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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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Vintage Asylum Classic gear from yesteryear; vintage audio standing the test of time. |
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In Reply to: RE: It's not about the circuit boards..... posted by Audio Mind on February 19, 2015 at 10:13:45:
IMHO, all things equal:
1) I'd rather have a choke input power supply with a tube rectifier.
2) I'd rather have a LTP splitter, then a split-load, and lastly a paraphase. If you can't tell from looking at a schematic it would help you to learn that skill.
3) Direct coupling, when done in a safe manner, is to be preferred.
4) For most output tubes, I'd lean towards ultra-linear or triode over pentode/tetrode.
5) I'm not a fan of high mu (gain), low current tubes like a 12AX7 (12au7/12bh7/12at7 aren't that much better). Much rather have an amp that used a 6sn7.
6) It all starts with great output transformers, then a good power transformer and choke. All the rest is easily/cheaply changed.
"If" you could find an Acrosound 20-20 for sale I'm not sure you could stomach the asking price. I couldn't and wouldn't. The pilot used to be a sleeper. Sherwoods have a cleaner/less tubey sound that I perfer but need a "lot" of part replacements and are hard to work on due to cramped chassis. Fisher typically has some of the best resistors and caps of all the vintage amps....nice euro (usually german) resistors/caps/tubes.
The biggest lesson I have learned in my journey! Great amp designs are usually great because of the nifty feedback circuits (and these circuit values are very dependent on parts, parts that can't be bought anymore, so are hard to duplicate without knowledge and test equipment). These feedback circuits reduce output impedance and increase damping factor. That allows the amps to cope with difficult speaker loads.
Moral of the story? Obtain speakers that have a constant impedance, are upwards/over 100dB per watt, and use an electronic crossover with solid state amps for the bass under 125 hertz. If you do that, then you don't need one of those great high power tube circuit amps. In fact you can get by very nicely with a zero feedback, simple, low powered amp. Those are really easy to build yourself. The approach also open the doors to otherwise unsuitable tubes, such as most of the directly heated triodes.
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Follow Ups
- RE: And know you understand the "personal" comment - Russ57 14:33:29 02/19/15 (3)
- RE: And know you understand the "personal" comment - Audio Mind 18:24:07 02/19/15 (2)
- RE: And know you understand the "personal" comment - Russ57 19:03:16 02/19/15 (1)
- RE: And know you understand the "personal" comment - Audio Mind 21:51:28 02/19/15 (0)
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