Anyone here build a Hammond-based amp?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by mbratch, Feb 17, 2008.

  1. mbratch

    mbratch Member

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    I'm curious about the Hammond amps (e.g., AO-35). Anyone here used one to build a guitar amp? I'm interested in your experience with it.
     
  2. DC1

    DC1 Member

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    Many years ago, someone gave me a Hammond tube amp and 2 field-coil 12's. I have no idea what the model was. I built cabinets for the speakers, had an input jack installed, and used a EH LPB-1 booster to get the level up.

    Sounded pretty good actually. With a real preamp in front, it could be a nice guitar amp.

    DC
     
  3. RobBozic

    RobBozic Member

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    The DrZ 'Carmen Ghia' is supposedely a Hammond AO-35.
     
  4. Robal

    Robal Supporting Member

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    I had one of those, and yes it was built from a salvaged Hammond chassis, using the transformers. I like Dr. Z and his company, but I did not like that amp much so I sold it. There are better ways to get a 2xEL84 guitar amp, since these old Hammond transformers weren't meant for guitar applications.
     
  5. mbratch

    mbratch Member

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    I had heard (read) also that the Goodsell Super 17 is based upon a Hammond design.

    I was really looking to know if anyone had ventured into their own Hammond-based amp, and any experiences with it.
     
  6. jh45gun

    jh45gun Member

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    Your comments about the transformers confuse me as if thats the case then how about all the early amps that were built using transformers that were probably made for some other application or the amps that are made today by DIYers who take amp chassis out of Phono systems or old PA heads ect and make excellent amps out of them:confused::confused::confused: I would bet when Leo and the other early amp pioneers made their amps they used parts they could get from other sources.
     
  7. PRNDL

    PRNDL Member

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    I've built a whole bunch of amps from organ chassis.

    My first two amps are Larry Rodgers' Metro, which is a cross between a Matchless Spitfire and Vox AC15. I called it the Christene 16.
    http://www.naturdoctor.com/Chapters/Amps/Christine.html

    Old Hammond chassis are harder to find and more expensive these days, so I began to use anything that was available.

    The Retro V was built from a 6V6 mono amp
    http://www.naturdoctor.com/Chapters/Amps/RetroV.html

    The Octal Champ was a very old mono amp that used a 6F6 output tube
    http://www.naturdoctor.com/Chapters/Amps/OctalChamp.html

    My latest was restoring a very old Fanon amp, which turned out to be a nightmare, although it ended up with novel amp design - 1 watt from a SE 6AK6 (the Living Room Amp).
    http://www.naturdoctor.com/Chapters/Amps/Fanton.html

    The Living Room Amp is a masterpiece in both build (a tweed cabinet) and tone. This little amp gets fantastic rock sounds with incredible touch sensitivity. A TS-808 pushes it into a metal monster (no wonder musicians love that pedal!)
    http://www.naturdoctor.com/Chapters/Amps/LivingRoomAmp.html

    I now have way too many amps and put several for sale at a local music store. The Retro V was purchased by an Indy guitarist from Austin. He tried all of my amps and picked pretty much the best for his style of music.
     
  8. Lil'Strat

    Lil'Strat Member

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    I respectfully disagree...
    After 15 years of building custom Hammonds and accumulating a vast pile of AO-35, -39, and -44 chassis, I have staked a career on this concept. I had built about 25 Super 17s before I learned DrZ had also based his early Carmen Ghia on the AO-35; but regarding the suitability of the organ trannies - most of them were hooked up to Jensen P12N, P12Q, and various Rola and Oxford speakers that were OEM in many Fenders of the same vintage - and in some cases (ie. AO-44) the trannies were the same identical OTs found in the BFDR, which many folks feel is an ideal "guitar application". As far as the PT is concerned, the AO-35 has roughly 150% of what is required to power a 2xEL84 design, and can nearly drive a 4x version.

    I'm currently finishing a Limited Edition run of 25 AO-35 based 5/17 combos; there are two left and the first 23 sold in just under two weeks. They are among the nearly 500 amps I have in the street, roughly half of which have some form of Hammond iron on board. You still get a Hammond OT in my 4-ohms apps, and if it is a deal breaker I keep a few 8s around - but there are Schumacher and Heyboer versions being made right now - paper-wound in the US - that are the same as the originals and are available as OEM replacements in 6V6 Fender applications.

