The Gustard X26 Pro is a slightly warm DAC that is not extremely detailed like some of my other ESS DACs. I used it with a bright and detailed headphone, and it was very good.
I sold it to buy a Musetec 005 for about 2x the price. That DAC is smoother sounding and overall better, but the Gustard X26 Pro is a very good DAC at that price range.