Well I am not totaly ok with your view.
In my view, the best way is to connect directly the NAS to a DAC in order to avoid any additionnal cabling and components that can only degrade the signal.
Some small interfaces like hiface evo2 exists to convert USB to spdif and then go into a DAC.
But again, in my view, the best is a direct connexion.
Why not using a computer?
Because if you connect your computer to the DAC, you can not use it anymore (except if you want to stay close to your dac or use a 10meter long USB cable!)
The more convenient is: you want to listen to some music, you switch on your DAC/preamp/amp, switch on your laptop or tablet, launch audio station and navigate into your discs from your couch.
That is easy and user-friendly. Then, once music is playing, I can surf the web or wathever I want to do.
Hello guilder0.
There are some drawbacks in using the nas as a network streamer/player.
Some might not be relevant to you but this is not necessarily everyone's case.
Here are some:
1) The solution you propose requires the NAS to be close to the hi-fi setup. Even in the case your storage in on SSDs (expensive), NAS boxes have fans, which produce audible noise. Also, which additional cabling should degrade the signal? Unless you think to use a very long usb cable: this is definitely not advisable for any worthy audio setup.
2) A NAS is designed to do different things. It may not have the necessary CPU power to stream audio to your dac reliably. Also, they usually have a very little amount of RAM, less than what you would put on a custom box built for the purpouse. Try setting high-quality upsampling (via the samplerate_converter "Best Sinc Interpolator" setting of mpd) and see what happens. Chances are the NAS simply can't keep up and play music correctly.
3) Power Supply. The PSU of a NAS is certainly not designed for audio. The electrical noise produced by a sub-optimal PSU might (in my opinion,
does) degrade audio quality.
4) Usually NAS boxes use custom operating systems, so it is not certain that at some time you might not be able to mantain your solution, maybe after some software upgrades. It's not a supported use-case of the NAS itself.
My suggestion is to use a dedicated box for audio. You won't regret it. Surf with your desktop, but play with a dedicated streamer/player (it may definitely be a PC).
Audio playback does not benefit from other processes running on the same machine. Audibly. I have experienced it in person.
All the claims like "a computer can process lots of tasks" simply do not apply, because audio playback is a real-time process. Even if any general purpouse PC can play audio, it does not mean that it must always play well
by-definition. The more loaded is the PC, the more the signal is degraded by jitter (time-domain deviations).
Instead, it is better to optimize the software to give priority to audio itselft. This can be done, for example, with linux and a low-latency kernel.
In my setup, a significant upgrade was obtained when I created a dedicated box (with an old mainboard with intel atom D510, an SSD, ubuntu server, mpd and upmpdcli) and start using that box instead of the PC I use to do other stuff. If you build something from scratch, a new generation, faster, but low-tdp cpu is advisable. With the correct case you can make the setup passive (no fans, like my atom setup) very easily, although it might not be as cheap as a matching intel NUC box). Also, you can use a linear PSU, which is a considerable upgrade compared to the standard switching power supply bricks.
My .02€
