I've owned an M Scaler no less than three times. Strictly speaking, I had a Blu 2, and then two M Scalers. Yes, the definition of insanity.
Short version
To cut a long story short, I think the M Scaler is a bit of a con. It does what it says it does, but it just doesn't sound very good. It makes a noticeable and quite significant difference, and most people seem to equate "difference" with "improvement". To my ears, with multiple Chord DACs, I found the M Scaler made the sound more detailed, but resulted in a sound that is lean and tonally bleached. The Chord DACs without the M Scaler sounded warmer, fuller and richer. The M Scaler produces the illusion of more detail and more dynamics but at a significant cost to musicality and natural sound.
These days, any powerful PC can produce similar upscaling to the M Scaler at a fraction of the cost, and the results are very similar. Rob Watts has obviously tuned the M Scaler to sound a little different to other software like Roon or HQPlayer, but even this could probably be replicated by someone willing to spend a bit of time playing with filter settings and maybe a bit of DSP. Even so, in my view it would be a waste of time because the effects of massive upscaling are as I've described - an etched, bleached un-musical sound which bears no relationship to the original. There are no free lunches in audio, particularly digital, and you cannot apply massive processing to a signal without there being a cost somewhere else.
Long version
I bought a Chord Dave a few years ago at a store after hearing it at a dem at a shop, alongside the top Audio Research DAC. The DAVE was played with the Blu 2, but at the time I didn't really think too much about its effect. The Audio Research DAC sounded as I expected - rich midrange, full sound. Not quite my cup of tea, but very good in a conventional way. The DAVE however sounded like nothing I'd ever heard. The sound stretched to the outer walls and beyond. The detail presented was extraordinary. It was like watching an MRI image of an orchestra, the level of detail was forensic to the extreme. It was an unfamiliar system and I can never really judge anything properly in a system I am not familiar with. But what I heard was something so extreme and so different that I thought that Rob Watts must really be onto something with his approach, and I ordered a DAVE. What I didn't realise was that I was mostly hearing the effects of upscaling from the Blu 2, which was producing that unexpected sound.
When I got the DAVE, I liked it. It sounded very good. At home, it didn't sound quite as radically different as I had expected based on the dem, but I was happy with it. And, as happens with these things, after reading up on it, I liked it so much I ordered the Blu 2 to go with it. (The M Scaler had not yet been released.) The Blu 2 arrived, I connected it, never really compared it with the "bare" DAVE, and just carried in listening to it. After some months I became vaguely dissatisfied with the DAVE/Blu 2. It was sounding tonally thin, lean, a little brighter than I remembered, and not very engaging. I didn't associate the Blu 2 with this sound (I naturally assumed it was an improvement, having drunk the Chord Kool Aid). After a year I sold both the DAVE and the Blu 2.
I tried a few other different DACs, but wasn't quite satisfied, and still believed there was something to the Chord approach that was fundamentally correct. I had read that the Hugo TT2 was fuller and more dynamic than the DAVE, but not as detailed. That sounded like what I wanted, so I ordered one, along with an M Scaler, since I still believed that upscaling would be an improvement. I quite liked the TT2 and did think it was an improvement over the DAVE for my preferences - it was smoother, fuller, tonally richer, and more dynamic, without quite the level of forensic detail. This time I did compare the different levels of upscaling, including comparing full upscaling to bypass mode (ie no upscaling). This time I could clearly hear that upscaling sounded brighter, more detailed, but lacked harmonic richness. Bypass sounded warmer and more natural. But did I prefer it? I didn't know. I couldn't reconcile the idea of having the M Scaler and not using it. I can't recall the thought process at the time, but after a few months I sold both, and moved on to something else.
Later still (all of this occurred over a period of about 4 years), I decided I still was interested in hearing the Chord sound, so bought a Qutest. It was good, if a little grainy and obviously a lesser DAC than the TT2. And again, I couldn't resist, I had to hear what an M Scaler would do to it, so I bought yet another one. I repeated the experiment with the TT2 and over time, I came to feel that the changes which the M Scaler made - which are clearly noticeable and not to be doubted - were definitely for the worse. I loaned both units to a friend whose ears I trusted, he did the same comparison without bias (and with little knowledge of the Chord DACs or upsampler) and came to the same conclusion much more quickly.
So after some years of listening to all of the Chord DACs with multiple M Scalers, I had come to the conclusion that upscaling just didn't produce the benefits claimed. There was some improvement in detail at the expense of a leaner, etched and bleached sound, but it was unnatural, and lost some of the warmth and richness of the original.
I sold the Qutest and M Scaler and have finally regurgitated all of the Chord Kool Aid, and will never go back there. I have moved on to other DACs and am very happy with what I currently have. And those who think that all DACs sound the same or that upscaling is not audible must either have an agenda of their own or be deaf.
It took me years, multiple DACs, endless listening comparisons and a ridiculous amount of money to figure out what the OP has realised very quickly. So my recommendation is: trust your ears, don't believe the hype and sell the M Scaler while there is a market for it.
