I did a fair amount of tube rolling, with both the AU7 and AX7. I started with new production EH 12AU7-they are ok, are dependable, and very quiet. The Genalex ECC82 is terrific for modern production tubes--good dynamics, resolution across the sound spectrum, are rugged, and again no microphonics. Tung-Sol 12AU7/6189 sounds terrific and have low microphonics. If you find NOS Mullard 12AU7 you will get a tube with the Mullard house sound--great creamy mids, a tad rolled-off at the higher ends. The new Mullard 12AU7 are Russian production and are detailed, low distortion and terrific for their price. FWIW, my F-I-L also had sets of G73R because he was an electrical engineer for Hewlett-Packard, back in the day. That’s how I acquired them.
Before selling the Cayin (which was paired with a 2005-era Jolida JD100 CD player-GE5751’s sound GREAT in it), I started rolling 12AU7 variants because my father-in-law was a ham radio enthusiast, and had a cabinet full. The Sylvania 6189W is a AU7 variant and I liked it very much--clear resolution, good top and bottom end. Raytheon 5814 is good, for the same reasons as the Sylvania 6189W. The AU7 variant I liked the most is the CBS/Hytron 5814a. It is detailed with great dynamics and low distortion. Ironically, with the rolling I did I did’t try the Amperex 7316.
Since the G73R are Telefunken’s, from experience I think Telefunken made awesome signal tubes across the board. As time has passed, they have gotten expensive. Sure enough, I looked up the pricing and Tube Depot listed them at $500 a piece.
Hope this is helpful!
What audio equipment do you have that has 12AU7s?
David