The problem I find I have buying expensive high end audio products used is not knowing for certain that a product is truly performing up to specifications as it should. That is what you are paying for, however good sounding gear might not perform as designed yet still sound OK. How to verify validate something sounds as it should, short of hearing some kind of obvious noise or distortion?
The most expensive used piece I ever bought on Audiogon sounded fine for over a year when I got it, then one day it developed a clear audible problem. The vendor determined there was a circuit board inside that had its foil largely separated. Luckily it was replaced promptly for very reasonable cost. Was there a prblem when I bought it that took a year to fully develop? Dunno. But I learned from that experience to not be afraid of asking questions up front when many dollars are involved. If a seller does not understand and cooperate, I will find another seller.
The most expensive used piece I ever bought on Audiogon sounded fine for over a year when I got it, then one day it developed a clear audible problem. The vendor determined there was a circuit board inside that had its foil largely separated. Luckily it was replaced promptly for very reasonable cost. Was there a prblem when I bought it that took a year to fully develop? Dunno. But I learned from that experience to not be afraid of asking questions up front when many dollars are involved. If a seller does not understand and cooperate, I will find another seller.