1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

6V6 2204...

Discussion in 'Shock Brother's DIY Amps' started by Che_Guitarra, Dec 5, 2017.

  1. justin.ramsey

    justin.ramsey Tele-Holic

    Posts:
    836
    Joined:
    Jun 3, 2009
    Location:
    Northern, KY
    I would wire it with an octal socket and play with tube rectifiers, solid state plug ins and copper caps to get the desired tone.
     
    robrob likes this.
  2. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Revised schematic, solid state rectification.

    Green = component value changes. 32+32uF cap can on screens and PI instead of 50+50uF (intended to gift a looser vibe, without stepping into ghosting territory). B+ expected to be around ~430V, first dropping resistor value TBC. Suggested value revisions around the power tubes. Any other suggestions to better optimise the circuit for 6V6s? i'm all ears.

    Red = path speculation for possible switchable GZ34 rectification. Bypass of diodes, lifting of a main 50uF filter cap, and an alternate first dropping resistor (value TBC).


    [​IMG]



    Was hoping to have progressed a ways on the fabrication side of this by now but i've cut the potential chassis too short for the layout as I would like it (@ 16"... chassis width really needs to be 17 - 18"). I've got another length of c-purlin steel section on the way, but until then, progress is on hold.
     
    Last edited: Dec 17, 2017
  3. printer2

    printer2 Poster Extraordinaire

    Posts:
    7,180
    Joined:
    May 24, 2010
    Location:
    Canada
    I had some crazy ideas to do with my build, then I checked how much room I had to play with on the chassis. Darn, it looked so big at first.
     
    Che_Guitarra likes this.
  4. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    I'm putting together a shopping list now @ Mouser, but I can't seem to find any blank turret boards. Turret lugs - yes. Turret boards - no. Do turret boards go by any other name?

    I guess could get from elsewhere, but ideally I want to source all my loose components from one source: the fewer vendors I use, the less money I am burning on shipping costs to Australia.

    And Mouser has free postage to AU on orders over $50, it's my preferred source.

    Hmmm... turret boards...
     
  5. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

    Posts:
    2,969
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    You're wanting blank fiberglass or phenolic board right? I'm not sure if mouser has any that isn't clad. I'd look for Garolite XX (also called Phenolic XX), which is paper and phenolic resin based, in sheet or strip stock. The phenolic stuff is easier to cut than G10/FR4.
     
    Che_Guitarra likes this.
  6. Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

    Posts:
    2,969
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    Last edited: Dec 19, 2017
  7. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    It's been a while, but this project is still 'go'.

    Had a side project to attend to first - the purchase / assembly / calibration of an infinitely useful tool which I had been eyeing off for years - an X-Carve CNC. It was a christmas present to myself, and today was the first (successful) test carve.

    [​IMG]

    Now I have an X-Carve, the only DIY limit is my imagination. No need for a turret board anymore - turrets will now be mounted on a PCB sheet, much like a Marshall Astoria circuit. The X-Carve can cut the traces.

    I can now cut the chassis myself too.

    A new learning curve to attend to, but i'm sure it will all be worthwhile.


    And the final schematic. I think the GZ34 route is the way to go - 6V6s seem to be more audibly pleasing when paired with a tube rectifier than via solid state. I'll leave solid state rectification for when I build a true 2204 JCM800.

    [​IMG]
     
    robrob, kleydejong and FenderLover like this.
  8. FenderLover

    FenderLover Poster Extraordinaire

    Posts:
    5,832
    Joined:
    Jun 11, 2009
    Location:
    Minnesota
    RE: the X-Carve, an engraved front panel would look pretty classy. Black anodize, back-filled lettering with gold paint a la Marshall. I'm sure you don't need any more bright ideas from the peanut gallery....:)
     
  9. robrob

    robrob Poster Extraordinaire Ad Free Member

    Posts:
    8,303
    Joined:
    Dec 29, 2012
    Location:
    United States
    I like the idea of a tube rectifier socket because as mentioned above you can run a variety of tube rectifiers to adjust the B+ and you can simply plug a Weber Copper Cap solid state rectifier into the socket too. A tube socket will help the amp's resale value too.
     
  10. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    The amount of side projects necessary to get a home CNC completely accurate and usable for production = totally underestimated. Anyway, headache over, nothing to do from here on but general maintenance and calibration.

    My first cutting-of-the-teeth CNC project - a pedalboard. Used to be an absolute mess - wires everywhere, no structured arrangement, and pedals shifting around with every stomp. A PITA to assemble/deconstruct - now it's a grab-and-go piece. It's a three-layer plywood (3 x 9mm marine plywood sheets) solution with a seating recess to hold each pedal and an internal cavity to run/hide wiring. Not without flaws, but very happy with the results, and a few steps of progression made along the CNC learning curve.

    Next step - designing/cutting a PCB.

    [​IMG]
     
    Last edited: Feb 24, 2018
    JeffBlue, robrob and FenderLover like this.
  11. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Hooray!

    Mouser parts bundle arrived today. Wima caps and metal oxide resistors all around, JJ cap cans, alpha pots... nothing too exotic. Stupidly, I forgot to order turret lugs and PCB eyelets... d'oh... will get on Ebay this evening and see what I can find.

    [​IMG]


    Now comes the fun part - designing a PCB to suit - and I have absolutely no idea where to start! Let the fun begin!

    I'll continue to document as I move along - this will be a completely different process to the regular turretboard-based build thread, which might interest some of you.
     
    Last edited: Mar 19, 2018
  12. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Back from the dead! Has been a very busy two years. Bought my first house... an endless renovation nightmare (and money pit)! A new career and new lifestyle. A new partner. And as a gift to myself, a bedroom converted into my very own recording studio.

