QM800 is a quadrophonic amplifier made by pioneer in the 70’s which has 4 amplifiers which are commonly used as surround system amplifiers.
INFO
In the era of the 70s, surround including a new technology in audio systems.
And Pioneer has an amplifier for this system. His amplifier has an output capability of up to 35 Watts per channel.
SCHEMATIC
It is mentioned in the service manual that the schematic consists of a circuit block diagram and several schematics in each block.
In this article, I only take the power amp for collection and review.
The following is a result of edit and crop schematic
Click to Enlarge
There are 4 parts to this amp schematic:
- Initial amplifier, using the differential amplifier method with transistor number 2SA572.
- Voltage amplifier, using transistor number 2SC627.
- Driver amplifier, using transistor numbers 2SC497 and 2SB497.
- Power amplifier, using only NPN amplifier system with transistor number 2SD793.
There is also a DC0 Volt circuit to make the output of this amplifier always 0 Volts contained in the input of the initial transistor using 2 zener diodes and 1 trimpot for each channel.
NOTE
The working voltage on this amplifier is 35 volts symmetrically.
According to the data sheet the 2SD793 transistor is capable of producing up to 60 watts of power ( SOURCE ).
