Pass Labs Amplifier Meter meaning?

It would seem the meter is of no practical purpose to an end user other than to verify that the amplifier is in "operate" mode.

It means more expense and more things to go wrong.

I received a reply from a knowledgeable source who chooses to remain anonymous:

In the XA series, the meter measures bias. From a practicality standpoint when the meter begins moving, it's an indicator the amp has reached rated output.

I think Zippyy is right, if my memory serves me right. My X250 runs class A for the first 40 watts, then switches over to A/B. The meter needle moves slightly in class A mode. I had the needle up to the 12 o'clock position once, and it was alot more than 40 watts, and so loud the sonics were terrible in my room, which is approx. 15x27x9. I think it just measures current, whether it be class A or A/B. I guess they figure since you're paying alot, you may as well have something to watch, even if it doesn't move very much.

Surely someone must have an operators manual for it.