filtering before LM386?

[newsci]

Hey,
im working with LM386.The output comes from 8bit DAC and i need a low pass series RC filter i suppose.The sampling rate is 8000/sec
Can anyone tell me the values for the filter ?

 

[AndrewT]

I'm guessing this is not for music?
What is it for?

 

[newsci]

No its for speech...its basically after desccrambling of voice message over wireless

 

[AndrewT]

frequency response 300Hz to 3kHz as in telephony or a bit wider?

 

[newsci]

yah upto 4 Kz not more...its over wireless

 

[AndrewT]

low pass at 40kHz (RC=4uS).
What about your high pass?

 

[newsci]

do i need one..i just needed the reconstruction filter.ITs a speech scrambler and descrambler.Well what exactly is the R and C value?

 

[AndrewT]

for RC=4.4uS, try R=2k0 and C=2n2F
If R=2k0 does not suit, then scale the numbers.
The RC does not need to be exact. It does not matter whether it is 9times or 11times the max speech frequency.

 

[mayank199325]

lm386 amplification and filter circuit

I am using lm386 for signal amplification recievied from microphone and then send them to analog pin of arduino..do i need a speech filter circuit also between lm386 and arduino or lm386 would limit the frequency response to 300-3400hz (the speech audio spectrum range)??....
{ basically i am trying to make a audio recorder..the arduino will store the data in a wav file and transfer it to sd-card for playback }..

 

[AndrewT]

The input to any receiver along the route could be susceptible to interference.
I suggest you fit RF attenuation at every input.