How Vacuum Tubes Work

I edited and annotated the original 28 minute film "Electronics at Work" down to 3.5 minutes. The annotations help explain how electronic vacuum tubes flow electrons to amplify guitar signals and rectify AC to DC.

[@wentaoqiu4072]

I’m always amazed at how old tutorial videos explaining things so well and in such a simple, elegant way.

[@pastaman64]

Not to sound like a stereotypical cynical boomer, but I imagine that's probably because back then they weren't trying to stretch out a tutorial to make it 10 minutes long just for some teeny tiny bit of extra youtube money

[@philipm3173]

@@pastaman64 Right because the government was funding the sciences and education

[@AwestrikeFearofGods]

Filming and animation were expensive, so they would be thoroughly planned. Only professional studios could afford to do it.

[@slawomirkulinski]

I just came here after listening to a guy who was trying to explain this for half an hour. Less then 4 minutes and I am done.

[@galzajc1257]

yeah many great ones. maybe the most insane one: kzbin.info/www/bejne/hXqQhaJnmrqnq7c. and this was like 30 years before 3b1b

[@animalblundetto5673]

I love these classic old American explanatory videos, military training videos etc. They're so clear and to-the-point, and always in that Transatlantic accent that you just don't hear anymore.

[@waylonk2453]

We could use some more clarity and conciseness in training videos these days. Now it's all about colors and graphics with new-age music!

[@KUSHALGOKHALE]

there was a channel full of such videos...by the name jeff quitney...now its gone...i dont know where

[@scottwentworth4720]

Old school physicists are good at breaking things down to layman.

[@huuballawick]

If someone isn't able to explain something simply, they don't have a complete understanding of it.

[@patrickjane6377]

@@huuballawick my thoughts exactly. Most people nowadays dont really understand what they learn anymore. They just memorize it.

[@Hezigrimm]

I have to give my instructors who were Automotive Techs some major credit for me to even remotely understand what is at play here. I do agree that old school physicists have a much better way of describing things than newer ones are, but I primarily think that is mostly due to the fact old school taught at a slower pace and new school flies through it.

[@Lyander25]

@@Hezigrimm Agreed, the sheer volume of information available to people in the internet age, not to mention the high value placed on producing skilled and learned individuals as fast as possible to enter the workforce means that education nowadays cannot help but accelerate the pace of things to the point where a surface-level understanding of concepts is all that's necessary. Experience and genuine depth of knowledge comes after, if at all.

[@bustedhonda]

That was exactly what I needed to learn. Thanls!

[@joewoodchuck3824]

One of the nice things about tubes is being able to actually see the elements being discussed which makes it, in my mind, easier to understand. If I had my way, tubes would still be taught to help visualize what happens in an amplifier, even in solid state.

[@jsmythib]

Same. Using heat and a vacuum to induce electron flow vs silicon doping layers near each other inducing electron flow, without heat. Its all very interesting :)

[@WaliSayed]

It doesn't matter if the video is old and classic, but the explanation is magical and made me understand a complete book. Thank you!

[@MundaneMuser]

Although this is many decades old, the technology described by the narrator is surprisingly advanced. It makes me appreciate old technology even more.

[@veepedaldude9404]

These videos are about as clear as it can get. Why do modern educational vids lack this.

[@jerryfacts9749]

These older films (transferred to video) were very well made. The explanation of how vacuum tubes work is interesting. I am in my 70s, and in my early years of working in electronics I was building projects and doing servicing of devices using vacuum tubes. The tubes in this video are of a much older generation of the ones I worked with.

[@SevenDeMagnus]

Thanks vacuum tube inventor for paving the way for the transistor.

[@chaudry123]

Agree. When I was not yet graduated, I was feeling like if more credit goes to Einstein than Newton and Galalio but the reality is the other way round. I mean the foundation always makes difference. So more credit should go to the founder.

[@AMStationEngineer]

I've held a General Radiotelephone Operator's License' "GROL", since before the days of the 'Supersede Order' for the "Second Class Radiotelephone Operator's License". This video is leaps and bounds above all the rest regarding "Tube Theory"!!

[@chetananam475]

Please post more videos like these. Real quality instruction! Makes learning enjoyable. Absolutely clear cut content.

[@milesnottage5900]

Thank you for this - it genuinely very useful for music tech classes. We talk about valve amps all the time without (in many cases) really understanding what they actually are.

