Volume control (Hardware) and DSD

Hi there,

New here. I have a Pi4+Topping E30, connected via USB and recognised as a mixer. I therefore use Hardware volume control and it seems to be working seamlessly (Spotify,MP3,FLAC), except it does not when I play DSD files? Apparently it doesn’t matter whether the DAC is in Preamp mode (volume control enabled) or not, behaviour is the same.
Not sure what’s going on here - please help?

Thank you!
Luca