My thoughts on the Pro-Ject Pre Box S2 Digital - terrific in its price range. Smoother, less edgy presentation than my Cambridge Audio DacMagic, without giving up any detail. I would describe the sound as right down the middle of the road: not bright, not warm. Different recordings sound different from each other, as you’d expect. Dynamic, good enough soundstage in all dimensions. Couldn’t ask more from a less than $400 DAC.
Plug and Play? No. Yes, you can plug it in with a USB connector, and all downloads will have CD quality sound, but this will not get you the MQA performance that you bought this for. Download the driver AND the digital firmware from the Project site or on the supplied CD.
MQA is available only when using a USB connector, and the external power supply is not required with connecting with USB. I haven't experimented with the power supply, upgraded power supplies (or even with non USB connectors).
With TIDAL: Settings - MQA Passthrough should be turned ON. You’ll know that you have it all correct - from listening, naturally, but also - when the S2 display shows the letters MQA and a blue dot. If you show MQB and a purple dot on the display, then you not turned on the Passthrough in TIDAL settings.
MQB vs MQA: MQA has two stages of unfolding its signal. With MQB you are instructing Tidal to perform the first of the two stages. I don’t know exactly the difference, but performance and sound are better on mine when set up as described above.
MQA vs. SACD: Usually MQA is a bit better to my ears, but its not a slam dunk, and not in all cases, at least not on my (decidedly mid fi) system, which is Adcom components and Tyler Acoustic floor standing speakers. Vs CD quality though, MQA is an enormous upgrade, in every respect.
UPSAMPLING? No. CD is CD quality, with no upsampling, and MQA is its own beast.
FILTERS: Filters are NOT engaged when listing to MQA. When not listening to MQA there are 8 filters to choose from. Too technical for my knowledge, but they all seem to deal with pre ringing, and to my ears have very very very very subtle audible differences.
PRE AMP: Meh. Leave it all the way open and use your existing pre amp. Listening direct to amp with the S2 pre amp, the sound was about the same as I described above, but lifeless - no punch, no dynamics.
Glitch: Switching back and forth from MQA to CD quality while listening throught TIDAL seems not to be perfected yet. When going from MQA back to CD, sometimes the sound quality will be thin, lacking in bass. My only solution so far is to disconnect the DAC then reconnect, or go into the TIDAL settings and manually change it from MQA to Lossless, which should happen automatically, but doesn't always. This seems to solve it. This problem does not seem to exist going FROM CD to MQA, only FROM MQA to CD.