Although some components ( power amps ) seem to react less than others ( preamps, DACs ) to power cord upgrades, I have found only one component which showed no obvious change. That one was the Cambridge Audio IsoMagic DAC. The fact that it was equipped with an external power brick may have had something to do with it.
component where PC does not make a difference
Has anyone ever had a component whose sound did not change significantly (or at all) with changes in power cords? I have found that different power cords don't really affect the sound of my amp (ARC VS60), but differences among those same power cords are revealed when hooking them to my DAC (ARC DAC7). Is that representative of tube amps in general or perhaps just this component? Would you expect that the differing "sonic traits" of various power cords would be better revealed on a DAC than a (tube) amp?