Sonos and Jolida

Maybe it's just me! I was an audio engineer back in the day (live not studio) and consider myself to have a pretty good ear. I bought a Jolida Glass FX tube Dac II and installed it into my system and can hear almost no difference between the Jolida and the Sonos Connect dac steaming FLAC lossless! The signal is transmitted to the Jolida using the digital coax output from the Sonos I can't believe that I don't hear any difference in the two devices but to my ears the sound is the same. Maybe I am missing something. Any insight would be appreciated. The original thought was to replace my analog system with a digital system if I could reproduce the near same listening quality.
Doug