Article
FET Amp with Valve Sound
Warm sound from FETs?
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.
Materials
Gerber file
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PCB
Component list
Resistors:
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
Capacitors:
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)
Semiconductors:
T1 = BS170
T2,T3 = BUZ72A
IC1 = 78L06
Miscellaneous:
K1, LS1 = 2-way PCB terminal block, lead pitch 5mm Heatsink, Rth < 1 K/W
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
Capacitors:
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)
Semiconductors:
T1 = BS170
T2,T3 = BUZ72A
IC1 = 78L06
Miscellaneous:
K1, LS1 = 2-way PCB terminal block, lead pitch 5mm Heatsink, Rth < 1 K/W
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