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1700ohms primaries for a 2XEL34 + 2X6L6 amp running about 450V?

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  • 1700ohms primaries for a 2XEL34 + 2X6L6 amp running about 450V?

    I want to build a Marshall-style 100W amp but I'd like to combine EL34 and 6L6s. For one thing I know the 6L6 don't want to be run over 500V, so I was thinking of using a PT designed for a 4X6L6 Twin Reverb, which would give me about 450V on the B+.

    Now, the OT I want to use is for a Marshall 100W, which has a 1700ohms primary.
    I guess something a little higher (like 2k) would be preferable.
    But it can't be that big of a deal right?

    How about if I want to run the pair of EL34 cathode-biased?

    Thanks

  • #2
    Originally posted by Hardtailed View Post
    I want to build a Marshall-style 100W amp but I'd like to combine EL34 and 6L6s. For one thing I know the 6L6 don't want to be run over 500V, so I was thinking of using a PT designed for a 4X6L6 Twin Reverb, which would give me about 450V on the B+.

    Now, the OT I want to use is for a Marshall 100W, which has a 1700ohms primary.
    I guess something a little higher (like 2k) would be preferable.
    But it can't be that big of a deal right?

    How about if I want to run the pair of EL34 cathode-biased?

    Thanks
    I use a marshall 100watt OT with 4 6L6's just fine. Sounds good too. Your only talking about 300ohms difference.

    Comment


    • #3
      Arghhhh, details details details!

      Twin Reverb transformers only have a 5.5A handling on the heater line, I need 6A because of the 2 EL34s
      Not to mention the relays that will run on this line.

      Now, if I go with a 100W Marshall power transformer, I might get over 500V, which is the max 6L6GCs are supposed to take.
      However, my 50W amp has a 345-0-345 PT and runs with about 485V on the plates at idle. The extra 10V of the 100W one shouldn't be that much (I have no experience with voltage doubling circuits).

      Maybe I should just use E34Ls to get that tone midway between EL34s and 6L6s (though I'd rather mix the two). But 4 of those brings my total current draw for the heaters to 7.2A, not to mention the relays. They're usually rated at 7A (I have a 4th preamp tube since it's a 3-channel beast).

      Oh well, I think I'll just go with the Marshall style PT and if my plates are over 500V I'll use some Zeners on the cathodes of the 6L6 to drop some voltage (the 6L6 pair will have their own biasing circuit, so I'll bias accordingly) to be safe.
      This also gives me 1A of headroom on the heater line to power my relays.

      Comment

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