Bass. Tubes. Don't like "Presence". Talk about it?

Discussion in 'Shock Brother's DIY Amps' started by LetItGrowTone, May 21, 2019.

  1. LetItGrowTone

    LetItGrowTone TDPRI Member

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    1. I know I could feed back more highs.

    2. Does not liking presence mean *the same thing* as not liking too much of the effect of the speaker's rise in impedance with frequency? (This could be reduced by driving a more resistive load (or an entirely resistive load, and taking the output from a "transformer out" or Fender's "Line/Recording" jack, which I never tried.)

    3. Do those infamous 220K local negative feedback resistors over the 6L6s in the AB165 address *this exact issue*, or something else?

    Anything else to learn? Thank you.
     
  2. LetItGrowTone

    LetItGrowTone TDPRI Member

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    I can't remember where I saw it, but one of our great tube experts explained (with an o-scope trace) that a rasp forms when... (paraphrasing loosely)... when the two PP halves of a squarish wave don't sum together perfectly and there are discontinuities that generate spikes that fill the gaps.

    But I don't know if *this* is the rasp in question.

    I'm guessing that it's lessened with a better balanced PI. My output section is now "all the way" to AA371. It's pretty solid.
     
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