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Problem using Ampeg "Power Amp In"... Ampeg Insider?

Discussion in 'Amps and Cabs [BG]' started by bassfroggy, Dec 9, 2004.

  1. Hello All,

    I recently purchased an SVP-CL (yes, SVP, the Preamp) and love the sound. However I cannot plug it in my 350H Power Amp Input.
    As soon as I power up the 350H it buzz like crazy. Unusable.

    For those who are wondering how I checked the sound of the SVP, I connected it directly to a Mackie mixer and used headphones...
    Anyway, if no input is connected to the 350H everything sound great. Actually, it even has nothing to do with the preamp because connecting a compressor from to the pre out and power in does the same thing (I also tried different cables, gauges etc) = big buzz

    Is it something wrong with the head?

  2. Tim__x


    Aug 13, 2002
    Alberta, Canada
    I may be wrong, and I would like to hear Ampeg Insider's view, but those symptoms seem to me, to point to a cold solder joint on the ground lug of the jack.
  3. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    I Think Tim__x is on the right track.

    When plugging two pieces of gear together that have unbalanced outputs/inputs, a small amount of hum is not unusual.

    BUT, a huge amount of hum is NOT normal.

    Sounds like either there is a problem with the cable, OR there is something wrong with the jack. You tried different cables, so that is probably eliminated, leaving the jack as the logical cause.

    The signal is actually routed through teh contacts on the return jack when nothing is plugged in, so any problem must be on the ground side. And, of course, hum makes you think of a bad ground anyway.

    I assume the head works fine otherwise, or that would be the question.

    So, it does indeed sound like a jack problem, probably something quite simple like a solder joint on the ground contact.

    If you got a little hum, enough to annoy, but not completely ridiculous, that might be a different thing.