Something ain't right...

Discussion in 'Shock Brother's DIY Amps' started by Jewellworks, May 12, 2021.

  1. Jewellworks

    Jewellworks Tele-Meister

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    I've tweaked my Deco Amp and got the tone control and gain just right, but when I turn the gain up, I get a really harsh top end. Very brittle. I thought I'd add a .002 "fizz cap" on V2 from the plate to cathode, which rolled off the highs just a tad, but even then, I'm still getting a harshness on the top. Too edgy.
    I'm wondering if I need to raise my grid stop resistors? Right now I've got 47K on V1, a 30K on V2 and the 6L6. I've even got a 1k on the screen (Merlin's idea). V1 and V2 are both 6SF5s.
    Thoughts?
     
  2. Nickfl

    Nickfl Friend of Leo's

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    Is you speaker new or broken in? I wouldn't make any judgements about harshness if the speaker isn't broken in.

    Do you have a scope? If you already out a snubber cap on there, it's probably not a high frequency stability issue, but it would be good to rule it out.
     
  3. Jewellworks

    Jewellworks Tele-Meister

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    New speaker. Don't have a scope. I put a .002 cap moved it to on V2, then V1, raised the V1 grid stop to 100k... Its like it's taking the edge off, but I still hear it above the muted top end. So I'm thinking it's coming from the 6L6. So I put a . 01 on the 6L6, and it definitely took away the harsh, but also the overall drive. I'm thinking about raising the grid stop on the 6L6. Muting the power tube seems like the wrong band-aid
     
  4. Sparky2

    Sparky2 Friend of Leo's

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    Amp Geek-Speak.

    It's a real thing.

    (Just one of many things I learned today.)
    God bless us, every one.


    :)

    [​IMG]
     
  5. Nickfl

    Nickfl Friend of Leo's

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    Do you have a broken in speaker you could try it with? Or a variac you could break this one in with? It would be good to eliminate the speaker as a possible issue because new speakers can definitely impart some harshness in the treble frequencies.
     
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