Trial 5G9 layout: Please review, critique, suggest

Discussion in 'Shock Brother's DIY Amps' started by King Fan, Feb 28, 2019.

  1. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Been planning this build off and on for a long time, and more recently trying to learn DIYLC. Here's what I've got so far. [Edit: added download link for a hi-res file in post #5.]

    5g9 02 27.png

    Various changes from stock, like adjustable bias, switched hot and neutral, filter caps inboard the chassis, 1x47uF reservoir cap in place of Leo's 2x22, simple split grounds but with the trem sector separately grounded at its jack, etc. The goal is basically to sound stock with modern safety, reliability, and convenience. What's wrong? What's missing? For comparison:

    5G9 BIG layout.png

    Notes: I owe a ton to @robrob both for his great DIYLC files (one was highly modified here) and for his great ideas (like the 6V6 resistors, trem circuit, etc.) The 3MRA speed pot is subbed for the 2M Fender original (no longer available), with its resistor upsized from 100k to 150k as per 5G9 guru @tubeswell . The PT choice is noted on the diagram; FWIW I'm planning OT = ClassicTone 40-18022, their DR OT, "20w at 8K", choke = CT 40-18040, their 50mA Fender choke.
     
    Last edited: Feb 28, 2019
  2. LudwigvonBirk

    LudwigvonBirk Tele-Holic

    Age:
    118
    Posts:
    886
    Joined:
    Aug 26, 2017
    Location:
    Madison
    For consideration:

    Since you already have a bias pot, and external points, also add a bias-balance pot.
     
  3. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Good suggestion. I'm not smart enough to really understand the tone benefits -- I guess perfectly matched power tubes are rare, but OTOH have I read somewhere that a slight mismatch actually increases 2nd-order harmonics and can sound good? I know Rob has a drawing...
     
  4. sds1

    sds1 Tele-Afflicted

    Age:
    43
    Posts:
    1,107
    Joined:
    May 4, 2017
    Location:
    Orlando, FL, USA
    Even matched tubes drift and then become unmatched. The PI is not perfectly balanced either. The bias balance pot gives you control over all of that, you can tweak it to taste. You might already have enough distortion to prefer a more balanced set of power tubes.
     
    LudwigvonBirk and King Fan like this.
  5. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
  6. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Well said, and makes perfect sense. The only downside then is complexity -- Rob does indeed have a drawing -- and conceivably real estate in a tweed chassis. If I do it, you guys are getting full credit. If I don't, blame my laziness and fear of failure. :D
     
  7. sds1

    sds1 Tele-Afflicted

    Age:
    43
    Posts:
    1,107
    Joined:
    May 4, 2017
    Location:
    Orlando, FL, USA
    Well you got quite a bit of real estate back from moving your 68K input grids to the jack! And even so, Rob's layout is pretty darn compact:

    [​IMG]

    Also -- if it helps, this is a link to the 15mm Piher trimmer (25K):
    https://www.mouser.com/ProductDetail/531-PT15D-25K

    And the datasheet:
    https://www.mouser.com/datasheet/2/18/14-PT15v03-1499163.pdf

    These are big trimmers that work well with turrets and terminal strips. The link above is specifically to this style with right-angled wipers and the output on both sides:

    [​IMG]

    And this is a pic of how I add bias adjust to Silverfaces with bias balance and no bias adjust. Just to show you the size of the trimmer compared to a Fender bias pot, and how well it mounts to a terminal strip:

    [​IMG]
     
  8. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    :lolol: You got me. Facts, logic, experience, evidence, pictures, and two amazingly specific links? Plus those are made in Spain? Cool. And cost 0.53 each? Ding ding ding, sds1 by a knockout. Thanks. :)
     
    sds1 likes this.
  9. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    You mentioning real estate and the input grids and all gets me thinking. I don't own a drill press, but I guess I could have Doug Hoffman make a custom board to actually reclaim that space. Or I could leave the input eyelets empty, but press those B+-to-doghouse eyelets into service, the ones that sit above the bias circuit. Hmmm.

