# Tube Talk



## Paul Running (Apr 12, 2020)

Would there be any interest in starting a section concerning the application of tubes in musical instrument amplifiers? This would be scientifically based, I shall provide an *objective *example:
Some amp builders may be interested in this fact concerning the overload characteristics of a tube, when considering the application of feedback (local and global). I shall quote a statement made in the RCA Radiotron Designer's Handbook 4th edition, a book read by many notable amp designers and builders.
On page 563:
(I) Overload characteristics- Owing to the crowding together of the characteristics at and below the knee of the curves, a pentode tends to give a smoother over-load characteristic than a triode. There is no point at which the distortion begins sharply, but rather a gradual flattening effect on the top, or top and bottom, of the signal current wave. Pentodes or beam power amplifiers with negative feedback lose most of this "cushioning effect," and more closely resemble triodes as regards overload."


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## WCGill (Mar 27, 2009)

There were spirited discussions awhile back when Wild Bill was on the forum but without him it would be no fun.


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## Paul Running (Apr 12, 2020)

By spirited do you mean as an example: You Might Be a Tubeneck if


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## jb welder (Sep 14, 2010)

Let's just say with that subject matter things get quite controversial and not very science based.
If it's about personal experience and anecdote, maybe better elsewhere than in the tech section. Maybe in amps & cabs would be better.


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## Sneaky (Feb 14, 2006)

I think it might fit in the politics forum.


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## Lincoln (Jun 2, 2008)

we were lead to believe that tube are devices that handle the flow of electrons, and electrons have absolutely nothing to do with tone or even sound. Sound is a product of the output transformer and speaker.


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## Paul Running (Apr 12, 2020)

The O/P transformer and speaker are part of the chain; both of these devices are passive and are incapable of controlling current by means of another electrical signal. A tube or valve is an active device and does have control of the signal. It all begins with the power supply, probably the most overlooked component(s) in the chain. In basic terms, an amplifier is just a modulated power supply.


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## greco (Jul 15, 2007)

Fun thread!

I often wonder how Wild Bill is doing.


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## Lincoln (Jun 2, 2008)

Gar Gillies agrees with you that the power transformer is very important in creating "the sound".


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## Frenchy99 (Oct 15, 2016)

6V6 and 6L6 tubes have a warmer tone.


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## Frenchy99 (Oct 15, 2016)

Canadian Iron and Transformers have better Tone !


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## Lincoln (Jun 2, 2008)

Frenchy99 said:


> 6V6 and 6L6 tubes have a warmer tone.


I was always anti-anything that used EL84 tubes. I've been that way since the beginning of time. Until I built a Marshall 18W. They're not so bad after all. B#(*


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## Frenchy99 (Oct 15, 2016)

Lincoln said:


> I was always anti-anything that used EL84 tubes. I've been that way since the beginning of time. Until I built a Marshall 18W. They're not so bad after all. B#(*


I have a YBA-2 with 6V6 in it and its amazing for bass practice.

I also have YBA-2s but with EL-84 which I use for guitar. 

Same amps, not the same tubes, Not the same tone... 

I had another YBA-2 with a replaced transformer for the US... had to get rid of it !!!


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## Lincoln (Jun 2, 2008)

But can you hear the difference between an EL34 and a 6CA7? Or a 7025 & a 12AX7


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## WCGill (Mar 27, 2009)

Paul Running said:


> The O/P transformer and speaker are part of the chain; both of these devices are passive and are incapable of controlling current by means of another electrical signal. A tube or valve is an active device and does have control of the signal. It all begins with the power supply, probably the most overlooked component(s) in the chain. In basic terms, an amplifier is just a modulated power supply.


Sorry, not this time.


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## Paul Running (Apr 12, 2020)

Sorry folks, it's off the topic that I have intended: at the top of the thread I made reference to overload characteristics of a tube as an *objective* view. I did not intend it to be a taste test. I was hoping to see some feedback from experimenter/builders who have made new discoveries in the application of tubes in musical instrument amplifiers from a scientific standpoint. I am not trying to re-invent the wheel here and I believe that their is some characteristic of the tube that has yet to be discovered. If you wish, I am open to a private conversation.


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## zdogma (Mar 21, 2006)

I want to talk about the crystal lattice and fragile harmonics!!!!


