How expensive are best NOS tubes ? And how difficult to find ?

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.

Isn't it unfortunate that even premium Western manufacturers are dependent on Chinese and Russian tubes ? To put it another way, if it were not for them we might not see VAC and other equipment except for some very expensive pieces with NOS tubes. Not to mention that there are probably many outsourced parts in the equipment. Hell, it's almost like Great Britain that no longer makes steel and matches. What are they doing over there ?
No, I wouldn't buy tubes on ebay, I would buy at reliable places.

When I had an Octave V70se and later the V110 I tried a lot of different input - splitter  and power tubes. I always preferred the sound of vintage/out of production tubes. With some the difference in sound was huge and in others not so much. As far as NOS who really knows if they really are NOS or used.

That said I started with Dyn C1 sig speakers. My favorite tube was the original TS 6550 black plate followed closely by the solid grey plate. With those the little Mullards were a great compliment. Then I got the V110 and hated the Russian KT120's. The old TS were still my favorite. I also tried some British Gec KT88's. Didn't really care for those but not bad. Jim McShane told me about Ei KT90's but he wouldn't sell me any. When I first found some here on the Agon I bought them. These IMO were very good and at the time pretty reasonable. Then I upgraded the Dyn C1's to Raidho D1's. Now I didn't care for the TS 6550 or the little Mullards. KT120's sounded a bit better but still not good. The Gec KT88's and Ei KT90's were the tubes that sounded best with the D1's.

My point is all tubes have a sound signature that will vary with manufacturers (not always labels for they may be only one manufacturer that makes many labels).

Different tubes with different sound signature. Different coloration ?

Inna
yea probably some coloration trades taking place like swapping boutique capacitor, resisters, etc.....
i was thinking a nice CA or WA red wine....
but the French gotta eat too