http://www.fair-rite.com/product-category/suppression-components/round-cable-snap-its/
Some will only present significant impedances at frequencies that are well into the RF region, even tens of MHz in some cases. Others will present a potentially significant impedance at frequencies well under 100 KHz (see the first graph here, for example; while the graph doesn’t depict what happens below 100 KHz, it seems clear that a significant number of ohms would be presented well below that frequency).
In various threads here Atmasphere (Ralph) has explained that the performance of power amplifiers will often be compromised to an audible degree if power cord bandwidth does not extend up to several or even many tens of KHz, because if it does not extend that high limitations may occur in responsiveness to abrupt changes in demand for current, that occur as rectifier diodes switch on and off during parts of each 60 (or 50) Hz cycle. A similar point has been made in some Shunyata literature, accompanied with comparative measurements of various power cords.
So if the chosen ferrite is effective at particularly low frequencies, it may have adverse effects on dynamics or other sonic characteristics, depending on the specific component it is used with. If is effective only at very high frequencies, it may or may not accomplish anything, depending on the specific component it is used with. And in that regard, keep in mind that digital components in particular may generate noise having significant spectral components as high as several tens of MHz, due to the fast transition times between their two voltage stages (i.e., their risetimes and falltimes), which could conceivably couple into other components in the system via their power cords and the AC wiring. (Those frequencies are of course much too high to be directly audible, but could have audible consequences as a result of effects such as intermodulation, AM demodulation, timing jitter in a DAC, etc).
Finally, there is the possibility that even if the sonic accuracy of a system is improved by filtering noise that enters or exits a component via its power cord, that might not be preferable from a subjective standpoint. To cite just one example, toward the end of this paper Steve Nugent of Empirical Audio explains that depending on its spectral characteristics a reduction in timing jitter in a DAC might be found to be objectionable from a subjective standpoint:
So as is usual in audio, the question of ferrites involves a multitude of complex variables and tradeoffs, and doesn’t have a great deal of predictability, and doesn’t have a one size fits all answer.Another interesting thing about audibility of jitter is it’s ability to mask other sibilance in a system. Sometimes, when the jitter is reduced in a system, other component sibilance is now obvious and even more objectionable than the original jitter was. Removing the jitter is the right thing to do however, and then replace the objectionable component. The end result will be much more enjoyable.
Jitter can even be euphonic in nature if it has the right frequency content. Some audiophiles like the effect of even-order harmonics in tubes, and like tubes, jitter distortion can in some systems "smooth" vocals. Again, the right thing to do is reduce the jitter and replace the objectionable components. It is fairly easy to become convinced that reducing jitter is not necessarily a positive step, however this is definitely going down the garden path and will ultimately limit your achievement of audio nirvana.
Best regards,
-- Al