Volume control at WiiM Ultra vs DAC

[pieterv1]

I used to run a WiiM Pro into SMSL SU-6 as well. It was always at max volume because I was running it through an analog preamp.

So it should have no problem doing so

 

[Mr Ee]

I'd like to use the Wiim to control the volume, so should I set the SU-6 volume to max?

Welcome.

You don't say what comes after the su6 (anything else that performs volume control?), but maybe consider setting the su6 to a level such that full volume on the wiim isn't ridiculously loud at the speakers / headphones.
And / or use the wiim's volume limit so that full volume on both the wiim and the su6 isn't ridiculously loud.
i.e. use them however you like so that 'full volume' doesn't blow your ears off!