Wired!!! Page 2

• The electrical signal is maintained by the flow of electrons in the conductor (the velocity of those electrons is surprisingly low). Does the mechanical structure of the conductor affect the behavior of the electrons? I remember the English audio engineer Stanley Kelly telling me how, as a junior member of the British team developing radar in the '40s, it was his job to pound pure-copper busbars with a rubber mallet until their resistance dropped to the specified level.

• With unbalanced interconnects and components, grounding problems are inherent. (When we measure the performance of review components with the magazine's Audio Precision test setup, the first thing that's always done is to try all the different possible ground arrangements to get the lowest noise. With some components, changing a ground connection can increase the level of hum and RF noise by a factor of 10.) The lowest noise may not be achieved with a typical coaxial cable. It may be necessary to run a separate ground reference wire and connect the shield to just one rather than both chassis. The system's noise level may well change depending on whether the shield is connected to the source component or the load component. Either way, the electrical signal—and, possibly, the sound—will be changed.

• Any feedback amplifier has two input ports: first, the "input" jack; second, the output terminals are the input to the negative-feedback loop. Except in systems where impedance-matching is employed, it's normal to load a source component with the high input impedance of the next component. In a system, therefore, you're hanging a cable terminated in a high impedance from one of the source component's input ports. There are two system-dependent effects that I can think of (there may be more).

As the cable is terminated with a high impedance and its shield may or may not be a very good shield at RF frequencies, and as the cable will always be immersed in an RF field, it's possible that, at frequencies where it best behaves as an antenna, it will inject RF energy into the source component's feedback loop in an unpredictable manner. Some "audiophile" cables use a weave to reduce RF pickup; others use an RC network; others don't do anything. Perhaps that may be one reason why they might sound different in different systems and locations.

• Take a 10' or so length of coaxial interconnect and terminate one end with, say, 47k ohms to represent a typical load impedance. Terminate the other with an RCA plug and hook it into your preamp's line input. Turn the volume up and bang the cable with a suitable blunt instrument. You'll find that some cables are very microphonic, others not at all. Some cables, therefore, will inject an electrical analog of the soundfield in which they are immersed into the source component's feedback loop—again with unpredictable results.

Some, none, or all of these factors may play a role in cable "sound." What I don't understand is why responsible engineers would dismiss any of them out of hand.

Article Contents
Share | |
Site Map / Direct Links