DC Block component appears to introduce gain in ADAU1452

Hello Ian,

I think the data format of your audio input may be incorrect. I have slapped together a project to test my theory. What I found was I could get around 30dB less gain out of the DC Block once the DC is removed. Here are the results of my tests and I attached the project in case you want to try to repeat my test.

First example is to take the oscillator and send it to the outputs and you see on the meters the levels are exactly the same.

Then I added was it close to full scale DC to shift the audio to what is basically an unsigned audio signal.

Here are the results on the meter. You see that the DC Block has removed the DC and the audio is back to the -41dB level but the unfiltered output shows the DC level and it is around 30dB higher.

Put some meters in your project and see if you have a huge DC offset. Also, put a mute on each individual output so make sure the output that is 30dB greater is indeed the one that is from the DC Block. It is easy to have the wrong LRCLK polarity on the I2S signal and have the channels reversed.

So have a look at these possible causes and see what you find. Let us know...

Dave T

Hi Dave,

thanks for the pointer. It was more fundamental than that in the end. I had changed the sample rate earlier today and missed one of the registers in the clock / core setup. All is well now.

Cheers

Ian.

Hello Ian,

Great! Glad you worked it out and thanks for letting us know about it.

Dave T