12au7 tube?

I remember conversation with Kevin of VAC and he said exactly the opposite.

I generally agree with what Kevin says, but we're all individuals and different in key ways. Anyways, he's almost certainly referring to rolling different makes of the same type. Meanwhile, I'm much more willing (than most) to play fast-and loose with rolling different types into power slots, as long as it's guaranteed safe. E.g. KT88 versus KT90 and KT120 or KT150. Depending on amp, you can even mix more different types in there, like EL34, 6L6GC / 7581A, etc. 

This will certainly make many cringe (maybe Kevin too), because the fact is an amp can only be "optimally" designed for the parameters of 1 output type. That's why I called it "playing fast and loose". But here clear as day, I can hear one of my VAC amps (450S) sounding far better with KT120 than the KT88 it was designed for - in THIS room, on THESE speakers. Meanwhile, another VAC amp (Master 300) sounds far better with the GL KT88 it was designed for, than those same KT120. The sonic difference from these KT88 versus KT120 rolls is far greater than any small-tube rolls. KT150 does the same again, but there I've always found the results too bass-heavy. 

mulveling,

I see, now I understand what you were saying. So you were both right.

Mulveling, good points on the 6SN7’s.

 Audiojan, reason why I think it’s important for one to hear the tube in ones own system is because what sounds good in someone else system may not sound best in yours and you might have a different preference. Example, many people like the 1940’s Metal base Sylvania 6SN7GT or 6SN7W. I really don’t, I prefer the Sylvania 1945 6SN7W short bottle because I find it sweeter and nicer than the more expensive and sought after metal base (taller bottle) which I find a little too analytical for my taste. The 1945 Sylvania 6SN7W short bottle and the 1951-53 Sylvania 6SN7GT Chrome Domes are probably my favorites from those type tubes. Mulveling, you mentioned Shuguang and JJ Czech in your post. Because I use so many EL34’s, I’m using 8 Shuguang in my CJ Premier Four and in my CJ Premier 1b, using 12 JJ from Slovakia Czech. My VTL all have 16 Russian EL34’s.

Inna, I never thought the Svetlana/SED EL34 "Winged" were anything special. And even though people claim they are a close copy of Mullards, they’re not. Not even close. I’ve found a few EL34’s that nicely outperform the Svetlana tube. One of my personal favorite EL34’s are the 1970 Tesla brown base. Very revealing and beautiful sounding tube. I like it in some ways better than my Mullards.  The Svetlana winged C doesn’t compete with these caliber of EL34’s even though people have falsely claimed so. I mention in a previous post, I would only use inferior tubes in my equipment because it might be too expensive to use premium tubes. On my amps that ONLY require 4 EL34’s, I have on most of the 1970 Teslas, 1960 Mullards or 1960 Amperex XF2. 

lowtubes, though I did not compare EL34 tubes yet, I too can't say that I hear anything special from SED tubes, not that I expected it. They seem to be alright, nothing more. That's why I of course want to find a reasonably priced matched quad of XF1 or XF2 Mullards, even used from a reputable source. Tesla, yes, I heard about them, saw them on ebay and nowhere else.

Mullard EL34’s are great and there is opinions about the differences in sound between the single and dual getters. I think I have both but never compared to hear which is better. I did evaluate between single getter 1960’s Mullard and 1970’s brown base Tesla dual getters. The amp I used to compare these tubes was a Conrad Johnson MV55, with 1945 Sylvania 6SN7W short bottle driver tubes and 1950’s Mullard MCI long plate 12ax7’s driver tubes. The Mullard is just a great all around tube. Very well balanced with Great detail, smoothness and musicality. I found the Tesla, in my amplifier tested, to be more euphoric and engaging. The Tesla had something special that fleshed out the information above the Mullards. Strange thing, even though I feel I was getting a more fleshed out midrange and more immediacy from the Tesla’s, they also had this sense of warmth to them. When I heard the Mullards, no warmth, just musical and straight up good tube. When I play the Teslas, warmth and euphoria and midrange clarity returns.