Portable Headphone Amplifier

3V Battery powered

High Performance unit

Circuit diagram:

3 Volt Headphone Amp


R1_____________10K   1/4W Resistor
R2____________100K   1/4W Resistor
R3_____________68K   1/4W Resistor (see notes)
R4______________1K5  1/4W Resistor
R5______________3K3  1/4W Resistor
R6____________330R   1/4W Resistor
R7______________4K7  1/4W Resistor
R8______________2R2  1/4W Resistor

C1______________1µF   63V Polyester Capacitor
C2____________100µF   25V Electrolytic Capacitor
C3____________470µF   25V Electrolytic Capacitor

Q1____________BC549C  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 (two 1.5V AA or C cells in series, but see Notes)


Technical data:

Current drain:
35mA per channel with 32 Ohm 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% into 32 to 600 Ohm loads and up to 1.5V peak-to-peak output.
Below 0.1% at maximum output
Unconditionally stable on capacitive loads