Amplitude Levels Differences at Higher Input Frequencies

Hello Hermione,

I can't simulate your issue. I just used your project, and everything works as expected for me. Please look at the below screenshots.

Tx side:

Rx side:

I even checked the analog output by sending the input stream to the CODEC.

Please explain how you measured this and come up with the results. So, I can try the same and try to simulate the same.

Regards,

Harish

Hi Harish !

I have this observation. But the difference is that we are interfacing two boards ( both ADAU1466 )

Sampling Fs is 192 kHz TDM4

Board 1 ( Master )

Sends TDM4 @192 Fs Via serial Out 0

Board2 (Slave)

Receives TDM4 @192Fs via Serial IN0

You then record the Serial InN 0 via SPDIF in APX

At higher frequencies such as 14kHz ,13kHz etc there is deviation from the original dB level .

Can you please check this in priority?

If you need I will supply the project file that we used

Regards,

Zayn

Hello Zayn,

You really should be posting this on the forum as a new post and not responding to an older post. It is easy for us to miss your response or not see it for a while.

Your situation is a little different. I would setup a new project where you are sending just an oscillator out the SPDIF and see what it looks like on the AP. Check that you do not have any filters or pre-emphasis set on the AP input or the AP output.

Then for the other side of this. The AP output going to DSP, place some meters right at the input to the core in the DSP program so you can see the level coming into the DSP. I am suspecting this to be an analog issue or a filter issue.

Doing these experiments will help identify if it is an issue on the input side or the output side.

Thanks

Dave T