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## zdogma (Mar 21, 2006)




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## Paul Running (Apr 12, 2020)

Globally, there seems to be alot of negative comments on his video and yet most of his amplifiers are fetching huge sums of money. Could it be that some people are envious of his accomplishments? Really, it is a theory that he believes and who are we to disprove the man...can you be 100% sure that his theory is incorrect?


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## Paul Running (Apr 12, 2020)

The term "valve" is a more accurate term because a true vacuum is a perfect insulator which has infinite resistance and by the application of Ohm's law: no current would flow; elementary school mathematics...if you divide any number with infinity other than infinity, you will get zero. A valve could not function in a true vacuum.


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## guitarman2 (Aug 25, 2006)

WCGill said:


> There were spirited discussions awhile back when Wild Bill was on the forum but without him it would be no fun.


Does anyone know what ever happened to him? I used to see him fairly often but not for many years.


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## Lincoln (Jun 2, 2008)

I noticed Electro-harmonix in Russia has started marketing 7025 tubes. I bought one to try out "just because". The etching on the tube says 7025EH. Must be a special Eddie Van Halen signature model.


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## Paul Running (Apr 12, 2020)

That would be the 7025EVH model.


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## Lincoln (Jun 2, 2008)

Paul Running said:


> That would be the 7025EVH model.


I couldn't afford the 7025EVH. I just got the plain old 7025EH.........


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## Lincoln (Jun 2, 2008)

Anything to say about Russian 6N2P (same as 12AX7) tubes? I picked up a couple just to see what they are all about. Yes, I know the wiring is different & I can handle that. 6 volt heater circuit using only pins 4 & 5, pin 9 is a shield that needs to be grounded.

I'n going to try them in some simple builds and see how they work.


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## tomee2 (Feb 27, 2017)

I think for every person with the tools and experience needed to discuss tube amps objectively, there's 100,000 people willing to talk subjectively. Most of those only have their ears and fingers as measuring instruments, and can only swap guitars, speakers, and tubes as part of an experiment. So they end up talking about sound and tone and feel. 
As some would say, it is what it is....


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## jb welder (Sep 14, 2010)

I thought this one to be quite well thought out and interesting:
Valve (Tube) Comparison Tests - Black Magic Amplifiers


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## Paul Running (Apr 12, 2020)

Yeah that is an interesting article. I like his conclusions...there is definitely a lot of stretching the boundaries, when they advertise these tubes. In the end your ear makes the decision.


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## Paul Running (Apr 12, 2020)

Here's another one on the subject of the "black plate" tube.









Black Plate Tubes - Effectrode







www.effectrode.com


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## Lincoln (Jun 2, 2008)

would high current applications be mostly the phase inverter tube?


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## Paul Running (Apr 12, 2020)

In certain situations...if the signals from the PI are high enough, the power tubes will begin to sink current as the signal ventures past the 0V region on the control grids...forward conduction, cathode to control-grid. During this condition, the input impedance to the power tubes becomes very low and will overload the PI unless it's output impedance is low enough to drive the power tubes...this would be a higher current application.


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## Paul Running (Apr 12, 2020)

The PI would have to be capable of sourcing the required current in order to maintain signal fidelity.


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## jbealsmusic (Feb 12, 2014)

Just for fun:





Enjoy and discuss.


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## Paul Running (Apr 12, 2020)

I agree with his statements concerning the inputs and loads to the amp...a mic or pickup and speaker load will have greater control over the tone verses the tubes in the amp. IMO the tube is more of a constant, the passive components within the amp are much more variable to the tone. The bias levels of the tubes will have some effect on the tone, depending on the level from the null-point which I believe is the main reason why a person may perceive a difference when changing tubes...a fair reason to check the bias when changing tubes, especially power tubes. Level from tone can be difficult to discern to untrained ears. I depend on my oscilloscope...probably more than my ears...a 100W amp is only twice as loud as a 10W amp...it's the way our hearing works.


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## nonreverb (Sep 19, 2006)

Paul Running said:


> I agree with his statements concerning the inputs and loads to the amp...a mic or pickup and speaker load will have greater control over the tone verses the tubes in the amp. IMO the tube is more of a constant, the passive components within the amp are much more variable to the tone. The bias levels of the tubes will have some effect on the tone, depending on the level from the null-point which I believe is the main reason why a person may perceive a difference when changing tubes...a fair reason to check the bias when changing tubes, especially power tubes. Level from tone can be difficult to discern to untrained ears. I depend on my oscilloscope...probably more than my ears...a 100W amp is only twice as loud as a 10W amp...it's the way our hearing works.


