KA56 is an audio Amplifier made by KENWOOD at 80s. Its can deliver audio ouput up to 75 Watts by using symetrical supply 50VDC.
Its using a pair of Power Transistor number 2SC3855 and 2SA1491 which is becaming and 100 Watts of Audio Output ( DATASHEETS ).
Appearance of amplifier unit are HERE. Inside of the Amplifier are HERE.
SCHEMATIC DIAGRAM
The re-drawing schematic are shown below:
From the schematic above, its consist of long tail pair pre-amplifier, 2 stages Voltage Amplifier and Current Mirror, Servo Bias Driver, Driver Amplifier and Transistor Power.
Pre-amplifier. Its uses 2SC1845 ( Q1 , Q2 ) and need summetrical supply voltages as big as 20VDC.
2 stages Voltage Amplifier Stages and their Current Mirror are Q3, Q4, Q6 ,Q7. 1st stage are using 2SA733 then second stage are using 2SC2632.
Next is Servo bias transistor , that is Q9 which driven by set the Trimmer IDLE 1K. Its set the Current ambien of Power transistor Q12 and A13.
Driver power transistor are using 2SC3244 and 2SA1384 which is has 900m Watt of Dissipation ( DATASHEETS ) .
Lastly is Final Power Transistor. Its using 2SC3855 pairing with 2SA1491 also it has 100 Watt output ( DATASHEETS ).
Apearance of Power Transistor are HERE.
