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Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

6V6 1987 Plexi Build

Discussion in 'Shock Brother's DIY Amps' started by Phrygian77, Nov 26, 2017.

  1. Phrygian77

    Phrygian77 Tele-Holic

    649
    Apr 30, 2016
    Crawfordville, FL
    I think I've settled in on doing a JMP 1987 inspired Plexi type build. I'm also set on doing it with an 18 watt power transformer, Hoffman style. Zachmdhunter happens to have some JTM45 chassis with everything punched/drilled except the PT/OT stuff, so that seems like a perfect fit. Maybe I can get them to bundle in the front and rear stainless steel faceplates also.

    I'm not settled on the output transformer, 6.6k or 8k for the just over 400 VDC B+?

    I also know nothing about Marshalls. I feel pretty good about duplicating Fenders now, but Marshalls? I don't know. I don't know that I even want to duplicate some things. I hate turrets. I think running the the heaters overhead is a better design. Opinions here are welcome. I'd like to make this look at least a bit like a vintage Marshall.
     

  2. arielyitus

    arielyitus Tele-Meister

    Age:
    33
    301
    May 4, 2016
    Clarkston, Mi
    Interesting project, subscribed!
     
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  3. jondanger

    jondanger Friend of Leo's

    Jan 27, 2011
    Charm City, MD
    I had a builder make a 6V6 Plexi on a Hammond AO-29 chassis. He used the original transformers, but I wanted to be able to use 6L6s as well, so I swapped in an Allen TO-26 OT. It lets you use both by switching the secondary. It's a hefty piece of iron, I can recommend it for this style of build.

    Excited to see what you come up with!
     
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  4. Che_Guitarra

    Che_Guitarra Tele-Holic

    607
    Mar 23, 2012
    Perth, Australia
    I'll follow this for sure. I'll be very interested to see how you adopt SS rectification into 6V6 topology. I've checked out a whole bunch of Plexi 6V6-style schematics over the last few weeks and no two B+ rails have been the same. And on Youtube, the best sounding ones all seem to use a GZ34... but if you use a tube rectifier, you're taking away a fundamental cornerstone of what makes a 1987 a 1987.

    Marshall guys seem to suggest an 8K OT will be a more Marshall correct fitment. I'll be using 6.6K in my build... because that's what I have.
     

  5. Commodore 64

    Commodore 64 Friend of Leo's Ad Free Member

    Age:
    42
    Mar 1, 2010
    Kent, OH
    Hard to beat the 1750PA for price/performance: https://www.mouser.com/ProductDetail/Hammond-Manufacturing/1750PA/?qs=lrqjml%2bjt8cxDhP5xJ0Rrw==

    I don't think there's any benefit to copying one layout vs another. Borrowing liberally from many is probably the technique I espouse (and use) most often.

    A bunch of 18W schematics on the PDF below. I've built the Lite II U 6V6 and a Super 36. The 6V6 has seen a ton of gigging use and currently lives in Nashville. The Super 36 is one of the best I've ever built (and one of the few I haven't given away). These schematics are limited to 2 preamp tubes (hence the MOSFET source follower) because they were designed for the Universal PCB. But there's still great info there.

    My Super 36 lives behind a faceplate that was for a different amp I built (A self-split fed by a triode/pentode 6U8A). The faceplate was more expensive than the transformers, so I couldn't bring myself to not use it. LOL.
    [​IMG]

    My final bit of opinion/advice is that the 18W are great circuits and sound good. Having built variants, and a 5F6A (but with MOSFET sourcefollower) for 6V6.... They are more similar than different. I've explored that road enough. I can pretty much swap those amps in and out depending on whatever I feel like taking to practice, and the tone and feel are very similar. Yes they are different. But they are also the same. Twisting knobs can get them really close to sameness.

    So the JCM800 circuit is much more compelling to me. Especially that funky input jack combo where the Lo bypasses a triode. Very different character from a typical Hi/Lo. And I like the thick preamp distortion tone and topology. The cold clipper. The true CF. There's a real difference in feel and tone. Our bass player is a clean freak. He hates it. ;) .

