Class A Bias Power
Class A Bias Power is the output power per channel up to which an amplifier’s speaker output stage stays in Class A, with its output devices conducting throughout the signal cycle.
The figure is stated in watts for a specified load. It is not idle power consumption. It does not describe a Class A preamplifier or headphone stage.
Class A Bias Power — Power Amp
An amplifier rated at 150 W per channel into 8 Ω might deliver its first 10 W in Class A into that load. The 10 W figure identifies the Class A region; 150 W is its overall output rating. Do not assume the same Class A figure into 4 Ω.
For switchable Class A/AB amplifiers, use the Class A mode’s rating. An amplifier that stays in Class A throughout its usable output has no separate transition figure: read its Rated Power for the relevant load instead. A larger Class A region does not establish better sound.
Sources
- Leaving Class A — Pass Laboratories
- SV-237MKII manual: Class A and overall output, p.50 — Vincent / Sintron
- SV-700 manual: selectable modes and ratings, pp.42,46 — Vincent / Sintron