How to get the best digital sound from computer to headphones

[DScarinci1]

I would like to hear what people are using with their computers to get the best digital sound possible to their headphones. I created a headphone micro-system to experiment with different products. The 30 day try out return period made it possible to test different products and the result was a series of articles about them. Here is the main article:

12 Tweaks to Improve Headphone Sound Quality | Donald Scarinci

 

[Big B]

System 1
Senneiser 800 Exumus Dp1 Oppo SE83 anti vibram feet Audio Sensibilities power cord. This is my main listening system and all listening is with discs.
System 2 is Senneiser 650 with moon audio silver dragon cables Ear max tube amp with mullard tubes Hrt music streamer 2+ dac this will be my computer listening.