Are These Tube Close Enough?

Discussion in 'The Workbench' started by BowerR64, Mar 10, 2019.

  1. anitoli

    anitoli Well-Known Member

    Joined:
    Jul 9, 2011
    Messages:
    5,229
    Likes Received:
    5,036
    Location:
    Lewiston, Maine U.S.A.
    So that calculates to 14 watts. If it sounds good that is fine.
     
  2. BowerR64

    BowerR64 Well-Known Member

    Joined:
    Nov 23, 2014
    Messages:
    4,193
    Likes Received:
    2,072
    I figured its around 60%, did you see how low it was when i got it with the stock tubes?
     
  3. charveldan

    charveldan Well-Known Member

    Joined:
    Jan 31, 2010
    Messages:
    7,371
    Likes Received:
    4,166
    Location:
    Somewhere with a Friedman Marshall & Les Paul.
    ......
     
    Last edited: Mar 15, 2019 at 1:34 PM
  4. anitoli

    anitoli Well-Known Member

    Joined:
    Jul 9, 2011
    Messages:
    5,229
    Likes Received:
    5,036
    Location:
    Lewiston, Maine U.S.A.
    There is NO arbitrary bias point that a tube has to be set at. Be aware the hotter you run them the lower the amount of headroom you will have and the shorter the tube life. I have a 6100 that i intentionally set the EL34's at 12w and it sounds and runs great. Does not have to be right at the so called 70% of max setting.
     
  5. charveldan

    charveldan Well-Known Member

    Joined:
    Jan 31, 2010
    Messages:
    7,371
    Likes Received:
    4,166
    Location:
    Somewhere with a Friedman Marshall & Les Paul.
    [​IMG]

    70% is industry standard. I bias all my amps @ 70% dissipation and have never had an issue.
    If the OP wants 60% or lower then good for him.
    I was having a hard time following the jist of this thread for a while.
    FWIW i bought new 6L6's for my MESA Dual Rec when i bought it but because MESA amps have non-adjustable bias from the factory the new tubes were only putting out about 40/45% dis. I switched to EL-34's and with the right tubes they were spot on 70%. The amp totally came alive & sounded way better.
    What works for me might not work for someone else & vice versa.
    Po-tate-o/Po-tot-o
     
    Last edited: Mar 15, 2019 at 5:37 PM
  6. BowerR64

    BowerR64 Well-Known Member

    Joined:
    Nov 23, 2014
    Messages:
    4,193
    Likes Received:
    2,072
    Charveldan, your right

    At first i just kinda wanted to know if it was ok to run the 2 tubes together that were so far off matched wise like one was almost half the plate current as the other. When i first checked it one was at 14.4 and the other was 6.7 and i bumped the bias up to 30-24

    There are a couple of things about this amp, it says in the manual that EL34 and 6L6 can be switch with no bias change, it says there is a switch or there was supposed to be one others say its a self biasing amp i dono ive read a bunch of different things about it. Also these tubes are china and they may of drifted a little after they were broke in?

    I usually use the weber bias chart and put it in the middle depending on the plate voltage.

    After i set the bias with the new tubes there is plenty of adjustment left on the bias pot i just got it in the middle and checked both tubes that they were closer matched and they are and just put it back together because i wanted to play threw it. I got tired of jacking with it

    weber bias chart.jpg
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice