Use of Ferrites to stop RF
Several companies offer clamp-on and slide-on Ferrites. Some audio manufacturers claim that their Ferrites stop RF currents from being "picked-up" by power cords and other audio analog and digital cables. Ferrites are routinely used on computer internal and external cables to block RF. What is really happening here is that these are blocking radiated emissions from the computer so that the computer will pass FCC and foreign emission standards (CISPR, CSA). Their purpose is NOT to prevent RF from being "picked-up" by the signal wires. In some cases they have been added to internal computer cabling to attenuate radiation as a band-aid after the design is complete. These Ferrites will "round-off" the signal edges, removing much of the high-frequency content. The energy that Ferrites absorb is turned into heat as they are lossy elements.
Ferrites on Interconnects
What happens when you put one of these devices on your interconnect? It adds inductance to the cable causing it to be a low-pass filter (passes only lower frequencies). The problem is: if it is a large ferrite, or the composition is not correct, it can roll-off the high audio frequencies. Bad idea. Better to get a shielded cable if RF is suspected to be a problem. Some very small Ferrite beads, however, can be useful in taming some unshielded cables, such as the Kimber PBJ, but the ferrite should be installed on one conductor, not clamped across both.
Ferrites on Speaker Cables
What happens when Ferrites are installed on speaker cables? This is a more interesting question. Ferrites, with the right composition and size can be helpful for optimizing a speaker/cable/amplifier combination. I would avoid using the large clamp-on Ferrites used for EMI (Electro-Magnetic-Interference), since these generally add too much inductance. The Image Clarifier offered by Empirical Audio is a device that works for audio because the composition and size of the Ferrites is specifically chosen for audio cables. The Ferrite cores should be installed on one wire, not across both wires. The reason that Ferrites can improve the performance of speaker cables lies in their ability to add inductance and loss to the cable. We believe that this inductance reduces the natural resonances in a cable, which we believe can become audible through secondary effects. The ferrite creates a low-pass filter at very high frequeny
http://www.empiricalaudio.com/computer-audio/technical-papers/myths-and-snake-oil
Δεν εισαι και τοσο σαφές αν τελικα βοηθούν σε ολες ή σε καποιες λιγες περιπτώσεις. Το "φιλτρο" που δημιουργούν μπορει να μην ειναι οτι καλύτερο για τον ηχο και οι κατασκευαστές PC που τους φορούν πολυ ειναι για να κρατάνε τα πεδια τους χαμηλά (για τις πιστοποιήσεις).
Στο ρευμα το συζητάμε, στο σημα θα ελεγα καλύτερα οχι.