QX8000 is a deluxe receiver or AM/FM stereo tuner at 70s made by PIONEER.
Its consist of 4 Amplifier or 2 stereo Power Amplifier for rear Amplifier and Front Amplifier.
The receiver has 2 kind of tone control, one for rear amplifier and last one for front amplifier.
Manual Service of this unit said that it can be making 4 x 22 Watts Quarophonic Audio and 27 Watts Stereo.
Here is the edited schematic diagram for power amp section.
The amp uses OTL system and need 48 until 54 VDC asimetrically supply. It looks same with the amplifier with OCL with 24 to 27VDC asimetrically.
The schematic is quite simple. No differential amplifier for signal preamp. No servo driver transistor and there are no Over Current Protection feature.