[@alpurl]

Thank you for sharing, and for pointing out that the full video is available. Vacuum tubes were still quite common when I was a kid, and I grew up through what I consider "The Digital Revolution" through the late seventies going through the eighties. I witnessed the demise of the LP, 8 track, reel to reel, slide projectors, and film projectors. I witnessed the development and demise of audio cassettes, VHS, and Betamax. I saw the rise and fall of CDs and the development of the dvd. I witnessed the war between Bluray vs HDDVD just like vhs and betamax. If seen the development of mp3, mp4, and streaming. I've seen numerous game systems from Atari 2600 and 5200, through NES, Wii, to XBox and PlayStation and their various associated handheld units. I remember when a 19 inch color tv tipped the scale at around 75# and was state of the art. Now we have displays that cover a wall weighing around 150# at barely 1-2 inches thick, and can project an image anywhere with no wires or cords from a projector the size of a deck of average playing cards. Personal computers were only for the rich, and only doctors, lawyers, and the occasional drug dealer had a mobile phone that was the size of a briefcase. Today, we wear and carry devices as phones that are far more powerful than all of the combined computing power of every computer NASA had when we sent astronauts to the moon. My first computer in 1998 was cutting edge technology with a 300 MHz processor, 4MB video card, 64MB ram, a 4.3 GB hard drive, and a 56K modem with 24K fax. It can't even come close to what my two year old Note 8 does. We also went from wired Ethernet which we still use, to extensive wireless home networks through 802.11 a, b, g, and n. Mobile phones are small and inexpensive enough that everyone has one in their pocket and they went through wireless technologies from Edge through G, 2G and 3G, 4G and 4G LTE and now into 5G. That doesn't even count the IOT or internet in general as we know it. All of this is only the tip of the iceberg. But now we're bringing back tube amplifiers, LP's, and the instamatic camera and now have instamatic photo "printers" that connect to our smart phones and "print" a photo that comes out entirely white and becomes a photo before your eyes, and call the technology "new." At best, it's old school with a modern twist. I'll be 47 in 2020, and as fast as technology changed then, it's nearly lightning quick today. We really do have the world at our finger tips.

[@louf7178]

Excellent post. I forgot about HDDVD.

[@ericscaillet2232]

Erm...we have 'our ' world at our fingertip,the world will remain as it has always been😒

[@westelaudio943]

Tubes never went away. Guitar amps (high end ones) always used them, as well as niche HiFi amps. LPs also, but there has been a resurgence since about the early '00s. Instant cameras aren't all that good, I don't know why people use them, I do love my 35mm film though.

[@whateverittakes1673]

So it's basically a transistor but with different physics

[@robrobinette]

Yes, transistors and tubes are similar in how they function.

[@BallistaBomber]

Rob Robinette except tubes are exponentialy bigger

[@luuk341]

Forrest Hildebrant And more expensive

[@walterbunn280]

mmm.... kinda. Transistors are mostly voltage controlled, where as Vacuum Tubes are mostly current controlled. Arguably Bipolar Junction Transistors are also current controlled, but, especially relative to a vacuum tubes, they operate more around the potential differences at the emitter-collector-base (or drain, source, and gate if we're talking Field effect...). This means that vacuum tubes are generally better at handling large currents relative to transistors, but most residential consumers don't have a use for a KiloAmpere of current. More over, a person might actually be able to make a vacuum tube at home. I don't think that's really an option with any of the transistors, but that's also probably not practical in most circumstances. It's great for the enthusiasts though.

[@g00glian0]

@@walterbunn280 Helpful!

[@steveperry1344]

this brings back some memory cells. worked on vacuum tube radio transmitters while in the air force 50 years ago.

[@CooKiesHouseCannabisCo]

makes me happy to see that 237,000+ people have chosen to watch this. :)

[@alecalfaras5936]

now almost 600,000!! Long live vacuum tubes

[@turbo5483]

How does someone even invent this stuff...amazing !!!

[@robrobinette]

Eddison accidentally discovered vacuum tubes while working on the light bulb.

[@jmg9509]

Actually I had this idea roaming in my head for a couple days now, only for someone to tell me it already exists today >.>. Actually I have a slight variation and application for what can be done using something similar.

[@philosophyofpolitics4504]

@@robrobinette Edison was a businessman, not a scientist. He had the money to put his name on patents, reports, inventions etc... Guys like Tesla were the unsung workhorses. Grinding it out at their towers all day... Getting no respect...

