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

Please Chime in on my AC10 build

Discussion in 'Shock Brother's DIY Amps' started by mishagolin, Feb 9, 2015.

  1. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    So I'd like to build an AC10. It's an uncommon amp so I think it will be fun to build. However, uncommon amps rarely have a published layout. So unless someone has a better one I'm going to attempt to roll my own. Please chime in and let me know if you see any mistakes or improvements. I'll be running off of this schematic.

    http://prowessamplifiers.com/schematics/thumbs/VoxAC_10_2.gif
    [​IMG]
     

  2. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    At this point my layout looks like a rats best of wires but I'm not sure what to do. I'm hoping someone has a better layout.

    [​IMG]

    Board components look manageable but the wires are everywhere. I know there's only so much you can do with that.
     

  3. tresspassor

    tresspassor Tele-Meister

    Age:
    43
    279
    Jun 17, 2010
    Austin
    Very interesting build.

    Just at quick glance, I would recommend mounting the input grid stoppers directly at the tube inputs. Just mount a small tag board to the tube connector screws. The grid leaks can probably be attached directly to the input jacks as well. Something like this:
    http://ax84.com/media/ax84_m213.pdf
     

  4. Fred Mertz

    Fred Mertz Tele-Afflicted

    Nov 11, 2011
    Indiana
    I just received a copy of "A Service Engineer's Guide to the Vox AC30 Valve Amplifier" in the mail today. The book includes the schematic and the layout for the AC10, as well as component values. This book would be worthwhile in providing a proven existing layout for a starting point. I want to build a copy of the 1960 AC15 circuit, but will forego cloning the folded chassis. I envision using an 8" by 20" chassis from Watts, and unfolding the Vox layout for implementation in a standard style chassis.
     

  5. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    Fred, I was doing a bit more research yesterday and came across the same book. i ordered it last night. I'll see how long it takes to get here from the UK. I'm also looking at unfolding the chassis. I want to build this into a head cab. I'm going to fold my own chassis so i can do whatever dimensions i want. i think i'm going to go for a 9" wide chassis and then just choose a length based on my layout.

    this amp has a lot more parts than any of the others i've built (18 watt lite ii, 5f2a, 5c1), more tubes a choke, a trem circuit, more than 2 knobs. i'm really excited about it but i also want it to be my cleanest build.
     

  6. andyfromdenver

    andyfromdenver Friend of Leo's

    Dec 21, 2011
    grandpa's
    i want to get that book too.

    OP, best wishes with your build. huge!
     

  7. Dave1234

    Dave1234 Tele-Afflicted

    Age:
    54
    Mar 4, 2012
    Leicestershire

  8. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    so another question about the schematic. just trying to understand why Denney did some things.

    looking at the power supply filtering the +305v comes off a 16uf cap to the top of the schematic where it goes to pin 9 of the el84s and the CT of the OT. It goes from the primaries of the OT through a 100r plate resistor at each el84 but then also goes through a 22k dropping resistor (R27) before a final 8uf filter stage and the 100k plate resistors of the 12ax7 phase inverter.

    it looks like the 22k dropping resistor is parallel with the 22k dropping resistor in the PS section that supplies the EF86 and ECF82 with 255v. This one also has an 8uf filter cap.

    What are the benefits of running these in parallel? why not just run all of the 255v lines in one shot and leave the 305v at 305v? does this increase the PS filtering by running in parallel. it doesn't seem like this was done for layout purposes because the 12ax7 is mounted with the ef86 not with the el84s.
     

  9. Fred Mertz

    Fred Mertz Tele-Afflicted

    Nov 11, 2011
    Indiana
    The power supply rail is in the bottom left corner of the schematic. There are two B+ nodes in the power supply rail. The first node immediately after the choke is the B+ for the phase inverter and output tubes. The B+ from this node connects directly to the EL84 screen grids and the output transformer center tap. The B+ for the phase inverter flows through the 22K dropping resistor.

    The 100 ohm resistors are between the EL84 plates and the output transformer primary connections. My understanding is that the AC10 used the same power and output transformers as the AC15 and that these resistors are the only difference between the two output sections. The resistors are there to drop the power down to 10 watts.

