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pre amp tube on the way out?

Discussion in 'Amps and Cabs [BG]' started by bassmachine2112, Sep 13, 2008.

  1. bassmachine2112


    Mar 23, 2008
    hi ,i have a marshall bass amp .the problem i,m havin is that when i stop playin the sustained note goes into bass feedback un til i hold the strings damped.this happens with different basses but does not happen with other amps.could this be the tube on the way out in the pre amp.it is a hybryd amp with a valve in the pre amp only.the model is a marshall mb 450.the low notes are very low mid sounding with a lot of volume n the higher registers almost dissapear ie the volume drops off.hopefully all that needs done is to replace the pre amp valve.it is a ecc83.would i be able to use a 12ax7 n what would be the difference in the sound .would it be safe to do?
  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    ECC83 is the European part number for the 12AX7. They are identical. You would have to do nothing except pull one out and put the other in. Can't hurt to try...12AX7's are cheap enough.
  3. I have that amp, I also had the same high notes not being loud thing. I'm not sure what happened but it works fine now. I have had the tube changed though. (When I first got it, it broke)
  4. bassmachine2112


    Mar 23, 2008
    thanks for replies,turned out it was a cracked preamp valve.problem sorted.thanks again

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