First Test for tube bias on ARC Ref 110?

inclusion of self-biasing circuit only improves sound.

I check bias first day of every month on my ARC amp. Tubes from ARC, very little drifting.

A properly implemented auto-bias system implies digital components, microprocessors, ADCs and DACs. In order to be reliable and not affect sound quality it will increase the price of the amplifier significantly. Also long term serviceability can be an issue, needing trips to the factory.

As I always use tubes pre-conditioned for 50 hours I check bias after the first 100 hours and then every 500 hours.

Marakanetz...I suggest you read what Microstrip has to say. I fully concur and any self-respecting tube amp designer will tell you the same. All the added microprocessors and digital circuitry will detract from the sonic quality. If you think Audio Research that has been in business for 30 years with too many awards and industry acclaim are cutting corners by excluding a sel-biasing circuit than I don't know what to tell you.

I have to agree that auto bias is a very convenient feature, but I think it slightly hampers overall transparency. I have also owned the Primaluna Prologue Two and then upgraded to the Dialogue Two (both with KT-88's) and both are lovely amplifiers for the money involved, but after comparing to others in relatively similiar price ranges (Rogue, ARC's integrated) I could definitely hear a more transparent sound in those without auto bias. These differences could potentially be many other things, but on first glance, that is my assumption as to what differs between them electronically. This is not meant to put down Primaluna in the least, again, they are great amps, though I think you pay a small price for the ease of use with auto bias.