OK you've explained more fully your statement since that's not how I originally read it.
And if that is the case, then speaker cables shouldn't affect the sound of an amplifier either?
I used to be much more concerned about wires than I am today. At line level, it can easily be shown that high capacitance cables can roll off both bass and highs, but high-cap interconnects are fairly common and some of the most expensive interconnects and speaker cables have those network boxes which contain various values of lumped capacitance, inductance, and resistance. Sure, those wires will sound different.
But I've found that if interconnects are mechanically well assembled and fit connections correctly and have low capacitance, there is really not very much difference among them--not enough to make me want to spend hundreds or more per meter at least. And I've found that in the analog realm using balanced connections further minimizes audible cable differences. An exception is digital audio links where transmission line effects come into play. There I hear definite differences and have definite preferences. The Apogee Wyde-Eye A/D is a very good value, I think, for such an application, at least in the lengths I've tried.
As to speaker cables, I prefer the sound of the ones with low resistance and fairly low capacitance and inductance. My current favorite is garden variety Belden 10-2 twisted pair cable sold by Blue Jeans, used unterminated except for ProGold spray. To me it sounds at least as good as any other speaker cable I've tried and better than most. I prefer no terminations because bad terminations, especially if corroded, can act as rectifiers and introduce distortion. Not terminating the cable and treating the cable ends with a corrosion inhibitor like ProGold will eliminate potential sources of such distortion.
If the speaker cables are short and heavy gauge, they should not add enough resistance/impedance to change the effective output impedance of the amp and thus should not change the frequency response of the amp. A long thin gauge cable might be a different story.
The other two lumped electrical parameters of a wire are capacitance and inductance. Capacitance should not be an issue with most modern amps which have some sort of output network or other circuitry to avoid oscillating in the face of highly capacitive loads. You may remember the problems that the highly capacitive Polk Audio Cobra Cable caused for certain amps back at the beginning of the high-end speaker cable era.
While actual amp oscillation SHOULD be a thing of the past, it is generally believed that not all amps are really comfortable driving highly capacitive electrostatic speakers and a highly capacitive speaker cable presents the same sort of potential issue. I think I hear audible problems with speaker cables having extremely high capacitance, at least with the amps I've used. These cables will generally be those which have the absolute lowest inductance, such as those where the positive and negative strands are interwoven, are arranged in concentric tubes, or are flat and separated by only a minute bit of insulation. As a general rule, to me such cables sound bright in a gritty, irritating way.
At the impedances faced in speaker wire, speaker cable inductance is definitely a factor which can affect an amp's sound. Greater inductance will modify the high frequency response of an amp. The farther apart the positive and negative runs of the speaker cable are on average, the greater the inductance. Parallel conductors with a lot of "land" between the conductors will have high inductance.
The flattest, most extended high frequency response will occur when inductance is held to near zero, but, as I said above I do not really like the sound of such cables with amps I've used. There are definitely audible high frequency differences between even garden-variety wire laid in parallel runs vs. the same wire in twisted pairs or the same gauge in flat wires very close together or in an interwoven Litz or concentric arrangement. Thus, differences in inductance alone or a combination of inductance/capacitance can cause audible differences among speaker cables. I prefer the sound of moderately low inductance of twisted pair speaker cables.
Skin effect might be able to cause differences in high frequency response if the effective gauge of the wire is large enough and the wire is long enough. I have not seen any reported evidence of frequency response differences caused by wire factors such as the type or purity of metal, the number of boundary junctions between metal crystals, dielectric type, direct current biasing, or any other factor trumpeted by cable companies as important. None of these factors seem to significantly affect the lumped electrical parameters of a cable, which factors can measurably be shown to determine potential frequency response of the amp/cable/speaker combination.
Frequency response may not be only factor to cable sound, but most controlled blind tests of the audibility of this or that come down to frequency response changes as the overwhelmingly important factor. Usually, if something is reliably audible in a blind test, it is because of some sort of frequency response change between A and B which exceeds the threshold of hearing. Mundane maybe, but it seems to be true, even with a complex device like a speaker. See, for example, the
Gradient Absolute Listening Test.