    For the first time in two years I seem to be in a routine - I now work 9 to 5 - the worst of my home renovations are completed - I now find myself with regular spare time in the evenings - my brain needs a tinkering project to keep it occupied.


    This pile of parts has been sitting and starting at me for a long time... time to pull a rabbit out of the hat and turn it into a working tool.

    My plan remains the same - I want 2204 front end sitting on a Fender Deluxe style power section. This would be my perfect amp, and it will go straight to use in my studio.


    I'll sit on this for a day or two as I consider things, and get my head around circuit design again.

    Any advice as I move forward with this plan - i'm all ears :)
     
    awasson and robrob like this.
  13. Badside

    Badside Tele-Holic

    Posts:
    502
    Joined:
    Jul 5, 2011
    Location:
    Montreal, Qc, Canada

    All I will say is that the best sounding amp I've ever built is a 2204 into a pair of 6V6.

    Some differences though is that I went cathode biased to shave off some extra watts and make it easier to swap tubes. I used a big 470uF bypass cap on the power tubes so it would still be tight like a Marshall (I don't remember the Rk value since this amp was sold to a friend, but it was fairly high, maybe even 470R! Can't bias as high when using a big cap so I aimed between 80 and 90% dissipation at idle).

    Also, power transformer I used is a Hammond 272FX and I went diode rectification. This gives me about 375V, so any 6V6 will work, especially considering the 25-30V lost on the cathode resistor. In theory, power should be below 20W, but let me tell you it's still loud AF.

    Not that I have built for myself a similar amp where I used a tube rectifier, a GZ34. That one is a bit quieter, though not by much. The lower voltage does change the response of the preamp as well, it's a bit woolier (more JTM45 than Superlead if you will). Fun fact though is that while chasing an odd microphonic issue, I changed it to diode rectification with a "sag resistor" to compensate last year... in the end the power tubes were defective, but I never went back to tube rectification. I can't really tell the difference, and I feel safer using 64uF on the plate supply (this did sound noticeably better than 32uF to my ears).

    Oh, and 330p treble cap instead of 470-500. Of all the Marshall type amps I've built, I always come back to that value. Also, typically I like 47k or even 56k for the slope resistor (instead of 33k). And I tend to prefer less NFB due to the different gain characteristics of the 6V6. But a cool thing I've been doing recently is adding a switch to the Presence circuit to add a big capacitor (4.7uF or more) in parallel with the 0.68uF, this turns the Presence knob into a NFB bypass knob. Gives a lot more grunt to the low end (some prefer to do a dedicated Resonance control)
     
    awasson and Che_Guitarra like this.
  14. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Thanks for that reply Badside, much appreciated experience / advice :)
     
  15. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Bump again... but don't blame me for any delays this time... you can blame a certain little virus for a whole lotta priority adjustment!


    Been toying around with my CNC to mill the PCB, getting the layout right... traces, holes, what have you.

    This is what i'm up to. Hoping to mill this PCB before the weekend is out. I've not toyed with PCB creation yet, so might make for an interesting project to watch as I ride the learning curve :)



    [​IMG]
     
  16. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Practice carve today. Revealed a couple of problems.

    First thing, I want wider traces to seat the turrets and eyelets with 100% confidence. So to not breach into the grounded area of the board. Just a setting error on my behalf - it's following the line, rather than following the outside of the trace.

    Issue number two. And much more serious. Inconsistent depth from left to right of maybe 0.5 of a millimeter. Not an issue for the usual things I make, but unacceptable for a 2mm thick PCB board, with a 0.2mm copper clad.

    [​IMG]
     
  17. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    But ready to go now. I bolted this sacrificial pine board to the bench and milled the full surface. In theory the height should now stay accurate when I go to mill the PCB.

    Hoped to get this finished today, but it's late here in Australia. Ready to go, first thing in the morning.

    [​IMG]
     
    JeffBlue, awasson and RollingBender like this.
  18. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    Well... that was a massive pain in the arse, haha!

    The program said it would take 15 minutes... four hours later i'm done! I went to take a video, but the amount of stuffing around between passes would have made it a very boring video to watch.


    Despite milling the mounting base flush, there was a 0.1 - 0.2mm variance in the PCB thickness that I didn't account for. Or maybe I didn't clean the mated surfaces as well as I though. Either way, each trace required an individual depth setting. And because the V shape bit only took out 0.2mm (width) of material per pass, I ran the program 5 times at fractionally larger concentricity per pass, to get a good amount of clearance between the traces. Probably not necessary to be this excessive, but it's my PCB and I kept going until my eyeballing was happy!

    Possibly could have gone deeper, but erred on caution to guarantee maximum strength in the board. Might need to go over the board with an exacto knife just to scrape out a few small copper hairlines in the routed areas.

    Checked with a multimeter- continuity is where it should be, and not where it shouldn't be. Phew!


    But the results - i'm very happy. Will drill the holes with my press in coming days.. But for now, I want to enjoy the last hours of my weekend :)

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: Jul 5, 2020
    RollingBender, JeffBlue and awasson like this.
  19. printer2

    printer2 Poster Extraordinaire

    Posts:
    7,180
    Joined:
    May 24, 2010
    Location:
    Canada
    I take it the remaining copper will be a ground plane. Lot of capacitance to ground there.
     
  20. Che_Guitarra

    Che_Guitarra Tele-Holic

    Posts:
    648
    Joined:
    Mar 23, 2012
    Location:
    Perth, Australia
    That's right. The board will be facing copper side down, mounted on six metal standoffs. The whole board will go to ground, unless isolated via trace.

    Will it work? I don't know. I can't see why not. I guess we'll soon find out :)
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.