18watt Audio Amplifier

High Quality very simple unit, No need for a preamplifier

Circuit Diagram:

Amplifier parts:

P1 = 22K
R1 = 1K
R2 = 4K7
R3 = 100R
R4 = 4K7
R5 = 82K
R6 = 10R-1/2W
R7 = 22R
R8 = 1K-1/2W (optional)
C1 = 470nF-63V
C2 = 100µF-3V Tantalum bead Capacitors
C3 = 470µF-25V
C4 = 470µF-25V
C5 = 100µF-3V Tantalum bead Capacitors
C6 = 100nF-63V
D1 = 1N4148
IC1 = TLE2141C
Q1 = BC182
Q2 = BC212 50V 100mA PNP Transistor
Q3 = TIP42A
Q4 = TIP41A
J1 = RCA audio input socket

Power supply parts:

R9 = 2K2
C7 = 4700µF 25V
C8 = 4700µF 25V
D2 = 100V 4A Diode bridge
D3 = 5mm. Red LED
T1 = 30VCT, 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.

Source : www.redcircuits.com