EL-84 to 6973 ?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by rreiser, Apr 25, 2016.

  1. rreiser

    rreiser Supporting Member

    Messages:
    1,787
    Joined:
    Dec 31, 2003
    Location:
    Wi
    Anyone convert an El-84 amp to 6973's ? I know the tube sockets would have to be rewired . Was it worth the effort ? Where could I find the correct pin out ? Thanks for any help.
     
  2. EFK

    EFK Supporting Member

    Messages:
    1,035
    Joined:
    Jan 18, 2009
    Usually people do it the other way around since real old 6973 have gotten so ridiculously expensive! You can wire the socket so you can run 6973, 6CZ5 (basically the same thing and a lot cheaper), 6CM6 (9 pin 6V6, much tougher than 6AQ5 imho) or 6EM5 (sweep tube, works well but needs a bias adjustment). Make sure your screen feed is on pin 1. Pin 8 is screen also on 6973 only, so put it on 1 and you can use all the above tubes. Pin two is no connection - you can use it for a tie point safely, or just leave it empty. Pin 3 is input grid, also pin 6 on 6973 only so make sure your signal off the phase inverter is feeding pin 3. 4 and 5 are heaters. 7 is cathode. 9 is plate.

    For best treatment of the screens *if* you are using real 6973, it's best to feed the screens on pin 1 of both tubes and then run a separate piece of wire from pin 8 to pin 8 of both tubes. This won;t make any difference to any of the other tube types mentioned above but with 6973, it helps act as a heat sink to keep the screens below their max dissipation rating. I read this on one of the old data sheets somewhere, don't remember where but I figure it can't hurt.

    You will need to change the cathode resistor if cathode biased, the above tubes will need a resistor of roughly double the value of what you have now to start, then you'll need to work out the math/dissipation from there to adjust to final value. Or if fixed biased, same thing - start with roughly double the bias voltage over EL84. Depending on the circuit, you may need to tweak the preamp signal as these tubes will handle more drive signal to saturation and full output compared to the highly sensitive EL84, but then most guitar amps throw way more signal then necessary at the output section anyway.
     
    Last edited: Apr 26, 2016
    fakeox likes this.
  3. EFK

    EFK Supporting Member

    Messages:
    1,035
    Joined:
    Jan 18, 2009
    About your 'was it worth the effort' question: what is it you're specifically after? In other words, I assume you want to change the sound, so what is it that you want to hear?
     
  4. rreiser

    rreiser Supporting Member

    Messages:
    1,787
    Joined:
    Dec 31, 2003
    Location:
    Wi
    Thanks for the data. I was thinking it may have a little more headroom and also just curiosity. I have a pair of RCA NOS 6973. I may end up getting a new Supro Tremoverb 1x10 and I can use them in that amp.
     

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