Yes Dave employs a SMPS, and all the DACs are absolutely full of switching regulators.
Using switching regulators started with the Hugo design, where battery operation forces one to use switchers. But I thought it would be a good idea to listen to the SQ damage that switchers generate, by comparing them to linear regulators. Before this time I used linear regulators exclusively, thinking the extra RF would cause problems. But when listening the switchers sounded a lot better - darker, warmer and smoother. I then discovered that there was two issues for the improvement by switching regulators - switchers are more efficient, so correlated noise levels at the PSU input side is much lower, and switchers force you to use more RF filtering localised to each circuit module.
Looking at RF filtering - we actually have two problems - one is random RF noise, the other is switching noise which is a fixed frequency (I always use fixed frequency regulators). When I design RF filters I check it out by running a SPICE simulation, and to do it properly you must characterise the PCB tracks, component internal resistance and inductance for capacitors and parasitic capacitance and resistance for inductors. When you do this careful simulation, you can get very close agreement to reality. The benefit of SPICE is that you can design filters to achieve unmeasurable levels of RF; so recently I wanted to design RF filters that had pV levels of voltage (a pico volt is 1 million times smaller than a micro volt so it's pretty damn small). What was curious was for switching regulators it was very easy to get pV levels when filtering - but with random noise it was an order of magnitude more difficult, requiring hugely more complex filtering.
And it's random noise that is the SQ killer, as this is responsible for noise floor modulation - a regular switching fixed frequency will not create noise floor modulation, but fixed intermodulation products outside of the audio bandwidth. The problem with the mains is that it is full of random RF noise, so you need extensive RF treatment on the PSU - something that I do post PSU as a matter of course.
So the idea that linear is best (no RF filters) against SMPS (lots of RF filters) is simply wrong. When you dig down it is very much more complex than one would imagine.