Do power cables make a difference in sound quality?
Yes they do. Power cables radiate pulses* that influence your interconnects up to distances of a meter. These pulses are caused by the rectifier which is standard for almost every piece of Hi-Fi, and is being picked up by nearby interconnects and enter your system where they interfere with your music signal. Crystal’s power cords do not radiate these pulses. *These pulses are double the main frequency; i.e. 100Hz or 120c/s. Cause is the rectifier together with the always charged electrolytic capacitors; the current needed to fill up those capacitors only flows in the top of the sine wave during a very short period. So instead of an average current consumption from the mains, the current peaks at twice the cycle sending out magnetic fields ranging from 100c/s to about 5000c/s.
