I've been listening to a lot (13 hours+) of music since receiving my m scaler (2 days) and am sharing my initial thoughts.
The set up of the m scaler took longer than I expected mainly because I hadn't realised that there were dual BNC input and optical output ports as well as dual BNC output and optical input ports. The labels on the ports are reasonably clear but requires good lighting to see (on the black m scaler the writing is an indentation above the port).
To connect the m scaler to my Hugo 2 I used the Audioquest adapter (together with RCA to BNC plugs mentioned in other posts). The BNC cables in the box work well with this adapter as they are reasonably lightweight and do not look like they will cause strain to the Hugo 2 3.5m coax socket.
I bought a Google Chromecast Audio specifically for the m scaler and a QED Reference optical cable. Rob has mentioned that optical provides complete electrical isolation from upstream components and
@musickid provided enough enthusiasm for optical to push me into a purchase. I use Roon as my server anyway and they recently supported Chromecast as a network adapter (with evidence of lossless 1:1 optical delivery of the files). For listening I have used my unmodded HD800 headphones with a Nordost Heimdall 2 cable plugged directly into the Hugo 2. All music is lossless 44.1/44/88/96 FLAC files with occasional Tidal 44.1 FLAC. No MQA or DSD tried yet. To test the differences with upscaling I used the m scaler sample rate switch with no other changes.
My first (1 hour) thoughts were very positive. I listen to and enjoy a lot of music (hours every day). I thought how the music sounded more alive and dimensional compared to other reproduction systems (with the exception of vinyl IMO). For me this was a big change, but I've thought about it as a result of comments from others that the changes are subtle and recognise that my big-change perception is a result of many subtle changes in the texture and timing of the music. The dimensional (soundstage?) impact of these many small changes is large for me - like looking at a scene with one eye and then opening the other eye (sorry!). This is especially noticeable for recordings that are recorded live or with the soundstage in a natural fashion - m scaler is able to convey this implicit information. I am now listening out for recordings that have this embedded soundstage info - it is magical and thrilling. Initial listening seems to indicate that many 50s / early 60s jazz recordings fall into this category, although more recent recordings are more varied. I really ought to start a thread to share.... Is this a new category - Music with dimensionality!
I'm pleased with my purchase.