I've owned 2 500T's. The first one sat on a shelf in my basement for about a year before I even fired it up. I bought it before I was an AK member and didn't even realize what I had.
I'll never forget the day I used it as background music while I cleaned the basement. Warm, tube-like sound. I think that was an epiphany. I had a Marantz 2230 as my main receiver and from that point on, I started lusting after 1960's gear and lost interest in 70's gear.
Here it is, playing through some cheap Bose indoor/outdoor test speakers (why did I even make a YT video with that embarrassing set up???) PS, the TT was only sitting on top of the receiver for a test....I don't think I would have blocked the air vents like that normally.
Well, the transistors went kaput in that one, so I sadly parted it out. Probably should have sold it as "for repair", but again....I didn't realize what a classic it was and figured that without the unobtanium transistors (the ones on the main amp board with the heat sinks) it was a door stop.
Second one was purchased at Twangfest and it was
pristine AND had a wood case. I recapped it and adjusted it and WOW, it sounds nothing like my first one. Super clean and bright, but in a good way. ( I like clean and bright). Still tube-like, but only in terms of detail, clarity and dimension. This one isn't warm and fuzzy, but it sounds better than most other SS amps/receivers I've heard.
It's a combination of the discrete transistors and the expert designers from the tube era that make this receiver sound so good. The 500T is my pride and joy and gets brought out on special occasions.