Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: SupLar on November 18, 2017, 09:17:00 am
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Hello!
I have acquired this set of Classic Tone/Magnetic Components transformers and I am wondering if they will be a good fit for a 6V6 Plexi project.
PT
40-18089
312.5-0-312.5
6.3V @ 5A
5V @ 3A
OT
40-18039
8K/45 watts
Choke
40-18032
5 Hy
Wondering if I should try 6V6s with the 8K/45 watt OT or just go with KT66s (as recommended by Magnetic Components).
Thanks!
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Sounds like the right ballpark for 6V6s. For comparison, the full-power models using EL34 or KT66 appear to use 3.6k. You could try drawing loadlines but in reality guitar speakers are never the advertised impedance (usually higher for most frequencies) so there's guesswork involved anyways, and this sounds about right to me.
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Thank you 92Volts. Since so many PP 6V6 topologies have an OT in the 6.6 to 8K range I assume this OT will be compatible. 45 watts does seem like a lot of beef for two 6V6s...
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the OT is for a JTM45. it'll work but is physically nearly 2x larger than it needs to be. The PT is also a 50W class and you may end up with a bit more B+ than you want: i calculate around 425V. Hoffman's 18W set works best for the 6V6 plexi, so will the classisctone 18W set. suggest to use a EZ81 if you're going to use that PT, then B+ is in the 410V ballpark.
if they were mine: i'd consider building a convertible; e.g., i'd use a 5U4GB for the 6V6 -or- use a 5AR4/GZ34 for the EL34 with a switchable cathode bias resistor.
with a 5U4GB B+ is down around 400V with 6V6, with a NOS 5Y3GT B+ would be around 370V.
--pete
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Thanks Pete. Much appreciated! Let me know if you (or anyone else out there) has any other thoughts/ideas on the best use for this set of iron. I'm open to anything...
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The PT makes 440V DC; the 8K OT needs ~~500V of B+ to near its 45W rating.
This is FAR past what 6V6 is good for. *Maybe* a quad of 6V6 selected for high voltage tolerance; some will some won't be happy working hard at 440V.
KT66, 6L6, EL34 are the obvious choices. You will get over 30 Watts with this iron.
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Thank you very much for chiming in. Much appreciated!
I wonder if a 50 watt version of Steve Luckey's AC-15 is worth considering?
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Pompeiisneaks built an AC-30.4 which is identical to my AC-15 except it has four EL84 output tubes. The board layout is also the same except it was lengthened a bit to accommodate the few extra components. Maybe he'll chime in and give you some feedback.
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Sounds good. Thanks! After reading what Ed C has said about your AC-15 it really makes me want to give that one a go.