That is the point. How does one know if a SMPS has a good spec?
From a company like Chord Electronics with the Qutest DAC or the Chord Company with the EE8 switch I am happy to accept that what they supply is perfectly OK.
But these are specialist audio companies, concerned of course with sound quality. They will not supply SMPS’s that spoil their products performance. Which is not to say that improvements can’t be had with ‘aftermarket’ supplies but that’s another story and not a route which I’m in any way keen to pursue for various reasons.
The concern for me is more with SMPS’s supplied with non-specialist equipment. In my case that means my BT router and ONT box. I’ve no way of knowing how good or bad these are, except empirically. I’ve already replaced the router SMPS with a MCRU LPS and it’s much better. Perhaps a good quality SMPS would have been better still or at least as good - but how do I know which one? At least a good LPS for audio use is almost guaranteed to sound better than a general use cheap SMPS from BT.
I replaced the medical grade SMPS supplied with my Melco with the Plixir LPS on the strength of various reviews that claimed it gave a very worthwhile improvement and also because Melco endorse it. Again maybe a very good quality SMPS would have been better - but how on earth do I find that? There is little or no interest amongst the reviewing fraternity in SMPS’s other than to say that they all bad news.