Internal Power Supply Technology Changes since 1999?

Thanks gdnrbob.I agree with you that technology is constantly evolving. I'm wondering about the specifics that have allowed the miniaturization of internal power supplies in very high end preamps.

Thanks Bombaywalla. I'm using a Spectral DMC20 and happy with it. But,my efforts on AC power improvements have shown that this preamp benefits enormously from "ultra clean" AC.(Naturally my amp & sources are also provided ultra clean and isolated AC) 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.  I use units that reduce differential and common mode noise and both contribute significantly. 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?  

Thanks Bombaywalla. I appreciate your knowledgeable comments; but we have a misunderstanding. It appears you overlooked 2 things: 1. my comments that theDMC-20 P/S was "designed exquisitely for 'precision' DC output", and 2. my basic question to you- "Are there components in the PS that would benefit from the latest iterations (of parts)? " .Also, Spectral did not "blow off" their power supply. Far from it. They emphasized that AC power to residential areas was so corrupted by noise that cleaning up the basic incoming AC power was (and still is) a necessity (as was isolating products emitting digital noise) . They emphasized that clean AC power was a requirement for implementing the development of their "ultra refined" power supply of the DMC 20. I mispoke. It's unfortunate my words gave you the impression " I get the feeling that Spectral does not know how to design power supplies - at least it did not know back then." Obviously you are not very familiar with Spectral products,their attention to detail in their power supplies, or the exceptional praise they have received from reviewers. I'm sorry I worded my question poorly. I should have said that AC power is so poor in my area that all my efforts at improving it have resulted in quite dramatic enhacements to my sound. Also I should have mentioned my system uses very upper end MIT power cables and i/c's, each/all of which contributes to the very refined sound I enjoy and allows me to more easily evaluate any refinements I try. It sounds like we agree on the value of clean power.