1985? Huh. Well for sure if there were 421a tubes being made in 1985, it wasn't Tung Sol making them, as Tung Sol was long gone by then. Cetron, who bought Tung Sol, continued to make some of Tung Sol's tubes like the 6336, sold under the Cetron name, for some time, maybe even as late as the 1980's. But not the 5998, I don't believe. So perhaps WE had to start making the 421a, and thus the slight design change.
Yup, I agree totally. I was just pointing out that exact thing...that we are using tubes for audio that were intended for other purposes. That does not mean they cannot be very good for audio - in fact, many are, as you point out. The 6AS7 is a good tube for driving headphones in an OTL design, as it just so happens
Hey, I think the 6AS7G can sound good in audio, but Glenn is right. The 6AS7 wasn't designed as an audio tube, plain and simple. Read the data sheet.http://www.nj7p.org/Tubes/SQL/Tube_query.php?Type=6as7g'Glass octal type used as a regulator tube in dc power supply units and in projection television booster scanning applications.' (Source ........................................ RCA DS 05/01/55)
Right. I wouldn't expect most old, unrestored, cheap Craigslist units to sound all that good either. Restoration is required to make vintage gear sound as good as it can/should. But I wouldn't call a lot of what goes into modern gear "improvements". My vintage gear use discrete components in many places where most modern gear would use an IC. Sure, maybe a decent one, in some cases, but certainly no guarantee it's going to produce better sound in any way.
I have a...
Neither of my Pioneer receives have that issue. Nor are their preamps sections noisy. But both of mine were fully recapped and they did have the transistors in the preamp (and phono and tone amp) upgraded.
If your second question was also directed to me, I'm sorry but I can't answer. I've never heard one of these strapped 6BL7 configs. I will say that the 6BL7 is a very good sounding tube but I have only every heard it used one tube per channel in the more conventional manner. I do think the Sylvania 6BL7 was a little better sounding than the Sylvania 6AS7 in an amp I had years ago that was able to use both optimally. But when one tries to use one kind of tube in an amp...
That's correct. There is no one currently manufacturing any flavor of the 6AS7G.
That said, it's hardly relevant for the small number of tubes that the current audio business requires, versus the mountains of Russian and Chinese NOS military tube stockpiles there are. One can still easily buy 100 tube cases of the very nice Russian 6H13C. 25 piece boxes run $150.
For the record - the 6AS7 is not still being manufactured. Don't confuse the mountains of Russian and Chinese military equivalents of this tube for new production. They aren't. There may be an essentially limitless supply from the perspective of audio needs, but no one is currently making the tube, at least at this juncture.