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Hoffman Amps Forum image Author Topic: Hammond AO-44 OT ohm range?  (Read 1734 times)

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Offline MWaldorf

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Hammond AO-44 OT ohm range?
« 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

Offline sluckey

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Re: Hammond AO-44 OT ohm range?
« Reply #1 on: November 24, 2019, 10:23:15 pm »
I've used mine with 4Ω cabs.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline MWaldorf

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Re: Hammond AO-44 OT ohm range?
« Reply #2 on: November 24, 2019, 10:57:32 pm »
great, thanks Sluckey! 

Offline sluckey

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Re: Hammond AO-44 OT ohm range?
« Reply #3 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.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline MWaldorf

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Re: Hammond AO-44 OT ohm range?
« Reply #4 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

 


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