    My next build for myself (and it's behind at least 3 projects for others right now) is going to be JCM800 with 6V6, in a 16x8 chassis so I can use my various head cabs to house it.
     

    Attached Files:

    Last edited: Nov 28, 2017
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  6. telemnemonics

    telemnemonics Poster Extraordinaire

    Age:
    58
    Mar 2, 2010
    Maine
    The two amps I play most are an 18w with 6v6 (otherwise stock 18w Marshall TMB circuit) and an old metal panel Marshall 50w Bass.
    While the 18w is certainly different sounding and has the more tactile feel from the tiny ez81 rectifier (which is actually about as fast as a 5u4), the two amps are more similar sounding than either is to a 5e3 or BF Fender.

    WRT the OT, I'm not sure an 18w OT would be bad, and I do find that the 18w OT has tighter more solid bass (with a solid non GB speaker) than many similar size amps, so IMO the 18w OT is not undersized for the wattage.
    OTOH adding 80v to the B+ might push it into premature saturation.
    A bigger OT is always a better idea!

    WRT the layout and your not liking turret boards, I'd lean toward keeping as close to stock proven design layout as possible with an unfamiliar build, to make it easier to get troubleshooting help from others who have vintage Marshall build experience.

    I don't build but have done basic repairs on lots of the old 50&100w Marshalls, and where the wires lay on the preamp sockets changes up the noise, even just a small move of a wire goes from noisy to quiet.
    Maybe relocating the heaters would be fine, others seem to do it in builds, but the Marshall layout works well too.
    Really a great layout to see what's going on and easy to work on.
     
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  7. CapnCrunch

    CapnCrunch Friend of Leo's

    Jan 7, 2011
    Washington, USA
    A 6v6 Plexi is on my short list of "want to build" amps. I'll be watching your thread. Have you visited the Hammond Forum? There is a lot of info over there on this topic. Also, Mark Huss is a good resource for 6v6 Plexi information, check his web site. I can dig up links if you need them. Here is a schematic and a link for some good info. as well.

    http://sluckeyamps.com/6v6plexi/6v6plexi.pdf

    EDIT: For some reason I can't get the Schematic to upload, so I added the link above which will take you to the Schmatic and other good info. Sluckey's build was part of a Thread over at the Hammond amp building forum. The link will give you his scheme. and layout and wiring and even a drill guide for the turret board. He also has the trannies listed that he used. His Chassis is one of the chassis' available over from Hammond as well.

    [​IMG]
     
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  8. Phrygian77

    Phrygian77 Tele-Holic

    649
    Apr 30, 2016
    Crawfordville, FL
    Sorry guys, after being out of town for Thanksgiving last week, and being in training most of this week, I haven't really had anytime to devote to the forum this week.

    I had seen you're recent thread about the Luxman. I subscribed to it. Although, admittedly, I've only really skimmed through most of it so far.

    I'm definitely going to go SS rectification, and the power rail will be just like a vintage Marshall. Although, I'm still kind of undecided on filtering and whether I want to go 8.2k or 10k for the dropping resistors... or really, it a question of do I want to go late 60's or early-mid 70's?

    I'm kind of leaning towards using the oversized Classictone 5E3 OT, which has 4, 8, & 16 ohm secondaries (40-18090).

    Similarly, I think that in my builds ... the 5F1 curcuit (with a 1uf bypass on V1A), the TW Express channel in my Blackface Bassman, and the Princeton Reverb with the raw switch on (75k mid resistor), all had very similar characteristics. I really wish I could compare them all again, but I dismantled the 5F1 to build the PR, and I sold the PR just as soon as I finished it.

    I'm still kind of considering a 16x8 chassis myself. I really want to do it in real JTM45 type chassis with a vintage style 26" small box head cabinet, but when I looked at Mojotone's pricing, I got sticker shock. Not to mention the cost of one of their vertical slant 2x12 cabinets, which is what I'd want to pair with it.
     
