From CCRMA Wiki
Quad Speaker System
UA-101 Audio Interface
Here's a review that explains things pretty well about the card .
Changing Sampling Rate
Changing the sampling rate requires restarting the interface. Turn the SAMPLE RATE knob to the desired new sampling rate (normally 48 or 44.1kHz). Nothing actually happens until you restart the interface with the OUTPUT/POWER knob turned all the way down (counter-clockwise) until it clicks (the power light goes off). Turn it back to restart. The knob then becomes the volume or OUTPUT knob which controls the headphone volume but not the volume on the quad speaker setup. It's best to make sure you've got it set to the sampling rate set to what you think you will be working with, before you start your audio software. Just makes things cleaner. If you have to change the sampling rate while you are working with applications, first make sure you've saved your session files, because doing so may have unpredictable results.