Pass Labs xa - .5 amps

Unlike most amplifiers the meter staff on the XA.5 series indicates bias, not power.

It will move only when the amplifier exceeds its' rated output.

Dealer disclaimer.

I would imagine it would tend to exceed its rated power on peaks, which can happen often. Is it necessarily a bad thing that the meter moves, or is that to be expected with music dynamics and nothing to worry about if everything sound fine?

So long as the amp output is not exceeding the bias point (in Class A operation) the staff does not move.

Above bias point, the XA.5 amps will source something above rated wattage (they have about 4 dB headroom) and at that point the staff will swing right.

At that point the amp is still in Class A to the rated wattage, but above rated wattage it's A/B. This would be the classic A-A/B operation.

Then, what's the class A/B rated wattage output above class A operation for the XA30.5?

I thought this amplifier was only class A.

Despite the marketing hype, I believe it's not at all uncommon for some supposedly "pure class A" amps to drop into class AB at some point. Perhaps due to volume demands, perhaps due to impedance load, perhaps it can't draw enough power from the wall, perhaps it can't dissipate the heat and perhaps because the manufacturer is exagerating it's products capabilites. I think I would prefer an amp to slide into class AB rather than choke on class A and run out of steam or worse yet damage my speakers. This might partialy explain why some might choose a high powered Class A A/B amp with their particular speakers.