Here are the modifications that would be required to convert the amplifier to +- 51V supply lines:
(1)
TRANSISTORS (see post #8)
(1.1) An analysis shows that, with a reasonable heatsink and an 8 Ohm speaker load, the 2SC5200 and 2SA1493 transistors would be able to handle +-52V power supplies to produce 138W RMS, with stabilized power lines. With typical music, the output transistors would have a relatively easy time.
(1.2) The two driver transistors, Q10 (2SC4171) and Q11 (2SA1930) would not need to be changed, but they would need to be mounted on small heat sinks
(1.3) Q14 (BC548) would not need to be changed, but Q14 body flat-face should be mounted in thermal contact with the output transistor heatsink, near to one of the output transistors.
(1.4) Q1 to Q7 (there is no Q3) would need to be 120VCo minimum transistors (2N6517 [NPN]), (2N6520 [PNP])
(1.5) Q4 and Q5 would benefit from small heatsinks.
(2)
CAPACITORS
(2.1) C17 and C18, change to 60V working minimum, 4.7uF minimum, but both capacitors must be the same.
(2.2) C10, C11, C12, C15 change to 60V working minimum.
(2.3) C16 Unchanged
(2.4) All other capacitors, change to 120V working minimum.
(3)
RESISTORS
(3.1) Change R47 to 13K
(3.2) Change R41 and R42 to 39K
(3.3) Change R24 and R27 to 470 Ohms
(4)
SETTING UP
(4.1) When the revised amplifier is built, the quiescent current (Iq) flowing through the output transistors will needed to be set back to 20mA to 30mA by adjusting the potentiometer (variable resistor) (TP4). Once the amplifier has warmed up re-adjust Iq, if necessary.
And unless I have missed something, that is it.
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