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Voice of Music 722 conversion

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  • #1

    Voice of Music 722 conversion

    i know there is another thread about this already, but i figured it couldn't hurt to start a new one...

    i'm planning on building this, https://taweber.powweb.com/store/maggie_schem.jpg and as of now my big question(s) has to do with the OT of the VOM 722. a simplified schematic can be found at the bottom of the first post, http://music-electronics-forum.com/t23803/.

    my hope is that i can setup the 6l6 with standard cathode bias and ditch the whole network between the the 6l6's plate and OT primary?

    from what i can gather, the 6l6 is setup for current negative feedback(?) and that the primary impedance will change if i don't use the winding. i'm guessing i'd have to do some testing to pinpoint actual numbers. i read in a tread (that i can not find now) now that the change probably wouldn't be enough to worry about, but if you have any info to offer i'm all ears?

    as for the network between the 6l6's plate and the OT, i don't have a clue as to what it's doing or how it would affect things if it weren't there? is it a master volume of some sort?

    as always thanks for any help you can offer...
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  • #2
    That network at the output of the 6L6 probably has something to do with driving the record head or the tuning eye. Ok to leave it out.
    WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
    REMEMBER: Everybody knows that smokin' ain't allowed in school !

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    • #3
      sounds good...thanks.

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      • #4
        just a quick follow up, i did the conversion and it does work and it does sound good but i have some noise issues i haven't figured out yet. i need to take some pictures and post some voltages. which will have to wait till i get back from tour, like i said this is just a quick follow up...

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        • #5
          Probably just a grounding issue. You can research here to learn more about it. Proper grounding is easily lost in a conversion project.

          I built an old VOM into a practice amp with very satisfying results. The OT was pittifully unersized but sounds really good and continues to perform even under fully cranked conditions!!!

          On an un related note... Do you know what "foxfire" actually is?
          "Take two placebos, works twice as well." Enzo

          "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

          "If you're not interested in opinions and the experience of others, why even start a thread?
          You can't just expect consent." Helmholtz

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          • #6
            I used a ground buss for my grounding doing my best to follow the Valve Wizards directions and I grounded the heaters CT on the 6l6s cathode. I have a low pitched hum and a higher pitch noise the got better after I changed my loopy chassis grounding to the buss wiring. I'm afraid it's a matter of bad layout and or lead dressing. I'll try to get some pics up before I leave. Aside from the noise issues it sounds pretty good. I have a 6l6gc in it biased to around 19 watts and it's got some pretty nice breakup.

            To you other question, I only know the term from the series of books on Appalachian life. My dad had a cabinet business named foxfire after the book. I've read/gone through a few of them and have always like the books and loved my dad so I use it for my online life...so in short beyond the books, no.

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