[@ivantacalo8802]

@@philosophyofpolitics4504 facts

[@justsumguy2u]

@@philosophyofpolitics4504 Edison was most certainly a scientist, most of the inventions he created were done by himself, without outside help. Steve Jobs on the other hand was a businessman with ideas

[@michaelbrady9170]

Thank you very much, Rob. BTW: I received the StewMac 5e3 15 watt amp kit, but i have a couple of weeks DIY work to be done before we can move into the older (but new-to-us) house we purchased. As I am writing this, it occurs to me that I had better check on the StewMac warranty for the amp and parts almost immediately. Nevertheless thanks again for the video here!

[@rockfordlines3547]

Love the modern graphics.

[@gavinlew8273]

This is what makes America so great, these instructional videos are clear, articulate and very instructional. Much better than many KZbin videos today.

[@dmsmhic]

For the first time I understand the concept. Thank you!!

[@Calligraphy-dilipaweeratunga13]

They explained it so well that now I can understand the usees of the transister.

[@fairnut6418]

It is unreal how the tube amplifier analogy is so much easier to understand than with transistors.

[@robrobinette]

The transistor gate functions like a tube control grid. The signal applied to the gate is amplified by the transistor.

[@ReneStover]

I knew a Mr. Robinette, he was a great and intelligent Man and great teacher!

[@TheDukeOfSaudi]

VTs explained in an elegant, simple manner. Thumbs up!

[@asadpuppy1259]

Thanks Rob Robinette

[@chaudry123]

Wow its amazing to see how vac tube used to work.

[@robrobinette]

Tubes are still used in guitar and audio amplifiers.

[@karhukivi]

Still used in high power radio and TV transmitters, although they are in ceramic tubes, not glass ones.

[@seankerr1187]

Awesome! Thanks for the upload! Wish professors these days could break down transistor op-amps in a simple way like this

[@carmineapplesauce7324]

This is the best video on youtube

[@walterkersting6238]

Some things they got right a long time ago.

[@nukeelda]

Best explanation I ever saw thanks for sharing..

[@soumyajyotikundu7147]

Crystal clear

[@matthewmuziani1961]

Wow, I just found out you have a KZbin. I have to thank you from the bottom of my heart for all the time you took on your website to explain the AB763 circuit. I went from not knowing a single thing about amp circuits to doing my own repairs on a fender drri during the pandemic because of your page. I even managed to re cap it. You do such a good job of explaining it to a lay person. Thanks again, and a side note I enjoyed the story about the military training plane that was a shit design/catastrophe waiting to happen

[@robrobinette]

I'm glad you found the website useful Matthew.

[@mohammadidrees5581]

Even though the video is old. Their explainations are still better than modern videos.

[@INDIAN-gz7xg]

Old is gold....

[@waylonk2453]

I always wondered how a tube amplifier works, and now I understand. Thanks Rob, you provide a wealth of knowledge!

[@moga1968]

When i was 10 years old, last.. 40 years, my trsurs were to colect those Tubs. I was so intersting, watcis all wires, grids use? I watced hours by hours. When we open our Blcj whote T.v I was so quries wat is all this elctronics part. This clip realy wonderful.

[@Wassenhoven420]

They are awesome, eh!

[@mubafaw]

Beautiful, clear, crisp explanation!!

[@pooja05rejoice]

Such an awesome Comprehensive video !! Hats off ... use of cartoon for the flow was really worth for easy understanding, Thank you so much :)

[@christiancompiles5549]

Thank you, Rob.

[@rafbi4874]

This is so well explained even tarzan would understand it

[@nehapal6888]

Very clear explained

[@jasminakter1445]

Thanks for the information

[@liamMaru]

This video is amazing. It's all so simple.

[@ianuragaggarwal]

Hi Rob, your website is very impressive and resourceful. Using clue from there i changed AC heater to elevated AC configuration.

[@nmps28274]

Wonderful explanation.

[@Shaker626]

I highly recommend kids be taught about vacuum tubes before transistors, the principles carry over easier as the vacuum tube is easier to visualize.

[@tglstudio]

Thanks Rob, love ur stuff pal!

[@user-wc6ri2tr5q]

Short and sweet

[@moga1968]

Great! Amaizing! Love This!! Remas in me Childhood, last 40 years.. I colect the tubes like some tresure.. now good to lesrn al this

[@lazzer408]

Just ignore the text being placed over the video. It's making things more confusing.

[@TechTed1]

great video

[@ivanalianza3500]

Amazing explanation

[@Nighthawke70]

If you want to actually see a Thyratron power supply in operation (That's three tubes, two of them are mercury vapor Thyratrons, third is a neon), take a peek at this. kzbin.info/www/bejne/jYmaZXqlfdqqfs0 It's a high power 200V .5A DC supply for a Teletype model 19.

