12AT7 tubes

As an alternative to the expensive telefunken tubes, you can try the Siemens 12at7, I liked them when I use to have an AVA preamp.

There is no need to stay with the JJs. I have a bunch of 12AT7s except the truly expensive and rare they all have their own sound, Start rolling.

I'm not all that familiar with 12AT7 types, but one not previously mentioned is the Sylvania Gold Brand 6201. I use a pair of these in my Lector CDP 0.6T and they work very well for that application although I've not made any comparisons between Sylvanias and other types. Worth looking into.

I am using Sylvania Gold Brand 6201 in the phono section of my VTL TL 5.5 with excellent results. I also tried Mullard CV4024 with very good results. I currently use the Mullards in my VTL ST150. Between the these two tubes I liked the Sylvania just a little better. The Sylvaias have a more pronounced but at the same time better controlled bass than the Mullards. Other than that I like them equally well.
Both were much better than the stock tubes.

Cheers,
Jim

Easytune: You wrote that you need to replace "one tube" in the phonostage. Do you mean by that literally a single tube? I mention this only because most phonostage circuits use L/R pairs of matched tubes, and you wouldn't replace one without replacing the pair with the same choice, tested and matched for gain. As for your question about the Mullards, the wisdom I've received is that in general, the earlier you go in manufacture date, the darker they will sound, whereas the Tele's are said to be pretty consistent throughout. I've tried versions of the Mullards, Teles, RCAs and Sylvanias, and they all sound different, but my best advice to you, with a phonostage (where quietness is at an absolute premium), is to make sure you're dealing with someone who can really test and vouch for his tubes' freedom from incipient noise and microphony issues, and will stand behind them if an audible problem develops within a reasonable period of time.