Very rarely, we get a report that after installing OS Yosemite (Mac) and installing the updated DAC 2 driver for it, music does not play. The first thing we suggest in these cases is to find and remove ALL old W4S drivers, as a conflict can occur.

• Make sure to do a computer-wide Spotlight search for "W4S". Delete any files you find.
• For added peace of mind, we suggest manually going into your Extensions folders to double check for any Wyred 4 Sound driver. These can be found at: Library > Extensions; and System > Library > Extensions

After doing this and ensuring no W4S files remain installed, restart your Mac, then go through the installation process of installing the new driver.