I owned an original 535 ( as well as other Adcom models ), and purchased a series 2, which had many upgrades ( circuitry ), including better rca inputs, speaker binding posts ( and eliminating the speaker switching ), and to my knowledge, heavily biased to class a for the 1st several watts. I still have the series 2 in my amp collection. Working within its limitations, it is a very good amplifier, slightly dry, but very accurate, and has always run hot.
What's Your Take on This ?