Thanks for your input Peter. Yes, it is hard to know if modding computer power is a valid path now or at another stage. I know it works in other systems and have seen a reasonably cheap and easy solution feeding three rails (12v, 5v, 3.3v) into the motherboard for a solid improvement in sound quality, but the question becomes whether it is all worthwhile.
I think that I will play around with it a little. How I plan to approach it is to get a good quality linear lab supply with 3 rails and poke power into different things and see what happens. I have a feeling that directly feeding the ram will have a good impact (because I use a RAMdisk) but that requires some de-soldering on the mobo so I will leave that one alone for a while at least.
If I can find a reasonable improvement using the lab supply then I will build or have built a higher quality supply for the computer.
I plugged my XXHE PC back into the UPS and re-ran my power draw numbers:
Power On (minimised o/s) 88w (normal o/s) 88w
Idle with XXHE open (minimised o/s) 58w (normal o/s) 78w
Playing Music (minimised o/s) 49w (normal o/s) 58w
Shutting Down (minimised o/s) 68w (normal o/s) 98w
Note that my UPS only updates the display about once a second so there may be peaks that I missed. To try to counteract this I repeated each process several times.
Anthony
PS: I think that this is a particularly good exercise for XXHE/NOS1 users because I think we mostly use the same mobo. If there is someone else that wants to duplicate these experiments and possibly give some corroboration please put your hand up.
PSS: Peter, should I start a new thread about developing an XXHE PC linear supply?