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Topic: How to remove pwn background audio noise (Read 426 times) previous topic - next topic

Anvay

How should i remove the backround crackling sound through the speakers when music played.?

Power_Broker

Filtering will do the trick. Try a low-pass filter circuit.
"The desire that guides me in all I do is the desire to harness the forces of nature to the service of mankind."
   - Nikola Tesla

Anvay

Thanks for replying. But sorry i didn't understand it. I am quite a noob in this. Can u explain in detail?

Power_Broker

A low pass filter stops high frequency noise from being passed to the speakers, but allows lower frequency signals (such as your music) to pass to the speakers. Thus, the noise will be eliminated.

Low Pass Filter Tutorial
"The desire that guides me in all I do is the desire to harness the forces of nature to the service of mankind."
   - Nikola Tesla

DVDdoug

#4
Sep 08, 2017, 05:17 pm Last Edit: Sep 08, 2017, 05:20 pm by DVDdoug
The PWM should be filtered-out before sending the audio to an amplifier.  (You should filter-out the DC too.)

Ideally, the PWM should be well-above the audible range so you can't hear it.   If the PWM is less than 20kHz, you may hear it if it's not filtered-out.   (You will  hear the default ~500Hz PWM, but I'm sure you're not using that!)  But for high-quality audio, you don't want to filter-out the high-audio frequencies.  ("Traditional" high-fidelity goes from 20Hz to 20kHz.)

Although you can't hear above ~20kHz, ultrasonic PWM can cause audible side-effects from the amplifier, or worse!    You might be amplifying an ultrasonic PWM signal to full-amplifier power, and that can fry an amplifier or tweeter.    (I once fried my power amp that way, but it was a homemade preamp oscillating at some RF frequency, not PWM.    The only thing I heard was a little "ffft" as the amplifier died.)

pjrc

A "backround crackling sound" is probably cause by some other problem.

Perhaps something you are doing is unwittingly causing Nyquist aliasing?

MarkT

Quote
How should i remove the backround crackling sound through the speakers when music played.?
By making appropriate changes.  But what's appropriate depends on what you have, which we
know nothing about because you've posted no details.

Details please for code, circuit, power source...
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Anvay

Thanks for your responses. I got it figured by using a 10k pot between pin9 and amplifier  :)

MarkT

Perhaps the problem was overloading the amp then?
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Anvay

Maybe. But I compromised some volume to remove the noise. The volume is lower than before.

Will using a dc module in between help better?

Grumpy_Mike

Quote
Will using a dc module in between help better?
You will have to be a lot more specific if you are going to get far with electronics. The term DC module could apply to hundreds of things, which one of these do you mean now?

Anvay


Grumpy_Mike

OK so then the point of using PWM goes out the window and you have to rewrite the software to talk to the DAC. This may or maynot reduce the noise depending on the cause of the noise which we haven't been able to established due to your none cooperation with are requests like this one:-

By making appropriate changes.  But what's appropriate depends on what you have, which we
know nothing about because you've posted no details.

Details please for code, circuit, power source...

Anvay

I am sorry for not giving details.
I will send each and every detail now

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