Cardas also says things like this below from their website. Note that any standing voltage is DC (music is AC). However, if I take a fairly inexpensive 2 meter interconnect I have lying around that has not been connected up to anything in months, load it with 100K ohms (higher than most inputs), and hook that up to a 6.5 digit Agilent 34465 meter, I measure <10uV, or at least 100db on a 1V signal, and lower than the offset of any practical amplifier. Of course, the source is likely around 2K, so that 10uV, would be much less.
There are many factors that make cable break-in necessary and many reasons why the results vary. If you measure a new cable with a voltmeter you will see a standing voltage because good dielectrics make poor conductors. They hold a charge much like a rubbed cat’s fur on a dry day. It takes a while for this charge to equalize in the cable. Better cables often take longer to break-in. The best "air dielectric" techniques, such as PFA tube construction, have large non-conductive surfaces to hold charge, much like the cat on a dry day.
Also said this, yet I can put an unused interconnect in front of a speaker playing loud, load one end with 2K (mainly to shunt RF via AC), plug the other end to the AP, and not measure anything above -120db except a spike at 60Hz if the cable is not routed properly?
Cable that has a standing charge is measurably more microphonic and an uneven distribution of the charge causes something akin to structural return loss in a rising impedance system
Cardas makes a lot of other claims, and like the ones above, while there is truth in them, it is the old "lie and statistics" thing. Let’s take that standing voltage thing. I measured <10uV. Cardas says in their marketing blurb, MV (millivolt range, or 100 times more). Who is telling the truth??? We both are. The difference is, I loaded the cable with a rather unrealistic 100K load. I should have loaded it with say 10K to represent a worst case source impedance. That would have brought it down to say 1uV or 1000 times less than Cardas’ marketing number. What did Cardas use? ... likely the input impedance of their meter, perhaps 10 meg (million) ohms. A completely unrealistic number for an interconnect, and a ridiculous number for a speaker cable to power cable.
For a microphone cable with low signal levels and high impedance, micro-phonics is an issue. Teflon being stiffer than say foamed PP/PE (or an air dielectric) is potentially much less susceptible to microphonics as you have less moving of the conductors, which causes pumping of the voltage as with any capacitor if you keep the charge constant. Of course in microphones you often have microphones with a high DC bias which forms a way higher charge on the cable than any "standing charge" ... many orders of magnitude.
You never really get all the way there, you sort of keep halving the distance to zero. Some charge is always retained. It is generally in the MV range in a well settled cable.
To be fair, it is a valid concern for MM cables.