Apalis iMX6 + Ixora analog audio feedback from DAC to Line In

We noticed that playing audio via the builtin SGTL5000 DAC causes a strong analog feedback into the LineIn input on the 7-pin header, even if no external devices are connected.

So playback on the left DAC channel leads to strong feedback into Line In left and playback on the right DAC channel leads to strong feedback into Line In right.

Is using the Line In together with the DAC an unsupported combination?

Any other combination (Line Out+Line In, DAC + Mic In) doesn’t cause this feedback, however we are kind of forced to use the DAC because Line Out is not available on Ixora.

Even if Line Out would be available the DAC would be still in use. A head phone output has just additional amplifier after same DAC. Please note that Ixora board is kind of evaluation board so high quality sound was not in consideration. You can check Ixora PCB design to see that Mic in and HP out lines placed close to each and relatively long. You can decrease SGTL HP amplifier gain to lower a microphone feedback.

Hi Alex, yeah we already noticed that the traces were relatively close on Ixora. However that wouldn’t really explain the channel pairing because on Ixora the audio lines are placed in a L|R|L|R pattern.
We can kind of work with it, I was just wondering whether this was a known issue with the SGTL5000. Also it doesn’t occur with Mic-In, just Line In.

I will try to test with the evaluation board and a different carrier to see whether it is related to Ixora at all.

Hi iSchluff.
Are you talking about feedback or crosstalk?