It's overwhelming how much variations audio amplifiers have. This power stage is very rare. I've only seen it in one other circuit. That's because it doesn't work like any other stage we've looked at before. The difference is in the constant current source it provides. The upper half of the power stage is basically an emitter follower where normally a varying load disrupts the Vbeo and shifts the bias point downwards, causing it to clip off prematurely, but here it is bootstrapped, so that the output signal is fed back to the base and follows the wave excursions keeping the Vbeo constant, thus stabilising the bias point and making it a good constant current source. The rest of the schematic is pretty much normal a differential amplifier and a common emitter amplifier to work the signal part. Anyway some of the specs are:
- Input Sensitivity - line level 0.7Vrms
- Output Power - 45Wrms
- Drawn Power - 288W
- Efficiency - 15.6% I know, right :x
- Frequency response - <1Hz - 200kHz @-3dB
- THD+N - 0.002% @ 45Wrms
- Ripple Rejection - -52dB
