Tbg, thus my final comment on my post!
Several decades back, this problem was addressed by the recording/broadcast industry, for pretty much the same reasons that audiophiles deal with today. The result was the balanced line system, which is actually a standard.
The standard requires that the source (preamp) be able to drive a 600 ohm load. There are several practical reasons for this, not the least of which is that the low output impedance of the source thus has the ability to 'swamp out' the effects of the cable caused by capacitance and other construction issues. The result was twofold: not only can a preamp that supports the 600 ohm balanced line standard control the interconnect so well that essentially the quality of the cable has little bearing on the sound, but also the length of the cable became all but irrelevant as well.
The number of preamps in the high end audio world that support the 600 ohm standard without any sonic artifact (loss of bass and/or dynamics) are very few. Some use output transformers, and that is why the termination standard is 600 ohms, so that the transformer can drive a reasonable load without ringing. If there is no transformer, then the termination is less important.
If you have ever wondered why 'audio engineers' say that the interconnect cables make no difference in the sound, this is why: in their world it is true because they use low impedance balanced lines. Audiophiles can take advantage of this though, as low impedance balanced lines offer the same advantages to them- the standard was in fact created to solve the sonic artifact issues that audiophiles routinely experience.