RPi Roon Bridge: USB vs coaxial and power supply

I’m running Roon Bridge on a Raspberry Pi 2, feeding my Yamaha A-S801’s built-in DAC. The RPi also has a Hifiberry Digi+ digital out. In direct listening tests, it’s difficult for me to discern a difference between the coaxial output (Blue Jeans Belden 1694A cable) and USB output (Schiit PYST cable).

I guess in principle, by using USB (if the transmission is asynchronous), the DAC is better able to reclock the signal to reduce jitter, but on the other hand, the RPi2’s USB ports have the downside of sharing their bandwidth with ethernet.

On the other hand, the Hifiberry Digi+ has an output transformer, which may do a better job of isolating the DAC from the RPi’s noisy electronics and in combination with a good quality coaxial cable, this interface may be preferable to USB.

Does anybody with a strong background in digital audio have an opinion on this?

I’m also interested in whether anybody has tried higher quality power supplies for their RPis like the iHifi iPower. Have you seen any benefit from a lower noise power supply? I am currently using the power supply built into my Belkin surge protector (http://www.belkin.com/us/BSQ1200-06-Belkin/p/P-BSQ1200-06/).

Does anybody have other tips about getting the best sound quality out of their RPis?

In case you are using the Hifiberry card, you don’t have to worry about the usb bus. The GPIO pins are connected separately to the BCM2836 chip.

For information about sound quality of raspberry pi and impact of the correct power supply I can recommend a video by Hans Beekhuyzen.