    I *love* the planning phase of amp building; maybe that's why I seem to stretch it out more with every build. Hey, it's fun, it's educational, and it's a darn sight cheaper than an actual build. With DIYLC, it's like a building a virtual amp. And it saves floor space!!! :D
     
    dan40 likes this.
  10. sds1

    sds1 Tele-Afflicted

    Age:
    43
    Posts:
    1,107
    Joined:
    May 4, 2017
    Location:
    Orlando, FL, USA
    I totally agree with this, it's like a build simulator. :)
     
    King Fan likes this.
  11. montana

    montana TDPRI Member

    Posts:
    75
    Joined:
    May 5, 2003
    Location:
    Seattle
    This will be fun to watch this build come together. So glad you're dong it!
     
    King Fan likes this.
  12. tubeswell

    tubeswell Friend of Leo's

    Posts:
    2,374
    Joined:
    Jul 1, 2008
    Location:
    NZ
    That layout looks good to me.

    Its definitely worth trying to shoot for a B+ of 270 to 280 (which goes good with stock circuit values). YMMV
     
  13. LudwigvonBirk

    LudwigvonBirk Tele-Holic

    Age:
    118
    Posts:
    886
    Joined:
    Aug 26, 2017
    Location:
    Madison
    If you have bias test points on the underside of the chassis (so you don't have to yank the chassis just to check bias), I assume one would also want your bias-adjust trimpot in an equally optimized ("don't have to yank the chassis") underside location. And if you had a bias-balance trimmer you would also want it underside for the same reasons as ^^, (which might change the trimmer type sds1 suggested?).

    [Confession:I haven't done all 3 of these but have been wanting to.]

    Noting the idiot-proofing/safety concerns, IMO it would quite nice to swap in new power tubes, measure the bias, "balance" the tubes (either if new, or once they drift), and then bias them to taste, without a chassis-yank (yeah it doesn't take that long, but there's fiddling, knuckle-nicking, cradling, meter-rigging, tolex scaping, rattle-tweaking etc, which one could avoid if the bias-measure+adjust features were all externally located).

    Looking fwd to how this goes!
     
  14. peteb

    peteb Friend of Leo's

    Posts:
    4,200
    Joined:
    Apr 25, 2003
    Location:
    Cascadia
    A tweed amps are easy to get inside. Back panel, that’s it.



    What I mean is there is less reason to provide access points to measure bias on a tweed amp than there is for a bf/sf amp where you need to remove the chassis, disconnect speaker and..



    3 amp fuse. Is that slo blo?
     
    Last edited: Mar 1, 2019
    keithb7 likes this.
  15. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Thank you. Your recent 5G9 just upped my motivation!

    Thanks, Tubeswell. I've been reading you on the 5G9 for years. And yeah, I'm hoping my lower secondaries (305-0-305) give me a B+ similar to the schematic 370. BTW, d'you agree with my 50mA, 4Hy choke?

    Yes for sure -- all my 'tray' (BF) chassis amps have 100% external TPs and bias pots with thru-hole screwdriver adjust. But this is a tweed Tremolux. To get at TPs up between the tubes, you'd still likely drop the back panel -- and at that point the need for TPs is gone. I admit, in my multi-year planning for this amp, I only figured this out recently, as we discussed here.

    Yep, tweed chassis building is hard -- but gut access is easy. And I dunno -- I thought amp fuses were always slow-blow?
     
  16. Mr Ridesglide

    Mr Ridesglide Tele-Afflicted Silver Supporter

    Posts:
    1,928
    Joined:
    Dec 11, 2009
    Location:
    Bloomington, MN
    I like it - I've got one underway as well -
    You decided to go with grid stoppers (1.5k)
    Not sure how much it matters, but the "stock" schematic calls for a 2A fuse.
    The only thing I have to decide is how much to spend on transformers. Have you fully committed to the MM ones?

