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AC97 Noise on right channel (iMX6 , SSI & WM9715)

Question asked by Andreas Zeiler on Feb 11, 2014
Latest reply on Feb 25, 2014 by Wigros Sun

Hello,

 

I'm using a iMX6 processor and the SSI for interfacing a WM9715 codec. So far it works fine. But I have a noise on the right headphone output. The jacks are only connected to headphone. So no other output is available.

When I play a wave-file with a moving sinus from 440Hz up to 880Hz the noise changes. Also, when I play a file with silence (created with audacity - there are some artefacts in this wav-file but not influencing) I can hear some clicks on the right channel.

They are not periodic, but the occur often. On the left channel everything works fine. Sound is good here. Also, there is no clicking or anything else. It not depends on the sample frequency. Noise is hearable with 8kHz up to 48kHz sample rate.

And when I just move up mixer volumes (headphone (analog) and PCM (digital)) I hear just a normal noise which comes from the internal amplification of the headphone out. But thats a normal case I think. So it occurs only when I play a file and open a pcm stream.

I also tried turning off some mixers and registers from the WM9715. But it didn't help. The cummunication over AClink is fine.

 

My concern is that this noise comes from the digital signal which is provided to the DAC from the ACLink. Maybe there is a wrong shift or a wrong adjusted alsa filter which influences the pcm signal from processor to the WM9715.

 

Does someone has an idea where the problem can be? It's realy confusing.

 

Kind regards

 

 

Andi

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