Battery-powered Headphone Amplifier

Low distortion Class-B circuitry

6V Battery Supply

Circuit diagram:

Battery-powered Headphone Amplifier


P1_____________22K  Dual gang Log Potentiometer (ready for Stereo)

R1_____________15K  1/4W Resistor
R2____________100K  1/4W Resistor
R3____________100K  1/2W Trimmer Cermet
R4_____________47K  1/4W Resistor
R5____________470R  1/4W Resistor
R6____________500R  1/2W Trimmer Cermet
R7______________1K  1/4W Resistor
R8,R9__________18K  1/4W Resistors
R10,R11_________2R2 1/4W Resistors
R12____________33R  1/4W Resistor
R13_____________4K7 1/4W Resistor

C1,C2__________10µF  25V Electrolytic Capacitors
C3,C5_________100nF  63V Polyester Capacitors
C4,C6_________220µF  25V Electrolytic Capacitors

Q1,Q2,Q5______BC560C  45V 100mA Low noise High gain PNP Transistors
Q3,Q4_________BC550C  45V 100mA Low noise High gain NPN Transistor
Q6____________BC327   45V 800mA PNP Transistor
Q7____________BC337   45V 800mA NPN Transistor

SW1____________SPST slide or toggle Switch

J1_____________RCA audio input socket
J2_____________6mm. or 3mm. Stereo Jack socket

B1_____________6V Battery (4xAA or AAA Alkaline or rechargeable cells, etc.)


Some lovers of High Fidelity headphone listening prefer the use of battery powered headphone amplifiers, not only for portable units but also for home "table" applications. This design is intended to fulfil their needs and its topology is derived from the Portable Headphone Amplifier featuring an NPN/PNP compound pair emitter follower output stage. An improved output driving capability is gained by making this a push-pull Class-B arrangement. Output power can reach 100mW RMS into a 16 Ohm load at 6V supply with low standing and mean current consumption, allowing long battery duration.
The single voltage gain stage allows the easy implementation of a shunt-feedback circuitry giving excellent frequency stability.


Technical data:

Output power (1KHz sinewave):
16 Ohm: 100mW RMS
32 Ohm: 60mW RMS
64 Ohm: 35mW RMS
100 Ohm: 22.5mW RMS
300 Ohm: 8.5mW RMS
160mV input for 1V RMS output into 32 Ohm load (31mW)
200mV input for 1.27V RMS output into 32 Ohm load (50mW)
Frequency response @ 1V RMS:
flat from 45Hz to 20KHz, -1dB @ 35Hz, -2dB @ 24Hz
Total harmonic distortion into 16 Ohm load @ 1KHz:
1V RMS (62mW) 0.015% 1.27V RMS (onset of clipping, 100mW) 0.04%
Total harmonic distortion into 16 Ohm load @ 10KHz:
1V RMS (62mW) 0.05% 1.27V RMS (onset of clipping, 100mW) 0.1%
Unconditionally stable on capacitive loads