Audio Research I/50

This was taken from the I/50 owners manual.

Vacuum Tubes
It is recommended that you replace the vacuum tubes of your I/50 in sets. All of the tubes in your amplifier have been matched to have similar operating characteristics, to provide the best sound quality and reliability. 6550WE tubes should be replaced at approximately 2000 hours. 6922 tubes should be replaced before 4000 hours. Upon replacing a power tube or tube set, the I/50 must be biased by a trained technician to ensure proper operating values.

It seems like the amp can’t be biased by the owner of the amp. If that is true that would definitely be a dealbreaker for me. Just sayin’.
 

@dweller The manual says "Upon replacing a power tube or tube set, the I/50 must be biased by a trained technician to ensure proper operating values."

@stone1 Where did you read that the I/50 has auto bias? I can’t seem to find it anywhere. May I just missed it. Thanks.

@stone1 The amp from Tone is indeed an I/50, but it isn't an ARC I/50. It's from a company in Portugal. The amp from the lbtech link is the ARC I/50 and the article does say auto bias. I think the author may have jumped the gun when he said all ARC amps are auto bias. I read the owners manuals for all of their current amps and it is true that all of the ARC power amps are auto bias, but the two integrated amps aren't. The VSi75 is user adjustable and the I/50 is not. I'm pretty sure if the bias on the I/50 was automatic or user adjustable it would say so in the manual just like it did in all the ARC amp manuals I've read. I guess when you manufacture a product to a certain price point you have to make some compromises.