Another view on this topic.
https://www.youtube.com/watch?v=PbZFt8eWjgQ
He makes some good points. I note that the British Audiophile acknowledges in his review that the actual power output is nowhere near the lofty numbers that Fosi publishes. I think Fosi does themselves a disservice by (i) publishing those specs and then (ii) bundling the unit with a power supply that guarantees it will not make the published specs. It would be far better for them to just bite the bullet and bundle the 48v power supply to maximize output. Even if it increases the cost a bit, it would still be a fairly low priced amp. That said, the Fosi amp has been reviewed by several reviewers and none of them, including British audiophile, seem to have heard the high pitched whine that Robinson encountered in his testing. It is quite reasonable to postulate that Robinson's setup/system has something that caused those amps to pickup the whine, since none of the other reviewers commented on it. I also note that Robinson does grudgingly recommend the Fosi amp out of all the amps he tested.