Thank you for touching base with me and taking the time to verify the requested information! Both are very appreciated, @Somboon_Vorapanyasak!
Can you verify which version of the Vanguard you are working with (i.e “Krell Digital Vanguard” OR “Krell Vanguard Universal DAC”)? The reason I ask is because I did a quick search on the site and came across this thread:
Synology NAS core won’t play to Krell Digital Vanguard
What is interesting to me is what the representative from Krell mentioned in regard to the firmware version here:
"In order to get the benefits of Roon* you will need to run the software update from the front panel menu of your Vanguard product and also update the firmware in the internal digital module. If the firmware in your digital module is V2.7.6 or later, you can update it directly from the mconnect control app. Otherwise please click on the link below to download the instructions and update files. The latest software version for the Digital Vanguard is V1.16, for the Vanguard Universal DAC V1.04, and the digital module is V2.9.21. "
-Eric