Confusing volume changes

My living room setup is driving me crazy. I use a pi3b+ running ropieee xl that feeds my Genelec speakers through an allo digione hat via spdif. Digione and speakers are connected by a cable that converts spdif to aes/ebu.

This worked well until three or four weeks ago, when transmission developed buzzing noise and frequent dropouts.

I chose to ignore this and try a usb to spdif ddc (SMSL PO100) instead, which worked just fine.

Just for the fun of it I ordered another ddc (Douk Audio U2 pro) with more features. This also worked well, until it didn’t.

Starting two days ago the audio level all of the sudden was about 20dB lower with the douk audio device, while it was unchanged with the smsl.

There was a change in the setup, though: I replaced an open frame case with a flirc case, lowering the operating temperature by some 15°C.

Today I tried several different setups in roon. In the process the smsl interface suddenly became 12 to 15 dB louder.

I am really confused, because all digital signals should produce the same output level. I do not understand what causes these differences.

Settings in roon are default, volume control is dsp based. Is there a hidden alsa setting or something else not immediately visible?

Any help is really appreciated! Input concerning the noisy DigiOne is welcome, too.

Problem solved. I had changed volume setting from device to dsp without resetting device volume to full (100). dsp volume worked based on lower device volume.