Meenkashi,

I think I am running into a similar issue as you in the AIC23 codec, although I am using the
C6713.  There is indeed an AC coupling cap between the line in and codec (if the audio port is
of similar structure to the 6713).  This will prevent any DC signal from passing through. 
However, I have tried bypassing (short circuiting) the cap and AC coupling-esqe effects still
appear when I measure the input in software.

The AIC23 line-in does have an ADC highpass filter which can be enabled in the Digital Audio
Path Control, but mine is disabled as far as I can tell.

- Louis
>  Hello,  
>I am working on the DSK5510 board that has the AIC23b audio codec. When   
>I do a simple audio loopback, I see that there is attenuation at the   
>output below 400Hz. The audio output seems to be at a stable maximum   
>value beyond 400Hz. But, between 1Hz to 400Hz, there is a roll-off.  
>Has anybody seen this before? Is this high-pass effect being introduced   
>by the audio codec?  
>On the schematic of the DSK5510 board I do see capacitors (AC coupling)   
>that are connected both at the input and output audio channels. That is,   
>there are caps connected between the audio input jack and the audio   
>input pin of the codec. There are caps also connected between the audio   
>output pin of the codec and the audio output jack. I am not sure if this   
>is causing the high-pass effect?  
>Could you please tell me what is actually causing this? I would be more   
>than happy to try a few things and provide more information if you have   
>a clue.  
>  
>Thanks,  
>Meenakshi.  
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