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Masco MA-8 for guitar

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  • Masco MA-8 for guitar

    I recently came upon a small Masco MA-8-N amplifier from the late 1940's that sounds really good and is in good shape. I've already put a 3 wire plug in and changed some of the jacks but I'd like to change some of the circuit to tailor it towards guitar. As far as tubes, it has a 6SF5, 6SJ7, 6L6, and a 5Y3 rectifier.

    It seems like I could take a cue from the Fender 5C1 Champ circuit, which has basically the same tube set-up minus the 6SF5, although it seems like a shame not to use all of the tubes. Maybe I should think about wiring an extra gain stage there? I'm still pretty new to these PA conversions– so far I've only changed the tone controls of a Bogen CHB-35 thrift store find. Does anyone have any advice? I have a schematic, but not sure if its ok to post it or not...

  • #2
    The 6SJ7 will drive the 6L6 well enough for guitar, but the 6SF5 is only a single triode. One interesting approach would be to rewire the 6SF5 socket for a dual triode like a 6SL7. Then you could have a pentode channel and a dual triode channel. Like an old Champ and a new Champ in the same box.


    • #3
      Hmm that is an interesting solution. The 6SL7 will fit the same socket as the 6SF5?


      • #4
        I rebuilt one last year.
        Couldn't get it to sound good with those tubes so I rewired it to use 2 6SL7's and set it up like a tweed type champ.
        Sounded pretty mean when cranked!