I have got a low pass sallen key filter on the output of the PCM5100A.
There is an attenuation stage (U4) followed by a single rail sallen key filter (U1). See the attached.
There is a AC coupling capacitor to bias the PCM5100A output to the op-amp filter stage.
I have set the PCM5100A to output at full scale (2.1Vrms). Directly on the output of the PCM5100A there are only odd harmonics (i.e. TP7).
When I probe the attenuation stage resistors (in between R29 and R30) - then I see even plus odd harmonics.
I removed the op-amp (U4) - then the even harmonics disappear.
I would expect the even harmonics to be on the output pin - why are they on the input pin?
Can the PCM5100A drive a op-amp?