    I still am thinking the ClassicTone 10028 for $83.00 vs. the Mercury Magnetics lower B+ at $165.00 for the PT
    and ClassicTone 18090 at $49.00 (8K primary) or a 19087 at $50.00 (6.6.K primary) vs. the Mercury Magnetics one at $111.00.

    So that's another point - best I can tell the Triad 108 was an 8K primary and the 125A1A I think was a 6.6K primary, and it would seem that this 125A1A replaced the Triad 108 in 1959 or so.... grrrrr... what to do?
     
  17. Mr Ridesglide

    Mr Ridesglide Tele-Afflicted Silver Supporter

    Posts:
    1,928
    Joined:
    Dec 11, 2009
    Location:
    Bloomington, MN
    And I noticed too, that you're going with a .047 coupling cap to Bright Volume in lieu of the "stock" version of .1 - For a different shape of the tone for the bright I presume.
    Perhaps a mistake on the "cathode" pin 8 on V3 to the cap on it's way up to the depth pot - you've got .01 spec'd there. I believe it should be a .1uf
    Other than that our diagrams are identical.
     
  18. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Well spotted, I have no idea where I came up with 3A fuse. Oh, wait, probably just left over from when I started with Rob's 5F6a. Double duh. Thanks!!!

    OTOH, I'm def *not* going MM. Do you mean am I committed to CT? Pretty much -- I've been thinking about this for years and can't rethink too much more. :)

    You're way ahead of me on all this, but FWIW here are the notes I wrote up on PT:

    MM ‘clone’ specs for the Triad 8160 are 160 ma, 6.3v @ 6 amps, 5V @ 3 amps; FTTP is 350-0-350, FTTP-M is 320-0-320. Both have bias taps, neither has filament CT.
    FWIW I hear the Fender 300-0-300 on the 5G9 scheme is pretty arbitrary or notional but the 270B+ target is a good one.
    Noted online: “Of these amps 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).” From http://forums.vintageamps.com/viewtopic.php?f=8&t=97487
    ClassicTone 40-18029 is 3.44 x 2.75 bolt holes, HV 305, mA 200, multi-tap; the ‘high’ HV is 710 (355). Lots of wires but good spec.
    Hammond 290DX is 3.44 x 2.75, HV 325, mA 230. This is the right physical size, has the right number of wires, tons of current, and HT not very different from the lower MM spec.

    For the OT, my notes say:

    People say Fender used a 5e3 OT…. Fender’s 5g9 schematic shows “Output Trans. — 108”. The 108 is a bit mysterious, but was apparently the Triad OT for the 5e3 and likely matches the 40-18022, CT's Tweed Deluxe OT, which is also 20W with 8K windings. Note 8K is said to be ideal for Fender-y 6V6s.
    What have you decided for a choke???

     
    Mr Ridesglide likes this.
  19. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Brilliant!!! This was the kind of detail I was hoping someone would pick up. Thank you x10^3.

    I actually forget why I put .047 coupling in the Bright channel -- maybe by analogy to my recent 5e3. But the 5G9 is a very different amp -- my usual guideline is build stock and then *see* if you want to mod at all. I think I'll revert that and then see.

    As for the .01 on V3 cathode, you're right, that must just be an error. Decimal points!!!

    I owe you, friend. Thanks again.
     
    Mr Ridesglide likes this.
  20. King Fan

    King Fan Friend of Leo's

    Posts:
    4,496
    Joined:
    Jan 1, 2013
    Location:
    Salt Lake City
    Here's a slightly revised version, then. For high-res version click here. I haven't drawn in the balance+adjust bias circuit yet, that'll take some whiskey and time.

    5g9 03 01.png
     
    dan40, Mr Ridesglide and CoyotesGator like this.
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.