SVP-PRO huming, and hissig me off!

Discussion in 'Amps and Cabs [BG]' started by Thumpinthenight, Jan 23, 2006.

  1. Thumpinthenight


    Apr 13, 2004
    New York
    So I have the SVP-PRO pre, and I run with a Carvin 1500 amp. Going direct out to the PA, now with powered subs, I hear this annoying hum, more so than a hiss. Is there a fix for this, or is this tha nature of the beast? I've heard somewhere on this forum it is a problem with older models? Is this expensive to fix? Any help is appreciated. :meh:
  2. I've heard people say that you need to swap out the tubes on those.
  3. Mine makes the same noise.

    But I've been too poor/lazy/and speakerless to fix it.
  4. Thumpinthenight


    Apr 13, 2004
    New York

    Any body else hear this? What kind of tubes would I need??
  5. NJL


    Apr 12, 2002
    San Antonio
    This has been covered in a lot of threads. How about a search?


    BTW, I had the same problem with mine.
  6. Search function really wouldn't find something like that too easily. :meh:
  7. If you're direct to the PA, I would blame the lack of a ground lift on these preamps at least as much if not more than I'd blame a tube. I don't have any problems with normal hum with mine, but it's about 50/50 on whether I'll be able to use it in any given venue without needing a D.I. with a ground lift.
  8. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Quite true, if the hum is not present when the amp is used alone and is there when any thing else is plugged into it or it is plugged into anything else then the problem is a ground loop, not the amp. To find out what a ground loop is and how to fix it go to
  9. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Most of the hum in those is tube-related. They are VERY fussy about tubes..... and it isn't just the first stage, which makes things more interesting.

    You might want to try NOS tubes, preferably ones pre-tested for filament leakage and related hum issues.

    Not all old tubes were tested for hum.... some of the NOS tubes being sold are just old, but are otherwise the "drugstore junk" of the 50's and 60's.

    I am not sure why those are so fussy, I haven't personally looked closely at them for that.