|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
69.141.96.215
In Reply to: RE: Looking for 12AU7 with "classic" tube sound, a.k.a. Mullard sound. posted by Opus 33 1/3 on February 06, 2016 at 08:50:53
Talk to Jim McShane about the latest New Sensor offering(s).
JMO, the makers of commercial tubed electronics need to stop "counting beans" and provide sufficient filament current to support 6FQ7s and/or 12BH7s, both of which are in production and beat the living guano out of any 12AU7/ECC82 ever made.
The 12AU7 contains triodes with serious linearity issues. The only HIFI jobs the type is at all suited to is cathode follower and "concertina" phase splitter. In those cases, degeneration (AKA local current NFB) circumvents the linearity problem.
Eli D.
Follow Ups:
But why would you bother with anything else?
low impedance goes with lo mu valves, because hi mu/hi impedance ones can't conduct current
Low impedance = big current.
The 12AU7 is fine if you use it for what it's for.
Btw you forgot one more important use for those so called "non linear" lo mu triodes.
Cascode stages, where in effect you are recreating a pentode anyhow.
(Top grid connection is SAME as screen grid, bottom grid connection is G1.)
Do you mean "Cathode" ~? As in autobiasing or cathode biasing?
RavenDave
Opus 33 1/3
Most modern gear does not have that 'classic' sound. An exception may be the Gold Lion Russian, which reportedly has a warm presentation. Failing that one perhaps the strategy could be the following
See if you can borrow/acquire some well used early, Mullards made at Blackburn, with long plates.In any event don't pay much for them. Get them from a friend or a tube vendor you truly trust. Check and see if that gives you the sound you want.
+,
Bland you may find
I agree that the 12BH7 and in particular the 6CG7 are better tubes, but if you use either of these tubes in a high sensitivity circuit you are going to have problems with microphonics. At least this will be the case with old stock tubes in these families.
I replaced the three small signal 12AX7s (used for gain and as phase splitters !!!!) in both of my LEAK Stereo 20s - with one input 6DJ8, and two NOS AWA / AWV 6CG7s with a FET CCS in LTP mode.
There's no sign of the slight microphony they had before.
Australia stopped making valves a long time ago.
And, of course both amps have lower total NFB than before.
As the LEAKs are close to the speakers they bi-amp, microphony was likely.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Low microphonics is 1 of the places reliable dealers, like Jim McShane, earn their money. Pay the man his money and get as advertised goods.
The common cathode gain behavior of the 12AU7, 12BH7, and 6FQ7/6CG7 is, for all practical purposes, the same. The 'U7 draws 1/2 the heater current of the other types, which pleases "bean counters", but sacrifices linearity in the process.
Eli D.
I think Eli is on the right track when he mentioned New Sensor as a possible choice. I would narrow that to the Russian Gold Lion, which has a warmer sound than most. Failing that establish a good relationship with a tube vendor you trust. A good dealer will steer you away from junk and point you to really good NOS.
https://www.tubeworld.com/12au7.htm
Scroll down slightly to see a good review of the NOS 12au7 family of tubes. A similar review of 12ax7's can be found here also.
Hope this helps,
Robert
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: