Why is the charger not included ?

To charge our audio equipment you can use a single charger and charge devices one by one. Most likely you will already have multiple 5V chargers from your (old) phone(s). By shipping a new charger with each device would not be good for our environment.

Also chargers must be suitable for your local mains supply, its better to buy one locally if you do not already own one (or more).

What host device can I use with the UTOS ?

We tested the UTOS with Windows/Linux and Apple PCs and with iPhone and iPad using the Lightning to USB3 camera connection kit.

What DAC can I use with the UTOS ?

If your DAC has a standard Toslink interface it will most likely work, but limited to max. 96/24.

What is wrong with streaming ?

Do you want the best sound quality or the ease of streaming ?
You can't have both !

The UPL is a very clean source, streaming will never be as clean.

Why offer a 16 bit DAC?

Each bit represents a dynamic range of 6dB. Perfectly healthy auditory system can detect up to 18 bits or 108dB where the lowest bit is just barely audible. With 16 bits we have 96dB dynamic range. Our auditory system has a protection mechanism that changes the gain depending on sound pressure levels. So we don't hear 18 bits all of the time, just for a brief moment before our automatic gain control sets in. There is always some ambient noise in the listening room, typically 30dB that will mask some lower bits. So these bits become inaudible or very difficult to hear. In general it is not comfortable nor safe to listen at high SPL for extended time periods, so we simply have to turn down the volume. This also lowers the practical dynamic range and the related number of bits we can still hear well below 16 bits.

Audio sets are not perfect and often fail to resolve 16 bits at top volume setting. So in practice it makes very little sense to use more than 16 bits for playback. For digital sound editing it makes a lot of sense to have more bits and related higher dynamic range.

Why offer a 24 bit DAC?

When we don't need more than 16 bits for playback, why a 24 bit MOS DAC?

We can play 24 bit digital audio files without the need for converting these to 16 bits.
And in general a 24 bit DAC has to be constructed with more accurate parts. So a 24 bit DAC can offer slightly lower bit errors because of this. Some customers simply want to be on the safe side and therefore choose a 24 bit DAC..