LM386 difficulties

Thread Starter

leejongfan

Joined Nov 5, 2008
1
I have been trying to use this LM386. Actually, when I used breadboard to build my 1st prototype, it worked fine (yeah still had noise but acceptable, at least i can understand the sound)

But now I am doing the prototype using PCB and its performance is very bad. I cant even hear anything except noise and buzz.



I also used decoupling cap for the power supply and an 8Ohm speaker.
 

Audioguru

Joined Dec 20, 2007
11,248
Hi Leejongfan,
You have a capacitor with backwards polarity connected between pin 1 and pin 8. This capacitor increases the voltage gain 10 times.

The capacitor from pin 5 in series with the 10 ohms resistor to ground looks like an electrolytic type instead of a 0.05uF (0.047uf) ceramic or metalized plastic film type.

With the very high voltage gain then the input must have a shielded audio cable because ordinary wires will act like an antenna and pickup mains hum and buzzing.
 
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