Blackfacing a Silverface

Discussion in 'Amp Central Station' started by racehorse, Apr 24, 2004.

  1. racehorse

    racehorse Tele-Meister

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    I need some good advice,from some of your personal experiance.

    I have an early 70`s vibrosonic, basicly a TR with 1/15.
    It has a master volume ,but no pull boost.
    I have had it since it was new, it needs a cap job.

    the MV iI never used , always kept on 10.

    If I remove this from the circuit , what sound differance will I here?

    the other BF mods etc.

    PI changes

    voltege changes

    The bias change is going to happen , I may just add a bias vari to the bias balance. seems like a good idea.

    but what audible differance`s will I hear , or am I suposed to hear ?BF vs SF?

    nothing I do will be irreversable .


    HELP
    Thanks
    Racehorse
     
  2. Stan Martin

    Stan Martin Tele-Afflicted Silver Supporter

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    USA
    differences

    your amp wil have a better livelier feel. less constricted especially when you change the PI circuit. those 2 330k resistors dampen way too much.
    clip off those tiny suppresssor caps that may be connected to the power tubes to ground. they will kill off high end. disconnecting the MV is no big deal tone wise. most guys do it just because.
     
  3. racehorse

    racehorse Tele-Meister

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    thanks

    Thanks Stan, that is just the kind of info I needed.
    I feel the need to BF this amp but wanted to make sure I`m not caught in the Hype of the day.

    Because the amp sounds pretty good as is.
    I am going to do the hole BF mod.though.

    Thanks again
    Racehorse
     
  4. AtomicMassUnit

    AtomicMassUnit Tele-Meister

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    Racehorse,
    Techs have been blackfacing those amps since the early 70's. I just got done with a Vibrasonic, and it's a nice sounding amp. The weak point in the one I worked on was the speaker and power tubes being very tired, but the BFing really added a lot more life to it. Blackfacing it will give you a much richer tone overall. Pay close attention to the PI, I really think this is one of the most important sections in the amp for getting the sound you want. A lot of people prefer putting a pair of .047s in the PI where the .1s are. This takes a little bit of mud out of the low end. See if you like it. Also, I wouldn't worry about adding a Level bias to the bias Balance, because matched tubes are so easy to come by these days. Just convert it to a level bias, and use matched tubes. The Master volume will still rob a little bit of signal when it's all the way up. It's best to disconnect it, if you're trying to get that last little Nth degree of tone out of it. But hey, that's why we use these things, right? Email me if you need anything..

    Atomic
     
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