I have owned 3 VAC 30/30's over the years, and have just upgraded again to the newest VAC Phi 30/30 which I am extremely happy with. I have stuck with the original 300B's for outputs, but have done much rolling with the 6sn7's in different positions. VAC runs all of the 6sn7's pretty hot in these amps, and they are 6sn7GTB's, which are designed to take the extra voltage. The driver 6sn7's are run with the most voltage, and the input tubes are run with a bit less, but still more than most non GTB tubes are designed for. That being said, you are better to run the GTB type as drivers. I have tried NOS Sylvania (1950's era) 6sn7 GTB's in the driver positions as well as the input positions. They will give you a tighter, stronger bass for sure, and a more forward, brighter presentation in the highs, sacrificing some "air" to the soundstage and making the amp less "lush" sounding. The highs were a bit brighter, but less sweet and extended. Then there are the wonderful sounding (non GTB) Sylvania VT231's from the 1940's... I tried them strictly in the input positions, not as drivers. They are more refined than the GTB's, with great bass, wonderful mids and plenty of extension in the upper highs, but not as forward as the GTB Sylvanias. They also have a faster, more lively sound than the stock tubes,
losing just a bit of "air" compared to the stock tubes, but not much. I have also tried Ken-Rads, RCA's, and many others, but preferred the stock tubes over them. If you find your 70/70 sounding a bit laid back or too lush for your tastes, try the 1940 and 50's Sylvanias. Hope this helps... Happy listening!
losing just a bit of "air" compared to the stock tubes, but not much. I have also tried Ken-Rads, RCA's, and many others, but preferred the stock tubes over them. If you find your 70/70 sounding a bit laid back or too lush for your tastes, try the 1940 and 50's Sylvanias. Hope this helps... Happy listening!