This fact proves to me the preamp itself is "vastly" superior to it's
power supply.When I spoke to Spectral about my experience with my
refined AC supply they commented that the unit was designed exquisitely
for precision DC output but was not designed as a basic filter for AC,
so the better the AC the better the preamp would sound.
Are there components in the PS that would benefit from the latest
iterations; or is it possible that the excellence in providing precise
DC; when fed by pristine AC; has not changed that much?
I've always held the opinion that the power supply for audio products is the key to their success in sounding their very best.
I'm confounded by Spectral's statement that the DMC20 is designed for precision DC output but Spectral did not pay much attention to its power supply.
For example, I have the best fighter jet for a dog-fight but it has crappy radar. Do you think it will last any amount of time in a dog-fight when we have fire-and-forget missiles?
By Spectral blowing off the DMC20's power supply they've taken their precision preamp active circuit & hacked it at its knees. They've made it immensely sensitive to AC power variations & grunge especially when the DMC20 is a 2-box solution. This does not make any sense. I get the feeling that Spectral does not know how to design power supplies - atleast it did not know back then. Has anything changed on that front today? Don't know....
Of course their power supply would benefit from good power supply design. There are some preamp manuf that use an isolation transformer (like Tice used in his power conditioner back in the early 2000s) that help to isolate the noise on the AC line. I know of other front-end component manuf that use Bybee filters or something similar to filter the AC without constricting the current.
Use of inductive power supplies is well-known for reducing the resulting ripple voltage on the DC supply rails. So, is the use of low-ESR power supply caps. Another well-known technique is local filtering. Separation of power ground from circuit ground that is eventually star-connected at the chassis.
With preamps often consuming currents in the 1A range it is very much conceivable to use a regulated power supply for the preamp this would make the DC power rails superbly stable i.e. excellent load & line regulation.
The manuf of precision DC output is taken to the limit by FM Acoustics of Switzerland (maybe even Goldmund, Soluution, CH Precision & Dartzeel do this but I dont know). That design methodology hasnt changed in that the main tenet is unchanged - precision matching between the channels to get extremely tight tolerances on the output. This of course does not always mean that one uses the lowest tolerance part - what it means is that if one channel is screwed up (whatever that means) then the other channel is equally screwed up so that the 2 channels match.
Needless to say that when the quality of the raw materials improves the job of the designer becomes less stressful & less tedious. Supplier + manuf are working hand-in-glove to achieve precision output.
Hope this helps.....