Ken fisher master vol. mods

Discussion in 'The Workbench' started by trent, Sep 6, 2006.

  1. trent

    trent New Member

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    Just wanted to see if anyone here had ever tried the Ken Fisher master vol.
    mods?
    I used his mods in a few old Marshalls from the 70's when playing out with 50
    watt heads in the clubs.
    Man those amps sound good.
    His mods are the ONLY MODS I would EVER try on these amps.
     
  2. Guv'nor

    Guv'nor New Member

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    What does he do? because installing a master volume is a pretty simple mod so I guess there's something more.
     
  3. trent

    trent New Member

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    There are MANY types of master vol. mods.
    Some sound good, some ok, some bad.
    Some even change the sound of the amp.
    I have used no less than 6 types of master vol. mods myself.
    I feel that the Fisher mods work very well and donot change the
    sound of the amp.
    Trent
     
  4. Guv'nor

    Guv'nor New Member

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    Could you explain this specific mode?
     
  5. trent

    trent New Member

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    Its fairly simple.
    I use a 100k dule gain pot in the phase inverter section.
    You do have to remove 2 resistors but on the old amps (pre '76)
    this is not a problem.
    As always you have to be sure not to touch the wrong thing in an
    open Marshall as the voltage in the filter caps can KILL.
    If you know what your doing its fun to work on these amps.
    If you don't know what not to touch its best if you don't open the amp up.
    If you think this is something you would like to try let me know and I will see
    if I can find a copy of the mod and email it to you.
    Thanks for the post.
    Trent
     
  6. drbob

    drbob New Member

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    This is also known as the Rich mod on the LPF, after one of the guys that usually goes to Dallas/Arlington and sets up shop there modding Marshalls...
     
  7. pedecamp

    pedecamp Well-Known Member

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    I wonder how trent, Guv'ner and drbob are doing, haven't heard from them lately. :)
     
  8. Michael RT

    Michael RT Well-Known Member VIP Member

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    and it's not Ken "Fisher". :facepalm:

    It's Ken Fischer. :)
     
  9. Alabama Thunderpussy

    Alabama Thunderpussy Well-Known Member

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    This sounds like a PPIMV with a less ideal pot value.

    Also, very few people are ever documented to have died from vacuum tube DC voltage in musical equipment. A healthy respect is necessary, but you aren't automatically dead if you touch a cap. Most common result at full voltage is a nice nasty burn down to the bone of your finger and general discomfort for a while. Certainly not fun, and enough to keep you careful from then on, but the "omgz t00b amp v0ltages will kills you!" chant is getting old.

    After a brief google, I believe this is what you are referring to:

    http://www.lynx.bc.ca/~jc/KenFischerMaster.gif

    The LarMar PPIMV is a better design.
     
    jgab and Michael RT like this.
  10. S9X

    S9X Active Member

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    Glad You pointed this out.

    I'd add that voltage doesn't kills. Current kills.
     

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