OK, I will give the basics a try anyway, trying to expand a little on some of Brian's points. No expert, my understanding is rudimentary and I hope this is relatively accurate, and useful in some ways. And please straighten me out if anyone sees any problems in this explanation.
It seems the basic concepts for a tube’s function are: a diode is like our rectifiers, a cathode and a plate (anode) being the electrodes, making the “di,“ and the “ode” being short for electrode. A triode...like our input tubes, the “tri” is the cathode and plate, plus a grid in between, so three electrodes, or a triode.
For a triode, inside the plates, in the center is the cathode, and between the cathode and plate is the grid. The cathode is negatively charged, and the plate is positive with high voltage. The cathode is heated up, usually by an internal filament inside the cathode tube, so that orange light we see is usually from the filament, or glowing cathode once heated up. This heat/energy, causes the cathode to emit clouds of electrons into the glass enclosed vacuum of the tube.
Next to and parallel with the cathode is the grid, also negative due to how it is “biased.” Then the, plate, outside the grid, set up with very positive voltage, causes the electrons from the negative cathode to be attracted to the plate. The grid in between, carries the signal, and acts as a “valve,” allowing more or less electrons through the grid to the plate depending on signal voltage. Signal voltage "controls" how open or closed the "valve" is. Being biased to be negative, like the cathode, wide open, as I recall, the grid needs to be a little less than 0 volts for clear sound…. Then with more negative voltage shifts from the signal, the “valve” "closes," letting less electrons through the signal carrying grid to the plate.
Dual purpose, the plate being strongly positive in order to attract electrons from the negative cathode through the negative grid, it is also generally the plate that acts as the signal output of the tube, collecting and moving the signal onward.
That we can't easily measure all we can hear, or in the case of complex things like tubes, clearly differentiate the exact causes of sound differences, I am pretty sure this would be a daunting task to solve with measurements.
In my experience with amp modifications and cable making, in wires alone, pretty slight variations in materials, gauges, purity, structure, damping, and dielectric can make notable sound differences. It is acknowledged that different metals, their purity, and structure make differences as conductors, and different gauges of same carry power and signal differently, and different dielectrics have measurable negative effects for pure signal flow....These are good rudimentary pointers to exploring sound if we are interested in using wires optimally.... But as far as I can tell, our measurements for wires are still not good enough to explain why very similar wires can sound pretty different.
So in more complex tubes, beyond the electronic designs that make it a variant of a tube type, like a 6DJ8/ECC88 as a variant of 6922/E88CC, all the parts and means of connections of a tube effect how the electricity and signal act, in turn, making the potentials for differences in sound pretty explainable, at least conceptually.
A lot of different metals, wires and connections in a tube, each choice effecting electronic flows, each would influence the sonic quality when the tube is put into action. Add to that material interactions with power and heat, design variations like glass shape and size, glass composition and weight, along with plate structure and micas effecting damping as well as heat dissipation.... the getter composition and the quality of the vacuum, etc. This presents a lot of potential variation between tube builds. Who knows exactly what just the glass composition, weight, and shape can do to the sound....not to mention all those little wires; getter compositions, shapes, and placement; the density, thicknesses, materials and numbers of “micas” used, and so on.…
On subtler levels I have no doubt each one of these and more effect the sound individually, and collectively they give us a distinct tube signature. So the individual variations in this complex of design and parts, cause equal measuring tubes of the same type, to sound quite differently….all of these things effecting how electricity acts….more easy flow or less, more or less noise and vibration, more or less synergy…..
So collectively, even with the same design and production methods, with even slight variations in the many natural materials and parts used, and slight variables in month to month, or year to year production effects on the designs and materials, it makes sense to me that this can make "the same" tubes sound differently. Then change up the internal design and spacing a little, the wire or getter compositions, the glass formula, shape, and thickness, etc, seems these will cause even greater sound differences, causing the same measuring tubes to sound even more different.
My take anyway. From here, talking about characteristic sonic qualities of different tube types, variants, and makes is a lot, and I am pretty tired
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Understanding tubes a little better (Read 4392 times)
