This is high fidelity, high quality audio amplifier circuit diagram. You don’t need pre amplifier circuit for this design.

25W HiFi Audio Amplifier with MOSFET

Component list:

R1,R4 = 47K1/4W ResistorsR2 = 4K71/4W ResistorsR3 = 1K51/4W ResistorsR5 = 390R1/4W ResistorsR6 = 470R1/4W ResistorsR7 = 33K1/4W ResistorsR8 = 150K1/4W ResistorsR9 = 15K1/4W ResistorsR10 = 27R1/4W ResistorsR11 = 500R1/2W Trimmer CermetR12,R13,R16 = 10R1/4W ResistorsR14,R15 = 220R1/4W ResistorsR17 = 8R22W ResistorR18 = R224W Resistor (wirewound)C1 = 470nF63V Polyester CapacitorC2 = 330pF63V Polystyrene CapacitorC3,C5 = 470?F63V Electrolytic CapacitorsC4,C6,C8,C11 = 100nF63V Polyester CapacitorsC7 = 100?F25V Electrolytic CapacitorC9 = 10pF63V Polystyrene CapacitorC10 = 1?F63V Polyester CapacitorQ1-Q5 = BC560C45V100mA Low noise High gain PNP TransistorsQ6 = BD14080V 1.5A PNP TransistorQ7 = BD13980V 1.5A NPN TransistorQ8 = IRF532100V 12A N-Channel Hexfet TransistorQ9 = IRF9532100V 10A P-Channel Hexfet Transistor

Use this power supply circuit to handle the amplifier.

Component list:

R1 = 3K31/2W ResistorC1 = 10nF1000V Polyester CapacitorC2,C3 = 4700?F50V Electrolytic CapacitorsC4,C5 = 100nF63V Polyester CapacitorsD1200V 8A Diode bridgeD25mm. Red LEDF1,F23.15A Fuses with socketsT1220V Primary, 25 + 25V Secondary 120VA Mains transformerPL1Male Mains plugSW1SPST Mains switch

Circuit Notes:

  • Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need.
  • Q6 & Q7 must have a small U-shaped heatsink.
  • Q8 & Q9 must be mounted on heatsink.
  • Adjust R11 to set quiescent current at 100mA (best measured with an Avo-meter in series with Q8 Drain) with no input signal.
  • A correct grounding is very important to eliminate hum and ground loops. Connect in the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 at output ground. Then connect separately the input and output grounds at power supply ground.

Technical data:

  • Output power: well in excess of 25Watt RMS @ 8 Ohm (1KHz sinewave)
  • Sensitivity: 200mV input for 25W output
  • Frequency response: 30Hz to 20KHz -1dB
  • Total harmonic distortion @ 1KHz: 0.1W 0.014% 1W 0.006% 10W 0.006% 20W 0.007% 25W 0.01%
  • Total harmonic distortion @10KHz: 0.1W 0.024% 1W 0.016% 10W 0.02% 20W 0.045% 25W 0.07%
  • Unconditionally stable on capacitive loads

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