Pre-amp or cd direct to XA30.5 ?

Your Pass XA30.5 has 30kohm input impedance, this is fine for you to direct connect from a source that has a digital domain volume control.
Just remember that some digital volume controls can "bit strip" if used below 2/3rds of full output.
Bit striping is a loss of bits, IE: instead of 16bit resolution it can be 14bit at volumes less than 2/3rds, which in some cases is not too bad as 14bit has a softer sound, which is better for background music anyway, such as dinner party music.

Cheers George

I had Mark Levinson No.39 a while back same setup, that's why Wadia did this also, so you could run it near full digital volume with the analogue gain selection so there was no risk of "bit Striping".
But to be honest the difference between full 16bit resolution and 14bit is not that huge, 14bit just sounds a little softened around the edges, which as I said is probably a good thing for dinner parties, or lift music.

Cheers George

Fsyme
I would set it .5v first and if you can get loud enough volume, then your your fine. I'm sure you will as that's around 2/3rds of the XA-30.5's full output.
If not then go to 1.1v

Cheers George

I think there is an ulterior motive for saying this, a standard Oppo 105 that has low output impedance would be fine driving into the XA30.5, but Oppo 105 with a modded tube output stage will be much higher in output impedance, and maybe have trouble driving into the low input impedance of the XA30.5

Cheers George