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resistor values in a fixed tone stack

Discussion in 'Shock Brother's DIY Amps' started by ruger9, May 1, 2009.

  1. ruger9

    ruger9 Poster Extraordinaire Ad Free Member

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    Just a quick one regarding resistor values in a fixed tone stack. Would you move the resistor value UP or DOWN to get LESS BASS out of a circuit? And, how many values? Meaning, if you've got a 68k in the bass circuit, for example, would you move up/down 1 value (75K/56K), or more than one, to notice a difference?

    Same question for the treble resistor as well.
     
  2. Guitar_Ninja

    Guitar_Ninja Friend of Leo's Silver Supporter

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  3. ruger9

    ruger9 Poster Extraordinaire Ad Free Member

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    Anybody who has the schem, can you tell me if the 2 treble resistors, R20 & R21, are in parallel or series? I'm looking at the schem, but being new at this, I can't tell. What I'm looking for is the "total treble resistance" so I can plug it into the Duncan Tonestack Calculator.
     
  4. pchilson

    pchilson Friend of Leo's

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    schematic to what?
     
  5. ruger9

    ruger9 Poster Extraordinaire Ad Free Member

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    whoops... sorry... Champion 600 (the new one).
     
  6. wnorcott

    wnorcott Tele-Holic

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    I glanced at the schematic


    R20 (75k) and R21 (180k) are in series, however they are tapped in the middle, and form a voltage divider.

    It is equivalent to the standard Fender 250K wiper-tapped treble pot when the knob is set to "7"

    R22 (75k) sets the bass response. Increasing this its value will increase the bass. The standard Fender uses a 250k log pot and a fixed 75k resistor is makes it like a Fender amp with the bass knob set on 4. Increasing its value adds bass: You would not hear a lot of difference unless you raised it to say, 120K

    The other question to ask is whether it is wise to increase the bass response much in an amp having a small 6" speaker. This is not a Twin Reverb: in the Champion 600, Fender is rolling of the bass response for a good reason. Still, changing the value to say 120K would not be so drastic.


    Bill
     
    Last edited: May 8, 2009
  7. ruger9

    ruger9 Poster Extraordinaire Ad Free Member

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    I'm actually trying to REDUCE the bass a little- the little 6" speaker (even the Weber I have in there) can't handle it. Just trying to de-woof it a little bit.
     
  8. Ben Harmless

    Ben Harmless Friend of Leo's

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    I always liked, as a general (non-binding) rule, to either double or halve the resistor value when tweaking for tone and such. You can always using something in between if you want something more subtle, but the factor of two thing is rarely an extreme change.
     
  9. wnorcott

    wnorcott Tele-Holic

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    OK well if you reduce R22 to 39K that should do the trick.
     
  10. ruger9

    ruger9 Poster Extraordinaire Ad Free Member

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    Thanks everybody!
     
  11. gionnio

    gionnio Tele-Meister

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    If it ain't broke...don't fix it.
     
  12. ruger9

    ruger9 Poster Extraordinaire Ad Free Member

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    It IS "broke". It has too much bass and gets woofy, especially with my Gretsch. So I'm "fixing" it. Thanks anyway.
     
  13. wnorcott

    wnorcott Tele-Holic

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    Glad I could be of help.

    Bill
     
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