Audio007

                                          

18 Watt Audio Amplifier
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Schematic design of 18W audio amplifier + Power Supply
Part Components of 18W Audio Amplifier:
Capacitors	Resistors
C1      = 470 nF / 63V Polyester C2,C5 = 100 μF / 3V Tantalum bead C3,C4 = 470 μF / 25V Electrolytic C6      = 100nF / 63V Polyester Semiconductors IC1     = TLE2141C Q1      = BC182 Q2      = BC212 Q3      = TIP42A Q4      = TIP41A D1      = 1N4148	R1      =   1KΩ ¼W R2,R4 = 4K7Ω ¼W R3      =  100Ω ¼W R5      =  82KΩ ¼W R6      =    10Ω ½W R7      = 0.22Ω 4W wirewound R8      =   1KΩ ½W Trimmer Cermet P1      = 22KΩ Log.Potentiometer              (Dual-gang for stereo) Others J1       = RCA audio input socket
Part Components of Power Supply :
Capacitors	Resistors
C7,C8 =  4700 μF / 25V Electrolytic Others T1 220V Primary, 15 + 15V Secondary 50VA Mains transformer PL1 Male Mains plug SW1 SPST Mains switch	R9 = 2K2Ω ¼W Diodes D2 100V 4A Diode bridge D3 LED (5mm. Red)
Notes
Can be directly connected to CD players, tuners and tape recorders. Don't exceed 23 + 23V supply. Q3 and Q4 must be mounted on heatsink.  D1 must be in thermal contact with Q1. Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical. Adjust R3 to read a current between 20 to 30 mA with no input signal. To facilitate current setting add R8 (optional). A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of J1, P1, C2, C3 &C4. Connect C6 at the output ground. Then connect separately the input and output grounds at the power supply ground.
Technical Data
Output power: 18 Watt RMS @ 8Ω (1KHz sinewave) Sensitivity: 150mV input for 18W output Frequency response: 30Hz to 20KHz -1dB Total harmonic distortion @ 1KHz : 0.1W 0.02% 1W 0.01% 5W 0.01% 10W 0.03% Total harmonic distortion @10KHz: 0.1W 0.04% 1W 0.05% 5W 0.06% 10W 0.15% Unconditionally stable on capacitive loads

Source : Electronics Lab