20 Year Old Amplifiers compared to 2017

@plutos 
I agree with you 100%. I hear the differences between amps, preamps, tube sets. And measurements aren't everything.

Dan D'Agostino, in his Stereophile interview, said, point blank, that some of his Krell offerings measured better than his current stuff. He specifically chose sound quality over measurements in his highly acclaimed breed of new Momentum components.

Older amplifers should be refurbished, of course. The first thing that has to be replaced would be the power supply caps, as these do degrade and can fail wtih nasty consequences. As I said earlier, with luck you can fit larger modern ones as they tend to be more compact for the same value. If the amplifier has been designed competently a slow ageing of the other components should not degrade sound, or not much.
I am currently using two refurbished Quad amplifiers (a 606-2 in the main system and a 405-2 in my study). The service engineer simply replaced all resistors and capacitors, arguing that these days quality components cost very little and labour is expensive. Why test a resistor if a new one costs peanuts?

Dan D'Agostino, in his Stereophile interview, said, point blank, that some of his Krell offerings measured better than his current stuff. He specifically chose sound quality over measurements in his highly acclaimed breed of new Momentum components.

Chasing measurements will give you that clinical, dry, and lean sound. My guess is that its the sound signature of too much NFB.