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simple amplifier lm386n-1

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m3a

New Member
hi all
i tired to made a simple amplifier by lm386 n-1 as the following:
- input variable resistance 1 k ohm to pin 3
- pin 2&4 earth
- 220 uf (+) to pin 5 and (-) to the speaker
- the other terminal of the speaker to earth
- 9 v to pin 6
the speaker 8 ohm 0.2 w

but the output is very weak nearly i can't hear it and so bad
how can i fix this problem
thanks for all
 

nettron1000

New Member
When you say sound from computer do you mean the LM386 is plugged into one of your computer speakers or is it directly interfaced from one of the computer ports? The LM386 cannot directly work with a digital signal, the signal as to be converted to analog.
Also to increase amplification put a capacitor (1 to 10 uf)between pins 1 and 8.
 

m3a

New Member
i take the sound from the output og the sound card ( jack to speakers )

i put the capacitor as you said put
before i put the power to circuit (vcc=9 v dc) i hear a weak sound from the speaker.
after i put the power as same before

thank you for your contact
 

nettron1000

New Member
Your circuit should work as discibed in your schematic. Have you tried increasing the input from the computer by opening the usual windows volume control ?
 

nettron1000

New Member
Have you tried plugging your circuit into a different audio source such as a radio or comp speaker headphone jack ? Im thinking the comp output jack doesnt have sufficient drive for the LM386.
 

mozikluv

New Member
lm386

:D hi m3a,

i have seen the circuit you have used and based on that it is suppose to work fine.

have you check whether you have a grounded traces specially the signal line?

have you soldered the components well?

whats the voltage at the output pin? is it half the supply?

if everything checks out good, i have only one conclusion, your 386 is defective. :D
 

mozikluv

New Member
lm386

:D ned,

here is a rejoinder for my previous reply, try this approach as a feedback series a 10K resistor with a 0.033uf mylar cap between pin 5 (output) and pin 1 (gain).

pls take note that this chip has two (2) gain pins, 1 & 8. do not connect the series components between pin 5 & pin 8 :!:

:) :)
 

StupidDum

New Member
I'm a beginner in this, well.
I'd built a very simple audio circuit using LM386 with microphone as input, and output to a loud speaker.
How do you connect the jack to input of LM386??
Previously i just connect the positive line of microphone direclty to LM386, and it didnt work.
Well then, i connected the positive line of mic to +9V supply through a pull-up resistor ;and connected a capacitor between positive line of mic to the potentiometer which is connected to pin 3 of LM386.


I have some questions..hmm...
What are the difference between audio IC and other general op amp?
Can i increase the gain by cascading two LM386?
I'd be most grateful to have your assistance. Thank you
 

mozikluv

New Member
lm386-1

:D hi,

if you want your system to work you have to make a mike pre-amp and connect the output to the non-inverting input of the 386. to increase the gain follow what i have previously posted. you dont have to cascade, rather do a bridge system to have a higher output. but you wont hear a big difference, so better stick to a single IC.

as to whats the difference between a gen. op-amp and power audio IC, nothing much. the gen. op-amp is used to increase the signal to a level that can drive the power audio IC. they are all amplifiers, the power audio IC just have a higher power output. :D
 

StupidDum

New Member
ehh..I have a little bit problem on amplifier..
I'm building a circuit that can detect the voice at certain frequency range, using microphone.
I use a LM386 as pre-amp of gain 200, connected to a Butterworth Bandpass Filter, and then to a LM285 to provide further gain.
However, i found out the output is still very small, around 1Vpp. Hence i added another LM285 with gain of 10.

The things work fine if i use the input from audio generator.
However, when i use microphone, the output dowan increase 10 times as expected. Wondering why.

Another question, in a non-inversting amplifier, we increase the gain by increasing the.. resistance. Is there a limit for the gain/resistor?
 

mozikluv

New Member
lm386

:D hi,

the only limitation is the value of the resistor available, however as to the gain of the IC, you are limited to what the manufacturer has designed and too much gain can set the IC to oscillate which would need more parts use to prevent such occurence. :D
 
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