    Check out the sound clips at www.goodsellamps.com if there is any doubt that organ parts can be used for guitar applications.

    Richard Goodsell
     
  9. jaydawg76

    jaydawg76 Supporting Member

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    This is one of my builds. Its a clone of a famous ao-35 based amp. It lives in a pine cab with 2 10" alnico webers and sounds great. The ao-35 is a very simple amp and responds well to changes in speakers and tubes. Lots of tone in a small package.
    [​IMG]
    [​IMG]
     
  10. hasserl

    hasserl Member

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    What an interesting thread. Thank you for starting it, and thanks for the contributors. I was blithely ignorant of the Hammond AO-35 and that it influenced the Carmen Ghia and Goodsell amps. How cool to stumble on this thread this morning and read up on it.

    Richard, your amps sound fantastic (they look gorgeous as well, and those models, oh boy, very nice!). I did find a Hammond schematic out on the net, very interesting stuff. Similar to other 2 x EL84 amps, but with some unique twists. Anyway, thanks for sharing.
     
  11. Lil'Strat

    Lil'Strat Member

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    In broad, architectural strokes, the AO-35 makes a neat little compact amp - chassis, trannies, and tube holes line up perfectly, though it's pretty snug. We strip the '35s down to the bare metal, re-finish them in Rustoleum Hammertone, put the old trannies back in, and then everything else is new, different, or proprietary - including tube sockets and multi-section can cap. On the last batch of AO-35 amps I used Fender-style eyelet boards for the first time, which greatly improved layout and consistency across all 25 units.

    I used the same chassis on the original Clairmont Super 17. Serial no. 0001, now in the hands of Brendan O'Brien for the last three and a half years, still has the phenolic Hammond board and the original power caps installed.

    Thanks for your positive comments - if you want to PM me your address, I can send you a poster of the lovely and talented Tamra - she likes hearing from the public as well...
    RG
     
  12. Lil'Strat

    Lil'Strat Member

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    Nice work... I can look at the underside and almost hear it - It looks like it would sound great...

    RG
     
  13. guitardr

    guitardr Silver Supporting Member

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  14. JasonG

    JasonG Member

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    Very cool! Would you happen to have a schematic/diagram for this guy? I'm geared up for an AO-35 conversion as we speak. Would be greatly appreciated. Can't quite see everything from the pic. Thanks. Jason
     
  15. Cyg_1963

    Cyg_1963 Member

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    Very nice stuff Lil'Strat.
    I have a working AO88 including the reverb unit that I am thinking about...gutting.

    I like to use what is there, where I can.
    1959 Conn organ amp, all I did was throw a very basic T-V stack on it, and it sounds wonderful as is (like a 50 watt 5D2 Princeton):
    [​IMG]

    [​IMG]

    I was dead set on subbing out the Mallory canisters but many hours of running it and there is no hum, and they run cool.

    Also have a Baldwin I am puzzling over, would make a very good stereo power amp but I'm not really sure where to go with it:
    A close gut shot, it is 4 6L6GC's split...one side drives a HF transformer, the other a more normal 16 ohm, not sure of the primary yet.
    [​IMG]

    And another which I turned into a Spitfire combo, a Gulbransen 2xEL84, what a trick this one was.
    Sounds very good, and I have cleaned up that wiring since:

    [​IMG]

    All in all if you do the research some of these old donors can make great amps.

    But PLEASE don't destroy quality vintage organs just to hack them either.

    :D
     
  16. LowellH

    LowellH Member

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    Here are a couple before and after pics of a Hammond A0-47 (also 2xEL84) I converted into a little gainer a few years ago. It now resides in a Leslie Model 25 cab.
    [​IMG]
    [​IMG]
     
  17. Cyg_1963

    Cyg_1963 Member

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    Very nice!

    Looks like you added a fixed bias with an adjustment pot?

    I'm seeing how far I can get away with the simpler cathode biased setups as usually found on these amps.
     
  18. LowellH

    LowellH Member

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    Nope, cathode bias. The pot is part of mosfet voltage regulator circuit. I think I've got a clip of that amp, let me see if I can dig it up.
     

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