I still don't quite understand your experience with NAD inbuilt amp. I have medium efficiency speakers and sub and I can drive it louder than my ears can handle with metal and pop. With classical and soundtrack there isn't much reserve left after Dirac but it is just enough for live levels.
Also, Fosis can't have (and I really mean can't, not an opinion) more detail than nCore. Having to adjust eq after changing an amp is not something that should be a thing.
I mean I'm happy it works for you but something is a bit odd here.
Although this is now old, I will have another go at explaining "Fosis can't have more detail than nCore".
It would argue this conversation is not about the amplifier alone providing more detail but the combination of the amplifier implementation and subsequent tuning in the system in the listening room. And for sure it sounds way better. Not an opinion.
Circling back to the original issue with the V1, the M10 would not trigger the sub. Not just me but many people face the same issue with subs of all type and BlueOS powered products at that time. The sub output voltage was half that of the previous 2 amps used so when it woke up there was insufficient volume to match the sub to the main speakers. All the issues and correspondence with NAD I documented elsewhere in the post, including their denial of any sort of problem in the face of overwhelming evidence to the contrary. For sure they knew all about it. This was subsequently rectified in the V2 when NAD changed the "gain algorithms" so it was no longer an issue.The SINAD dropped in the V2 as well.
What I have done is replace the onboard nCore amps with 2 FOSI V3 mono and 5W power supplies. Lets say that's close enough to the on board nCore amps in power output, but these measure better than the M10 (not an opinion). In addition the Fosi V3 mono has multiple options for input gain which was a selection criteria. In the end I chose the XLR input @ 20db (
SINAD : XLR: 101dB) as the best match to the sub output on the M10. Obviously the M10 outputs are not balanced, in this application it doesn't matter. You can see it sits alongside the NAD C298 which is an Eigentakt powered stereo amp with the M10 way back at 86 and the v2 in the 70's.
So its not just about the technology, nCore is just fine, but rather the implementation in the M10V1 was terrible. The Fosi amps are not driven flat out, but I still get plenty of volume. A common observation is class D amps can sound right on the edge at about 85+ db, certainly this was true of the M10 in my listening room and its nCore amps. Now with the Fosi amps installed and the way they are connected, it seems there is much more headroom. I am not offering any science, but I am not the only one who listens and others are not privy to the changes made but they do comment. So maybe we are all imagining it.
In any case I am quite satisfied with the result and it was way cheaper than outboard NAD amplification or some other outboard option. C298 was under consideration but obviously its at a different price point. You can see below input gain can be adjusted with the C298. Fosi amps were an inexpensive experiment that worked out just fine and these are fitted with Muses op amps also.
Bear in mind this is in my view a small room system, its connected to a pair of small speakers and a small sub. It now does exactly whats needed for reasonable money in the small room where it resides. If I had a larger room and the budget I'd start with a pair of JBL or Altec speakers and the M23/66 pair. But that's a whole different level of cost and performance and a completely different listening experience.