Which one is that? I'd like to know.
People got it right: CJ Premier 12 monoblock amps, 140W/side. Here's one of them on the top of my rack:
All my amps/source equipment is in a separate room from my speakers, so I don't get to see the glowy tubes while listening. But I prefer a clean look in my listening room, with little equipment to distract.
My first tube amp many years ago was the smaller CJ MV55 EL34-based amp (45W). Subjectively, it was what some people think of as a classic old tube amp sound: lush and relaxed, not very powerful sounding. As I got ever larger speakers going through my system it seemed to run out of steam and bass could get flabby. I splurged for the Premier 12s and those issues largely were solved. Still not the tightest bass in the world, but no speaker I've had, even "tough to drive" speakers, have sounded starved of power or flabby. (Though I don't listen super loud).
When I had a Bryston 4B3 in my system a while back to compare to the Premier 12s, I felt I heard cleaner, tighter sound from the Bryston. For instance: A sonic spectacular like the Conan soundtrack theme uses an extra massive orchestra and expanded horn section, playing as loud as humanly possible. Especially in the loudest sections the brass seemed to be more cleanly rendered, like I could keep turning it up and it would stay super clean. Likewise, in sections that had always sounded a bit muddy on my system - where the brass plunges down to join the cellos and double bass in their power region, things could get sort of blurred and indistinct and slightly bloated. The Bryston seemed to have the speakers in firmer grip, so the brass/cellos/double bass cleared up and I could finally hear the separate lines more easily. I leave the plausibility of any of that to the reader.
And while we are in the realm of the un-demonstrated, somewhat apropos to the theme of the thread:
I've also mentioned before that I bought a second pair of CJ Premier 12s a while back. Mine are old and a bit more moth eaten, and I got a great deal on a pair in mint condition that had more recently been to the CJ factory for a full check up and replacing anything that was looking tired. It was also the case that the owner had paid a wack of money for the "Teflon Cap Upgrade" (vs the I-can't-remember caps those replaced). My main motivation was being able to replace my old CJs with a refreshed pair.
But...again, subjectively (see my tag line) I was surprised that this second pair sounded distinctly different. It came with totally different power tubes (KT120s vs 6550s, as well as different brands of input tubes). When I tried the same tubes in my originals, the new and old amps sounded much more similar (and I bought the same tubes for my originals, hence both were then matched tube-wise). But even with the same compliment of tubes, the "upgraded" CJs still seemed subtly but distinctly different, less bright a bit darker up top from my originals, but more distinctly the bass seemed reliably tighter. All my usual bass torture tests, which could make my system sound more flubby, were tightened up, as was pretty much any track with bass.
Ideally I wanted to do a blind test between the two sets of amps, but in the end it wasn't as easy as I'd hoped, and I had to sell one of the pairs for some money. I sold the upgraded pair because they were a faster sell (and, subjectively, I ended up slightly preferring my originals anyway). Too bad, as it sure would have been interesting to me to have tried to confirm or disconfirm what seemed like distinct differences.
So, in the context of the Jim Austin "tube magic" discussion, my own approach to the above would be:
1. If in fact I was hearing a real difference, it would be measurable. No magic.
2. If I wasn't in a position to measure (not my forte) or blind test to confirm what I was hearing, I wouldn't claim to any skeptic my subjective impressions demonstrated anything at all. I would also hold my own impressions with the caveat it could be imagination. However, if the impressions remained distinct and reliable that I liked one over the other, I would be ok going with those impressions. It's my system, I only have to please myself, biases included.
Cheers.