18Watt Audio Amplifier

High Quality very simple unit No need for a preamplifier.

18Watt Audio Amplifier Circuit Diagram and Power Supply 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___4700?F 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

Source : RedCircuits