Seems like I’m doing this backwards...

Discussion in 'Shock Brother's DIY Amps' started by RollingBender, Mar 29, 2020.

  1. RollingBender

    RollingBender Tele-Afflicted

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    My typical order of build for an amp that isn’t a reproduction of an existing amp is to build the board, make a chassis that will fit the board and all the parts and then build a cabinet around the chassis and speaker.

    This current build is working it the other way. I have some rough design and circuit criteria but the driving force is to make it fit into a specific sized cabinet. Here’s the box...
    4F50A933-4F1C-4550-BEA5-8922B339DAF4.jpeg
    775ECA79-5CB8-4553-B1A7-DB662848CAC4.jpeg
     
  2. Dismalhead

    Dismalhead Poster Extraordinaire

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    Nice cabinet.

    What hast thou planned to put in thy box?
     
  3. jsnwhite619

    jsnwhite619 Friend of Leo's

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    Nice job on the fascia boards!
     
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  4. RollingBender

    RollingBender Tele-Afflicted

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    Oops...I forgot one more step backwards. The 1st goal is to make it fit in a carry on suitcase.
    7B08EA02-8C30-455A-849C-978C6CF543E1.jpeg

    Not quite sure what to call the circuit. It’s mostly AB763 but, to keep the tube count low, I’m using a 1-tube reverb circuit, a 1/2 tube term circuit (blackface Princeton), LTP phase inverter, EL84 power tubes and doing the bias tap like the Princeton also and an EZ81 rectifier. The speaker is a 10” Eminence Ramrod.
     
  5. ArcticWhite

    ArcticWhite Tele-Holic

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    Ha! Love this picture of the cab in the suitcase.
    And since you've already placed your speaker in the baffle, you need to design your chassis and tube layout around that!
     
  6. Badside

    Badside Tele-Meister

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    I also always start with the "amp" first then the cabinet, then realize that glue needs time to cure and I should have started the cabinet earlier (work on the amp while glue cures)
     
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  7. tah1962

    tah1962 Friend of Leo's

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    Have amp, will travel. Very :cool:
     
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  8. RollingBender

    RollingBender Tele-Afflicted

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    Idiopathic Pinus Radiata fracture!!!
    0707DA33-50E3-43B5-B4C2-DADA970E58CC.jpeg
    Guess I will be adding the dowels to this one after all. I have the chassis designed to have 4 mounting screws....2 in the top like the tweeds have and one in from each side to prevent this sort of catastrophe.
     
  9. Lowerleftcoast

    Lowerleftcoast Tele-Holic

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    I hate it when that happens!:mad:
     
  10. Commodore 64

    Commodore 64 Friend of Leo's

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    I'm very interested in this build, as I am looking to rebuild a Epiphone Comet with damned near the same circuit as you describe. Can you post the schematic or layout you are working on? I'd be happy to review (if needed), but it would also be a great jumping off point for me, as well.

    I've got an Emi Copperhead, for mine.
     
  11. RollingBender

    RollingBender Tele-Afflicted

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    As to the schematic/layout, I’m still working on that trying to make it fit. I’m taking the schematic for a Hoffman single channel AB763 and replacing his reverb circuit with the 1-tube reverb and replacing his trem and bias circuit with that of a Princeton Reverb.
    V1= first gain stage, EQ,
    V2= reverb
    V3= second gain stage, trem
    V4= LTP phase inverter
    V5/6= power tubes
    V7= rectifier
     
  12. schmee

    schmee Doctor of Teleocity Silver Supporter

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    For me:
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  13. Commodore 64

    Commodore 64 Friend of Leo's

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    I think I'll go with cathodyne to free up another triode. Maybe.
     
  14. RollingBender

    RollingBender Tele-Afflicted

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    I went with the 1-tube reverb to free up that extra triode for the LTP phase inverter because I want to get into the realm of AB763 rather than blackface Princeton (I already have one of those). Looking for a bit more clean headroom and SPL.
     
  15. RollingBender

    RollingBender Tele-Afflicted

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    Got the baffle completed and grille cloth on. The cloth came from a 1963 Baldwin organ. I’ve used the recycled organ speaker cloth on 4 other builds and I am always pleased with the look. But usually I just hit the cloth with an air hose to get the 50+ years of dust off and then staple it on. This time I actually washed it (by hand) and was disgusted by the amount of ick that came out of it. The gold thread really “pops” now. Sometime down the road I’ll take some more outside, sunny shots to really show this.
    E01E7D28-D3B8-492A-86C8-C1B124842A88.jpeg
    I mounted the speaker and plugged it into my blackface Princeton Reverb. Even with this Eminence, which is supposed to be “British” voiced, it still sounded like a Princeton.
    8BD02701-A1A7-4C1E-AF46-D190C29E73AE.jpeg

    I’m still working on making all the parts fit on the layout but I know where all the iron will be mounted (not a whole lot of choice) so I taped the PT and OT to the chassis blank and held everything in place and confirmed fit (clearance) between the OT and the speaker. Success!!!
     
  16. RollingBender

    RollingBender Tele-Afflicted

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    Right now, I’m not feeling a bit sorry for the crybabies who say there is so little room to work in a tweed chassis. Here’s my chassis blank with the iron sitting where it will be going along with the tube compliment and the board mock-up. 5E3 chassis beside it for size reference.
    360EF973-1CAA-414F-9AAC-D027F5C06476.jpeg
    a couple more times through comparing schematics to my layout and I should be carving the chassis and making the board this weekend. No mother-in-law visit this holiday to mess with my shop time!!!!
     
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  17. RollingBender

    RollingBender Tele-Afflicted

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    I don’t think this will buff out....
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    Bad things can happen very fast with a CNC machine. The machine does what you tell it to do even if you tell it to do bad things. I forgot to reset the tool height.
    1D7DCDA9-68C7-4240-87C0-FB9846802FED.jpeg

    I’ll pull the end caps out and start over with a new piece of tubing.
     
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  18. tubeswell

    tubeswell Friend of Leo's

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    Yep - might be too much to buff out
     
  19. RollingBender

    RollingBender Tele-Afflicted

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    Yea...it buffed right out...
    55CE3E50-0297-45AC-9CBA-5CC4565D944F.jpeg E1FCF4DF-5E24-4758-AB75-5A07C88938B8.jpeg 5D3A0846-206B-493A-91B3-F8DA2136C55B.jpeg 836B68DB-F6C4-4C69-979B-1F9F5A20E2DC.jpeg
     
  20. tubeswell

    tubeswell Friend of Leo's

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    Very tidy
     
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