60W Class A Power Amplifier Circuit

60W Class A Power Amplifier Circuit

60W Class A Power Amplifier Part List :

R1=47Kohm	R31-32-35-36-39-40=0.22ohm 5W	D1-2=15V 1.3W zener
R2-9-27-28=1Kohm	R41=10ohm 3W	Q1-3-8-9-10-15-18=MPSA06
R3-18=10Kohm	R42=10ohm 1W	Q2-4-5-6-7-19=MPSA56
R4=18Kohm	R43=5.6Kohm	Q11-13-14=MPSA93
R5-13=3.9Kohm	R44=330Kohm	Q12-16-17=2N6515
R6-12=560ohm	TR1=22Kohm trimmer	Q20-21-22=BD379
R7-8-19=2.7Kohm	TR2=2.2Kohm trimmer	Q23-24-25=MJ802
R10-20=120ohm	C1=10uF 16V	Q26-27-28=MJ4502
R11=12Kohm	C2=1.5nF 100V MKT	Q29-30-31=BD380
R14-21=680ohm 0.5W	C3-9-10=100pF ceramic or Mylar	L1= see text
R15-22-29-30-33-34-37-38=100ohm	C4-5-6-7-8=100uF 25V	F1-2=5A fuse fast
R16-17-23-24=220ohm	C11-13=220uF 63V	.
R25-26=22Kohm	C12=220nF 250V MKT	.

There is one amplifier configuration that is universally accepted as the ideal for audio use: Class A operation . Many early amplifiers operated in Class A, but as output powers rose above 10W the problems of heat dissipation and power supply design caused most manufacturers to turn to the simpler, more efficient Class B arrangements and to put up with the resulting drop in perceived output quality. Why Class A ? Because , when biased to class A, the transistors are always turned on, always ready to respond instantaneously to an input signal. Class B and Class AB output stages require a microsecond or more to turn on. The Class A operation permits cleaner operation under the high-current slewing conditions that occur when transient audio signal are fed difficult loads. His amplifier is basically simple, as can be seen from the block diagram.

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