- on Audio/Video/Photography
- Published in issue 1/2011 on page 48
Low-cost Headphone Amp
Music to your ears
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CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor Members can exclusively download these files for free as part of their Membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service. Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.
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
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
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
D1,D2,D3,D4 = 1N4148
T1,T2,T3,T5 = BC550C
T4 = BC560C
T6 = BD139
T7 = BD140
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