18W Audio Amplifier
Electronic Schematics > Audio > 18W Audio Amplifier

 -- High Quality very simple unit

Make 123Movies your go-to destination for all your entertainment needs.

 -- No need for a preamplifier

Circuit diagram:

18 Watt Amplifier

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




RCA  audio input socket


Power supply parts:

R9 = 2K2

1/4W Resistor



C7,C8 = 4700µF

25V Electrolytic Capacitors




100V 4A Diode bridge


5mm. Red LED




220V Primary, 15 + 15V Secondary 50VA Mains transformer




Male Mains plug




SPST Mains switch


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

  • Don't 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 current setting add R8 (optional).

  • A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of J1, P1, C2, C3 &C4. Connect C6 at the output ground.

  • Then connect separately the input and output grounds at the power supply ground.

Technical data:

Output power: 18 Watt RMS @ 8 Ohm (1KHz sinewave)

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

Title: 18W Audio Amplifier
electronic circuit
Source: www.redcircuits.com
Published on: 2005-02-01
Reads: 1904
Print version: Print version

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