7591A full base vs. coin base

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by tastylicks, Jan 14, 2015.

  1. tastylicks

    tastylicks Supporting Member

    Messages:
    767
    Joined:
    Mar 1, 2006
    Location:
    Brooklyn
    For the many resident experts: Any difference in durability/ruggedness between a 7591A power tube with a full base vs. with the coin base? I understand that electronically the tubes are the same, I'm just wondering if anyone has knowledge about the durability with respect to the two different base options. For use of course in my vintage Ampegs. (G-12 and J-12-A)

    Thanks!
     
  2. mark norwine

    mark norwine Member

    Messages:
    16,143
    Joined:
    Jul 25, 2005
    Location:
    NJ...GSP135
    The overwhelming majority of my experience has been with full-base 7591A tubes, but the coin base that I've encountered seem to be just as robust.
     
  3. EFK

    EFK Supporting Member

    Messages:
    1,023
    Joined:
    Jan 18, 2009
    I've used quite a lot of 7591 tubes and I've never noticed any practical difference other than that the full base tubes work better with a given amp's tube retainers (bear traps).
     
  4. Diablo1

    Diablo1 Member

    Messages:
    622
    Joined:
    Nov 22, 2013
    The more important question is NOS vs modern production.
     
  5. Blue Strat

    Blue Strat Member

    Messages:
    30,033
    Joined:
    Aug 2, 2002
    Location:
    Sterling, VA (not far from Washington DC)
    Tube retainers, as above, is the only "issue". These, like 6V6s, aren't heavy tubes so even this shouldn't be an issue. If you're lucky enough to find a matched pair with ANY base at all consider yourself fortunate.
     
  6. mark norwine

    mark norwine Member

    Messages:
    16,143
    Joined:
    Jul 25, 2005
    Location:
    NJ...GSP135
    Plow horse vs. unicorn...

    The JJ 7591A (plow horse) gets the job done & sounds "not at all bad". To my ears, the ones from Reflektor (EH, Sovtek, whatever you call them) don't sound as good. Neither truly, really sound like 7591As to me, however. The early ones that required the resistor....those sucked.

    NOS (unicorn) just have "that magic".

    I say "unicorn" because.....well, try to find a pair. Do they exist? Well, they did once....so maybe it's better to call them "wooly mammoths" or "saber-tooth tigers": extinct.

    Mike could say better, but of all of the "dwindling supplies" of NOS tubes, I think it's fair to say that the 7591A is the first to become just about non-existent. Sure, there's probably a storage shed chocked full of them in Montana somewhere, but unless / until they surface, NOS 7591A tubes can just about be considered gone.

    I bought a pair from Mike about 2 years ago, and I'm darn glad I did!
     
  7. Silent Sound

    Silent Sound Member

    Messages:
    4,211
    Joined:
    Jun 8, 2012
    I bought a pair of JJ's a while back, and to my ear, they sound pretty darn close to the RCA branded and Sylvanias I have used in my Ampeg RRII. The only real difference I've noticed, is the JJ's have a bit less volume. It being a cathode biased amp, it's not fair to compare them directly, but to me, the JJ 7591's do a lot better job of approximating NOS version of their respected type of tubes than most other new production tubes.

    As for the coin base versus full base, I can't tell the difference there either. Honestly, I've yet to run across a 7591 that I didn't like. But I haven't tried the EH brand tubes yet.

    I went into a local music store a while back and they had a shelf full of NOS tubes. Prices were good but most of the tubes they had I didn't need. I did, however, buy all but two of their RCA 7591a's. The two I left were unmatched and labeled as though they tested pretty far apart from any others they had, so I passed.
     
  8. slider313

    slider313 Silver Supporting Member

    Messages:
    7,443
    Joined:
    Jul 28, 2005
    Location:
    NC
    Has anyone tried the new Tung Sol 7591?
     
  9. mark norwine

    mark norwine Member

    Messages:
    16,143
    Joined:
    Jul 25, 2005
    Location:
    NJ...GSP135
    Just a new name for the Reflektor tubes....

    Just because Mike Matthews bought the name "Tung Sol" (and others), doesn't make it a "Tung-Sol". All of his stuff...irrespective of name...is Reflektor.
     
  10. slider313

    slider313 Silver Supporting Member

    Messages:
    7,443
    Joined:
    Jul 28, 2005
    Location:
    NC
    Yep, but it looks nothing like his EH 7591. I was just asking for any input from those who may have tried them.
     

Share This Page