I'm using the Magnius for 2 purposes: (1) proper unbalanced to balanced conversion, and (2) set the "max volume."
I set an arbitrary max volume on the Magnius (based on wife and dog acceptance criteria) and leave it alone. I then use the Blue OS SW volume control to manage the volume below that preset maximum.
I decided to use the "Low Gain" setting on the Magnius. I experimented with both High/Low and felt that the added granularity (greater ability to fine tune the potentiometer setting) was meaningful. And, with the gain set on "High Gain," not only is it loud AF, it adds unnecessary risk when the wife occasionally decides to take matters (the volume knob) into her own hands.
Oh, I assumed that you used the preamp due to the relatively low sensitivity of the 502. Since the Bluesound as well as the Topping both max out at 2V and the sensitivity of the 502 is 2.38V (meaning that you need 2.38V to get max output from the amp), if you don't preamp you are not within the amps power envelope and not getting max performance or output.
The 502's have an input sensitivity of 2.35v and the 252's 1.66v
Why IS the 502 sensitivity so much lower than the 252's?