Circuit Diagram:How to build 18watt Audio Amplifier - circuit diagramCircuit Diagram:How to build 18watt Audio Amplifier - circuit diagramAmplifier 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.
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