B450m dsh3 ...That is because your phone has no connection to ground. On the plus side this pretty much eliminates any ground loop between your DAC and your speakers.
By far your best solution is going to be toslink to your DAC - though I very much doubt you'll hear a difference between your USB connection and an APTX bluetooth one - except for the noise being eliminated.
What motherboard do you have?
HDMI to otpical splitter ? Will it work ?
Use the HDMI port of my card to send sound and with a HDMI to optical converter use it to send sound ?