2019 #6 amp build - 6AQ5 P/P

Discussion in 'Shock Brother's DIY Amps' started by RollingBender, Sep 28, 2019.

  1. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    Time to build another amp. I’ve gone round and round on what to build and after a few false starts, I finally settled on this odd mixture.... a Carmen Ghia front end and a 6AQ5 power section, long tail pair phase inverter and cathode biased.

    Chassis starts as a section of 2” x 4”, 1/8” wall rectangular aluminum tubing.
    51B3B11F-1756-4264-9E43-E8A172D6640A.jpeg

    End caps are made from solid aluminum and are machined to fit into the ends of the tubing.
    AA09832A-1383-46CB-A80E-57232FE4B790.jpeg

    The ends are installed and then the tubing is machined top, bottom, front, and rear.
    03F44557-B897-4B9B-A7F4-F459E73A3B4A.jpeg E9B83554-100B-4A97-AEF3-83EE5018DDB0.jpeg

    Then I fill in the engraving with black paint, let it dry, then sand the whole thing with a random orbital sander and 220 grit paper. Clean it all off and give it a coat of satin clear.

    5B5C5A90-3FBA-4E68-B7BC-B8EA2E56E7DF.jpeg

    While the chassis cures, drill the board and install the turrets.
    C7DBCC56-ED13-4805-8D68-E16BBD7B77EF.jpeg

    ....and then solder on a bunch of passive electronic components.
    A01B2920-FD9D-4BDC-B328-29BA5244BE8C.jpeg

    It’s a tight fit!

    This build is actually a bit of experiment in packing 10 pounds of stuff into a 7 pound bag. If it works out, I hope to do another build with a similar circuit packed into half of the total space.
     
    Wally and jsnwhite619 like this.
  2. jsnwhite619

    jsnwhite619 Friend of Leo's

    Age:
    35
    Posts:
    2,521
    Joined:
    Sep 10, 2013
    Location:
    Georgia
    Nice! Love the chassis work!

    Sent from my moto g(6) using Tapatalk
     
  3. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    Definitely a very tight fit!!!
    D702A26A-1DBA-403F-9FE1-908A3D46D4C3.jpeg 4FE79247-95A6-4337-A657-6279686327A0.jpeg 543E0141-8D60-471A-9505-C91D7875B0D9.jpeg
     
  4. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    Got it all stuffed in and wired up only to discover that my PT is smoked. New PT on order, scheduled to arrive on Thursday. I opted to jump it up a notch and ordered a Hammond 269BX which has secondary voltage more appropriate to the 6AQ5 tubes and it has the same footprint as the 269AX that is on there right now.
    E33FE8E3-5C59-4B02-ACEE-67F5DEB4C264.jpeg
     
  5. magic smoke

    magic smoke Tele-Meister

    Posts:
    287
    Joined:
    May 28, 2017
    Location:
    Quantum Entanglement
    What smoked the power transformer?
     
  6. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    ...my lack of understanding of solid state rectification probably. I may have done something when I was bench testing diode and filter cap combinations.
    Lesson learned...thankfully it isn’t too expensive of transformer.
     
    magic smoke likes this.
  7. magic smoke

    magic smoke Tele-Meister

    Posts:
    287
    Joined:
    May 28, 2017
    Location:
    Quantum Entanglement
    Beautiful work, thanks for the process shots!
     
  8. Diverted

    Diverted Tele-Meister

    Age:
    49
    Posts:
    299
    Joined:
    Nov 11, 2016
    Location:
    Bristol RI
    Bummer on the transformer. But a really cool build!
     
  9. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    While I wait for the big brown truck to arrive, I decided I might as well keep things moving forward by filling my shop with sawdust and wood shavings. Ended up with this...
    B0290413-22F2-430B-AEF2-4BFFB704219D.jpeg
     
  10. BigDaddy23

    BigDaddy23 Tele-Meister

    Age:
    45
    Posts:
    274
    Joined:
    Jan 4, 2019
    Location:
    Australia
    Great stuff! I love the chassis you build.

    What is the circuit based on? SS rectified by the looks
     
  11. avspecialist

    avspecialist TDPRI Member

    Age:
    65
    Posts:
    52
    Joined:
    Sep 18, 2019
    Location:
    avon,ct
    I HAVE TO SAY THIS IS THE NICEST FULLY SCRATCH BUILT PROJECT INHAVE EVER SEEN, I WISH I WAS THAT GOOD.
     
