Apogee Mini-Dac FW / SRC / Clock / Toslink ?

[notengewirr]

Hi,
i have some Questions about the Settings:
All my Files/Music is Cd 44,1kHz ,so i set my Mac's Audio-Midi the same.
Does the Mini-Dac Upsample generally like the Mytek DACs ?
Better to set the Mac to 192Khz ?(so the upsampling is done by Software)

With Firewire i can choose the Clock-setting in the A/M setup, with Optical Toslink only the Mac is clocking.
Is it an advantage to use the Apogee Mini-Dac Clock ?
With the FW connection i notice a very little whistle coming out of my Tweeters.Only audible by putting my ears direct to the speakers-horn.
With the Toslink it is quiet.Ok i think there is a little Grounding Problem between my Mac >Dac