Burkhard Kainka
About the article

FET Amp with Valve Sound

Warm sound from FETs?

FET Amp with Valve Sound
A class-A FET amplifier can be made to sound as good as a valve amp when you follow the right design principles. This amp may not have a particularly high output power but using just standard components it produces a ‘warm sound’ reminiscent of a valve amplifier.This purpose of this design is not to produce an amplifier to compete with modern high quality sound systems in terms of output power and low distortion figures but instead to be a bit more experimental and use modern FETs in a valve circuit configuration to try and recreate the warm ‘valve sound’ produced by valve amplifiers and much appreciated by many audiophiles.
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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.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1,R3 = 1k?
R2 = 220k?
R4 = 22k?
R5 = 100?
R6 = 1?5 5W
R7 = 0?18 5W
R8,R10 = 10k?
R9 = 27k?
R11 = 1?
R12 = 220?
P1 = 100k? preset
C1 = 1nF
C2,C6,C9 = 100nF
C3 = 470nF
C4 = 4700µF 10V (radial, max. diam. 18.5mm, lead pitch 5mm or 7.5mm)
C5 = 47µF 25V radial
C7 = 4700µF 25V (radial, max. diam. 18.5mm, lead pitch 5mm or 7.5mm)
C8 = 220µF 25V (radial, lead pitch 2.5mm or 5mm)
C10 = 330nF
C11 = 1000µF 63V (radial, max. diam. 18.5mm, lead pitch 5mm or 7.5mm)
T1 = BS170
T2,T3 = BUZ72A
IC1 = 78L06
K1, LS1 = 2-way PCB terminal block, lead pitch 5mm Heatsink, Rth < 1 K/W
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