Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: MWaldorf on November 24, 2019, 09:51:16 pm

Title: Hammond AO-44 OT ohm range?
Post by: MWaldorf on November 24, 2019, 09:51:16 pm

I've got an AO-44 based guitar amp that I really enjoy.  I know these expect an 8 ohm load, but can the OT handle 4 ohms or 16 ohms?  I'd like to try some different cabinets, but I don't want to unintentionally kill the OT or the tubes.

Thanks, Mel

Title: Re: Hammond AO-44 OT ohm range?
Post by: sluckey on November 24, 2019, 10:23:15 pm

I've used mine with 4Ω cabs.

Title: Re: Hammond AO-44 OT ohm range?
Post by: MWaldorf on November 24, 2019, 10:57:32 pm

great, thanks Sluckey! 

Title: Re: Hammond AO-44 OT ohm range?
Post by: sluckey on November 24, 2019, 11:45:28 pm

That is a beefy OT, especially for 6GW8s. It's also used in the AO-43 with EL84s. And I used it in my 6V6Plexi.

Title: Re: Hammond AO-44 OT ohm range?
Post by: MWaldorf on November 25, 2019, 02:04:01 pm

Great, that's good to know.  A friend built the amp, basically putting a tweed Harvard pre-amp in front of the AO-44 power section.  I added a bass control and a cathode bypass cap switch on the second gain stage, and removed both the negative feedback and conjunctive filter, and also added a solid state three knob reverb and a tremolo in front of it.  I've currently got it running through 2 10" 16 ohm Celestion golds, but I got a deal on a cab loaded with 2 x 12" 8 ohm Celestion blues. 

Thanks again, Mel