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High pitched squealing/screeching through amp

Discussion in 'Amps and Cabs [BG]' started by FireBug, Nov 28, 2005.

  1. FireBug


    Sep 18, 2005
    I had my M-Pulse at practice a week ago and everynow and then it would start to hum loudly and then start screeching madly. It happened a couple of times and when it started happening one time, I turned down both pickup volumes on my bass...still the sound came and I had to shut the amp off.

    The conditions:
    *We were playing loudly in flannel shirt weather. I've run the amp very loud in hotter weather.
    *Using a speaker cable and 8 ohm cab
    *We practice in an old guest house in the backyard...possibly unstable voltage

    Any ideas what this could possibly be? It's never happened in my house, but then again I never run it that loud in my house. The vents are always unblocked. Could this possibly be a sign of bad tubes?

    Please :help:
  2. AlembicPlayer

    AlembicPlayer Im not wearing shorts

    Aug 15, 2004
    Pacific Northwet, USA
    yes..sounds like it could be a preamp tube going.

    use a pencil...when the amp is running...tap each tube until you find the microphonic tube. then replace it.
  3. yup, i agree..... get some new tubes :)
  4. FireBug


    Sep 18, 2005
    Ah ok good. This initially sounded like a much worse problem...I didn't know tubes could literally scream "replacement". I've heard bad tubes whistle before, but how often is it you get a screecher?