Article
Simple Hybrid Amp
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The debate still goes on as to which are better, valves or transistors. We don't intend to get involved in that argument here. But if you can't make your mind up, you should try out this simple amplifier.
This amplifier uses a valve as a pre-amplifier and a MOSFET in the output stage. The strong negative feedback makes the frequency response as flat as a pancake.
This amplifier uses a valve as a pre-amplifier and a MOSFET in the output stage. The strong negative feedback makes the frequency response as flat as a pancake.
Materials
Gerber file
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PCB
Component list
Resistors
R1 = 1M?
R2,R4 = 180
R3 = 2k2
R5 = 1k
R6,R7 = 100k
R8, R9 = 4k7
R10 = 47k
R11,R12,R13 = 1.5 5W
P1,P2 = 4k7 preset
Capacitors
C1 = 100nF 250V MKT, lead pitch 15mm, dim. 7x18 mm max.
C2 = 220pF
C3 = 10µF 400V radial, lead pitch 5 mm o 13mm max.
C4 = 2µF2 250V, lead pitch 27.5 mm, dim. 11x30 mm max.
C5,C10 = 100nF
C6 = 100µF 25V radial
C7 = 2µF2, lead pitch 5 or 7.5mm
C8,C9 = 4700µF 25V radial, lead pitch 7.5mm, o 18mm max.
Inductors
L1 = ? 50 mH, not on board, see text
Semiconductors
D1,D2 = 1N4001
T1 = BC337
T2 = BUZ11 (or IRFZ34N)
Miscellaneous
V1 = ECC88 with 9-pin valve socket (Chelmer Valve Company)
Heatsink for T2, ?1 K/W
PCB, ref. 050153-1 from The PCBShop
R1 = 1M?
R2,R4 = 180
R3 = 2k2
R5 = 1k
R6,R7 = 100k
R8, R9 = 4k7
R10 = 47k
R11,R12,R13 = 1.5 5W
P1,P2 = 4k7 preset
Capacitors
C1 = 100nF 250V MKT, lead pitch 15mm, dim. 7x18 mm max.
C2 = 220pF
C3 = 10µF 400V radial, lead pitch 5 mm o 13mm max.
C4 = 2µF2 250V, lead pitch 27.5 mm, dim. 11x30 mm max.
C5,C10 = 100nF
C6 = 100µF 25V radial
C7 = 2µF2, lead pitch 5 or 7.5mm
C8,C9 = 4700µF 25V radial, lead pitch 7.5mm, o 18mm max.
Inductors
L1 = ? 50 mH, not on board, see text
Semiconductors
D1,D2 = 1N4001
T1 = BC337
T2 = BUZ11 (or IRFZ34N)
Miscellaneous
V1 = ECC88 with 9-pin valve socket (Chelmer Valve Company)
Heatsink for T2, ?1 K/W
PCB, ref. 050153-1 from The PCBShop
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