It's always puzzled me. This tube, which was introduced at the height of the Golden Age (1953) and was specifically designed for AF applications including first stage, somehow don't get no respect today. Nor does it seem to have been widely used in its day. Fender used it in later tweed models, but never in the PI, and I don't think it got a lot of use in hi-fi at the time either (could be wrong on that, it's not my main bag).
I know its mu is low by modern standards, but the 12AX7 preceded the 12AY7 by eight years (1945).
So, was it just a redundant design, too little too late, or what?
OTOH, it's recommended as a PI and SRPP by The Valve Wizard in the UK, one of the more useful sites I have run across. As a PI because you can run higher current than a 12AX7 for a bit more grind, as an SRPP because it gives big headroom.
If you run the numbers on it, it looks good in parallel as a linestage grounded cathode.
12AY7 -- The Rodney Dangerfield of 12A*7s
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David Root
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Re: 12AY7 -- The Rodney Dangerfield of 12A*7s
No arguments here. I built an amp for my nephew with a 5751, a 12ay7, and a 12at7 for the PI. It's a clean machine. With 12ax7's it's a bit too bright and the baseline hum & hiss is noticeably louder.
Re: 12AY7 -- The Rodney Dangerfield of 12A*7s
+1 valve wizard is great!
the couple of 12AY7 i tried were EH not bad but i prefer my NOS sylvania gold pin 5751 in PI ( and i bought the sylv. cheaper than the EH!)
may be a different story with NOS 12AY7...
in SRPP or CF don't forget the heater/cathode max voltage is a bit lower than 12ax7...90v IIRC
the couple of 12AY7 i tried were EH not bad but i prefer my NOS sylvania gold pin 5751 in PI ( and i bought the sylv. cheaper than the EH!)
may be a different story with NOS 12AY7...
in SRPP or CF don't forget the heater/cathode max voltage is a bit lower than 12ax7...90v IIRC
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David Root
- Posts: 3540
- Joined: Fri Aug 04, 2006 3:00 pm
- Location: Chilliwack BC
Re: 12AY7 -- The Rodney Dangerfield of 12A*7s
Good score on the Sylvania! I've run the numbers on 12AY7, 5751, 12AX7 and 12AT7 as PI, and if you run enough plate voltage they all look good in the classic 5F6A PI w/470 Rk and 10K tail w/5K to ground. Guess I'll have to try 'em all.
12AY7 is 90V heater to cathode, but the 6072 is 100V. Which reminds me, sort of off topic, but how come Marshall used 12AX7 cathode follower cathode voltages up to 220V? No elevated heaters either. Even the 5F6A cathode follower cathode runs 180V, for that matter.
12AY7 is 90V heater to cathode, but the 6072 is 100V. Which reminds me, sort of off topic, but how come Marshall used 12AX7 cathode follower cathode voltages up to 220V? No elevated heaters either. Even the 5F6A cathode follower cathode runs 180V, for that matter.
Re: 12AY7 -- The Rodney Dangerfield of 12A*7s
Why does Fender run 420V B+ on 6V6GTs?David Root wrote:Which reminds me, sort of off topic, but how come Marshall used 12AX7 cathode follower cathode voltages up to 220V? No elevated heaters either. Even the 5F6A cathode follower cathode runs 180V, for that matter.
Cause they tried it, and most of em didn't blow up, at least not right away.