Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: blindopher on November 12, 2016, 02:45:36 am
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I'm interested in building an AC 15 a la sluckey's design. How would an OT with 6K primary figure out, (i was thinking about using one) knowing the effective load impedance for a pair of EL84s is 8K? I notice quite a few trannys on the market advertized as AC15 compliant have a considerably lower primary impedance than 8k. What tonal implications would be involved? In addition, is it safe to use a tranny rated for 15w? Thanx.
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Classic tone's OT for an AC15 is a 6K primary. Output transformers in the early Vox's changed a couple of times. I used an 8k multi-tap on mine, but I am also dead on with my voltages compared to the original schematic of the early 60's ac15.
The amp does not have a lot of headroom, but will have quite a bit more if you run plate voltages around 350vdc. It is a great amp and quite an undertaking due to the parts count.
If you already have the OT that is rated at 15 watts it will not hurt anything to find out. Sometimes mismatch makes for pleasing results. For instance, I really like a 6K primary on a 6L6 cathode bias like in the old Tweed Pro. It gives the 6l6 a sound that is raw on the attack, but has a very nice bloom I do not hear with a 4K primary.
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:worthy1:thanks