Finally, at long last, that 5G9 build...

Discussion in 'Shock Brother's DIY Amps' started by King Fan, May 27, 2020.

  1. King Fan

    King Fan Poster Extraordinaire

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    Seems like I've been thinking about this build forever. I don't even know where I got the bug -- in my early years reading about amps, there just seemed to be a mystique about the 5G9 Tremolux (1957–1960). They aren't that common, and they seemed to create a reverent hush when they were discussed in amp forums by builders and by wistful former owners. With their 5U4 rectifier, 40uF reservoir cap, choke, fixed bias, LTP inverter, and huge cab, they seemed to be viewed in a different class than the other 6V6 tweeds. The term 'Baby Bassman' gets tossed about, and though clearly they aren't actually a Bassman or Tweed Twin, here are some blurbs from amp-forum webspace.

    "This is absolutely the most amazing Fender Tweed amp. It is in a class all by itself!!!!"
    "The 5G9 is the king of the Fender tweed trems."
    "I have played a few original 5G9s and they are really a wonderful amp."

    First hurdle was finding a chassis. Basically the same size and hole count as a 5E7, but with different labels on the dials. I eventually learned Weber had done a run of 5E7 chassis's screened with 5G9 labels, and although they no longer listed 'em, they had a few in the storeroom. I ordered one in -- and then it sat.

    54D775F0-B23C-45A2-9817-B6B4F00FA24A.jpeg

    Besides the question if I really *wanted* a 'big' little amp (these are reputed to be loud, given all the factors mentioned) there were a number of other puzzles to be solved. A big puzzle was a PT; quoting vintageamps.com: “...the Harvard has the smallest PT, then the Vibrolux PT is a step up, then the Deluxe PT is a step up, then the Tremolux has the largest PT in this class (Triad 8160).” I was never able to find 8160 specs (Triad told me they're still proprietary) but various hints said it was big in mA (maybe ~ 160?) but fairly low in HV. Here's the schematic with voltages.

    5G9 BIG schematic.png

    Over the years I got a lot of help from 5G9 guru @tubeswell, both reading his many posts on various forums and in his answers to my many questions. He noted that a target HV might be 300-0-300, with a target B+ of 370 or 380. Plus of course you want a 50V bias tap.

    To be fair, some people just use a Deluxe or Deluxe Reverb PT in these, but I knew from experience that those with HV windings for 325V would come in hot especially with a 5U4, and even if I got a cooler HV, I had another problem: physical size. I'll admit this may be a problem of my own creation. I'm not sure about the size the 8160. Here's a pic of an original 5G9.

    Primo Chassis backside.png

    So medium? But the PT cutout, at least on my relabeled 5E7 chassis, is for a Bandmaster-sized PT (bolt holes ~ 3.44" x 2.75") -- and I got stubbornly set on a PT that would drop in without an adapter plate or other trickery. This road turned out to be winding -- and will have a detour at the end.

    A few other notes for anyone planning a 5G9 in future: That choke follows the first filter cap, so the 'small Fender choke' (4Hy) will do fine. For the OT, quoting a VintageAmps post, "The Tweed Deluxe, Tremolux, Harvard, Vibrolux all share the same Output transformer. (125A1A)." The original speaker was most often a P12Q. And yeah, the cab is big: 22"W x 20"H x 10 1/2"D at the bottom and 9 1/2"D -- some sources say 9" -- at the top.

    Oh, and a layout:

    5G9 BIG layout.png
     
  2. jsnwhite619

    jsnwhite619 Friend of Leo's

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    So, have you picked your transformers yet, or have a short list?
     
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  3. CapnCrunch

    CapnCrunch Friend of Leo's

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    After building several amps, I have more than I can really play, but this is the one that tempts me to fire up the soldering iron again. I'll be watching this closely, because if you come up with good sources for trannies, I think I'll dive in the pool with you.;)
     
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  4. jsnwhite619

    jsnwhite619 Friend of Leo's

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    They must be taking that one to the grave! It's been 60 years!! :lol:
     
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  5. Paul-T

    Paul-T Tele-Meister

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    Ooh, this is exciting. I feel drawn to it, like a moth to a flame.
     
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  6. CapnCrunch

    CapnCrunch Friend of Leo's

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    If you had enough builders commit to buy them, could you talk Triad into doing a run of the original PT? I've been part of these group buys with Heyboer over at the amp garage. I suspect Triad will not be as accommodating as Heyboer, but it might be worth a try. I'd jump in for one or two if Triad would play. Another option might be to approach Heyboer to see if you have sufficient specs for them to do a run of a custom PT and how many a group would have to order for them to do it.
     
  7. D'tar

    D'tar Friend of Leo's

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    And we've been waiting just as long!!!

    Subscribed!!!

    I have to seek out some sound clips here! Looking at the ole schematic... The only tweed left may be in the interacting volumes and on the cab itself! Perhaps that's why people like them? I'm considering a 6G3 which is almost the 5G9's fraternal twin or perhaps its younger more refined sibling with 2x gain stage.

    Looking forward to the build! Take too many pics:)
     
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  8. David Barnett

    David Barnett Doctor of Teleocity

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    And it's open-loop.

    I agree though that the 6G3 is the next evolution of this circuit. They stole that lovely cathode follower from the oscillator and added a gain stage, I guess to make up for the feedback loop?

