Marshall Bluesbreaker RI tubes swapping

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by hw2nw, Sep 10, 2006.

  1. hw2nw

    hw2nw Member

    Messages:
    2,125
    Joined:
    Sep 28, 2005
    Location:
    Nashville, TN
    Hey guys! I'm looking at some BBRI combos, they are kind of intriguing. I see that most people are swapping out the stock tubes and putting in different things...instead of 6L6s I see people with EL34s, KT66s, and KT88s. Out of all of these, which (with a proper bias) could be set to have the least headroom? I'm not looking for headroom on this amp, I'd want it to roar! Granted I don't know too much about tube power and biasing, so I thought I'd ask it here.

    Any feedback would be great. Thanks! :AOK
     
  2. AdmiralB

    AdmiralB Silver Supporting Member

    Messages:
    3,072
    Joined:
    Aug 24, 2004
    Location:
    Central Indiana
    Been a long time since I was around a BB, but I've had a number of JTM 45 reissues and IMO the PT is under-speced for anything but 6L6s or 6V6s. With a pair of KT66s (1.4A per tube filament current, v. 0.9A for 6L6), the PT gets too hot to touch just idling, let alone playing.

    Since the BB uses the same PT but has one more preamp tube to heat, I don't think I'd do anything with one unless I either swapped the PT or added an auxiliary filament transformer.
     
  3. hw2nw

    hw2nw Member

    Messages:
    2,125
    Joined:
    Sep 28, 2005
    Location:
    Nashville, TN
    Wow, I could run 6V6's? Wonder what it sounds like and what the wattage goes to.
     
  4. AdmiralB

    AdmiralB Silver Supporting Member

    Messages:
    3,072
    Joined:
    Aug 24, 2004
    Location:
    Central Indiana
    Yeah, the voltage is low enough for 6V6s and the OT primary is actually a better match for them too. Power is probably in the 20W-25W range.
     
  5. hw2nw

    hw2nw Member

    Messages:
    2,125
    Joined:
    Sep 28, 2005
    Location:
    Nashville, TN
    if I bias the 6L6's on the "hot" side can I reduce the headroom?
     

Share This Page