    It took exactly 7 days to get my book. I ordered my copy on Sunday February 1. It left the UK Monday February 2 and I received it in Indiana on February 9..
     

  10. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    I understand the B+ at 305v going to the power tubes. What I don't understand is why they have the 22k dropping resistor going to the phase inverter when there is already a 22k dropping resistor going to the preamp section. Is it good practice to filter the phase inverter separately from the preamp or could you just run the phase inverter off the same 255v rail that supplies the preamp tubes.

    I'm only asking because I have to believe there is a reason why the vox method is better than a shared B+ between the preamp and phase inverter.
     

  11. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    Oh and thanks for the shipping info Fred
     

  12. Fred Mertz

    Fred Mertz Tele-Afflicted

    Nov 11, 2011
    Indiana
    The configuration does provide better separation in the B+ rail between the PI and the preamp sections. With the relatively low number and value of capacitors used, this is an efficient configuration to maximize filtration.
     

  13. R. Stratenstein

    R. Stratenstein Doctor of Teleocity

    Aug 3, 2010
    Loganville, Ga.
    As far as improved layout goes, what if you moved the PT and rectifier tube to the right side of the chassis, then swapped ends of the bottom board, so the tubes are closer to the points they connect to on the board? I think I'd run the wires under the board, or flip components (not the filter caps) end for end, so the leads for the tubes come off of the near side of the board.
     

  14. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    Thanks Fred. I figured the isolation improved filtration.

    Rick, thank you for the layout suggestion. I agree with moving the filter caps and rec to the other side of the board. I started just drawing it up as I went through the schematic so it needs some tweaking. I'm going to wait on the book to arrive before I put a drill to anything. Hopefully I learn something from the published layout.

    The old AC10 super reverb twin is interesting as well but I've heard the circuit is very much different. I don't believe there is an ecf82 in there. It's more 12ax7s. So a bit more like a top boost. I'm going to see how this build goes as is but I'll leave some room in the chassis in case I decide to top boost the normal channel later. I like the vibe channel how it is so not TB there.
     

  15. Dennis Perusse

    Dennis Perusse Tele-Meister

    157
    May 12, 2011
    Amesbury Mass
    I think that I'm probably the few people that love the folded chassis. That service book is one of the nicest books that I've owned on the Vox. You get a really good appreciation of how those amps are wired and yet a wonderful sense of awe how good it is to read a Fender schematic. :)
     

  16. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    Got my book yesterday!! Its beautiful.

    [​IMG]
     

  17. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    So, I redid the layout to more closely match the traditional layout except without the folded chassis. I did condense the board down a bit so that it would fit the eyelet blank i have while still fitting the filter caps on the board. Moved the grid resistors on the preamp tubes to the sockets and tag strips. I'm using a 5y3 rec instead of the EZ80 because i have one and the transformer i stole from the old record player has a 5v tap. Still a bit of messy wiring but i think it'll work fine. I tried to find tag strip components in the DIY Layout Creator but couldnt so i just thre in some single eyelet strips as place holders. The tag strips will take up less space in the actual build so thats fine.

    [​IMG]



    Next up. . . Chassis Bending. My layout fits nicely on 11x17 paper so i think a 9x17 chassis will work out great for a head cab.
     

  18. flyswatter

    flyswatter Friend of Leo's

    Jan 12, 2013
    Quebec
    I should get that book, too. I'm starting on a Vox-esque 30-watter based on the Ceriatone Trainwreck Liverpool layout (basically a Vox-style EL84 amp with simpler 5e3 style inputs and controls). It would be helpful to know what Vox does, and I'll also be following this thread for Mishagolin's tips.
     

  19. mishagolin

    mishagolin Tele-Meister

    143
    Aug 14, 2013
    Atlanta
    Didn't get the chance to bend a chassis today. Maybe tomorrow. But I did have a few minutes to throw the eyelets and turrets on my board.

    [​IMG]
     

  20. flyswatter

    flyswatter Friend of Leo's

    Jan 12, 2013
    Quebec
    Mish, I'm about to start this phase on my own build. So I'm curious why you use a combination of turrets and eyelets. Which components will go to which? Thanks.
     

IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.