Circuit diagram:
Amplifier parts:
P1_____________22K Log. Potentiometer (Dual-gang for stereo) R1______________1K 1/4W Resistor R2______________4K7 1/4W Resistor R3____________100R 1/4W Resistor R4______________4K7 1/4W Resistor R5_____________82K 1/4W Resistor R6_____________10R 1/2W Resistor R7_______________R22 4W Resistor (wirewound) R8______________1K 1/2W Trimmer Cermet (optional) C1____________470nF 63V Polyester Capacitor C2,C5_________100µF 3V Tantalum bead Capacitors C3,C4_________470µF 25V Electrolytic Capacitors C6____________100nF 63V Polyester Capacitor D1___________1N4148 75V 150mA Diode IC1________TLE2141C Low noise, high voltage, high slew-rate Op-amp Q1____________BC182 50V 100mA NPN Transistor Q2____________BC212 50V 100mA PNP Transistor Q3___________TIP42A 60V 6A PNP Transistor Q4___________TIP41A 60V 6A NPN Transistor J1______________RCA audio input socket
Power supply parts:
R9______________2K2 1/4W Resistor C7,C8________4700µF 25V Electrolytic Capacitors D2_____________100V 4A Diode bridge D3_____________5mm. Red LED T1_____________220V Primary, 15 + 15V Secondary, 50VA Mains transformer PL1____________Male Mains plug SW1____________SPST Mains switch
Notes:
- Can be directly connected to CD players, tuners and tape recorders.
- Do not 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 quiescent current setting add R8 (optional).
- A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 & C4. Connect C6 to the output ground.
- Then connect separately the input and output grounds to the power supply ground.
Technical data:
- Output power:
- 18 Watt RMS into 8 Ohm (1KHz sine wave)
- 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
