Hi-
I, too, am having issues with the DAC + ADC PRO. This model has a different dtoverlay, for this one it should be dtoverlay=hifiberry-dacplusadcpro
There are a number of differences in the chip used on this model, which include customized amixer settings and a PGA for the input gain.
Since M2P does not know about this card, it forces you to use hifiberry-dacplusadc, and the PGA settings get set to maximum and the amixer settings are inaccessible which results in unrecognizably distorted input when used with line level inputs from a phono preamp. In fact, the gain is so high, even direct cartridge connection to the input is still too high (let alone missing the RIAA equalization curve).
So, basically, we need a specific output device entry for this card so it sets the correct dtoverlay on boot. The custom amixer settings for input, bias, and gain could be left to /boot/config.txt because for me these are ’set once and forget‘ parameters.
Thanks
