Moving Electrical Current Through a Vacuum ( ! )

The Miracle of Electricity Flowing In A Vacuum

by Cliff Henricksen

At the AES show, sharing a booth with Doug Fearn and his vacuum-tube creations, once again I puzzled endlessly, looking at his big Simpson meters flicking back and forth as visitors spoke into the RM1 and listened over Sony cans: So I'm thinking "this sound is being processed by electrons flowing through a vacuum, in a bunch of little heated tubes in there.  How can this be possible?".  Well, it's not possible, but there it is anyway.  My only conclusion, thus, is that it's a Miracle:

The flow of electricity in circuits and in solid state electronics is almost understandable:  You connect copper wires to solid objects and you can get electrical current flowing thru them.  In audio and musical instrument amplifiers, these create enough current to move loudspeaker diaphragms enough to create heroic excursion and forces (“of love”, say some artists). 

 Moving to “tube amplifiers”, this is more of a stretch, for me anyway.

 Let me try to explain all this dilemma further:  Electricity is a common invisible force.  "Electrons", small elements of electrical current, allegedly "flow" through electrically-conducting metallic wires into and out of all kinds of things.  We deal with this conceptually by likening the flow of electricity to the flow of water in pipes.  Ohm's famous law still holds true today and I use it with great confidence myself, without reservation or suspicion, in my work.  I can depend on it, because it appears to describe one of the dependable laws of physics, engineering and of Life (possibly even  “love”) itself.  Today, the electric and electronic working and organization of our entire society is almost totally based on Ohm's famous law, itself based on a totally abstract model of what electricity and electrical current flow is.  We can certainly deal with electricity this way, but do we really understand it and know what it truly is?  Knowing PhD candidates in Physics, not to mention practicing Physicists themselves, all confirm a resounding “yes we do!”.  I think Douglas W Fearn and William Hughes (inventor of the Ampeg SVT) also feel this way, inexplicably.  They say “of course we do”.   

We can break an electrical wire that is passing current and cause sparks to jump across the break in the wire, just like if we cut a pipe with water flowing through it.  Splish/splash.  In this case “zapp”:  there it is!!  If we have high voltage, we can actually feel the effect on our skin and body hairs if we pass our hands through the gap between the wires or by touching the wires directly (zzappp!!! owie).  But the effect of these "charged electrons" or whatever they are, is invisible.  Electrons are now thought of in terms of even smaller particles, which are in turn thought of in terms of even smaller particles.  The more we look, the more we find.  And the more we look, the more evidence we find that everything is mostly unoccupied space.  How can there be basically nothing there but the probability of whirling energies and yet the natural universe and all of creation is so solid and real?  Wow; Science Fiction.  I love it. 

A common but more fascinating energy phenomenon is the passage of electrons through a total vacuum, as in a vacuum tube used in the amplification of electrical signals, like in electric guitar amplifiers.  Think about it: no copper wires; just a bit of space with nothing in it and all the air pumped out.  Talk about “Science Fiction”.  Inside the vacuum tube, from which all the air has been evacuated (thus “vacuum tube”), there is a “plate”, a “cathode”, a “grid” and a device to heat up the cathode, basically a small length of special wire that has a lot of “electrical resistance” and gets red-hot when you put electrical current through it.  In other words, this length of wire can easily convert electrical energy to heat energy.  I can relate to that. 

You can see these elements as pieces of metal inside the glass tube, all arranged in a mysterious (but somehow intriguing) geometry.  Here’s how this works:  A steady, high positive DC voltage (300-500 volts or so) is placed on one metallic piece inside the tube (the plate), the cathode (another metallic piece) is heated until it glows red and an electrical circuit is made between the plate and cathode, typically outside the tube using its “pins”.  The main conductor of current is (get this) the expanse of, basically, vacuum, or what’s in outer space, between the plate and cathode.  The grid (yet another metallic object with open spaces in it) is placed in the path between the plate and the cathode.  An electrical signal placed on this “grid” acts as a variable “valve” that regulates the “flow of electrical current” through the vacuum, between the plate and the cathode.  The small to-be-amplified grid or input signal causes large changes in the power flowing from plate to cathode, thus the signal is amplified.  You want a Space Odyssey?; you got it right here!  I mean, you can stare at this tube all day and night and there is not going to be any indication that there is something going on in there, other than a soft light and heat such as you get from a light bulb.  But, if you connect this up in a typical amplifier and put your hand on the speaker cone it is driving, there is no doubt that amplification is working and some real physical stuff is being unleashed.  I mean, if you put your hand close to the cone of an aggressively-played bass guitar amp (like if you take the grille off and expose the actual speaker), your hand will get spanked good and proper.  Whew!  But the electrons (or whatever they are) that cause these forces are invisible, as is electrical current flow. 

 I guess that this is probably as close to witnessing a Genuine Miracle as anything I can think of.  Maybe that’s why electric guitar players love their tube amps so much.  Serious Religion.