35W Power Audio Amplifier based LM391

Here the 35W power audio amplifier circuit based on LM391. Inductor L1 is constituted by 20 coils of wire, with thickness 0.9mm, round resistor R16. The transistors Q3-4 are the final amplification section, it should be placed on heatsink. If are used the Q3-4 in packing TIPxxxx they can be placed straight above in PCB. If however they are used transistor in packing TO-3, then it will be supposed they are connected with short cables in the corresponding places on PCB.

Schematic Diagram:

Component part list:

R1-3-5-8-10=1Kohm R2-7-11=100Kohm R4-6=4.7Kohm R9-12=100ohm R13=47Kohm R14-15=0.15ohm 5W R16=1ohm 2W carbon 5% R17=10ohm 1W carbon 5%

C1=2.2uF 63V C2=4.7uF 25V C3-17=47uF 63V C4-8-9=1nF 100V MKT C5=47nF 100V MKT C6=22pF ceramic C7-11-12-13=100nF 100V MKT C10=22pF ceramic

TR1=10K Trimmer D1-2=IN4002 IC1=LM391 Q1=BD139 Q2=BD140 Q3=TIP2955 Q4=TIP3055 L1=See text

PCB Layout:

Component Placement:

Take a note that this amplifier requires dual polarity power supply. Build the power supply using center tap transformer with output current 2A minimum and output voltage 30V, use about 6800 uF – 10000 uF electrolityc capacitors (elco). Good luck.

source: http://users.otenet.gr/~athsam/power_amplifier_35w_with_lm391.htm