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LM 386 is mad at me...

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i made an lm386 audio amp with 200 gain and hooked it up for use with an iPod and an optional mic. the circuit worked fine on the breadboard but when i soldered it, it got cranky and started oscillating (i think that there is some feed back)

the only differences are that on the breadboard R3 was 200Ω, R5 and R6 were replaced with a 100Ω pot.

on the soldered board C3 was 330µF. and all of the components were really close together.

i need to get this circuit working so i can start selling it for my next project.
 

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audioguru

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Why do you have a 5k pot or a 200 ohm resistor in series with the 8 ohm speaker? They reduce the max output to almost nothing. Use the volume control at the input to set the volume instead.

Your circuit is missing a very important supply bypass capacitor. It should be from 10uF to 100uF and connected very close to the power supply pins of the LN386.

C1 is supposed to be 0.05uf (47nF) so your 10nF is too small.

If the mic can hear the speaker then the circuit will produce acoustical feedback howling.
 
i chose to use the 10k to adjust the gain and keep the distortion low. the people that buy the circuit from me won't really care if there are a few extra parts on the board (that's something extra i can charge them for)

i did have a 47uF filter capacitor in the circuit near the power supply.

on the protoboard the 10nF was plenty go get the circuit to work (but i will try replacing it with 47nF)

the mic and the speaker were no where near each other. but i did find out why the aux connection was not working... it was not grounded at all for the common. (pure stupidity on my part)
 
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