My Volumio PRIMO is connected via USB to an external DAC. The DAC has extremely high technical parameters. The USB bus is galvanically isolated. The DAC, in turn, is connected to the headphone amplifier. The DAC output is also galvanically isolated. The headphone amplifier has parameters adequate to the DAC. For listening, I use studio headphones that are able to bring out every nuance of the sound. My sound source is TIDAL (Volumio is connected to LAN via WiFi), mainly Master files. Volumio does not interfere with MQA files and delivers them to be decoded in the DAC. This set allows you to analyze every nuance of the recording. The Volumio has proved to be perfect and so far I have no negative comments. I highly recommend buying this streamer. If there are any problems with the sound, it will usually be a different component of the listening path. One more important note, I use the standard SMPS power supply provided by the manufacturer, as I found out that the voltage is stabilized inside the Volumio. In fact, the sound quality is confirmed by the use of very good stabilizers. I haven't checked the sound quality using the internal DAC yet. When I check, I will describe my impressions. Meanwhile, I cordially greet the Volumio constructors for their fantastic work and I recommend everyone to buy it and enjoy the very high quality sound. Greetings to everyone, Andy ;-)