It comes as part of the Realtek audio driver version *.6870 which unfortunately isn't posted on the ASUS download site (the newer posted driver versions don't include it if you check this thread
Waves MaxxAudio gone???), but may have come with your original ASUS factory image if you still have it.
If you can get to the original ASUS factory image, check under the 'C' drive for the 'eSupport' folder and 'eDriver' folder to create a copy of the G750 driver DVD or audio driver.
Check the 'Filelist.txt' file under the 'eDriver' folder to find out which driver versions are included.
Edit: Glad to hear you could solve it and thanks for letting us know what happened!