I believe that the AMD high definition audio is the audio that is available from the HDMI output of your AMD graphics card.
The other High definition audio is from your motherboard audio that goes to your headphones/Speakers,etc.
My Computer
Computer type
PC/Desktop
Computer Manufacturer/Model Number
Custom Built
OS
Windows 10 Pro x64, Windows 8.1 Pro x64, Windows 7 Ultimate x64 SP1,
CPU
INTEL i9-7920X LGA 2066
Motherboard
Gigabyte X299-WU8 F3
Memory
64 GB (4 X 16 GB) G-Skill V Series DDR4 3200 Quad Channel
Graphics Card(s)
EVGA GTX 1060 SC 3 GB
Sound Card
Realtek Onboard ALC1220
Monitor(s) Displays
2 x Samsung S27E310
Screen Resolution
1920x1080
Hard Drives
Samsung 2 x 970 EVO Plus 500 GB NVMe
1 x 6TB WD 6003FZBX SATA
1 x 6TB WD 60EFRX SATA
12 x 3TB WD 30EFRX SATA