I do not know how they can do too, I just guess, for sure after burn in, the sound quality really changed, I did the home made interconnect cable with a DC voltage potential surround the cable, switch on and off or change it higher and lower of those DC voltage also got difference in listening too, I don't have much knowledge and equipments for accurate measurement, what I can do is just guess from the result
I did use same conductor like 4N silver to make interconnect cable in different style of constructions or combine with different materials like air tube and wrap with Teflon tape, also come out in different sound. I guess the LC + magnetic field to effect themEven if you had very precise instruments, you would be loosing your time - there will be a variation in capacity, as the electric field due to DC will create a force that will change the cable dimensions by a minimal amount, changing the capacity by a minimal amount, but it will not be significant at all. I doubt it can be measured. IMHO , the key to understand the effect of DC polarization must be in the dielectric noise, due to its electromechanical properties. If you accept to consider only RLC you must accept all cables sound the same.
-- I played around with biasing cables and found a significant (few dB) lowering in noise and distortion, but only with a certain preamp. The cable mattered little in that case, but the effect seemed only significant with that preamp. Turns out I was biasing the balanced output stage, shifting the bias across the coupling capacitors. The capacitors were a grouping of a big electrolytic and smaller films; it can be shown that biasing an electrolytic cap can improve (or not) its performance. )
This is my guess again (only thing I can do can't prove) causing sound change in bigger difference is harmonic frequency timing shift , most of the musical tone isn't just single frequency, they combine so many harmonics to create its own sound. but those frequency come out from speakers ( sub + mid + high ) join again in the air to repro the original sound like, if they can't join in the same position exactly of the original (impossible thing ) that makes sound change, but the closer is the winner, cap can shift timing + or -, so different cable can sound different from different amp because we don't know the final timing shift from the speakerFor the record, and IMO, considering just RLCG can indicate why some cables sound different in some systems. I am not saying that is all we should measure or consider, but sometimes it is enough.
I have measured the variation in capacitance with d.c. bias and it is very small for most cables; I would certainly expect it to be inaudible.
Filling the charge traps/voids, well, I can in no way see how that would be enough to change the the "sound" of a speaker cable given the impedances and signal levels involved, and it seems unlikely to significantly (i.e. audibly) reduce the noise floor even of an interconnect, but I have not run the numbers nor made any measurements to support that. The data I collected (for an RF/mW test system, several years ago), the effects were in the uV region. Enough to matter in a 100+ dB RF front end, but would be less notable in an audio system, I would think. The catch that holds me back is that charge traps lead to things like flicker noise that affects lower frequencies more than higher, thus even though the measured data is tiny, it would be more observable at audio than RF frequencies. In my case, it affected the close-in phase noise around the carrier.
One interesting side note (perhaps): a long time ago in a galaxy * -- oops, it was this galaxy!
One of many little experiments that lead to insight about the reason why, even if not what we expect, and a caution to not dismiss our ears out of hand. Nor to dismiss the techies' reasoning and ability to find the cause (alright, I am biased on that last...
