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Thread: Adapted 5F2A with EZ80 and EL84

  1. #36
    Senior Member
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    We finally got our 5w 5F2A/EL84 amp sorted and it sounds awesome - and very loud! I'd just like to thank everyone for their help.

    With the 275-0-275 PT, the plate voltage is 333v - a cathode resistor of 250R is giving a dissipation of around 13W.

    The break-up into brittle distortion at 2 was sorted with a grid-stopper resistor of 100R.

    The hum is low and the tone is quite responsive.

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  2. #37
    Old Timer Tom Phillips's Avatar
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    Jun 2006
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    Thanks for reporting the outcome and I’m glad you got the amp sorted out. It is interesting that a such a low value (100Ω) grid stopper resistor would make such a significant improvement.

    What was the fix for the excessive buzz that you reported when no guitar was connected to the input?

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  3. #38
    Don't forget the joker g1's Avatar
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    Also, the 100R grid stop was control grid and not screen grid, correct?

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  4. #39
    Bent Member Chuck H's Avatar
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    Right! I'm thinking it's a screen grid resistor and not a control grid stopper resistor. It was sort of hinted at earlier.

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    "...less ear-friendly but handy for jazz." Leo_Gnardo

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