tube amplifier auto bias- accurate?

Ed your wrong on this one.
Only way you can bias a tube amp correctly is to use a scope and a dummy load. A440 cycles when it starts to clip you then adjust so the cross over notch disappears. You have to look at the wave form! If a manufacturer says its autobias its either full class A or if its not class A they are lying to you.

Bin...Actually it was Ed_sawyer who suggested that a voltage measurement was all that is required, and I merely pointed out that you can utilize a scope as a voltmeter. It doesn't make sense to do that, (like adding on the log scale of your sliderule) but it can be done. Most bias setting is done using a voltmeter, often a meter that is built into the amp.

Your method sounds good, although it's not obvious that the end result would be any different from using a voltmeter.

Eldartford,
In my opinion you are one of the most knowledgeable here on tube amps and often find myself silently nodding my head to your conclusions. You have provided excellent insight to both the novice and expert. I agree to your last sentence in this thread…So which way would you rather have your tube's biased? :-)

Bin, please see my comments above, which is my opinion of Eldartford being "one of the most knowledgeable here on tube amps".

I'd rather have auto bias. I don't have the time or the patience to do it any other way. I have an amp that I turn on and play music, end of story.