    The Tremolux evolved pretty quickly too, the 5E9-A still had a floating paraphase inverter and cathode bias, jumping straight to the 5G9 with long tailed pair, fixed bias, and a doghouse for the caps.

    Too bad they didn't do one tweed 6L6 amp with trem.
     
    Last edited: May 27, 2020
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  9. CapnCrunch

    CapnCrunch Friend of Leo's

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    Rumor was that TBone Burnett played a 5G9 all over the Allison Krause/Robert Plant album Raising Sand.

    Here is a clip with Burnett playing two different tweeds the one to the right could be a 5g9 Listen the trem in the opening number. It's got that quality.

     
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  10. theprofessor

    theprofessor Poster Extraordinaire

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    AWWWW YEAH! Subscribed!
     
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  11. David Barnett

    David Barnett Doctor of Teleocity

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    Every time Buddy Miller takes a solo the camera zooms in on T Bone Burnett.

    Burnett's amps are too small to be Tremoluxes, they're either Deluxes or Vibroluxes (or one of each).
     
  12. CapnCrunch

    CapnCrunch Friend of Leo's

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    I'll take your word for it. The one on the left is smaller than the one on the right that's all I could tell. And that they sound Tweedelicious.;)
     
  13. tdoty

    tdoty Tele-Meister

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    Too bad all the info likely bit the dust. Back in the 90's I worked for a transformer company that had been around since the mid '50s. Companies like Ampeg, Fender, SLM, and Triad were among our clientele. I had several file cabinets with the prints and specs of, basically, every product they ever made....going back to 1956 (the oldest one I was able to find). Transformers aren't that mysteriously magical.

    A dead 8160 might be worth searching out to have it disassembled and recreated.
     
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  14. David Barnett

    David Barnett Doctor of Teleocity

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    burnett.jpg

    Is it?
     
  15. King Fan

    King Fan Poster Extraordinaire

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    OK, cool, I sense a certain interest. :)

    Usually I try to quote and answer various posts, but there are a *lot* of good ones up there, so I'll just let my Swiss-cheese brain comment on things I know something about. @D'tar -- yeah, sound clips. Actually, that's one thing that adds to the mystique -- there aren't many. More for 5e9a, but still not that many, and they're way different. Some of the best demos (as usual) are from the amazing Greg, but yeah, they all seem to be 1956, 5e9a. Not the same thing.

    You may do better than I've done, but I really find very few good ones. I started a thread about that a while back in fact. Lemme know if you find good *5G9* demos.

    Which brings us to an issue to be aware of if you research the 5G9 and 5E9a: Many folks can't tell 'em apart in the shop / studio, though they're very different inside. Why? Well, Leo loved a mystery. For whatever reason, and even more than usual, Fender muddied the water by never (or hardly ever?) printing up *any* 5G9 tube charts. So some unwary demo dudes (and sellers, and buyers) think they have a 5E9a when they have a 5G9. (Hint: look inside -- among many differences, the most obvious is that the 5G9 has a funky green selenium bias diode between PT and board.)

    BUT the 5e9a is also a lot more common than the 5G9, so it's pretty common to see a "Tweed Tremolux" wishfully ID'd as a 5G9 (the big box versions look much the same on the outside) when it's a 5e9a.

    To switch from sacred to profane, I was guessing one reason Triad still guards the specs (good point, @jsnwhite619 ), is A) they may already have revealed them to Mercury for $ and a contract -- maybe not, just a thought, but also B) they actually wanted to know if I was interested in a manufacturing run. So @CapnCrunch , you may want to contact them. Heyboer is a good idea too.

    What PT did I end up with? Well, here's a hint, our Hammond-wise friend @jsnwhite619 was a big help. But as I say -- stay tuned. My initial research years ago led to an answer that suddenly became unavailable a couple months back, just as I started my final push... due to a certain virus that shall remain un-named. And I'm not sure even now that my original answers or substitute answers were the right ones. All shall be revealed in time....
     
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  16. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    Tune in tomorrow—same Bat-time, same Bat-channel!

    :D:D:D
     
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  17. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    There is usually a size difference, but it is not spoken about in polite company.
    I didn't hear any motor-boating.:lol:
     
  18. jsnwhite619

    jsnwhite619 Friend of Leo's

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    I can't find it now, but not long ago Hammond had on their site somewhere about contacting them if you had a classic transformer they didn't offer a model and they would be happy to work out something to be able to examine/clone it. They may be worth contacting, even if it's to put a bug in their ear.
     
  19. tubeswell

    tubeswell Friend of Leo's

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    IMHO to get the 5G9 vibe, you want a PT with the following specs

    HT = 300-0-300VAC @ 120mA to 150mA (important to get the right voltages with a 5U4G)
    Heater = 6.3VAC @ 2.5A min
    Rectifier = 5VAC@3A
    Bias = 50VAC

    a 50mA choke will work fine

    OT rated for 15 to 22W 6k6 to 8k

    A 2M pot for the trem speed is ideal, but a 2.5M RA will work well. Either of these may be impossible to find, so you can make a 3MRA work with a bit of tweaking of the circuit
     
  20. Lowerleftcoast

    Lowerleftcoast Tele-Afflicted

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    @tubeswell I am not trying to be argumentative. I am interested for my understanding.

    Why would the 6.3VAC need to be 2.5A min?

    Am I wrong in figuring 6.3VAC current draw?
    2x 6v6 = .9A
    3x 12a_7 = .9A
    Pilot light 47 = .15A

    Total current draw = 1.95A
     
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