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Retubing an Excelsior

Discussion in 'Amp Central Station' started by justin.ramsey, Jun 16, 2012.

  1. justin.ramsey

    justin.ramsey Tele-Holic

    681
    Jun 3, 2009
    Northern, KY
    Okay I have a couple of tube amps but have never retubbed one before. I believe mine has a tube that is a light bit microphonic a little bit of ringing going on. So I believe I will just replace all the tubes. I know the preamp tubes are 12AX7's and the power tubes 6V6's so can I just buy a matched set of each, thinking JJ on the pre and EH on the 6V6's pull the old ones out and stick the new ones in or do I need to do more?
     
  2. tele salivas

    tele salivas Poster Extraordinaire

    Sep 5, 2008
    Tulsa
    For the Excelsior, that is all you have to do since it is a fixed-bias amplifer.
     
  3. justin.ramsey

    justin.ramsey Tele-Holic

    681
    Jun 3, 2009
    Northern, KY
    Sweet, thanks for the quick reply. Do you think the tubes I have chosen are a good upgrade or should I spend more money on something else. I know the best tube question has been asked to death just wanting an opinion.
     
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  5. FMA

    FMA Friend of Leo's

    Apr 29, 2003
    E-H are fine 6v6s. And I know they get a lot of hype, but I like JJ 6v6s too.
     
  6. Billm

    Billm Friend of Leo's

    Mar 26, 2008
    New Jersey
    I don't think either brand is your best choice. Tung-Sol are probably the best current production version of the 6V6, while JJ's 6V6-S has larger plates and a beefier tone.

    Among 12AX7s, my current favorites are TAD 7025WA Select/Premium, Sovtek 12AX7 LPS, or, if you want brighter, the Tung-Sol 12AX7.
     
  7. drdos

    drdos Tele-Meister

    Age:
    50
    366
    Sep 24, 2008
    Rockies
    I retubed my Excelsior with a matched set of EH6V6's and Ruby 12ax7's. The amp sounds fantastic. I think your choices are fine, but if you could get the JJ 6V6s tubes they are a popular and great sounding tube.
     
  8. t-luxe

    t-luxe Tele-Afflicted

    Nov 23, 2009
    so. cal
    I've got JJ 6v6s in mine, ( Tung Sols sound very good as well), a Mullard RI in V1, and a Sovtek WC in V2. JJs are good, too.
     
  9. Pointmonger

    Pointmonger Tele-Holic

    584
    Aug 29, 2009
    Austin, Texas
    I originally had that light ringing going on with mine. It turned out one of the metal covers on the preamp tubes wasn't seated well. Once I made sure it was on there correctly, it went away.
     
  10. justin.ramsey

    justin.ramsey Tele-Holic

    681
    Jun 3, 2009
    Northern, KY
    Where is a good place to get tubes? I dont mind spending a little extra to get a better tube/tone.
     
  11. Billm

    Billm Friend of Leo's

    Mar 26, 2008
    New Jersey
    Tubedepot.com, tubesandmore.com (who first clued me to the TAD 7025WA).

    Also KCA NOS Tubes. Mike Kropotkin knows more about new and old tubes than almost anyone.
     
  12. jh45gun

    jh45gun Banned

    Age:
    64
    Jan 20, 2006
    Northern WI Gods Country!
    a

    You sure you do not have that mixed up Fixed Bias you adjust and Cathode Bias you do not have to.

    Cathode or self biased tubes are arranged in an amp's circuit such that a single component - a resistor commonly called the cathode bias resistor - placed between the tube's cathode pin and ground determines the bias voltage. As current flows through the tube it also flows through the cathode bias resistor and a voltage is developed across the resistor - the bias voltage.

    If you change tubes the cathode bias resistor remains constant of course. If the new tube's operating characteristics are slightly different than the old tube's either more or less current will flow through the new tube compared to the old one. That means more or less current flows through the bias resistor and the bias voltage will automatically change as well. That happens automatically because as the current flowing through a resistor changes, the voltage across the resistor changes along with it (according to Ohm's Law).

    As can be seen above, the bias circuit develops its own bias voltage according to the tube's operating characteristics and that's why it is called 'self bias' - the circuit biases itself when a tube is changed!

    Fixed bias refers to a constant (or fixed) voltage that is created in the amp's power supply and wired to the tube's grid pin. In this case, the bias voltage is completely independent of the tube.

    Therefore, if a tube is changed and the new tube's operating characteristics cause more or less current to flow through it, the bias voltage must be manually altered to maintain the correct voltage difference between the grid and cathode pins.

    That means a tech has to change the fixed bias voltage in the amp to ensure that the new tube is properly biased and operates the way the designer intended.
     
  13. BiggerJohn

    BiggerJohn Friend of Leo's

    Jun 1, 2009
    California
    Man I would not use EH 6V6s if you gave them to me for free. I've seen too many of them blow and damage the amp. At a gig. Pass.

    The best Russian 6V6 today is the Tungsol. However, I personally prefer the beefier JJ 6V6.

    When it comes to 12AX7 types, I must say i really like the sound of the long plate varities.

    I wonder what an Excelsior would sound like with the JJ 6V6, Sov LPS 12AX7s, the Bill recommended Emmi speaker upgrade, and the sag resistors bypassed.
     
  14. t-luxe

    t-luxe Tele-Afflicted

    Nov 23, 2009
    so. cal
    Doug's Tubes are great as well. GC wanted $43 for a matched set of JJs, Doug had 'em for $30.
    I also use TubeDepot and KCA.
     
  15. TNO

    TNO Friend of Leo's

    Apr 25, 2003
    NC-USA
    The Tung Sol reissues are good enough that I sold off a pile of old RCAs a while back. The TAD 6V6s are also good. EHs sound kind of brittle to me and the JJs are sturdy but don't really sound like 6V6s at all.
     
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