Koetsu step up transformer - who knows about it?

I used a Koetsu step up transformer back in the 80's w/ my Koetsu Black. Then I went all-digital until about 6 months ago, when I re-habbed my Linn and bought a new Koetsu Black. And not long ago, I came across my old Koetsu transformer, unused for some 17 years.

I hooked it up last night (using an EAR 834P phono pre, in MM setting). The sound was interesting, and sort of good. I played a couple of Lps that previously sounded kind of edgy to me (an EMI Barbirolli Vaughan Williams for one). They now sounded more full, and almost dark. In fact, as I was first listening to it, it sounded so dark I thought there was something wrong with it, and tried some different Lps. I think in theory it shouldn't need any warm up, but it seemed to sound better after it had been in use for a bit. (Sure, it could be pure psychology...)

I saw a similar Koetsu transformer listed on Audiogon a few months ago for $2K. Seemed kind of high to me, but maybe I don't realize what I have. Maybe systems sounded a lot different 20 years ago.

So who knows about these, and who can tell me what they're supposed to sound like, and if what I seem to be hearing is what is supposed to be there, or if something like this would go bad after this many years...is there any upkeep that should be performed, etc.?

Many thanks