This is purely my own experience and it may drastically differ from yours. In my experience power cables do have a burn-in period, it is real, it lasts several hundreds of hours, sometimes much less, but they don’t change dramatically, the changes in fact are very small (apart from a mandatory short period of a temporary "lost bass" with some cables, why on earth does it happen, I have no idea, but it almost always does. Saying that, with some cables/systems I can hear no changes at all). The sound signature is here from the start, and the new cable should sound great from the word go, just give it half an hour to settle. If it does not, then don’t waste your time hoping for a miracle and trying to convince yourself that it is getting better. P.e. if you think that the voices are thin, there is not enough body, or there is too much bass, or sibilance etc. etc. no burn-in will change it. You may somehow adjust to it and start believing that it is better now, but you won’t fool yourself for more than a very brief period, eventually it will leave you disappointed. You need to bear in mind 4 factors that can affect the sound during the burn-in: 1. The physical changes in the cable that do affect the sound (don’t ask) 2. Power line/supply quality fluctuations that may make your system sound better/worse 3. Cold/warm condition of your gear 4.Your own condition and your hearing/adjusting to the new sound: first the differences pop up, you hear something new and concentrate on these new details and accents, then it blends with the whole pic and you can’t recognise it as easily if at all, and after a while the new balance/signature starts revealing itself with different kinds of recordings and you realise that yes there is a difference that matters. At this stage you put the old cable back and immediately recognise the old familiar sound signature that was gone with the new one. That’s how it almost always works with me. YMMV.
