over time i have had the 535 545 (i and ii) 555 - it was years ago of course
yes papa nelson pass designed them when he was a pup - but one needs to separate design and execution...
the adcoms were designed and spec’d to a specific (quite modest) price point, even for back in the day, so there were numerous execution tradeoffs in parts spec and quality, mechanical and electrical isolation... result is a nice sweet sounding product at fairly modest volumes but a glare, grain and glassiness that comes through once there are some demands placed on the amp and its power supply, especially into more reactive speaker loads
no free lunch here... take a nice resolving pair of speakers, like maggies, vandersteens, harbeths, revels, focals, get a clean source, run one of the old adcoms and then a modern day pass amp... there is a substantial, immediately audible difference
even leaving aside the capacitor aging issue, if a 30 year old 545 worth $400 could deliver for a discriminating audio lover what high-level modern ss amps can, we would all have them, and hegel, ayre, pass labs, belles, naim, exposure would all be out of business