[@stan1845]

It might be old but it does the job. I now know how it works

[@bluesbondsman]

Hey Rob, Glad to see you have a channel here old friend.

[@vkm1986]

I am very thankful to you

[@wreignone]

And, thats how the Korg Volca nubass works ;-)

[@bobmorgan1762]

I’ll have to watch this, again.

[@davidtaylor857]

Thanks Rob . Your information is always great

[@hayden3281]

You wouldn't happen to have the full 28-minute film available, would you?

[@robrobinette]

Google "Electronics at Work". That's how I found the original.

[@curtpiazza1688]

Great explanation!

[@lousekoya1803]

Thank you Sir for your immense work and great heart to share your knowledge !.......Appreciate !......Greetings from Quebec !

[@JohnSmith-qn3ob]

If negative voltages reduce the flow wouldn't the tube only amplify the positive part of the wave? How would you amplify the negative?

[@robrobinette]

The power tubes idle at half output power so you can increase and decrease current flow through the power tubes so both positive and negative voltage on the grid is amplified.

[@westelaudio943]

The tube amplifies only negative voltage. The damping of the electron flow IS the amplification. The plate current flow is inverted in relation to the grid negative voltage. How does the tube amplify the positives then - it doesn't. The tube is biased for the signal to always be negative. That means, a positive, low DC voltage is added to the cathode, or a negative one to the grid. So the positive half-waves at the grid become negative, just less negative. At the output a 1st order high pass (capacitor or transformer) filters the DC offset out again, to have a pure AC signal. Keep in mind this only describes the class A (most common and simple) amplifier type.

[@jasonvincent2367]

@@westelaudio943 Dumb question perhaps, but where does the extra energy (or electrons?) come from to amplify the signal? Feels like we get something from nothing when the grid is in place.

[@westelaudio943]

@@jasonvincent2367 From the B+ supply voltage going through the load and then to the plate. The tube doesn't add power to the signal itself, it transfers it to the plate curcuit by varying it's resistance depending on the instantaneous grid voltage. Thus, based on Ohm's law (current decreases with resistance), it forms a voltage divider with the load. The load receives a signal that's amplified and inverted relative to the input (and DC biased, if the input is AC). Usually, in an AC curcuit, a high pass element is then used to remove the DC bias (offset) to get pure AC again.

[@robertwhitley6233]

I always wondered what all those huge Vacuum Tubes inside my PC did.It all makes sense now.

[@robrobinette]

I'm sorry to say that PCs have never had tubes in them. There were tube based computers in the 40's and 50's but by the time the PC came along in the 80's tubes had been replaced by transistors and integrated circuits.

[@emperorfaiz]

Those aren’t vacuum tube. Vacuum tube is a dead technology replaced with transistor and integrated chip. I’m assuming based on “huge vacuum tubes”, most likely you are referring to large capacitors and diodes I think.

[@random_ramblings]

Sarcasm guys.

[@robrobinette]

@@random_ramblings Sorry, it went right over my head.

[@dmsmhic]

LOL The smartest people sometimes miss things like humor and human emotion. Data from Star Trek knows what I mean.

[@onemansamband]

More please.

[@pfsmith007]

What a gem! I really enjoyed the video.

[@neilrigby9260]

A good original video improved with your efforts. Thanks!

[@RoXx1811]

Totally tubular!

[@lucysluckyday]

Pretty easy to see how the BJT transistor, while certainly revolutionary, was actually an evolution of the same concepts of switching and amplification. Then the jump to field effects, when magic met physics.

[@Galatians.3.26-29]

High tolerance to high temperatures. No wonder why vaccum tubes are immune against E.M.P., unlike transistors.

[@BCTGuitarPlayer]

I love this vintage demo! Why all the thumbs down? Too difficult to comprehend? 😏☹️🤣

[@robrobinette]

With 285,901 views 84 thumbs down isn't too bad.

[@jrcenina85]

Thanks for taking the time to translate

[@HikikomoriDev]

Beautiful.

[@terrylaissy3313]

Super intéressant 😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊😊

[@tareksma1]

Does the heating element take time to heat and start closing the circuit? Because the transistor can swich on and off very fat. Does the vacuum tube swich on and off fast too❓️

[@paulthepainter2366]

The heating element takes time to get to operating temp. So it stays on all the time during use. Fast switching is done via the weak input signal

[@AhmetYusufYatkin]

Found It ! Found It !!!! Now I can do a basic computer :D (Hello from 1940's)

[@lousekoya1803]

Good day Mr Rob .....I'm new to your amplifier site and couldn't find any contact infos so decided to leave a message here ............How can we thank you enough for all the infos you have on your site ,......this is MASSIVE work !!!..........don't know how you found the time to do this but Thank you SIR !!!.......................Lou

[@robrobinette]

Thanks Lou. The key is I've been working on the website for years, doing a little here and a little there. It all adds up in the end.

