Attymbb 8-25-2017I’m wondering if a possible contributor to the failure may have been the fact that your active speakers most likely present a very high impedance to the amp at deep bass frequencies. Which would mean that during notes having substantial deep bass content the amp would have been running essentially unloaded at those frequencies. And as you probably realize, as a general rule tube amps that have output transformers should not be run unloaded, especially when they are processing a signal. Otherwise damage to the output tubes and/or the output transformer can occur due to a phenomenon known as "inductive kickback."
I was previously using a bought new Ref 75 se which blew 2 tubes at the 30 hour mark. Despite being biased every 2 weeks. However, not only did the tubes blow ( due to the deterioration of the of the cathode coating of 2 tubes, I was told ) and the biasing resistor, it took a big chunk of the gold trace on the pcb and shortened the transformers as well.
I’m just speculating, of course, and I assume there are many audiophiles who use ARC Ref amps in conjunction with speakers of various kinds that have powered woofers. But it’s a possibility I wouldn’t rule out, and if you are looking for a tiebreaker in choosing between the two amps that might be a factor to consider.
Good luck. Regards,
-- Al