Paging Rob Distefano: MMB build

Discussion in 'Shock Brother's DIY Amps' started by bluesfordan, Feb 15, 2009.

  1. bluesfordan

    bluesfordan Friend of Leo's

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    Hi Rob,

    Not doing this to save money, but think it would be a fun project. I'd like to build a MMB. Is it doable?

    thanks in advance,

    Dan
     
  2. muchxs

    muchxs Doctor of Teleocity

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    What's an MMB?
     
  3. bluesfordan

    bluesfordan Friend of Leo's

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    sorry, that's on a need to know basis, only. :lol:

    Just kidding, don't hurt me:neutral:

    MusicMaster Bass amp. Rob is quite the conne-sewer-something or other when it comes to these little beauties.
    :D
     
  4. muchxs

    muchxs Doctor of Teleocity

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    Oh. I'm not don't why you'd want to clone one but suit yourself. Hint: Build it on a Champ chassis. Marsh has the chassis.

    http://www.marshamps.com/

    It's not a big deal to change the circuit so you have volume/treble/bass instead of the volume/tone on the Musicmaster. Good luck with the driver transformer the Musicmaster uses instead of a PI tube. There are enough holes in the Vibro Champ chassis Marsh sells that you could build a non-reverb Princeton with an SS rectifier, that sidesteps the issue of the driver transformer.
     
  5. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Sounds like an interesting build. The interstage transformer is still findable, but at $45, it's certainly less economical than scooping up the whole amp on eBay for $200-300! :lol:

    - Scott

    P.S. The Hammond 269GX would make a good power transformer for the project.
     
  6. muchxs

    muchxs Doctor of Teleocity

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    269GX = wimpy, wimpy, wimpy.

    269GX: sec. 225-0-225, DC ma 65.

    It's adequate for a little SE amp but only just. The Musicmaster Bass uses 250-0-250 on the high voltage. It's also a plate to plate output section. You want to see 50ma per 6V6 so the 269GX falls short.

    If one were to beef up a Musicmaster the Weber VST W022772 would be a good start. 100ma on the high voltage is adequate, you also get a useful increase in voltage. Bear in mind that the Musicmaster PT was intended for 6AQ5s in some versions, the voltages are on the low side for 6V6s.

    If money is no object try an Allen TP25. It makes sense to spend the bucks up front for a heavy duty power supply, that way the groundwork is done to support any mods you might want to try later.
     
  7. celeste

    celeste Friend of Leo's

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    http://www.edcorusa.com/products/transformers/xpwr/index.html

    Seems like the 106 or 107 would be a good choice.

    As for the interstage, is there a reason the Hammond 124 series does not work?
     
  8. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    Don't forget that the Hammond is rated at 115V -- the 225-0-225 would come very close to the required 245-0-245 when plugged into an outlet today in 2009. At the MMB's original operating point, the 6V6's don't need that much current, either -- perhaps 90mA max at peak. Now, if one wanted to build a beefed-up MMB... they'd probably be well-advised to scrap the idea and build something else! :lol:

    - Scott
     
  9. muchxs

    muchxs Doctor of Teleocity

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    90ma is still almost 50% more than 65ma. The Musicmaster is underbuilt to begin with, no use underbuilding it more. Better safe than sorry.
     
  10. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Here's a schem:
    http://www.schematicheaven.com/fenderamps/musicmaster_bass_schem.pdf

    A 12 watt, with three transformers (Power, Output, and Interstage), for a '70s (albeit a Leo) design? The parts cost on trannies alone would make it a questionable endeavor.

    Build a Princeton or even just a parallel 6V6'ed Champ into a 1x12" cab and save some dough.

    MMB's are great for the price on the used market, but the circuit isn't that awesome to be blowing a lot of dough on building a clone... there are other circuits that can get similar (and better) sounds for cheaper.
     
  11. muchxs

    muchxs Doctor of Teleocity

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    CrashMan has spoken! :lol:

    When a project makes you scratch your head and ask, "WHY?!" sometimes you gotta scratch your head and ask, "WHY?!"

    There's a reason Musicmasters are affordable, used...
     
  12. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    I think it was mainly their "bass practice amp" status and the fact that it is not great for bass at any volume. :)

    Very cool amp for guitar, but similar to a Champ (or even a Princeton in some ways), so if you find one used for cheap - snatch it up! If you plan on building something similar though, a Champ (or two 6V6 parallel'ed Champ) may be a cheaper build for similar results.
     
  13. muchxs

    muchxs Doctor of Teleocity

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    Similar to a Champ... same chassis. Similar to a Princeton (roughly) because it's plate to plate. It's like a Princeton with weak transformers.

    I've been watching Champs @ around $350 each. Musicmasters go around $200. The advantage of a Musicmaster over a Champ is the MM cabinet will fit a 12" speaker, stock.
     
  14. bluesfordan

    bluesfordan Friend of Leo's

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    basically what I'm trying to achieve here is an amp with reasonable power and simplicity. I could deal with a princeton with a 12" speaker, if it had a tone stack of a single knob, two 6V6s, and a tube rectifier. Does such a beast already exist?
     
  15. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    That's starting to sound like a tweed Deluxe... :p

    - Scott
     
  16. JohnnyCrash

    JohnnyCrash Doctor of Teleocity

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    Other than portability (a 1x12"), what kind of sound are you going for?

    Tube rectifier generally = sag and a syrupy/sloppy response. Tight bass and decent articulation calls for a SS rectifier (or a more robust rectifier tube).

    One knobbed "tonestacks" are sorta not tonestacks. You only have flexibility over darkness/brightness, not really Bass and Treble - and your guitar already has a tone knob. They generally have more preamp gain but a lack of tone shaping controls.

    Nothing is more simple than a BF style Bass and treble tonestack - for flexibility. For pure simplicity, a simple Tone knob is limited in many ways.

    In any case, small, portable, and around 15-20 watts - it depends on the sound you're going for.

    Cleans/Country a Deluxe Reverb or Vox AC15 (or AC30) - dirt/Rock, a Marshall 18watter. Raunchy blues (or blues/rock), a 5E3 Deluxe. The list can go on and blur together (depending on the amp and sound you're looking for).

    A MMB is not exactly a tube rectified "sag" machine and is more Champ than Princeton in overall sound. For best Champ-like experience I'd recommend a SF Champ (cheaper than BF, easy to put a 10" in and has great tone PLUS flexibility - cool cleans, nice overdrive, takes pedals well).
     
  17. celeste

    celeste Friend of Leo's

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    How about a Princeton reverb, but ditch the tone stack and and reverb/tremolo, add a Garnet one knob tone control. They are about the most flexible of the one knob controls. You get extra gain with the Garnet, but loose some because you have to loose the cathode cap on the first stage.
     
  18. bluesfordan

    bluesfordan Friend of Leo's

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    well, I do have a silver face champ, my mmb cabinet AND a Jensen 4 ohm 12" speaker. I could put the three of them together, but then I've got nowhere for my mmb chassis to go (haven't got any 8 ohm 8" speakers hanging around).
     
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