Audio 180 degree out of phase

Hello Prabhakar,

Can you supply your schematic so I can see how you are connected to the part?

Dave T

Hi Dave,

Attached is the schematic.

Cheers,

--Prabhakar Lad

Hi Prabhakar,

Where are you measuring the audio as being 180 degrees out of phase, on the analog or digital outputs? I notice that you are using LOUT2L/LOUTLN and LOUT2R/LOUTRN for your analog outputs, which are the inverting differential line outputs. If you are measuring the phase shift at the analog output, I recommend you move these to LOUT1L/LOUTLP and LOUT1R/LOUTRP, as these are the noninverting analog outputs.

Regards,

Tyler

Hello Tyler,

Lout pins are just used for test points.  The path is as follows

Input 1 -->>|

                   |------>>ADC >>> DSP channel 0--->> Mcasp (record)

Input 2 -->>|

The product records data all the time in stereo mode. So it can be configured in mono/stereo/mixed. The inputs are configured to be differntial

So now for mono case: In this mode Input 2 is disabled. Input 1 is connected to left ADC & right right ADC, which means same signal is going to left and right channel of ADC. Since the input is configured as differential the left becomes positive and right becomes negative, since its the same signal the left and right channel become 180 degree out of phase.(The recorded wav file shows the phase difference)

Also now when I configure the inputs to stereo instead of differential, and give the same signal (Input 1 only mono microphone) to left and right channel of ADC and record the audio, I see that right channel is always muted, When configured in stereo mode

the adc's are smart ? (by smart I mean left adc accepts only left data & right adc accepts only right data as I can see that input1 is configured to both left & right adc but still the right channel is muted)

Cheers,

--Prabhakar Lad

Hi Prabhakar,

I assume when using the AIN1 as Mono you set it as Mono/differential in the input mode register. If not then that could explain what you are seeing.

Is it possible for you to send us the input mode and ADC Mixer settings for mono and stereo case?

Thanks

Rajeev