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Do I need new tubes?

Discussion in 'Amps and Cabs [BG]' started by levis76, Sep 8, 2008.


  1. levis76

    levis76 Seconds from getting ba...

    Apr 14, 2007
    Metro Detroit
    I have a Ampeg SVP Pro that makes a loud popping/cracking noise while I play. It only seems to do it during the first 30 min or so. I do let the tubes warm up for around 5 min before adding any volume, but my guitarist turns on his Mesa triple rec and just starts whaling noise free immediately and his amp has pre and power tubes. The noise seems to be mainly in the highs as I can almost eliminate it by turning off my tweeter and rolling off the treble a bit. Adjusting the gain or drive does not seem to have an effect either. I had a preamp tube go bad in a SWR head once, but it was a constant hissing and crackling, this is an intermittent problem that does seem to vanish after a bit of playing time. All my connections seem tight as well. I don't want to have to replace the tubes if they don't need it as I don't have a lot of cash at the moment. I don't know exactly what tubes are in it now, I'll check tonight at practice and post it later. Any assistance would help greatly.

    My setup is connected as follows: bass to preamp input, preamp output to BBE input, BBE output to power amp in.
     
  2. Getting your tubes checked would be a first move. What you are describing is also indicative of one or more leaky filter caps and that should be your next move. I'd get it looked at by a good tech.

    Paul
     
  3. levis76

    levis76 Seconds from getting ba...

    Apr 14, 2007
    Metro Detroit
    I hope it's not a cap. Thanks though.
     
  4. levis76

    levis76 Seconds from getting ba...

    Apr 14, 2007
    Metro Detroit
    Went to the practice space today with the intent of finding the cause of this problem and I found it. First I A/B'ed the cab with a borrowed Mesa head. Mesa had no noise, so my cabinet is sound, as is the cable. Next, I plugged the preamp directly into the power amp to eliminate the signal processor. Didn't hear any noise. Hooked the BBE back up and got no noise. So I cranked it up a bit and started jamming :bassist: , and bingo, there it is. A scratchy noise right in upper frequencies. Hmm, seems to only be present when I stroke the lower strings, especially open strings. Turns out, the cab is vibrating so much, its shaking the poop out of the tubes and causing noise. I moved the head over to another location, and no more noise no matter how much I dig in. Problem solved, I guess. So I can't put my tube preamp on my cab if I have a lot of low freq vibration? That sux, but I guess I have to deal with it.
     
  5. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    You shouldn't have to do that. I could be wrong, but I think you have a bad tube that only shows itself when you vibrate it. Next time you go to practice, buy a 12AX7 and try swapping it out with the other 12AX7(s) in it. If you can't do that, maybe stick a piece of foam under it. But 12AX7's are fairly cheap, and you probably only have one bad one.
     

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