I agree...The only exception to this would be power tubes (preamps too but not as common) who's emission coating material has degraded excessively. They do start to sound muddy and their dynamic range narrows when they're pooched.


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## jb welder (Sep 14, 2010)

Lincoln said:


> would high current applications be mostly the phase inverter tube?


The 12AT7 reverb drive in classic Fender circuits is essentially a little single-ended power amp. The reverb drive transformer is a mini OT and the tank input coil is 8 ohm impedance. You can hook up a speaker instead of the tank and it will happily drive it.
So that is a higher current application as far as pre-amp tubes goes.


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## cboutilier (Jan 12, 2016)

jb welder said:


> The 12AT7 reverb drive in classic Fender circuits is essentially a little single-ended power amp. The reverb drive transformer is a mini OT and the tank input coil is 8 ohm impedance. You can hook up a speaker instead of the tank and it will happily drive it.
> So that is a higher current application as far as pre-amp tubes goes.


Especially in the 70s amps. They were tough on the T7s


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## Paul Running (Apr 12, 2020)

cboutilier said:


> Especially in the 70s amps. They were tough on the T7s


Reverb tanks were designed to be driven from a constant current source, a pentode provides a CCS. Fender's standalone unit with the 6V6, was a smoother application.


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## Paul Running (Apr 12, 2020)

Here's an early RCA AN for operation of the 6L6...not too technical and you may find it interesting.


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## Paul Running (Apr 12, 2020)

And one for the 6V6.


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## Paul Running (Apr 12, 2020)

I imagine that these would be some of the documents that Leo Fender would read through in his younger years.


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## WCGill (Mar 27, 2009)

Paul Running said:


> I imagine that these would be some of the documents that Leo Fender would read through in his younger years.





jbealsmusic said:


> Just for fun:
> 
> 
> 
> ...


Randall Aiken posted a graph a few years back measuring distortion from EL84 tubes, specifically EH (Sovtek?) and JJ's. One exhibited 4db more 2nd harmonic distortion than the other, not sure which as the graph has disappeared into the web black hole. Now if you are familiar with Mr. Aiken, you know this is all copacetic. This was the point of contention with former member Mr. Wild Bill and myself, I arguing if 3db is twice as loud, this difference must be significant and possibly audible, he arguing all tubes sound (and therefore measure) the same. 

Once upon a time, long ago and far away when I was still working on amps I had a Dr. Z Carmen Ghia in for a gander and yanked the Soviet EL84's out and put in a pair of Mullards - great galloping grids, what a difference! No, the Soviets weren't the ones. 

Earlier in this thread there were some tube tone comparisons, which I must unfortunately take issue with. I'm fairly certain that both of the test amplifiers employed feedback, local or otherwise, the great characteristics "leveller", making tonal differences insignificant and impossible to distinguish. A better test bed is an AC30 circuit which employs no feedback. 

_Disclaimer Alert_ - I'm not sure if the Carmen Ghia has a feedback loop as I've lost my hand-drawn schematic, pretty sure it does, making the difference in what I heard all the more shocking.
Happy New Year fellow music aficionados!


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## nonreverb (Sep 19, 2006)

WCGill said:


> Randall Aiken posted a graph a few years back measuring distortion from EL84 tubes, specifically EH (Sovtek?) and JJ's. One exhibited 4db more 2nd harmonic distortion than the other, not sure which as the graph has disappeared into the web black hole. Now if you are familiar with Mr. Aiken, you know this is all copacetic. This was the point of contention with former member Mr. Wild Bill and myself, I arguing if 3db is twice as loud, this difference must be significant and possibly audible, he arguing all tubes sound (and therefore measure) the same.
> 
> Once upon a time, long ago and far away when I was still working on amps I had a Dr. Z Carmen Ghia in for a gander and yanked the Soviet EL84's out and put in a pair of Mullards - great galloping grids, what a difference! No, the Soviets weren't the ones.
> 
> ...











Perhaps the emission was bad on the Sovtek set?


