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speaker noise reduction?

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ahgu

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What are the ways to reduce noise on the speaker?

I have white noise from my speaker from otuput of the codec, even outputting zero.

My setup:

DAC---> differential output --> 10X power amplifier(bridged connection).


From some measurement, I found the noise from the DAC is higher than the ground even though it outputs 0.

Also, there is noise in the circuit that contribute the the speaker before 10X gain.

I measure the AC voltage across the some points. I don't know how to measure the noise, measuring AC voltage using a 6.5digit DMM is the only way I can think of.

Regulator: 0.4mV
DAC output at 0: 0.8mV.
Input to the power amplifier is min 0.4mv even if DAC is removed.
With these combination, I hear white noise from the speaker.

Now how can I remove the white noise? This seems a tough problem.
 

echo47

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Do you have an oscilloscope with a high-gain input channel? The noise waveform may suggest what's causing the noise.
 

mr_ghz

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Hi ahgu

Measuring the noise with a DMM is nearly inpossible. For a correct
measurement you need a oscilloscope.
In my opinion your noise could be generated in the DAC or in the
amplifier. Is the noise still there if you short the input of your amp
(the DAC not connected)? --> It could be that a capacitor is the noise-
source
If the amp itself generates no noise, it's possible that the DAC generates
it. The problem is often, that the DAC has an analog and a digital
supply. Is your analog supply (if you have both) proper? Do you have
enough decoupling-C's near the DAC?

Greets
 

gauiver

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nomally noise is high frequency signal u can elimninate that by using some sort of low pass filter rejecting the high frequency noise. it will imrove things a bit. also the human ear can't hear all the frequencies, but using a filter will reduce the clearity a bit
 

richmon74

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I'm used to amplifiers. If after shotting the amp input with or without the DAC connected the noise is still there, then the prob may be from your ground line. check your gnd connections well. it could also result from ur pcb layout.

if i knew more details of ur work i would have known how to help more
 

pqtam

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Hi,
Fully right. One-point grounding should be applied, right?. I faced that kind of noise.
 

mubeen630

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You want to check and see if any fast rise time edge's harmonics are not coupling to your speaker traces.
Possibly a star ground connection to main ground plane will help.
Need more information.
In such cases layout has lot to do with your noise....
 

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