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Low-cost Headphone Amp

Music to your ears

Low-cost Headphone Amp
Low-cost Headphone Amp
There have of course been numerous designs for headphone amplifiers before this one, either more or less successful and simpler or more elaborate. The design presented in this article is straightforward, sounds quite good and can be built using well-established components.
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Materials

Gerber file

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PCB

Extra info / Update

Specifications (output load: 33 ?, supply voltage: ±9 V)

• Input impedance (without P1) 10 k?

• Bandwidth 3.4 Hz – 2.4 MHz

• THD + Noise (1 kHz, 1 mW/33 ?) 0.005 % (B = 22 kHz)

• THD + Noise (20 Hz - 20 kHz, 1 mW/33 ?) 0.01 % (B = 80 kHz)

• Signal to noise ratio (ref. 1 mW/33 ?) 89 dB (B = 22 kHz) 92 dBA

• Max. voltage (into 33 ?) 3.3 V (THD+N = 0.1 %)

• Max. input voltage 0.57 V (with P1 set to maximum volume)

• Current consumption 19 mA

Component list

Resistors
R1,R6 = 10kOhm
R2,R3 = 1kOhm
R4 = 270Ohm
R5 = 1.5kOhm
R7 = 4.7kOhm
R8,R9 = 150Ohm
R10,R11,R12 = 10Ohm
P1 = 10kOhm
P2 = 100Ohm trimpot
Capacitors
C1 = 4.7µF, lead pitch 5mm or 7.5mm
C2 = 6.8pF, lead pitch 5mm
C3 = 10pF, lead pitch 5mm
C4,C5,C6 = 100µF 16V radial
Semiconductors
D1,D2,D3,D4 = 1N4148
T1,T2,T3,T5 = BC550C
T4 = BC560C
T6 = BD139
T7 = BD140
Miscellaneous
Connection for P1 = 3-pin pinheader, lead pitch 0.1 in.
Connection for P1 = 3-way socket strip, lead pitch 0.1 in.
7 pcs 1.3mm diam. solder pin

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