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Q-Watt Audio Power Amplifier

Lots of power with low distortion

Based on a Labs project | May 2013 | Find it here
Q-Watt Audio Power Amplifier
Good news for all audio enthusiasts: we are proud to present yet another all-analog circuit developed entirely in house. Despite the simple design of this audio power amp with just one pair of transistors in the output stage, Q-Watt can deliver over 200 quality watts into 4 ohms with exceptionally low distortion thanks to the use of a special audio driver IC.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD 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.

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Download the BOM list
The BOM (Bill of Materials) is the technically exhaustive listing of parts and other hardware items used to produce the working and tested prototype of any Elektor Labs project. The BOM file contains deeper information than the Component List published for the same project in Elektor Magazine. If required the BOM gets updated directly by our lab engineers. As a reader, you can download the list here.
Want to learn more about our BOM list? Read the BOM list article for extra information.
Component list
(5%, 0.25W, unless otherwise stated)
R1,R3 = 390Ohm
R2,R4,R17,R18,R22,R23,R30 = 15kOhm
R5 = 8.2kOhm
R6,R20,R28 = 1.2kOhm
R7 = 220Ohm
R8,R9 = 100Ohm
R10,R11 = 0.2Ohm 1% 5W, low inductance (Vishay Dale LVR05R2000FE73)
R12,R13 = 3.9Ohm 5% 5W
R14 = 220kOhm
R15,R16 = 10MOhm
R19 = 27kOhm
R21 = 470kOhm
R24 = 1MOhm
R25,R26 = 820kOhm
R27 = 68kOhm
R29 = 1kOhm
P1 = 470Ohm trimpot, horizontal
C1 = 4.7?F 63V, MKT (metal/polyester), 5mm or 7.5mm pitch
C2 = 1 nF/400 V, MKT (metal/polyester), 5mm or 7.5mm pitch
C3 = 18pF 500V (replacement for the original trimmer 5-57pF 250V)
C4,C6,C7 = 100nF 100V, 5mm or 7.5mm pitch
C5 = 47nF 400V, 5mm or 7.5mm pitch
C8,C9 = 4700µF 100V, 10mm pitch, snap-in, 30mm diam. (Panasonic ECOS2AP472DA)
C10 = 2.2µF 63V, 5mm or 7.5mm pitch
C11 = 33nF 63V, 5mm or 7.5mm pitch
C12,C13,C16 = 10µF 100V, 2.5mm pitch, 6.3mm diam.
C14 = 1µF 250V, 2.5mm pitch, 6.3mm diam.
C15 = 220µF 16V bipolar, 5mm pitch, 10mm diam.
L1 = 450nH: 13 turns 14AWG (1.5 mm) enameled copper wire, 7mm inside diam.
D1,D2 = 15V 0.5W zener diode
D3,D4 = 1N4004
D5 = 1N4148
D6 = LED, red, 3mm
T1 = BD139
T2 = MJE15032
T3 = MJE15033
T4 = MG6330-R
T5 = MG9410-R
T6–T10 = 2N5550
IC2 = OPA177GPG4
IC3 = 4N25
K1 = 2-pin pinheader, 0.1’’ pitch
K2–K6 = Faston (blade) plug, PCB mount, 0.2’’ pitch
K7 = 3-way PCB screw terminal block, 5mm pitch
RE1 = relay, PCB mount, SPCO, 16A, 48V coil, 5.52kOhm (TE Connectivity/Schrack type RT314048)
TO-220 isolating washer for T1, T2, T3, Kapton MT film, 0.15mm, 6kV
TO-3P isolating washer for T4,T5, Kapton MT film, 0.15mm, 6kV
TO-220 3-mm isolating bush for T2,T3
Heatsink, 0.7K/W (e.g. Fischer type SK 47/100 SA)
Heatsink for IC1, dim. 25x 80 mm, 2 mm thick aluminum
PCB # 110656-1, see www.elektor.com/110656
Power Supply (for one amplifier)
Power transformer: sec. 2x40V, 500VA (e.g. Nuvotem 0500P1-2-040 for 230 VAC mains)
Bridge rectifier: 200V, 35A (e.g. GBPC3502) (Fairchild)
Four 10,000?F, 100V electrolytic capacitors (2 in parallel on each supply rail)

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