Eico HF-81 -- best output tubes?

Discussion in 'Eico Place' started by ssouci, Mar 20, 2017.

  1. ssouci

    ssouci Well-Known Member

    Messages:
    535
    Location:
    Vancouver, BC, CANADA
    I have a completely rebuilt Eico HF-81... virtually every part and wire has been replaced with careful choices by an experienced HF-81 rebuilder

    I've tried 3 sets of vintage NOS output tubes, with surprising results:

    #1. Siemens E84L / 7320 (heavy duty version of EL84 that can sub as a 7189)
    - sounded OK, but mid and highs lacked life and sparkle and sounded noticeably veiled)

    #2. Russian 6P14P-ER (heavy duty long-life version of 6P14P that can sub as a 7189)
    - sounded OK, but mid and highs lacked life and sparkle and sounded veiled)

    #3. Russian 6P14P ("plain" Russian tubes, inexpensive)
    - sounded very good all around, very good highs/mids, with maybe a tiny bit less strength in the bass vs. the others

    so I'm running the amp now with the plain cheapo Russians because they clearly sound the best, but I'm wondering why the two other tubes -- both of which should be "much better" tubes -- did not sound as good

    also, can anyone suggest the best output tubes to use specifically in an HF-81, where everything just clicks and they sound really great?

    hoping for a best-bang-for-the-buck option, and also an option that is simply the best (but might cost more)

    ideally, the options should reflect tubes that can be located and purchased within reason, and have a decent expected lifespan

    any advice or suggestions greatly appreciated, thank you!
     
  2. tube-a-lou

    tube-a-lou Super Member

    Messages:
    4,043
    That's surprising, I use 6P14P-ER's on mine and sound real nice in mine amp, do you have any pictures
    of your amp underneath?
     
  3. ssouci

    ssouci Well-Known Member

    Messages:
    535
    Location:
    Vancouver, BC, CANADA
    sure, attached here is a photo of the underside

    I should mention that this unit has been sitting unused for approx. 6 weeks, and I just recently powered it up... I could swear that prior to this, even the plain Russian output tubes were sounding a bit more lively with better high end... not sure if anything could have changed while the unit sat idle?

    the restoration is pretty recent, and there are fewer than 100 hours on this amp since that

    thanks
     

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  4. tube-a-lou

    tube-a-lou Super Member

    Messages:
    4,043
    That could be, everything has to charge up a bit, mine is a ongoing project I changed the coupling caps to pio's
    and the caps everywhere else to poly, I would give it time to settle in again and see. What kind of 12AX7's are you using
    and 12AU7's that makes a different's in the tone as well.
     
  5. ssouci

    ssouci Well-Known Member

    Messages:
    535
    Location:
    Vancouver, BC, CANADA
    my 12AX7 are Rogers (made in Holland)

    my 12AU7 are Mullard
     

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