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:
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