[@lousekoya1803]

Well thank's again !!............you are a National Treasure !!..haha! Again,........Massive documentation you shared with us ! Very generous of you !

[@diegoochoa572]

Wait, so is the signal input clamping the Waveform output up? Makes sense if we decouple the DC shift. Then it would work like a bjt amplifier. Can anyone with tube experience confirm? It almost seems too easy

[@kimjong-un4411]

Great! To the point! Thank you! Now the internet should delete every other useless video out there.

[@teknical100]

Thank you.

[@dribblersmy]

thank you

[@rcervantes1083]

I could've used this guy in my earth sciences class

[@osGFXman]

wow! 😂 i need these tutorials, all episodes! please help, where can i find it?

[@nostalgicoescritor]

Magnífica animación! Gracias por compartir.

[@YeeThirty]

Hey buddy... fancy seeing you on youtube instead of facebook lol

[@EvilSandwich]

God, no wonder so many devices used these things back then. Vacuum tubes look dirt simple to manufacture and operate, despite their extreme limitations. Unlike transistors, despite being superior, require; cooking, carefully tracking oxide layers, acid baths and toxic doping chemicals. No big deal to modern factories, but imagine mass producing something that involved back in the very early 1900's. Yikes!

[@arthurpozner7701]

Oh...it is not as simple as it seems...and every vacuum tube is handmade.To a very high degree of precision!

[@jmg9509]

Can the vaccuum tube hold free electrons? Basically what I'm saying is: If you used an electron gun to fire electrons into the vaccuum tube and held them there with a momentary magnetic field, would the electrons stay in the vaccuum if it were completely insulated and you turned off the magnetic field? Keep in mind, there's no anode attracting the electrons, only the magnetic field confining them in the space till it(the magnetic field) is turned off. If not, where do the electrons go if the vaccuum is insulated, therefore they can't be absorbed by the vaccuum itself? Wouldn't that mean they'd have to stay in the vaccuum indefinitely until the tube is connected to an anode, or other positively charged objects?

[@robrobinette]

I don't really know. I would think most of them over time would be absorbed by the glass tube and interior metal parts.

[@KB4QAA]

If you remove the positive charge from the Plate, while still heating the Cathode/Filament, electrons will be emitted but have no place to go and will fill the tube space.

[@gavincurtis]

It's really simple. The power and audio goes into the tube. The output of the tube goes into a speaker or headphone apparatus; triggering a release of endorphins causing extended ASMR.

[@mattsmallwood8579]

Fantastic!

[@Tay-ky3fi]

how is it... that its 2020, and I'm still looking for videos made in the 1940s to explain important concepts?

[@swisstraeng]

That's because a 1940's video or a 2020's video are actually pretty similar. Thing is, a video like this could take a week to make, with 2+ people. In 2020 someone can do that in an hour. Issue is, 2020's videos are made in an hour, thus they aren't better than 1940's videos sadly.

[@Dang...]

Thank you!!!

[@yaminijanghel1630]

It was interesting and I got my answer. Thankyou.

[@baconology3065]

thank you.

[@gizmoguyar]

This is fantastic video, but I can't find the answer to one small question: What is the difference between the anode and cathode that allows the cathode to emit electrons while the anode cannot? Is it just the fact that it's heated? And if that's it, then what is the temperature difference in question? I've seen vacuum tubes running, and the entire thing gets super hot. Is the ability to thermionically emit electrons a sudden change with increasing temperature?

[@robrobinette]

Yes, it's the extreme heat of the cathode and the cathode is also coated with a substance that helps it shed electrons.

[@robrobinette]

Electrons are only shed at high rates when metal is near white hot. Heated cathodes glow yellowish-white they are so hot--much, much hotter than the anode.

[@christopheb9221]

thanks for the video. why id you cut it 2:33 what were the other 4 of 6 basic things

[@robrobinette]

The other 4 were not related to tube amplifiers.

[@clembaker9960]

oh eric barbour you're in the shit now man, i'm coming after your job.

[@MartinAbouttone]

great work! tnx

[@connorfisher1651]

Wheres the full video?