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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