The comments have been interesting. I don't think that really high transconductance pentodes are needed. Just running the 6AU6s with more current would pep them up quite a bit. I have 6AW8s, 6U8s, 6BL8s, and some really high transconductance triode-pentode combos like the 6LQ8 that could be used. I'm interested in the pentode-pentode output stage, but have other plans for the input, most likely involving a pinch or two of sand. This project would take a distant back seat to a bunch of others farther along the pike.
Anyway, I saw the schematic, though it was a bit unusual, and plonked it down here for comment and dissection. If another interesting design comes out of it, all the better.
Anyway, I saw the schematic, though it was a bit unusual, and plonked it down here for comment and dissection. If another interesting design comes out of it, all the better.
I agree, 6AU6s will be plenty for driving typical pentodes - gm is fairly high, and they are nicely linear. In most cases, more than 9000 gm will be hard to manage, unless you run a very low screen voltage, or are willing to waste 10W on the driver plates
Hi Miles,
Luckily, ears and oscilloscopes do
Looks good on paper, will sound flat... breadboard it.
Since we're talking different bottles now, the 6JW8 is a good one too!
Cheers!
Luckily, ears and oscilloscopes do
Looks good on paper, will sound flat... breadboard it.
Since we're talking different bottles now, the 6JW8 is a good one too!
Cheers!
hey-Hey!!!,
This is the circuit used by the RCA SP10 and SP20. So far the '20 is the best sounding commercial amp I've wrapped my ears around so far. I've got about the same sorts of feelings about low current 6AU6 operation as the rest ov youse, and it is easy to address.
I don't particularly like the input stage; I'd rather use a LTP. Build it from a much better tube than the 12AU7 is a no-brainer. Paired 6S4P-EV for instance. The pentode stage would do well with EF184 or 6AC7 for instance...and run at much higher current.
This is the first post-ground up build/original design schematic I've considered. Modifying the circuit values to run the front end at wider BW/cleaner OP's is not quite so difficult...
cheers,
Douglas
This is the circuit used by the RCA SP10 and SP20. So far the '20 is the best sounding commercial amp I've wrapped my ears around so far. I've got about the same sorts of feelings about low current 6AU6 operation as the rest ov youse, and it is easy to address.
I don't particularly like the input stage; I'd rather use a LTP. Build it from a much better tube than the 12AU7 is a no-brainer. Paired 6S4P-EV for instance. The pentode stage would do well with EF184 or 6AC7 for instance...and run at much higher current.
This is the first post-ground up build/original design schematic I've considered. Modifying the circuit values to run the front end at wider BW/cleaner OP's is not quite so difficult...
cheers,
Douglas
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.