Monoprice Two Stroke

Discussion in 'Shock Brother's DIY Amps' started by Drew617, May 17, 2021.

  1. Drew617

    Drew617 Tele-Meister Silver Supporter

    Posts:
    460
    Joined:
    Mar 4, 2014
    Location:
    North Shore, Mass.
    Hey, I completed another silly build today. I haven't had a chance to really dig in and tune it, but I did have about 20 minutes to play, confirm it sounds healthy, and doesn't redplate. So I'll share, since it is at least viable/permanent in this configuration.

    I've got a few "real" builds queued up but keep collecting stuff, mostly transformers and speakers I have no immediate need for, so this is at least the third parts build I've done just to use that stuff up. That's turning out to be folly since I collect more in the process, but no matter. I had fun building a @robrob Blackvibe into a Peavey Rage for the same reason.

    So this is a single-ended 6L6 tweed-ish amp built into the $115 Monoprice Champ chassis and cabinet. I bought two of these as-is/for parts a while ago from some online returns liquidator. Figured they were pleasantly generic looking and flexible enough, easy to turn into something else.

    This is very close to the Weber Maggie schematic with very slightly upgraded filtering and diode rectification. Neither were really a design choice, although I don't have much need for tube rectifiers in SE amps. Or in many PP amps. :eek:

    PT is a used Hammond 290AX, OT is a yuuuge WSE15. The Hammond's 275-0-275 secondaries get B+ correct-ish, where the Weber schematic calls for 325-0-325 with a 5Y3. Had to nibble the chassis a bit to get a Champ PT in the original cutout, and the OT could only be surface mounted. I punched out the noval socket hole so I could swap the tubes' location for saner wire routing.

    The Weber design calls for a 1x8 + 1x10 cabinet which I'd like to hear. Obviously don't get the same complexity out of a single 8" but I like that this thing is so tiny and relatively potent. I like the Weber Sig 8 better - sounds "smaller" but more interesting - but used a WGS G8C here because it holds together longer, and I guess I'm going for loud-from-tiny. The real answer for an efficient 8" is probably a Weber 8F125/150 but I don't think they'll fit here, and one of those might double my investment in the amp.

    Used a preamp ground bus tied to chassis at the input jack and the amp is plenty quiet.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
  2. James Knox

    James Knox Tele-Holic Silver Supporter

    Posts:
    960
    Joined:
    Aug 13, 2003
    Location:
    Phoenix
    Cool and fun project!

    Looks great...
     
    Drew617 likes this.
  3. archetype

    archetype Fiend of Leo's

    Posts:
    6,082
    Joined:
    Jun 4, 2005
    Location:
    Williamsville NY
    Cool! What does the second switch do?
     
    Drew617 likes this.
  4. Peegoo

    Peegoo Poster Extraordinaire

    Posts:
    8,492
    Joined:
    Oct 11, 2019
    Location:
    Between the Raindrops
    Looks like nice clean work!
     
    Drew617 likes this.
  5. Drew617

    Drew617 Tele-Meister Silver Supporter

    Posts:
    460
    Joined:
    Mar 4, 2014
    Location:
    North Shore, Mass.
    Thanks! Hunter's book calls that a "boost/voicing switch," really selectable bypass caps on the first triode. You get either 25mfd, .47mfd, or just the bias resistor.
     
    archetype likes this.
  6. archetype

    archetype Fiend of Leo's

    Posts:
    6,082
    Joined:
    Jun 4, 2005
    Location:
    Williamsville NY
    Excellent. I like voicing you can change on the fly
     
    Drew617 likes this.
  7. Drew617

    Drew617 Tele-Meister Silver Supporter

    Posts:
    460
    Joined:
    Mar 4, 2014
    Location:
    North Shore, Mass.
    Yeah, more useful than I imagined. I suppose I copied Ted Weber primarily since I built this as a SE 6L6, but I think Ted copied the selectable bypass from the Two Stroke. Hunter's description is hilariously optimistic, something to the effect that "shimmering blackface" tones are available, and uh, no, not really. But that's still a useful and elegant solution that could be applied to a lot of other amps, and I imagine I'll apply it.
     
    archetype likes this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.