[p-funk]

At my last company, we tested tons of combinations of class D modules with various power supplies, and the best sounding results tended to be with linear power supplies. Don't get me wrong, there's tons of tricky stuff when it comes to the subjective side of audio, so it may be at least partially placebo effect. But we pretty consistently found that off the shelf switching PSUs sounded worse subjectively, even if they measured the same on the bench.

I haven't been doing audio for a while, so I don't remember more of the details. But audio signals tend to need all their power in short bursts all at once, when a low frequency bass note hits for example, and so the transient current tends to be much more important than a stable voltage rail. A lot of switching supplies do not optimize for this. Well designed versions can both sound great, but a cheap linear supply is going to sound much better than a cheap switcher. Audio is stuck with 1960s technology for the most part anyway though.

[balfirevic]

> so it may be at least partially placebo effect

That really sounds like a kind of thing that should be tested blinded.

[p-funk]

We did a lot of blind testing, but blind testing takes more effort and we were always swamped. Usually the engineers would just test things ourselves, and then I would give my boss a blind test for the final approval.

[klodolph]

You could add the massive capacitors if you needed the bursts of energy, it just seems like the mains transformer itself is out of place.