Marshall 50w - Bright Cap

Discussion in 'Shock Brother's DIY Amps' started by itsGiusto, Sep 13, 2019 at 3:48 PM.

  1. itsGiusto

    itsGiusto Tele-Meister

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    I'm building a plexi, not sure which bright cap value to use, if any. I expect I'll end up making it switchable, either between two values, or one value and no-cap. I know that the values Marshall used varied quite a bit over the years.

    Did Marshall always feature bright caps on their bright channel, or did they sometimes leave it off? Any suggestions on which value to use, or where I can hear what different values sound like?
     
    Last edited: Sep 13, 2019 at 4:53 PM
  2. dan40

    dan40 Tele-Afflicted Silver Supporter

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    4700pf was a value frequently used on the "lead" circuits. The large value cap caused the volume on the bright channel to ramp up extremely quick from 1 to 2 and helped the amp transition into dirt very quickly. Many of the earlier amps used a smaller 500pf which allowed only the highest of frequencies to past around the volume pot. Many builders will drop the value down to 100-200pf to add a bit of extra sparkle at lower volumes.
     
  3. dan40

    dan40 Tele-Afflicted Silver Supporter

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    This excellent data base at the Marstran website has a bunch of info on various older models. Click on the "Marshall pictorial page" link at the top of the page for pics and other data.

    http://www.marstran.com/Historic Data Base.htm
     
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  4. itsGiusto

    itsGiusto Tele-Meister

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    That site's incredible!!
     
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  5. RLee77

    RLee77 Friend of Leo's

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    If I can find my old schematic I’ll let you know what I settled on... it was WAY smaller than the stock 4700pf. Best way to find your own preference is to just sub in a bunch of values from as low as 50pf to the original 4700pf.
    At the high end it will be shrill and fizzy; if you go too low it will sound a bit lifeless and bland.
     
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