    Last edited: Dec 1, 2017

  9. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    In my 6V6 amp I probably will be using the 1750PA, you guys talked me into it. I was going to use the 1760H but I have some other tubes that will like that transformer.
     

  10. Phrygian77

    Phrygian77 Tele-Holic

    649
    Apr 30, 2016
    Crawfordville, FL
    I'm starting to think, if I'm going to build this thing in a JTM45 type chassis, maybe I should go with the Classictone 40-18095 PT and the 40-18025 OT. I could add a switch for the secondaries, and run 6V6s on the 560 VAC secondary (with an 8 ohm load on the 4 ohm tap or 16 ohms on the 8 ohm tap), or EL34s on the 625 VAC secondary.

    Or ... Maybe use the Trainwreck iron and build the output stage like an Express.
     

  11. ephshoe

    ephshoe TDPRI Member

    7
    Mar 17, 2005
    Ephrata, PA
    Just thought I would show the 6V6 Plexi that I built a year or so ago. I got the transformers custom would for me by Heyboer to give me about 395 on the plates. Works great.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     

  12. Commodore 64

    Commodore 64 Friend of Leo's Ad Free Member

    Age:
    42
    Mar 1, 2010
    Kent, OH
    Great work there, ephshoe. Very nice lead dress, I'm jealous.

    Also dig the standard color coding for plate/cathode/grids. Would be a pleasure to service that amp!
     
    Last edited: Dec 6, 2017 at 8:02 AM

  13. kplamann

    kplamann Tele-Meister Platinum Supporter

    496
    Mar 19, 2003
    Paris region, France
    Not an expert, but I have a 1980s Plexi and had a good tech work on it. Already, the original channel switching had quite a bit of crosstalk, which is why I had him do the work. Also he says that some of the layout is somewhat awkward (a ground wire running all around the amp?) so you might want to rethink some details which do not merit an exact reproduction.
     

  14. arielyitus

    arielyitus Tele-Meister

    Age:
    33
    301
    May 4, 2016
    Clarkston, Mi
    Wow, that is some good looking amp, I wonder what it sounds like, do you happen to have sound clips/videos?
     

  15. Phrygian77

    Phrygian77 Tele-Holic

    649
    Apr 30, 2016
    Crawfordville, FL
    Well, until you posted this, I was pretty much settling into the idea of building the amp in a 16x8x2 Hammond 1441 chassis. I even started working on a layout for it.

    I'm assuming this was a from scratch build. Where is that chassis from, MetroAmp/Metropoulos?

    What's the primary impedance on the OT? It looks like 6.6k or 6.8k printed on the sticker.

    What do you have in V2, since it's obvious the plate structure is different. The heater-cathode voltage issue is something I've never really given much thought to since I've never owned, worked on, or built anything with a cathode follower. It's seems people have had good luck with Sino, and even the short plate JJs and Sovteks.
     

  16. ephshoe

    ephshoe TDPRI Member

    7
    Mar 17, 2005
    Ephrata, PA
    OT is 6.6K. Most parts are from ValveStorm. I made my own board as none were available that suited me. Tubes are now ANOS Mullard 12AX7's, NOS JAN Philips 6V6's, and a ANOS Mullard GZ-34. It's basically a 1987 except for a few mods as in a Masonette. It puts out and would benefit from a master volume. Here's the build thread if any one is interested.
    https://www.thegearpage.net/board/i...e-build-for-anyone-who-is-interested.1519472/
     

  17. Phrygian77

    Phrygian77 Tele-Holic

    649
    Apr 30, 2016
    Crawfordville, FL
    So you didn't like the Tung Sol reissues in it?
     

  18. ephshoe

    ephshoe TDPRI Member

    7
    Mar 17, 2005
    Ephrata, PA
    Only had them in to fire up the amp. I have plenty of NOS tubes so there is no need to use the Tung Sol's.
     

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