmetal likes this.
  7. ThirdBird

    ThirdBird Active Member

    Joined:
    Dec 4, 2007
    Location:
    Toms River, NJ
    That certainly clears things up! Would running an extension power cable to make sure they are plugged into the same power strip (socket board) work? They are in different areas of the room.

    I still have to check out what happens when things are plugged in.
     
  8. Boswell

    Boswell Moderator Well-Known Member

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    Yes, the idea was to test whether you still got the problem when both units were fed from the same wall outlet.
     

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