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In Reply to: RE: The Holy Grail posted by FenderLover on August 09, 2016 at 07:09:12
That's interesting, I was thinking the 5U4s would produce the most PS sag and maybe the best tone. I didn't want to bias the question though by mentioning that. So... the guitar amp I'm planning to eventually build should probably be different than the prototype power stage I designed a few months back. As it stands, it's a very clean amp with EL34s and a stiff solid-state supply. Maybe I should add a 5V filament transformer and a pair of 5U4s. That would result in a much softer supply. This is totally contrary to amplifier design for hi-fi. Is it reasonable to simply copy the original 5E6A schematic as a first-time build? Will the EL34s degrade the tone? My OPT is low-Z, about 4K, so it matches those better than the 6L6 family.
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Buy Chinese. Bury freedom.
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FWIW, I think you will get closer to 6L6 sound by employing either KT77s or "fat bottle" 6CA7s. Those 2, like the 6L6, are beam power tetrodes, even if they are "electrically equivalent" to the true 3 grid pentode EL34.
Eli D.
Yeah, the dual 5U4GA was part of the incentive for Jim Marshall's early 40 watt EL34 and KT-66 amps. He decided on the GZ34 rectifier (as it was actually CHEAPER in UK, compared to imported 5U4G or -GBs).
Stiff PSU is ok. You just need to adapt to it, with playing style (pick attack, heaviness of pick, etc). The sustain is more dramatic with solid-state. But, tube rectifiers kinda have this "breathing" quality. Where you hear the notes fade and come back. Like a singer's voice, trying to hold a note.
For smaller gigs or just having fun with friends --- I find the tube rectified, 10-25 watt amp the best. One that you can crank up and get some nice overtones, without blowing yourself out the window. And causing the neighbors to call the cops.
A nice amp to model your DIY after might be the Matchless Chieftain. AWESOME amp! Plenty of juice when you need it. But, also good at lower volumes.
The big question is this: Do you like the tone of the Chieftan? It does have more features than the Bassman. I already have a reverb tank and driver transformer ready to go. Also, I have parts to build a true vibrato (like Magnatone) that could plug into the effects loop. On the other hand, I wouldn't want to sacrifice tone for either of those. With a little more work, those effects could be configured to plug in between the guitar and the amp.
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Buy Chinese. Bury freedom.
Edits: 08/09/16
I like the 12AY7 input, dual 5U4GA Bassman. Quite unique tone. Chieftain has a bit more modern tone. Maybe, due to Matchless use of Mills resistors in the circuit. And Jupiter style coupling caps.
Guess it depends out what product you are after. The coke bottle tube Fender tweeds have a unique tone, that is a big part of a lot of famous recordings. Hard to duplicate that tone with pedals and fingers.
I think those 1940-50s 6L6GA tubes are under-rated. Warmer mids than the later 6L6GC. Kinda mix of a good 6V6GT and 6L6GC.
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