Anyone ever change an EL84 socket to an Octal socket?

Discussion in 'Amps and Cabs' started by eru, Feb 22, 2008.

  1. eru

    eru Member

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    And if so, what does it involve?

    What changes need to be made to the circuit? Or is it just wiring a socket with the right connections to the rest of the board?

    I'm thinking about doing this to a valve junior and preserving the single-ended class A operation to play with different tubes. Since the amp is so cheap, it might be worth getting one to just screw around with.
     
  2. Blue Strat

    Blue Strat Member

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    Of course you'd need to enlarge the socket mounting hole. Best way to do this would be with a Greenlee chassis punch (not cheap) but there's probably a less expensive hack way to do this (metal file? Be careful of the filings. Getting them inside the amp could be a disaster).

    EL84s require more drive than most other power tubes, so you'd need to change the driver circuit too.
     
  3. hasserl

    hasserl Member

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    What do you mean by they need more drive Mike? IME EL84's require much less voltage swing from the PI to be driven into the non-linear operating range and provide lot's of breakup. That's why they'll work in a circuit like the 18 watt Marshall, where the common bigger power tubes would never see enough of a voltage swing to be driven into distortion.
     
  4. Blue Strat

    Blue Strat Member

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    Ooops, had it backwards (caffiene deprivation). In any event, the driver circuit will require adjustment.
     
  5. Jonny

    Jonny Member

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    www.sewatt.com

    Wiring diagrams galore including switching to an octal socket.
     
  6. hasserl

    hasserl Member

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    I know what you mean. I had a major brain fart here on a thread last night, and I can't blame it on lack of caffeine, just a brain fart. Old timer's disease I guess. :(
     
  7. eru

    eru Member

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    Cool information. I think sometime next month, I'll be modifying a Valve Junior to use octal tubes and have controls on the back for bias adjustment.

    This is dependent on the cost of an appropriate output transformer, since adding too much money to that amp would be somewhat ridiculous.
     
  8. Groovey Records

    Groovey Records Member

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    Let us know how it turns out !
     

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