This is an easy built portable headphone amplifier circuit. You can use this headphone amplifier to amplify your radio receiver, mp3/mp4 player, computer or dvd/cd player. You may connected the input channel directly to those devices.
R3 value was calculated for headphone impedance up to 300 Ohms. Using 600 Ohms loads or higher, change R3 value to 100K.
Take a note that above circuit only show single channel.
R1 _______________ 10K
R2 _______________ 100K
R3 _______________ 68K (see notes)
R4 _______________ 1K5
R5 _______________ 3K3
R6 _______________ 330R
R7 _______________ 4K7
R8 _______________ 2R2
C1 _______________ 1uF 63V
C2 _______________ 100uF 25V
C3 _______________ 470uF 25V
Q1 _______________ BC239C 25V 100mA NPN High-gain Low-noise Transistor
Q2 _______________ BC337 45V 800mA NPN Transistor
Q3 _______________ BC327 45V 800mA PNP Transistor
J1 _______________ Stereo 3mm. Jack socket
SW1 _______________ SPST Switch
B1 _______________ 3V Battery (2xAAA)
R3 value was calculated for headphone impedance up to 300 Ohms. Using 600 Ohms loads or higher, change R3 value to 100K.
Take a note that above circuit only show single channel.