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## WCGill (Mar 27, 2009)

Very possible. The Carmen Ghia wasn't very old but I don't recall if I tested the tubes. The Mullards were not new either but they sure had sparkle and chime.


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## Paul Running (Apr 12, 2020)

Save those toilet-paper tubes. They are the proper size for storing your loose tubes. Here's an example with some 6L6 types.


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## Hammerhands (Dec 19, 2016)

jb welder said:


> The 12AT7 reverb drive in classic Fender circuits is essentially a little single-ended power amp. The reverb drive transformer is a mini OT and the tank input coil is 8 ohm impedance. You can hook up a speaker instead of the tank and it will happily drive it.
> So that is a higher current application as far as pre-amp tubes goes.


You can make a mini Herzog with one.


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## Paul Running (Apr 12, 2020)

What do you think of the Kay 550?


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## Paul Running (Apr 12, 2020)

A few changes...it's a neat design.


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## Paul Running (Apr 12, 2020)

Driving the reverb tank through a pentode makes sense to me however, the triode has an attraction too and the nice thing about the pentode is that it can be strapped as a triode...I believe that it require more components for triodes to emulate pentodes.


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## Paul Running (Apr 12, 2020)

This lad has fun working on a Kay 550:


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## Lincoln (Jun 2, 2008)

Oh, that guy. Does he really need all that test equipment? Is he a collector of test equipment or something?


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## cboutilier (Jan 12, 2016)

Hammerhands said:


> You can make a mini Herzog with one.


Mini Herzog is on my mile-long to-do list.


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## jb welder (Sep 14, 2010)

Lincoln said:


> Oh, that guy. Does he really need all that test equipment? Is he a collector of test equipment or something?


Yes he is.
Mr. Carlson is a BC guy who is semi-famous in tech circles world-wide.


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## nonreverb (Sep 19, 2006)

He has almost as much shit as I do....


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## Lincoln (Jun 2, 2008)

nonreverb said:


> He has almost as much shit as I do....


I remember you put up a picture of your tube stock once and it made my mouth fall open.


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## nonreverb (Sep 19, 2006)

That's only part of it. 😁


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## Lincoln (Jun 2, 2008)

jb welder said:


> Yes he is.
> Mr. Carlson is a BC guy who is semi-famous in tech circles world-wide.


he scared the hell out of me with the "you're installing your capacitors backwards" video


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## jb welder (Sep 14, 2010)

Lincoln said:


> he scared the hell out of me with the "you're installing your capacitors backwards" video


I think with that kind of gear he lives more in the RF world. He seems to be involved in HAM stuff.
So for that kind of ultra sonic application, capacitor orientation can actually matter.


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## Lincoln (Jun 2, 2008)

Paul Running said:


> This lad has fun working on a Kay 550:


Well, I managed to sit through the whole thing. Two questions if I may. What's so special about his home-made capacitor tester? Why would you build something like that? Using up surplus LED's? And I was surprized that he left the 3 ceramic disc caps. They're drifty, they're microphonic as hell, but they add to the individuality of the amp???


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## Paul Running (Apr 12, 2020)

Lincoln said:


> Well, I managed to sit through the whole thing. Two questions if I may. What's so special about his home-made capacitor tester? Why would you build something like that? Using up surplus LED's? And I was surprized that he left the 3 ceramic disc caps. They're drifty, they're microphonic as hell, but they add to the individuality of the amp???


If you take a look at some of the gear he builds...it's amazing. I have followed him for a while now and you are correct about the length of his videos...if I can sit through some of these flics that are on now, I have no problem watching this lad talk for an hour.


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## Paul Running (Apr 12, 2020)

Terry Dayton at Dlab has a few good videos too on youtube, another ham hound, with interests in VTT.


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## Lincoln (Jun 2, 2008)

Paul Running said:


> Terry Dayton at Dlab has a few good videos too on youtube, another ham hound, with interests in VTT.


I'm a long time subscriber of his channel. Mostly good stuff for sure.

He seems to be all about reliability with little regard for preserving vintage mojo


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## Lincoln (Jun 2, 2008)

How many of you techs own a "Mr Carlson Super Probe"???


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## jb welder (Sep 14, 2010)

Lincoln said:


> How many of you techs own a "Mr Carlson Super Probe"???


If I need a signal tracer, I grab my practice amp, cord, a couple alligator test leads and a meter probe.


