Glory,
I first heard Tenor amps, pre-Zu and then when I first got Def1.5s, early in the last decade, both their 15w and 75w amps. I have a friend who cycles through high-end gear at whirlybird frequency, including the existing Tenor stereo amp. I haven't heard the $90k monoblocks on Definitions. He brings some of his gear to me because he hears attributes on crossoverless Definitions that he doesn't hear through his Magicos, which is how I heard the current stereo amp. Look, Tenor makes drop-dead gorgeous gear that sounds lovely in isolation.
Now, keep in mind, I have been an OTL advocate in the past. One of the longest continuous amplifier stints in my systems over the past 40 years was held by Futterman OTL monoblocks, hand-built by Julius, which I bought from him directly back in the late 70s. I used those amps for 12 years. So, believe me, when I've listend to Tenor and Atmasphere amps in my Zu-based systems, I *wanted* to like them, and they are certainly quite good in an isolated sense. Both are particularly notable for being "fast" amps that happen to use tubes.
But I have something that changes the context from evaluating Tenor and Atmasphere in isolation, and that is my Audion amplifiers. How expensive does an amp have to be to seem credible to your threshold for "expensive gear?" My Audion Black Shadows are $12,995 per pair and they are the not only the best 845 amps I've heard at *any* price by anyone, they are among the five best amps I've heard, period. But then I have something else: my Audion Golden Dream 300B PSET monoblocks. These amps cost almost $20,000/pr in the configuration I have and can be ordered in configurations up to $36,000/pr. Very few people have them and few here in the US have heard them. But these are the best overall amplifiers I've listened to regardless of price; and yes, used with a speaker with which their power is adequate, I prefer the Audions to Tenor and easily over Atmasphere. They are tonally more complete and musically convincing with Zu Definitions and more so now with Def4. I hear five and six figures amplification more than you probably suspect, and very little of it impresses me. The extreme cost high end in audio generally heads down a resolution vector detached from tonal authenticity, that is unrelated to the way we actually hear music if heard live. This is the central disease of hifi over the last 30 years. Audion's upper tier amplifiers are sonically swift, transparent, dimensionally convincing, dynamic and, best of all, tonally complete.
I don't doubt that you "hear huge sound differences" as you change out gear. Of course you do. The question is entirely whether those huge sound differences are enhancing of or deleterious to convincing musicality in playback. For me, and anyone taking my advice, you are takiing a path that meanders from musical realism *compared to some other options you could take* and which I have taken. But you're convinced of the musical authenticity of the gear you've assembled, so be happy. What does it matter what I think? Regardless, we are talking differences of degree at high cost compared to the gear decision most people have to make.
Generally I've seen very little correlation between most expensive and best, in hifi, so cost doesn't impress me. But best is certainly seldom cheap. We all just decide how much is appropriate. It's not a competition, Glory. Anyone who is attracted to what you describe in cost and sonic consequence, is free to follow. It affects me not at all. I've made no power amplification changes since 2005 in both my systems and I'm only now about to make one preamp change. I bet a lot of people here would like to find that stability in their hifi.
Phil
