Very simple 18Watt Audio Amplifier Circuit project with schematic and explanation

High Quality very simple unit No need for a preamplifier.

18Watt Audio Amplifier 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 :

18Watt Audio Amplifier Power Supply

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 

Source : RedCircuits