Analog & Digital – Part I

There is no question that we live in a digital world.  What does that mean?  Is there another world?  What is the difference?  We live in a world of computers.  Computers are based on components of electrical circuits.  The basic part of the circuit is defined by either being “on” (conducting electrical signals) or “off” (not conducting).  Each of these basic circuit parts in considered a “bit”.  So, a 32 bit controller divides the control in to 32 steps, while a 64 bit has 64 steps.  Notice, the term “steps”.  If one considers a child’s slide, it is a continuous slope.  If we were to make that digital, it would have small steps in place of the continuous slide.  We would not do that, of course.  But we do that with electronics.  Have you ever tried to adjust the volume from a speaker and found one setting was too much and next lower setting was too little?  That is due to the digital steps in the controller.  It is possible to increase the steps to make it appear to be smooth, but it would still be steps.

From Reference 1: “An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (analog signals) to model the problem being solved. In contrast, digital computers represent varying quantities symbolically and by discrete values of both time and amplitude (digital signals).”  Analog computers were used in the 1940 to provide assistance with fire control weapons systems during World War II among other applications. 

The digital computer became the standard for multiple reasons.  The speed of calculation became greater and greater than analog computers.  There was one fundamental issue that hindered the application of analog computers.  Reprogramming was accomplished by rearranging the interconnecting wires/cables within the assembly.  Digital computers in the early days had basic system instructions (neumonic identifiers) that were entered into the computer via numerical codes.  This was slow but faster than rewiring the system.  When the operating systems emerged for digital computers, the computer could perform a multitude of tasks and not be designed for specific problems.

If digital is faster (and better?) than analog, why are people going back to vinyl records?  Why do these people state that the quality of the music is better?  Vinyl records are made by equipment that records the actual frequencies as analog signals into to a master copy that captures the nuances of the changes in frequencies.  This implies that the equipment can record the analog signals, which implies a system with vacuum tubes and not computer-generated analog to digital converters.  To obtain the true effect of the music to be similar to being at and actual performance (not amplified by digital equipment) requires the equipment playing the sounds is also capable of producing analog signals with out electronic digital to analog conversion. 

In a very crude example.  A piano key strikes a chord that vibrates at a given frequency.  The key next to it is at a known, discrete frequency.  E.g., the middle C of a piano is 261.6 HZ, the black key to the right has a frequency of 277.18 Hz.  This is not continuous as it would be for an instrument like a violin.  The piano is the digital instrument (discrete bits) and the violin is the analog (continuous frequencies).  The recording in Reference 2 was done during a practice session by “eg” and has both piano and violin music.  The quality of the recording is not very good, but the differences between the piano (digital) sound and the violin (analog) sounds are obvious.  This example was recorded in an auditorium with a small voice recorder, which was digital.  The point is there is a recognizable difference between the analog and digital type sounds.

Next month, Part II will delve into some of the subtleties of employing digitally modified analog signal along with more on sound itself.  The modification does not come without consequences. 



About Walt

I have been involved in various aspects of nanotechnology since the late 1970s. My interest in promoting nano-safety began in 2006 and produced a white paper in 2007 explaining the four pillars of nano-safety. I am a technology futurist and is currently focused on nanoelectronics, single digit nanomaterials, and 3D printing at the nanoscale. My experience includes three startups, two of which I founded, 13 years at SEMATECH, where I was a Senior Fellow of the technical staff when I left, and 12 years at General Electric with nine of them on corporate staff. I have a Ph.D. from the University of Texas at Austin, an MBA from James Madison University, and a B.S. in Physics from the Illinois Institute of Technology.

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