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## Lincoln (Jun 2, 2008)

jb welder said:


> If I need a signal tracer, I grab my practice amp, cord, a couple alligator test leads and a meter probe.


He's miles over my head obviously, but I can follow along, understand, and learn things, until he picks up one of his "gadgets". At that point, I'm done. He's lost me.


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## Lincoln (Jun 2, 2008)

And speaking of Terry at DLab, he just pronounced a Traynor YBA-3 Custom DOA. 😞 

DLab Traynor YBA-3


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## nonreverb (Sep 19, 2006)

Lincoln said:


> And speaking of Terry at DLab, he just pronounced a Traynor YBA-3 Custom DOA. 😞
> 
> DLab Traynor YBA-3


Where's this guy located? I'm looking for a replacement face plate for a late '60's YBA-3!
*UPDATE *Nevermind I found out.


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## epis (Feb 25, 2012)

Paul Running said:


> This lad has fun working on a Kay 550:


That guy is full of BS, that video is great for average Joe's who don't have a clue about electronics, especially tube guitar amps.
Yes I did watch video for 10 min.


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## Lincoln (Jun 2, 2008)

epis said:


> That guy is full of BS, that video is great for average Joe's who don't have a clue about electronics, especially tube guitar amps.
> Yes I did watch video for 10 min.


10 minutes is nothing. Some of his videos are 2-1/2 hours long! You need to sit through a couple of those to get the full effect.


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## Paul Running (Apr 12, 2020)

Lincoln said:


> And speaking of Terry at DLab, he just pronounced a Traynor YBA-3 Custom DOA. 😞
> 
> DLab Traynor YBA-3


Too bad...it would have been nice to see him restore that amp.


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## Paul Running (Apr 12, 2020)

zdogma said:


>


On the subject of the crystal lattice. I believe I may have discovered the origins of Mr. Dumble's line of thinking concerning *crystal lattice*. It is located in a book authored by Albert Preisman: "_Graphical Constructions for Vacuum Tube Circuits_". a 1943 publication...it can be found under the subject of Space Charge, pages 19 and 20; here is the excerpt:

*Space Charge:*
At first thought it would appear that a small voltage would be sufficient to draw all the emitted electrons through the obstacle-free space or vacuum over to the plate, since the thermal energy has done that which the voltage was unable to do, viz., carry the electrons through the surface of the cathode (emission). A moment's reflection, however, will indicate that this is not so, that there are obstructions in the space in the form of mutual repulsions between the electrons themselves and that these hinder the plate potential in its effort to transport the electrons. This repelling effect is known as space charge. In the conductor it is neutralized by the positive space-charge effect of the metallic ions in the *crystal lattice* structure and the only opposition to the movement of the electrons is that of ohmic resistance-possibly the result of collisions of the electrons with the ions. But when the electrons are " out in the open," remote from the ions, their negative space-charge effect becomes evident and it will be found that a low plate voltage causes but a small current to flow, a higher plate voltage causes a greater current to flow, etc., until a voltage is reached which causes all the electrons emitted to flow. Higher voltages than this can cause no further increase in current, and the latter maximum value is known as the temperature-saturation value of current, whereas the former values are known as voltage-saturation values.


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## Hammerhands (Dec 19, 2016)

In a solid metal and in crystals, atoms are arranged in a regular or lattice pattern.

Preisman’s article is talking about the crystal lattice structure of a metal’s atoms, I think*.

I think** Dumble is talking about the crystal lattice structure of the atoms of whatever semi-conductor is being used in a transistor.

I’m not sure how fragile harmonics are eliminated or squashed in a crystal lattice. I guess every electron counts, or since fragile harmonics are represented by fewer and possibly more erratic electrons, they are more likely to be suppressed?

See here:








Course Hero







courses.lumenlearning.com





and the link in the linked page:




__





The Structure of Metals






chemed.chem.purdue.edu





*You could call a screen grid a lattice structure.
**Similarly, Dumble could be talking about a physical structure in a transistor, like the gate of a fet.


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## Paul Running (Apr 12, 2020)

Some history and info on the EL34:


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## WCGill (Mar 27, 2009)

A blast from the past, VTV, a monumental publication, sadly not around anymore. Thanks Paul.


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## Paul Running (Apr 12, 2020)

Some general info on tube care.


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