I just received a reply from Diego Estan who was recently hired to measure the equipment under review for the SoundStage Network of web sites. I asked whether or not he used special power supplies for the equipment under test. Here is his reply (edited for typos):
To answer your question, absolutely not. All devices under test, [other] than amplifiers and integrated amplifiers, are directly plugged into the same, standard 120V/15A circuit, as the Audio Precision analyzer. This is a typical circuit in a spare bedroom of my home and is shared with lighting, my home PC, etc.For amplifiers and integrated amplifiers, these are plugged into a dedicated 120V/20A circuit, and the minimum observed AC line voltages are provided in the report. Nothing else is plugged into this circuit other than the amplifier. There's only one 20A electrical outlet on this circuit, and it's a relatively short run to the electrical panel.I live in Canada, and electrical code dictates 14ga solid copper for 15A circuits, and 12ga solid copper for 20A circuits.I will also say that my home is relatively new (2012), and I have pretty stable power.