Audio Research CA50 + tube rolling

7308/6922/6H23/E88CC/CV2492/E188CC are all just 6DJ8 variants, and direct replacements. No voltage adjustment should be necessary. Any paired tubes in any circuit should be balanced/matched, triode to triode and to one another in the case of his 6922's. Any responsible tube seller would have seen to that(like Kevin at Upscale), if the application was mentioned.

I had a CA50 and the ONLY thing that I really disliked about it was the fact that the voltage needed to be changed/adjusted whenever your swapped out the driver tubes. I would call AR back and ask to speak to someone more seasoned, they will be able confirm the procedure. Yes, you can just drop in new tubes w/o adjusting the voltage but it will not be optimized plus it will shorten the tube's life. The CA50 is not a friendly tube roller's amp. Also, AR uses the Sovtek because the circuit is tough on tubes and the Sovtek have a reputation for being rugged. I tried using NOS tubes but the amp ate them within 6 months (I never adjusted the voltage) and I did nit want to send the amp back to AR as they requested.

Testpilot, which NOS tubes did you try ?

I used 4 different tube sets.

Favorite - Amperex 7308 white label. Caveat, the amp eats up these tubes. I went through two sets in 8 months...no more.

Ediswan CV5358 - I liked these tube a lot. These tubes gave the amp some added jump. The highs are a tad rolled off, but that was okay since I was using the amp with CD only.

Valvo 6922 - nothing special in this amp. Did everything okay and they were durable.

Amperex Bugle Boy 6DJ8 - I settled on these tube because the amp and tubes got along. A touch of the magic of the Amperex 7308 and gave the amp some needed dynamics with a nice bottom end.

If you really like to roll tubes, these is not the best amp, but it is a keeper. I wish it wasn't so big, otherwise, I would have kept it for a second system.

I have owned my CA50 for the last 3 or so years and I am very happy with the amp. I currently use it full range driving fairly high efficiency speakers and a pair of add-on ribbon tweeters and the sound is very neutral.
You perhaps should have checked here or any of the other audio boards before getting upset as it is fairly common knowledge the CA 50 is not a good candidate for tube rolling.
I tried both JJ 6922's, Amperex Orange Globe and Bugle Boy 6DJ8's and it ate all in short order. The JJ's (which are nice warm sounding tubes in most amps) actually shorted and damaged the Amp while the Amperex's merely became noisy. This gets expensive in short order. Audio Research and Audible Illusions really stress the 6DJ8/6922's in their products and the Sovetek, Electro Harmonix and some versions of the NOS 6h23 (the 6h23EB I believe but you should check)are all that will last long term in the amp. See Jim McShanes website for his take on the subject. The EH69222's that ended up replacing the original Soveteks are not bad with a smoother less strident sound. I have heard that 7308's may work and I have some Valvo's and Tunsgrams I may try when I get brave (and perhaps foolish).
On the other hand the CA50 seems to tolerate different output tubes with just the normal re-biasing. Currently I am using the Tungsol 6550 Re-Issues with good results.