25 Watt Audio Amplifier Circuit

High Quality simple design, No need for a preamplifier

This is a 25 Watt basic power amp that was designed to be (relatively) easy to build at a reasonable cost. It has better performance than the standard STK module amps that are used in practically every mass market stereo receiver manufactured today. When I originally built this thing, it was because I needed a 25 Watt PC amp and did not want to spend any money. So I designed around parts I had in the shop.

Circuit diagram:

25 Watt Audio Amplifier Circuit Diagram


R1 = 47K
R2 = 4K7
R3 = 1K5
R4 = 47K
R5 = 390R
R6 = 470R
R7 = 33K
R8 = 150K
R9 = 15K
R10 = 27R
R11 = 500R-1/2W
R12 = 10R
R13 = 10R
R14 = 220R
R15 = 220R
R16 = 10R
R17 = 8.2R-2W
R18 = 22R-4W(wirewound)
C1 = 470nF-63V
C2 = 330pF-63V
C3 = 470µF-63V
C4 = 100nF-63V
C5 = 470µF-63V
C6 = 100nF-63V
C7 = 100µF-25V
C8 = 100nF-63V
C9 = 10pF-63V
C10 = 1µF-63V
C11 = 100nF-63V
Q1 = BC560C
Q2 = BC560C
Q3 = BC560C
Q4 = BC560C
Q5 = BC560C
Q6 = BD140
Q7 = BD139
Q8 = IRF530
Q9 = IRF9530

Power supply section:

Power supply circuit diagram:


R1 = 3K3-1/2W
C1 = 10nF-1000V
C2 = 4700µF-50V
C3 = 4700µF-50V
C4 = 100nF-63V
C5 = 100nF-63V
D1 = 200V 8A Diode bridge
D2 = 5mm. Red LED
F2 = 3.15A Fuses with sockets
F2 = 3.15A Fuses with sockets
T1 = 220V Primary, 25 + 25V Secondary 120VA Mains transformer
PL1 = Male Mains plug
SW1 = SPST Mains switch

source: RED Free Circuit Designs