Portable Headphone Amplifier Electronic Circuit Diagram

Portable Headphone Amplifier Electronic Circuit Diagram

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On: 13 Jun, 2016

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Category: Audio

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Portable Headphone Amplifier Circuit Based 3 Transistors

his simple headphone amplifier circuit can be directly connected to other compact devices such as CD player, Walkman, Tuners and tape recorder. In theory, the s...

Portable Headphone Amplifier Circuit Based 3 Transistors

his simple headphone amplifier circuit can be directly connected to other compact devices such as CD player, Walkman, Tuners and tape recorder. In theory, the series of headphones amplifier circuit is able to work well on different impedances. The impedance is 32 ohm, 100, 300, 600, and 2000 ohm. The shown circuit scheme is for one channel (mono). If the stereo will be built live two series.

As shown in the figure, components B1, SW1, J1 and C3 are for both channels if stereo is to be made. The resistor value R3 has been calculated for 300 ohm impedance. If it will be used for 600 ohm impedance or higher, change the resistor value R3 to 100K. Actually Battery B1 can be replaced with power supply if possible, provided it is well regulated.

If the battery is still in use, the battery type can be replaced with rechargeble. The listed R3 values for 300 ohm and 600 ohm impedances are for 3.7 Volts. When used with batteries in a stereo system, the battery will usually drain within 20 hours.

portable headphone amplifier circuit based 3 transistors.gif

Portable headphone amplifier based 3 transistors parts list:

  • R1 = 10K
  • R2 = 100K
  • R3 = 68K
  • R4 = 1.5K
  • R5 = 3.3K
  • R6 = 330R
  • R7 = 4K7
  • R8 = 2.2R
  • C1 = 1µF-63V
  • C2 = 100µF-25V
  • C3 = 470µF-25V
  • Q1 = BC239C
  • Q2 = BC337
  • Q3 = BC327
  • J1,2 = Stereo 3mm. Jack socket
  • SW1 = SPST Switch
  • B1 = 3V Battery (two 1.5V AA or C cells in series, but see Notes)


Portable Headphone Amplifier Circuit

portable headphone amplifier circuit.gif

The portable headphone amplifier circuit is very easy to build because it uses only 3 transistors. The portable headphone amplifier can be directly connected to the CD player, or tape recorder.

The headphone amplifier circuit works well on headphones with impedance 32, 100, 300, 600 and 2000 ohm. Because the headphones have two speakers for stereo channels, it is recommended to make two series of the same.

If this circuit is built for stereo channel, then B1, SW1, J1 and C3 also be done with the stereo. R3 resistor value listed on the headphone amplifier circuit to the impedance of 300 ohms. If you are going to use headphones with an impedance of 600 ohms, then replace the value of R3 to 100k.

Portable Headphone Amplifier Circuit Technical Data:

  • Current drain: 35mA per channel with 32 Ohms impedance headphones. Much less with higher impedance loads
  • Output voltage: Above 2V peak-to-peak on all loads
  • Sensitivity: 90mV RMS input for 2V peak-to-peak output
  • Frequency response: Flat from 30Hz to 20KHz
  • Total harmonic distortion @ 1KHz & 10KHz: Below 0.05% on 32 to 600 Ohms load and up to 1.5V peak-to-peak output. Below 0.1% at maximum output

Unconditionally stable on capacitive loads.

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