Detailed explanation of 18W audio amplifier circuit diagram

Amplifier Section:

P1 = 22K potentiometer

R1 = 1K 1/4W resistor

1/4W resistor R2 = 4K7

R3 = 100R 1/4W resistor

R4 = 4K7 1/4W resistor

R5 = 82K 1/4W resistor

R6 = 10R 1/2W resistor

R7 = R22 4W resistor (wire wound)

R8 = 1K 1/2W metal ceramic trimmer (optional)

C1 = 470nF 63V polyester capacitor

C2, C5 = 100uF 3V bead tantalum capacitors

C3, C4 = 470uF 25V electrolytic capacitors

C6 = 100nF 63V Polyester

D1 = 1N4148 75V 150mA diode

IC1 = TLE2141C low noise, high voltage, high slew rate operational amplifier

Q1 = BC182 50V 100MA NPN transistor

Q2 = BC212 50V 100MA PNP transistor

Q3 = TIP42A 60V 6A PNP transistor

Q4 = TIP41A 6A 60V NPN transistor

J1 RCA audio input socket

Power supply part:

R9 = 2K2 1/4W resistor

C7, C8 = 4700UF 25V electrolytic capacitors

D2 100V 4A diode bridge

D35mm. Red LED

T1 220V, 15+15V, 50VA power transformer

PL1 power plug

SW1 Single Pole Single Throw (SPST) Power Switch

Notes:

Can be connected directly to CD players, tuners and recorders.

Do not exceed 23+23V supply voltage.

Q3 and Q4 must be equipped with heat sinks.

D1 must touch the heat sink.

Quiescent current (best with an AVO meter in series with Q3 emitter) is not critical.

Adjust R3 to read the current between 20~30 mA with no input signal.

To boost the current setup add R8 (optional).

Proper grounding is very important to eliminate hum and ground loops. Connect the ground sides of J1, P1, C2, C3, C4 at the same point. C6 is connected at output ground.

Then connect to the power input and output ground respectively.

Technical data:

Output Power: 18 Watts RMS @ 8 Ohms (1kHz sine wave)

Sensitivity: 150mV input 18W output

Frequency Response: 30Hz to 20kHz -1dB

Total Harmonic Distortion @ 1KHz Comprehensive: 0.1W 0.02% 1W 5W 10W 0.03% 0.01% 0.01%

Total harmonic distortion 10KHz frequency: 0.1W 0.04% 1W 5W 10W 0.15% 0.06% 0.05%

Unconditionally stable capacitive load