Digital Room Correction with the HiFiBerry DSP card

[adamdea]

A hardware mixer might be obsured using plughw:

I never use it as it "hides" the actual audio formats supported by the dac, which cripples many of the features that are built into squeezelite, like the resampler.

Try

squeezelite -o hw:CARD=Out -L

I'm afraid that draws the same blank. I don;t know if this is relevant but alsamixer says this
This takes me back to wonderign how it is the volumio controls the dac vc.