NAD! Silverface fun!

Discussion in 'Ampage Area' started by markeebee, Jan 4, 2019.

  1. markeebee

    markeebee Country Gent

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    This turned up for sale on a Facebook group.....I ended up trading another amp for it, probably got the bum end of the deal, but the heart wants what the heart wants, you know how it is.

    1973 Musicmaster Bass. Really interesting little circuit. 12AX7 preamp valve. Two 6AQ5 power tubes, which are basically the same as 6V6 but in a physically smaller package. That's it. It's like Fender said "how can we make the simplesst amp in the world?".

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    CTS speaker. Take a look at the chassis.....there's almost nothing there.


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    On my messy workbench (ignore the other amp above it). Same chassis as an AA764 Champ. What's really interesting, for other amp geeks, is the transformer at the bottom right-ish. It's an interstage transformer, and the the primary receives a signal from the preamp valve, and then a signal is fed from one end of the secondary to a power tube, and the other end of the secondary feeds an out of phase version of the signal to the other power tube. Voila! No need for a phase inverter valve!

    I'm guessing that maybe it was cheaper for Fender to buy a bunch of these transformers than pay for another valve and the labour to add a few resistors to make a normal phase inverter.

    So, how does it sound.......?
     
  2. markeebee

    markeebee Country Gent

    The answer is........totally amazing!

    I changed out all the caps, valves, and upgraded to wimpy 12" CTS to a Jensen P12Q.

    It doesn't really sound like a Fender. It has lots of chime, and lots of snarl, it's like a very bratty garage-punk viking pirate astronaut. Only 12 watts (at most), but it's easily EASILY loud enough to keep up with a committed drummer (and they all should be committed) unless you want it to be clean.

    Up to about 3 on the dial it has a fairly meek and mild clean sound, beyond that it just gets progressively thicker. At full tilt, it's quite incredible. Very much a one trick pony, but the trick is very much like a flying pony that craps the words "VOX FENDER HYBRID" in stars.

    Apparently, you lucky guys in the US can still frequently pick these up for around the $200 mark. They're rubbish for bass, so a lot of them just never got used, but they're just like a Punk Princeton and if you ever see one at a decent price I'd jump on it before the world finds out. Definitely file under "Great Sleeper Amps".
     
    Last edited: Jan 4, 2019
  3. swivel

    swivel Gretschie

    337
    May 13, 2018
    PNW
    Cool, yes a fun format to make experiments! I had a couple of the 6V6 versions but never had the small bottle valve type. What's that long screw hanging down off the transformer?
     
  4. markeebee

    markeebee Country Gent

    That screw's quite a novel idea. In the pic I posted, it's screwed too far in, it should actually be unscrewed so that it's slightly taller than the valves. Then when you take the chassis out you can sit it on your bench (like in the last pic) without crunching the valves. I guess it made the test procedure at the factory easier.
     
  5. markeebee

    markeebee Country Gent

    I kind of have a yen to upgrade the transformers to an 18 Watt set and use 6BQ5/EL84 output tubes, for a bit more headroom and volume. On the other hand, it's a lot of fun as it is and it would seem a shame to 'unoriginal' it.

    I think I'll make a copy, with EL84 tubes, if I can find a suitable transformer for the PI. Classic Tone make one in the States but the shipping to the UK is exorbitant.
     
    Bertotti likes this.
  6. swivel

    swivel Gretschie

    337
    May 13, 2018
    PNW
    You are saying that's from the factory? Neither of mine had it... Looking at on line images it appears to be a non 6V6 version thing. Interesting! That and the oddball knobs...
     
  7. markeebee

    markeebee Country Gent

    Yeah, it's definitely factory. You're absolutely right, as usual, it was only on the early models.

    I kinda like the weird knobs, but I think I'd prefer a more classic silverface look. The power light is also weird, it's a flat disc rather than a jewel.
     
    swivel likes this.
  8. swivel

    swivel Gretschie

    337
    May 13, 2018
    PNW
    Seen this version? Weren't these MM Bass units? or maybe Bassman 10?
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    6124Bassman and Bertotti like this.
  9. markeebee

    markeebee Country Gent

  10. wildeman

    wildeman Gretschified

    May 10, 2015
    norcal
    Cool, i've actually seen a couple of those with Champs stuffed into them.
     
  11. hcsterg

    hcsterg Country Gent

    Feb 13, 2012
    France
    Good score, markeebee !

    A friend of mine has exactly the same as yours : 2x6AQ5, flat pilot light, square magnet speaker (sorry I do not remember : is it a 12" or a 15" ?), fuzz-face like knobs, phase inverter Xfo in the chassis (very hum induction sensitive)... I think that it had that famous jack screw too.

    I agree, indeed : moreover you will loose that good tone. Maybe some new caps, a few details, cleaning, and that's all !

    A+!
     
  12. Grand Marquis GT

    Grand Marquis GT Electromatic

    37
    Mar 2, 2017
    Abilene, TX
    I would love a cabinet like that to put my ‘78 VC chassis into. Love me some Silverface Fenders!
     
  13. Tony65x55

    Tony65x55 Gretschified

    Age:
    62
    Sep 23, 2011
    The 'Shwa, Ontario, Canada
    Good thread Markebee. I've seen these old Musicmasters go by and the prices were good. I always wondered if they would be any good for guitar as you hear very little about them.

    Thanks for posting this.
     
    markeebee likes this.
  14. 6124Bassman

    6124Bassman Gretschie

    334
    May 20, 2018
    Tempe, Arizona
    This is the Bantam Bass model, with the Styrofoam Yamaha speaker that is usually blown. Cool amps, a shop I frequent had one, with a replaced speaker though.
     
    swivel likes this.
  15. swivel

    swivel Gretschie

    337
    May 13, 2018
    PNW
    The Japanese do make some cool speakers...
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    TestPattern and new6659 like this.
  16. LivingMyDream

    LivingMyDream Country Gent

    Do you suppose they made this one, too?

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    Seriously, thanks for the information on the Musicmaster Bass amp Markeebee.
     
  17. markeebee

    markeebee Country Gent

    Thanks chaps.

    I should add that I gave it a whirl at a practice session last night. I was wondering whether ir would keep up a drummer and a 500W bass stack. Turns out that I couldn't get it past 2.5 on the dial before the others were shouting at me. The dairy goodness doesn't really happen until 3 though, so I'm gonna have to use an attenuator next time.