Help me convert a Hammond AO-43

Discussion in 'Shock Brother's DIY Amps' started by Salty_critters, Dec 4, 2019 at 12:18 AM.

  1. Salty_critters

    Salty_critters NEW MEMBER!

    Sep 16, 2018
    First time poster, long time lurker.
    I've got a minty fresh Hammond AO-43 chassis that I would like to turn into a guitar amp, and from what I've been reading this is a fairly straightforward matter, if you have sufficient competency with an iron and some know-how when it comes to tube amp design.

    I've got lots of ideas as to the layout of the pre and power amp. I've been turned on to 6HB6 power pentodes recently (EL84 subs, different pinout) and I would like to experiment with a few NOS 6BL8 pentode-triode tubes I've got laying around.

    But the first thing I need are specs! Specifically PT and OT impedances, voltages, etc. I have found only a handful of online threads pertaining to AO-43 conversions and none of them seem to use the same tranny's that I have. From what I've read, the power transformer produces a higher B+ than most EL84's would care to see. If I want to stick to 9-pin, noval base power tubes do I have any other options?

    I'll post pics so that you can see the transformer serials #'s (threw the choke in there too). I know there is an AO-43 schematic floating around online but it wasn't copied well and is rather difficult to read, from what I've seen.

    Feel free to chime in!

    Attached Files:

  2. RollingBender

    RollingBender Tele-Afflicted Vendor Member

    May 14, 2011
    SW Minnesota
    Earlier this year I did an AO-43 organ donor build. I made a Matchless Spitfire clone. Some of the specs you seek can be found in the build thread.’s-house.927191/

    One word of advice from one who has done quite a few builds from organ amps.... pretty much iron, tubes, and sockets are the only parts worth your time. Modding organ amps to make a guitar amp typically yields a less than stellar performer. Using the above mentioned parts to construct a proven guitar amp is a very satisfying thing indeed.
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.