I have found that with cables, if I don’t like them right out of the
box, no amount of running them in, sprinkling with fairy dust or, using
Voodoo won’t make them sound better. If you like the sound when new,
then you will get refinement as the cables get run in.
Never, ever in all my life heard anything start out bad and magically become good. Got one PC right now, it was analytical etched hyped and lean in the beginning. No bass. Let it run in 24/7 and after a week or so it was not nearly so analytical or harsh but just as hyped and lean. No bass to begin with, no bass now either. Haven't done a survey but suspect there are a whole hell of a lot of em out there just like it. Why I am happy to stick with Synergistic. Never had a bad one yet- PC or otherwise.
Is it perhaps a wrong match with the phono preamp,
This is another one where I diverge from the crowd. There is no such thing as matching. One power cord (speaker cable, interconnect, whatever) does not magically change and go from sounding bad to sounding good simply by being connected to a different component. They are what they are, period.
What happens instead is a lot of people have components that have all kinds of faults in different areas. Which they all do. No such thing as perfect. Memorize this if you can, it will serve you well. The power cord (IC, speaker cable, etc) performs the same everywhere. But sometimes the faults are complimentary. Other times not. People confuse this and say its better with this or that. No. Wrong. It is the same always and everywhere. What you are doing if you follow this approach is using one fault-laden component to cover up another fault-laden component. It is what I call the band-aid approach. Cover it up.
DO NOT ever try and "match" components this way. Because if you do, then even though you might be able to get everything all bandaged up and covered over and sounding good, this will only be the case until you change something. Then your upgrade reveals all the crap you cobbled together with band-aids. Sound familiar? This is why we hear so many people talking about their new upgrade revealing all the faults everywhere else. If this doesn't sound familiar, hang around a while, it will soon enough.