Pass Labs xa - .5 amps

Seems to me that Audiofeil might be in the position to offer the best advise on this one.

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.