In my time I've had lots of vintage amplifiers some recapped some original most sansui .
But I've never directly compared a full rebuilt vintage amplifier with a modern of the same quality.
Has anyone out there done this ? And what do you think ? modern sound or rebuilt vintage sound?
Having researched this, and chatted to a couple of electronics engineers who repair th9is stuff for fun, it seems that in general the early vintage Japanese hifi from the 70s and early 80s are all well built, good components, but pigs to work on. As they evolved, many of the brands moved their manufacturing overseas to Taiwan, China etc, and sourced cheaper, lower quality components, but the designs are easier to work on as they are better laid out and simpler designs. Some are noted as better than others, e.g. early technics, most of Denon up the 2000s are examples of better specced designs wrt to components, whereas NAD are viewed as cheap and inferior (so I avoided buying a used NAD for that reason). The main culprits are capacitors - electrolytic caps dry out over time, so their spec changes, until they can sometimes eventually explode (hello NAD), pots can corrode, become gunked up which often just requires cleaning.
More modern amps use a lot more SMD designs rather than through hole which are cheaper but not as durable apparently.