Due to the mechanical contruction of the glass tube valves, if the enclosure receives a knock they filaments will vibrate for a short period of time and produce a ringing sound. This will fade away within 20 seconds or so. It is very hard to hear the ringing when the musci is playing and will not lesson the enjoyment of your music.
The Digital to Analog converter inside the X1 and X8 bypasses your computer or smart phone's audio device so you can enjoy your music in HD. For Apple users there is usually nothing to setup other than plugging in connecting to your Mac to the amplifier via a USB micro cable.