7.1 ch 電腦sound card及喇叭

1. Seperate the noisy source from SMPS (power supply)

2. The S/N ratio show in the sound card may be the figure of the S/N ratio of DAC (from DAC datasheet)

3. Suggest sending out the SPDIF to decode in external source. Like DAC.
Or direct drive the Class-D using Digital input class D. (HiFifever coming soon)

No.

You can use simple measuring equipment to test your S/N ratio.