Author Topic: Does the Shape & Size of the Glass Valve make a Difference to the Sound ?  (Read 228 times)

Offline marantz123

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Fellows

Is it possible that the shape of the glass, and its volume make a difference to the sound ?

Take a 300B or a 2a3 tube, with its gorgeously styled curves and the relatively large amount of "empty" internal volume that is un-occupied by the mechanical components.....do these attributes make a difference to the "sound" of the valve, contributing to its desireable sonic signature ?

Compared to a relatively compact, plain looking EL34 / EL84  / 6L6, etc. which are minus the generous attributes mentioned above, if these valves were styled as such each with their exact same internal mechanical structure, would they sound different ?

Taking into account that one can configure the pentodes mentioned to work as triodes, in this configuration do they sound anything like the 300B or the 2a3...?

My first thoughts on this is considering the electron bombardment off the glass and the relative variation in time of this in a larger space, and then taking into account the curvature of the glass that may also affect this, as compared to the " straight" tubes, makes me think that this may be of some influence. Then I thought of the resonant Hz of the larger curvy glass tube as compared to the straight smaller tube, (which accounts for the thickness of the glass as well)....could this make a difference ?

If we could make the glass tube sonically invisible or its internal "acoustic volume" much larger to somewhat mimic or approach the generous volume of the 300B or the 2a3,  (you can laugh at this, its ok...something like an open baffle effect, but from an electrical "inside the valve" perspective), or change its resonance, would this make any difference ? ( this last sentence is probably the funniest thing I have written, and im killing myself with laughter... :BWAHAHAH: but I have some ideas )

 :popcorn:
« Last Edit: June 10, 2019, 10:49:52 PM by marantz123 »

Offline Ampdog

Basics:

One should not confuse the shape of electronic components with any 'audible signature' that they might have in whatever field they operate. (Exception is micro waves, where the physical distance between elements influences the time electrons travel, in the sense that they can arrive a notable fraction of a wave 'later' at their destination. But there one speaks upwards of some 600 MHz.

In the case of 'slow' radio short waves (1 - 60 MHz), the time taken for electron travel in a vacuum valve is negligible; certainly so at audio frequencies.

Then also, these electrons travel strictly form cathode to anode. Unwanted 'reflection' off any surface other than the desired one is normally negligible. This is certainly so for any unwanted electron 'bouncing' off the glass envelope - in fact even after first reaching it at all!

One comes close to the popular concept of the "sound of valves". There is no such phenomenon, in the sense, again, of the type of valve being responsible for a particular sound. Valves regulate the flow of current through  them. That gets converted to 'pulsations', usually of voltage over a resistor/impedance. This behaviour has nothing to do with any particular eventual sound. Electrons  have no sense of how many of them go from a cathode to an anode. They only react to voltage polarity. It is the rate of this reaction that eventually determines the sound (threw a loudspeaker of course).

[Going somewhat outside the scope of the question: It is erroneous to state het brand A 'sounds' better than brand B. A valve works in conjunction with many electronic components, all of which shapes the output characteristics. With the spread in valve specs these days it often depends more on the exact characteristics of a particular specimen than the brand.]

Regarding pentodes/tetrodes working triode connected, there is no case of a semi- or part-triode. It works exactly as well as any other triode, with its own specific characteristics. (A pentode can work just as well as a triode with only its screen used as anode (only then with much reduced maximum 'anode' dissipation).
Audio must be the only branch of engineering where lack of basics' knowledge is considered a superior form of wisdom. (Anon)

Offline chrisc

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I've always thought that a valve should be in the shape of a pine tree, ie tapering towards the top.   This will focus the moving electrons towards the plate and enhance the efficiency

In addition, the valve should be encased in an earth-potential metal tube.  Here is such a device

Music is the shorthand of emotion

Offline fredeb

I've always thought that a valve should be in the shape of a pine tree, ie tapering towards the top.   This will focus the moving electrons towards the plate and enhance the efficiency

In addition, the valve should be encased in an earth-potential metal tube.  Here is such a device



Here's a pic of the internal construction of a tube ( on the right ) , the symbols ( on the left ) are merely a figurative representation . In fact , the electrons travel from the centre , outwards . In most of the tubes we use , anyway .



Source : http://education.lenardaudio.com/en/14_valve_amps_2.html

There is sense in an earthed shielding around each tube , but then you can't see the pretty glow .  :D
« Last Edit: June 12, 2019, 08:39:16 AM by fredeb »
...evolution is the gradual development and stratification of progressive series of wholes, stretching from the inorganic beginnings to the highest level of spiritual creation.
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Offline chrisc

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I don't think you appreciated my argument.  The sound will be appreciably purer when the electrons are forced upwards through a conical glass tube.   However, this will probably only apply to music recorded prior to 1984, since by then the digital revolution was in full swing...

Music is the shorthand of emotion

Offline Ufudu

In support of Ampdog... (assuming we are not being trolled  ;D):

I can only comment from a scientific/engineering perspective (as opposed to a metaphysical/spiritual/perceptive standpoint), (this engineering perspective being the same perspective that created the valves in the first place....)

As Fredeb noted, the anode/grid/cathode is essentially cylindrical in nature with the electrons moving from the cathode to anode from inside to outside, impacting the external anode and not getting anywhere near the glass envelope.

The electrical characteristic of the tube is determined by the mechanical design of the electrodes (anode/cathode/grid) structure which has to be VERY precise. During construction these components are all jigged together in various stages, and the support structure assembled. So, looking at a typical 300B, there is a mica disc at the top that acts as a primary support, and another disc below; the entire structure is cylindrical. This must now be placed into a glass tube and the base (a sintered glass base containing the pins) sealed onto the tube. The glass worker used to do this by hand on a glass lathe (in the olden days) and it was a work of art!

The primary variability between OEM tubes, replicas, and batch variation is due to the assembly process. Jigs wear out, tolerances increase, operators have differing skills, modern tubes are no longer using original tools & jigs etc etc.

The glass must provide support to the top mica support, but should be sufficiently clear of the hot anode, but again provide support at the bottom.

Thus the glass envelope, whilst providing an aesthetic pleasing structure, is that shape because of practical/mechanical requirements.

To suggest that the sound is influenced by the glass shape is perhaps like suggesting the earth is influenced by the shape of the universe.

It may be, but so far nobody has been able to measure this, and until they do, it simply remains that, a suggestion...




Offline chrisc

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I tried hard to make this into a joke....     >:D
Music is the shorthand of emotion