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SWR SM900 Tube Noise

Discussion in 'Amps and Cabs [BG]' started by DRN, Jul 17, 2003.

  1. DRN


    Mar 17, 2002
    Las Vegas
    I thought I would do some experimenting with tubes. So I went to the tubestore.com and ordered three different tubes to try. I put the highly recommended Electroharmonix tube in and the entire amp hummed really loud. The tube had a great sound but the amp hummed. So I changed to the next tube JJ and the same thing happens but not as bad as the first. I am going to put the third in Friday.

    Have any of you run into this? Am I doing something wrong?

    Please help

  2. How do you get the tube out in the first place.
  3. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Could be that the heater supply has a circuit to balance out hum. If so it might need to be reset for each new tube for best results. I am assuming you replaced the tube with one of the exact same type?