20W amplifier schematic with mute

This is a series of audio amplifier using ic and equipped with a mute switch. This circuit using ic and has 20W output impedance 4 ohms. Scheme and a list of components can be seen below.
20W amplifier schematic with mute

Part List :
Resistor 
R1 =  3.3K
R2 = 39R
R3 = 39R
R4 = 3.3K
R5 = 3R
R6 = 3R
Capacitor
C1 = 1uF
C2 = 1uF
C3 = 10uF
C4 = 100uF
C5 = 100uF
C6 = 220uF
C7 = 0.1uF
C8 = 0.1uF
IC
IC = ULN3793W