Holo Cyan2 Isolation

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Cyan2 from Holo Audio is a pure NOS (non-oversampling) R2R DAC that's a perfect candidate for software upsampling using PGGB or HQPlayer. Its a great sounding DAC that can be transformed to be amazing with RF isolation. In order of priority (sound quality benefit), here's what I recommend:

1. USB•FILTER (with USB-A Adapters). Even a well designed source component with low RF noise USB will also benefit from additional USB filtering. USB-FILTER is an all-passive design with excellent RF/EMI line noise suppression on +5V/GND power and common/differential mode noise suppression on D+/D- data lines. 
2. DAC•WRAP. Made from laminated foil sheets of highly permeable alloy, DAC•WRAP prevents external electromagnetic energy from inducing electrical current along signal and power paths. Instead, impinging magnetic fields are deflected by the foil to flow along the outside of Cyan2. The beneficial effects are immediate and obvious. I recommend the double-wrap option.
3. RF•STOP LRC AC Filter. Use this filter to isolate Cyan2 from AC noise: from the AC mains or generated by the household environment and digital devices.
4. USB•CABLE. Use your existing well shielded/filtered USB cable or consider my own offering. Keep this cable as short as possible to avoid antenna effects. Note: due to Cyan2's proprietary USB receiver design, OPTO•USB and other (active) optical USB cables are not compatible.

Regarding software upsampling, I have tested the following: PGGB-RT (foobar2000), PGGB-IT! (foobar2000, JRiver MC) or HQPlayer (V5.11 Desktop).  The consensus among industry reviewers and forum posters is that the DSD path is more transparent and pleasing than the PCM path. However, IMO, my kit of Cyan2 isolation helps to close the difference between PCM and DSD.