Many of the best video cables on the market today were designed primarily for use in the digital domain but can a digital cable really perform well as an analog cable? Can an analog cable be used as a digital cable? What’s the difference, between digital and analog cables? They both move electrons, don’t they? All of these are interesting questions, and bear some discussion. To begin that discussion, let’s first talk about what digital and analog signals are, and how they perform in cables.
Digital and Analog Cable Signals:
The first generation of video and audio cables was designed with analog signals in mind. An analog signal represents the information it is intended to convey by presenting a continuous waveform analogous to the information itself. If we could use that electrical signal to drive a speaker cone to physically move in and out in that same pattern, we did hear the tone come out of the speaker.
A digital signal opposite to analog signal, bears no superficial resemblance to the information it seeks to convey. Instead, it consists of a series of “1” and “0” bits, encoded according to some particular standard, and delivered as a series of rapid transitions in voltage. Ideally, these transitions are instantaneous, creating what we call a “square wave.”
Most interesting distinctions between digital and analog signals is that they degrade in rather different ways. Both are electrical signals, carried by a stream of electrons in a wire, and so both are subject to alteration by the electrical characteristics of the cable and by the intrusion of outside electrical noise. But while the alteration of an analog waveform is progressive and continuous–the more noise is introduced, the more noise will come out of our speaker along with the tone–the digital signal suffers alteration quite differently.
The result is that digital signals can be quite robust; they can exhibit no functional degradation at all up to a point. But the difference between perfect rendering of a digital signal and total loss of signal can be surprisingly small; one can reach a threshold where the digital signal begins to fall apart, and not long after that threshold, find that there is no signal at all. The signal which gets through flawlessly over several hundred feet may be unable to get through at all, even in a damaged condition, when the cable run is lengthened by another fifty feet.