  12. corliss1

    corliss1 Friend of Leo's

    Posts:
    3,493
    Joined:
    Sep 13, 2008
    Location:
    Lansing, MI
    You should leave more room between the cathode resistor and bypass cap. Much like old champs, that resistor will cook the cap over time.
     
  13. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    New transformer arrived a day early!!!

    All wired up, start up procedure complete....an amp is born. Doesn’t sound like anything I have built or played but it sounds really nice so far. I need to check the bias and such. The tone control is very unique. It’s almost like sweeping a wah pedal and it works opposite of normal (that’s how the Carmen Ghias operate). I may go in and rewire the pot “backwards” just because of that oddity.

    586F295D-F0CD-4BE8-9832-5DD2930FF2FC.jpeg
     
  14. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    I’ve been “field dressing” leather couches and chairs for a couple years...the ones which are thrown out on the curb during city wide clean up days each spring. The great thing about couch hides is they are already tanned and dyed.

    I took one of the smaller strips and covered the head cabinet. This is the first attempt at using leather to cover a cab and I must say that it is wonderful to work with. I have some details to attend to yet...a bit more glue in a couple corners and dab a bit of matching color shoe polish here and there and it should look pretty good.

    68024843-E42F-472F-942D-A4E806730C03.jpeg

    I did some experiments with adhesives a while back and found ordinary Titebond to be the best choice. It holds pretty quickly but gives enough time to move things around so it all fits nice.

    Best of all, if it starts looking ratty I can take it to the guy at the airport for a fresh shine!!!

    I will make the front panel from plywood and cover it with a cream color leather from a different couch.
     
    King Fan, Prophetsnake and Snfoilhat like this.
  15. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    Every head deserves its own cabinet. This will be a sealed back single 10” speaker.

    16E9218D-9634-4C01-8635-C3D5C1372A79.jpeg

    I have 4 choices of recycled organ grill cloth to use. Which one do you like best? (Far left is the burgundy colored leather which will cover the cab. Far right is the cream colored leather that will be the head’s faceplate).

    DD37652A-484A-45AA-BA50-2945F517DAD1.jpeg
     
  16. monkeybanana

    monkeybanana Tele-Meister

    Posts:
    265
    Joined:
    Aug 6, 2016
    Location:
    mmhmm
    Wow, what a pro. Never seen Olson capacitors before. Will have to Google.

    Hope you record it for us!
     
  17. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    Front panel on the head cut, covered and installed and progress on the speaker cabinet.

    CD20418E-5997-4F27-8DCF-A7CB63D219B3.jpeg

    I went through my stash of 10” speakers and this one sounded the best. From it’s reported history, it is theoretically a 16 ohm speaker. I think it’s a CTS and those should be 8 ohm. It meters at 23 ohms. Shouldn’t an 8 ohm speaker read 6 or 7 and a 16 ohm speaker read 12-14 ohms on the meter?

    DCB8076A-224B-4850-AECC-5266994E19C3.jpeg
     
    Last edited: Oct 8, 2019
    jimytheassassin and Edvin like this.
  18. jonrpick

    jonrpick Friend of Leo's

    Posts:
    2,246
    Joined:
    Mar 17, 2014
    Location:
    Marietta, GA
    It's probably a 32-ohm speaker... They used 4 of those in the Bassman 10.
     
    David Barnett likes this.
  19. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    This is why I love this forum....you learn stuff! Probably should dig a little deeper in the speaker stash.
     
    jonrpick and Junior Little like this.
  20. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    Posts:
    1,047
    Joined:
    May 14, 2011
    Location:
    SW Minnesota
    Got the cab covered and grill cloth installed.
    A4BD5CDA-5B12-4BCC-87FB-C30062F0373B.jpeg

    9F2BE2E9-F6EB-44B1-8557-0E06512FAFE9.jpeg

    Just need to figure out what I want to do for the speaker jack, cover the back panel of the cab and figure out some sort of handles that will match the rest of the build. (and either find a way to get that little stain off the grill cloth or tear it off and install a new piece)

    I also ordered an Eminence RF10C to go in the cab. Currently I have a gold Celestion which sound OK but I would like to squeeze as much SPL out of this as I can.
     
    Edvin likes 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.