VAC gear is voiced to sound like a VAC with the stock tubes -- which are generally very carefully selected Chinese tubes, but sometimes military overstock NOS. I got mixed results rolling NOS tubes into the Renaissance Mk 3 preamp; the stock tubes (mostly Chinese Penta-Labs labeled 12AX7) ended up going back in, *except* for a very specially selected "MC grade" single 12AX7 in the phono stage (RCA) from Andy at Vintage Tube Services.
Some gear is voiced very specifically for the tubes it ships with, which will usually be Chinese and/or Russian. That can be good or bad. I think it’s good in VAC’s case; if you bought a VAC is was probably because you fell in love with their "house" sound. And that's what you get, with no fuss! In other scenarios, I’m not sure it’s a great idea to voice gear around Electro Harmonix 12AX7/12AU7/6SN7/EL34/6CA7/KT90 -- those tubes are much zingier up top, and grainier, than the numerous other alternatives (but the EH is cheap).
In my Rogue amps I go nuts rolling small signal NOS, because they respond very well to it. It actually shipped with all EH tubes and sounded bright (imagine my shock), which it SHOULD because that’s how those EH tubes are. Nowadays I've settled on Mazda silver plate 12AX7 (rare and very expensive at 350-400 a matched pair) and Sylvania Black Plate 12BH7 (rare but not too expensive when found), after MUCH experimentation with the usual suspects. The sonic difference is WELL worth the cost to me. Now that I know what I want and what it should sound like, I will in fact source used Ebay tubes if I have to -- if it sounds great it probably is good.
