Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: tubenit on April 12, 2025, 11:21:32 am

Title: Hammond AO-44 conversion
Post by: tubenit on April 12, 2025, 11:21:32 am

I bought a Hammond AO-44 with the hopes of using ECL84's which didn't work out.  So, I decided to make it a single ended amp similar to a Fender Champ but with a 5E3 tone stack. I was able to make this conversion fairly inexpensively in that I had a speaker, tubes, wood, grill cloth and many components left over from other projects.  Maybe $185-200 total?

It sounds great! Very happy with it. Despite the exceptionally crowded chassis,  it's almost dead quiet at idle. I'm thinking it's probably around 4-5 watts total?  I initially tried it with NFB, but like it better without ......... so it currently doesn't have NFB.

I didn't want to use 6GW8 tubes as they aren't manufactured anymore and they're expensive.

Instead I used a 12AV7 in V1 and Tung-Sol 6V6 and a JJ EZ81. 


With respect, Tubenit

Title: Re: Hammond AO-44 conversion
Post by: tubenit on April 12, 2025, 11:26:23 am

It's almost the same size cab as a VibroChamp.  I set it up so I can switch to a 10" speaker later IF I want to.  It has a Weber 8"  8ohm currently.  And the OT is a Champ replacement that allows 4 ohm or 8 ohm choice.


The cab top is spalted maple and there is some trim on the front spalted maple also.  The front panel is a scrap piece of black walnut that I book matched.


All and all, I'm pleased with it.   :icon_biggrin:     I will say the small chassis was a challenge to wire up, but any concerns about floor noise disappeared after turning it on and playing it a couple of hours.


With respect, Tubenit

Title: Re: Hammond AO-44 conversion
Post by: Latole on April 12, 2025, 12:39:27 pm

Nice job !

Title: Re: Hammond AO-44 conversion
Post by: Platefire on April 12, 2025, 02:57:15 pm

Sweet looking amp tubenit!!! Very nice work! You must of got it right the first go around. You didn't mention any tweaking other than the NFB.
I love my Champ also. Funny, it's the first amp I built and now seems to be my main amp I use now. I have done some tweaking over the years. Anyway Great Job :thumbsup:

Title: Re: Hammond AO-44 conversion
Post by: dogburn on April 12, 2025, 03:39:40 pm

Looks great! And it's nice when you can cobble something together with bits you have lying around.

With adding a tone control, wouldn't it be pretty close to a 5F2a Princeton?

Title: Re: Hammond AO-44 conversion
Post by: pullshocks on April 13, 2025, 01:58:24 pm

Tubenit, what power transformer did you use?

Title: Re: Hammond AO-44 conversion
Post by: tubenit on April 13, 2025, 03:03:51 pm

I used the Hammond AO-44 power trannie that came with it.


With respect, Tubenit

Title: Re: Hammond AO-44 conversion
Post by: tubenit on April 13, 2025, 05:37:14 pm

If anyone would like to hear how the amp sounds, I did a quick demo here:


Old R&B tune new amp build (https://el34world.com/Forum/index.php?topic=32665.0)


With respect, Tubenit