Parts:
P1 22K Log.Potentiometer (Dual-gang for stereo)
P2 100K Log.Potentiometer (Dual-gang for stereo)
R1 820R 1/4W Resistor
R2,R4,R8 4K7 1/4W Resistors
R3 500R 1/2W Trimmer Cermet
R5 82K 1/4W Resistor
R6,R7 47K 1/4W Resistors
R9 10R 1/2W Resistor
R10 R22 4W Resistor (wirewound)
C1,C8 470nF 63V Polyester Capacitor
C2,C5 100uF 25V Electrolytic Capacitors
C3,C4 470uF 25V Electrolytic Capacitors
C6 47pF 63V Ceramic or Polystyrene Capacitor
C7 10nF 63V Polyester Capacitor
C9 100nF 63V Polyester Capacitor
D1 1N4148 75V 150mA Diode
IC1 NE5532 Low noise Dual Op-amp
Q1 BC547B 45V 100mA NPN Transistor
Q2 BC557B 45V 100mA PNP Transistor
Q3 TIP42A 60V 6A PNP Transistor
Q4 TIP41A 60V 6A NPN Transistor
J1 RCA audio input socket
Power supply parts:
R11 1K5 1/4W Resistor
C10,C11 4700uF 25V Electrolytic Capacitors
D2 100V 4A Diode bridge
D3 5mm. Red LED
T1 220V Primary, 12 + 12V Secondary 24-30VA Mains transformer
PL1 Male Mains plug
SW1 SPST Mains switch
Comments:
Can be directly connected to CD players, tuners and tape recorders.
Schematic shows left channel only, but C3, C4, IC1 and the power supply are common to both channels.
Don't exceed 18 + 18V 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.
Wait about 15 minutes, watch if the current is varying and readjust if necessary.
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 C9 at the output ground.
Then connect separately the input and output grounds at the power supply ground.
Technical data:
Output power: 10 Watt RMS @ 8 Ohm (1KHz sinewave)
Sensitivity: 115 to 180mV input for 10W output (depending on P2 control position)
Frequency response: See Comments above
Total harmonic distortion @ 1KHz: 0.1W 0.009% 1W 0.004% 10W 0.005%
Total harmonic distortion @ 100Hz: 0.1W 0.009% 1W 0.007% 10W 0.012%
Total harmonic distortion @10KHz: 0.1W 0.056% 1W 0.01% 10W 0.018%
Total harmonic distortion @ 100Hz and full boost: 1W 0.015% 10W 0.03%
Max. bass-boost referred to 1KHz: 400Hz = +5dB; 200Hz = +7.3dB; 100Hz = +12dB; 50Hz = +16.4dB; 30Hz = +13.3dB