6L6's to EL34's

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Red Planet, Jan 9, 2006.


  1. Red Planet

    Red Planet Member

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    Heres a brain teaser (for me at least). I've got a Tweed Deluxe with bigger Iron and 6L6's in it. It has Mercury Magnetic Trannies in it. Can it be converted to EL34's? I know the pins are different. Is it possable to rewire the socket and then Bias it up for 34s or not? It also has a Bias Pot installed when it was built that has a fairly good range on it.
     
  2. Shea

    Shea Member

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    Ask whoever made the power tranny if it can handle the extra heater current that EL34s will require.

    To wire a socket for EL34s, you need to connect pin 1 to pin 8. Is there anything else connected to pin 1 now?

    Shea
     
  3. Chrome Dinette

    Chrome Dinette Silver Supporting Member

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    +1 on the extra heater current. If the existing tranny can't handle it, you can add an auxilary xfmr for the power tube heaters.

    The screen resistor (pin 4) should probably be changed to 1.5k.

    Depending on how the bias supply is wired, you may need to change a resistor or two to get what you want.

    I converted my Sovtek to EL34's and had to add the extra xfmr. That was the only really difficult part, finding the real estate.
     
  4. hasserl

    hasserl Member

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    Tweed Deluxe's were cathode biased. This is a clone with fixed bias? Or maybe even has a switch to selecty between cathode & fixed bias? If so, you should also take a look at the operation when in cathode biased mode.
     
  5. Red Planet

    Red Planet Member

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    Its by no means a clone. It is a Tweed Deluxe but with bigger Iron and 6L6's and fixed Bias. No switch. It does have the 5Y3 no Choke.


    It has MM Trannys. I emailed the builder and he said it wouldnt do it.
     
  6. Matt H

    Matt H Guest

    for reference- instead of connecting pin 1 to pin 8, it's better practice to just connect pin 1 directly to ground.

    if you use metal shelled tubes- it'll be grounded


    added bonus- when using el34's (or tubes where pin 1 is a suppressor grid) and the amp is cathode biased (as a tweed deluxe is), this will keep the suppressor grid operating at a lower voltage (more negative) than the cathode... theoretically this increases the efficiency of the tube and tube life. there's info up on the tone lizard site about it...

    (additionally, if the amp is fixed bias, you can even connect pin 1 to the negative bias supply... though, this makes the use of metal shelled tubes a not-so-great idea).
     

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