How to build Headphone Amplifier

October 20, 2010 - category: Audio amplifier

High Quality unit. No need for a preamplifier.

Circuit diagram

Headphone Amplifier-circuit diagram

Amplifier parts:

  • P1 22K Log.Potentiometer (Dual-gang for stereo)
  • R1 560R 1/4W Resistor
  • R2,R3 10K 1/4W Resistors
  • R4 12K 1/4W Resistor
  • R5,R6 2R2 1/4W Resistor
  • R7 22R 1/2W Resistor
  • C1 1uF 63V Polyester Capacitor
  • C2,C3,C4 100uF 25V Electrolytic Capacitors
  • C5 22pF 63V Polystyrene or Ceramic Capacitor
  • C6 22uF 25V Electrolytic Capacitor
  • IC1 LM833 or NE5532 Low noise Dual Op-amp
  • Q1,Q3 BC337 45V 800mA NPN Transistors
  • Q2,Q4 BC327 45V 800mA PNP Transistors
  • J1 RCA audio input socket

Power supply parts:

  • R7 2K2 1/4W Resistor
  • C7,C8 2200uF 25V Electrolytic Capacitors
  • D1 100V 1A Diode bridge
  • D2 5mm. or 3mm. Red LED
  • IC2 7815 15V 1A Positive voltage regulator IC
  • IC3 7915 15V 1A Negative voltage regulator IC
  • T1 220V Primary, 15 + 15V Secondary 5VA Mains transformer
  • PL1 Male Mains plug
  • SW1 SPST Mains switch


  • Can be directly connected to CD players, tuners and tape recorders.
  • Tested with several headphone models of different impedance: 32, 100, 245, 300, 600 & 2000 Ohms.
  • Can drive old 8 Ohms impedance headphones, but these obsolete devices are not recommended.
  • Schematic shows left channel and power supply.
  • Numbers in parentheses show IC1 right channel pin connections.
  • 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. Then connect separately the input and output grounds at the power supply ground.

Technical data:

  • Output voltage: Well above 5V RMS on all loads
  • Sensitivity: 250mV input for 5V RMS output
  • Frequency response: Flat from 30Hz to 20KHz
  • Total harmonic distortion @ 1KHz & 10KHz: Below 0.005% on 32 Ohms load and up to 4V RMS output (typical 0.003%)
  • Total harmonic distortion @ 1KHz & 10KHz: Below 0.005% on 100 to 2000 Ohms load and up to 5V RMS output (typical 0.003%)

Unconditionally stable on capacitive loads

author: RED Free Circuit Designs
circuit from http://www.redcircuits.com/

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