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6550s in a Germino Club 40 (JTM50 Marshall)???

Discussion in 'Amps and Cabs' started by dewman, Feb 4, 2006.

  1. dewman

    dewman Gold Supporting Member

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    I know that you can run 6L6, 6V6 and EL34s in a Germino Club 40 (a Marshall JTM50 CLone). Can you run 6550s in that amp? And if so, are they a direct plug in with no alterations necessary and no impedance selector changes? Thanks-

    D
     
  2. Lord Valve

    Lord Valve Active Member

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    If it can use 6L6s, the bias circuit can produce
    negative voltages in the range required by 6550s.
    If it can use EL-34s, the filament winding in the
    power tranny can supply enough current to run
    6550s. If it's like a JTM-50, you have the option
    of changing the feedback wire to the 4-ohm tap
    when running the cleaner 6550, but this isn't
    strictly required. Without eyeballing the schematic,
    I'll give you a provisional "yes" in answer to your
    question.

    Lord Valve
    Expert
     
  3. riffmeister

    riffmeister Gold Supporting Member

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    I know someone who would know.

    ;)
     
  4. Lord Valve

    Lord Valve Active Member

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    My, what a useful reply.

    LV
     
  5. riffmeister

    riffmeister Gold Supporting Member

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    hint:

    first name begins with a G

    last name begins with a G


    and he uses this email address:

    ggermino@triad.rr.com

    ;)
     
  6. Lord Valve

    Lord Valve Active Member

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    Hint: I have no time for smart-asses or tellers of
    technical fairy tales. You got something to say,
    say it and stop playing games.

    Lord Valve
    Expert

     
  7. Roe

    Roe Member

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    Someone has qouted greg germino on this forum earlier saying that the club 40 can use 6550s, kt88s, 5881s, 6l6s, 6v6s, el34s, and kt66s
     
  8. Kiwi

    Kiwi Silver Supporting Member

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    Hint: Decaf. It'll deflate your self-importance, and up your civility.

    Love,

    Miss Manners
     
  9. Lord Valve

    Lord Valve Active Member

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    Clue: Why, Miss Manners - how kind of you to make
    such a useful suggestion. Upping civility is certainly
    a goal all of us should pursue. Up yours, too.

    Lord Valve
    As civil as possible, given the circumstances...
     
  10. samtheman

    samtheman Member

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    Yes, it´s me, Greg sent me mail when I ask swap a tubes my LoVo55

    " You can use 6V6´s, KT-66´s, 7581´s even 6550´s or KT-88´s if you wish. Allwould require the bias set for particular tubes being used"

    "Only when using 6V6´s is it necessary to impedance mismatch. So when using a 16 ohm cab, set amp to 8 ohms. When using 8 ohm cab, set to 4 ohms. This in effect doubles primary O/T impedance. In the case of this O/T from 3.4K to 6.8K. This is a better plate load for 6V6 tubes. All other tubes types you can observe standard impedance settings. You can try the same mismatch using KT-66`s which would sound good and even EL-34´s. You will notice a slight loss of power and lack of midrange. Some folks dig it, others not. It is safe for the amp, regards, Greg Germino"

    So, that Greg sent me. My amp is Germino LoVo55

    sam
     
  11. ROKY

    ROKY Member

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    Could Greg's 6V6 amps use EL34s w/ an impedance mismatch ?
    I've read that these 2 power tube types share similiar internal specs ..
     
  12. Leonc

    Leonc Wild Gear Hearder Gold Supporting Member

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    Guys, maybe we can do without smartalec remarks for a while. It's fun to be a smartass. I definitely know. But in hope of keeping things cool and helpful on this thread, let's chill with the wiseacre stuff on this thread.

    My suggestion: if you want to be helpful, be helpful. If you want to be a smartass, create your posts...and then just close the browser window before posting. It really works pretty well :).
     
  13. Lord Valve

    Lord Valve Active Member

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    Yeah, it is. You may need to adjust the value of the
    bias range resistor a bit to get the bias supply into
    the right neighborhood for EL34s, though. However,
    if you're looking for better low end, give the EL34s a
    pass - try some 6550s.

    Lord Valve
    Expert
     
  14. bluessyndicate

    bluessyndicate Member

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    http://www.getodd.com/stuf/treefall.html


    If a tree falls in the forest and there is noboday around does it make a sound?..no wait...

    If a wisecracker posts, but there is nobody around to read the browser...no wait....

    If a tree falls on a browser, but noboday..n o wait...
     
  15. outtahear

    outtahear Supporting Member

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    Depends-if the tree grows in Brooklyn, and the caged bird sings......
     
  16. dewman

    dewman Gold Supporting Member

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    Thanks guys. Will try the 6550s, any suggestions Lord on where to set the bias range for 6550s and for KT77s and KT88s?

    I've had KT66s and 6V6s in this amp and each give a different tone. I figured the 6550s might get me more bass and a little more headroom, like the American versions of the plexis likely had since the EL34s didn't ship well in the old days...
     
  17. Lord Valve

    Lord Valve Active Member

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    My article on biasing is archived on the Duncan Amps site,
    one of the *very* best places to go for tube amp tech info.
    (No technical fairy tales, internet lore, urban electronic
    legends or musician myths there, guaranteed. ;-)

    http://duncanamps.com/technical/lvbias.html

    Read it three times. For your purposes, ignore the OPT
    shunt method - Marshall amps have very low DCR in their
    OPT primaries, and most DMMs have an internal shunt
    resistor that is too high in value to give sufficiently
    accurate readings when doing an OPT shunt. You'll be
    using the cathode resistor method. If you have a "bias
    probe" type device, substitute the readings you get from
    that whenever you're instructed (in the article) to take
    a reading across a 1-ohm cathode resistor. If you have
    questions, feel free to E me at tubes@prodigy.net for
    guaranteed fairy tale-free technical assistance.

    Lord Valve
    Expert
     
  18. dewman

    dewman Gold Supporting Member

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    Thanks Lord- I've purchased great things from you in the past and think NBS electronics rules. As always, a big thank you!

    D
     

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