By using the above amplifier circuit you can hear the sound quality is quite good by a high output power. Maximum voltage circuit pa approximately 55Volt DC. 70-140W output power with impedance 8Ohm. Part List R1 = 10K R2 = 1K R3 = 0.4R R4 = 0.4R R5 = 4.7R C1 = 0.015 C2 = 10uF C3 = 220uF C4 = 0.15uF C5 = 220uF C6 = 47uF C7 = 0.047uF U1 = STK050 , STK070