How Tube Amplifiers Work, Part 1: The Power Supply

[@AtOddsAlways]

I was a US Navy Tradevman (Training Devicesman) from 1965 to 1969 and attended almost a full year of electronics training to qualify for my rating. This is, by far, the BEST explanation of vacuum tube theory I have ever seen, anywhere! Kudos for your insightful and fascinating work!

[@UncleDoug]

Wow......high praise indeed. Thanks so much, Joel :)

[@jasonlmusic]

I cannot overstate what a tremendous asset you are to the KZbin, amplifier, guitar and electronics community. If only my science teachers in school were 1/2 as good at explaining this as you are. And if only someone who have explained it to me this way 30 years ago. Very grateful for you!

[@UncleDoug]

Thanks for your kind words, Jason :)

[@captainfineweather5610]

I can't but agree 150%.

[@kolasinskipiotr]

This is the best video clearly explaining not only "what", but "why" and "how" as well, as I've ever seen.

[@UncleDoug]

Thanks, K. We're glad you enjoyed it.

[@edwardkujawa]

Uncle Doug your tops i echo what he said my teachers were god but not as good as you thanks

[@UncleDoug]

@@edwardkujawa Thanks so much, Ed :)

[@wynandvanreenen2612]

October 2024 and I finally found a 10 year old video explaining exactly what I needed explained. You deserve a medal and lots of money for your service to all perplexed diyers. Thank you so much!

[@UncleDoug]

You're welcome, Wyn. I'm glad it was helpful :)

[@andrewmills8545]

I wish Uncle Doug would have been one of my professors in college. His ability of explaining electrical circuit behavior surpasses many of the instructors I've dealt with. Although I am an electrical engineer now, I review these videos to solidify my knowledge by giving my brain a different viewpoint. Thanks for your work.

[@UncleDoug]

Wow, high praise indeed from an EE, Andrew. Thanks so much. We're quite flattered that our videos were helpful and informative. You're welcome :)

[@PatrickjazzguitarBro]

I have looked for a presentation that teaches me a foundational understanding about tubed amplifier theory. I am a teacher who has had to deal with dyslexia for almost 60 years and I have only known of my deficit for about 20 years. I am also a guitarist who loves tubed amps and have worked only at a rudimentary level on amplifier building and repair. Studying books on the subject is slow and helps some, but your presentation with verbal and visual cues is illuminating for me. You break down concepts (of which I have never been able to master nor gain fluency) into simple bite-sized (accessible) ideas and make them "visible" for me. That, sir, is a breakthrough I have not been able to experience on the subject. You are a rare talent and a true teacher of the sort I aspire to become! You not only teach electronics, but you also teach "teaching." You have made a difference to me. Thank you.

[@UncleDoug]

Wow, thanks so much, Patrick. Your very kind remarks, especially coming from another teacher, are particularly rewarding and appreciated.

[@derekec]

Not exactly the same for me but very similar, the rudimentary building and repairing with tons of trial and error mistakes, none of which I even recall now. And thank you Uncle Doug for making this new epiphany possible. I'll be subscribing.

[@Wizardofgosz]

I agree with Patrick. I have been an electronics hobbyist for more than 30 years and have come to understand these concepts on my own, from my dad, and of course from school, but this video is the best I have ever seen and breaking down these concepts. Bravo sir.

[@highpath4776]

@@UncleDoug It is simple to say, What I am Going to Say, what i am saying (with visual demonstration), what we have learnt. (repeat as needed for each extra bit that builds on that), it is less easy to actually do that, which you do well.

[@groovee63]

Excellent!!!

[@ME16510]

Thank you so much. This is probably the most helpful and best explained video made by an individual on any topic that I've ever seen (and I've seen a lot). I know you're probably making little to no money off of this, but this is honestly hugely appreciated.

[@UncleDoug]

Mark Emhoff You're quite welcome, Mark. Rusty and I are really glad to hear that the video was clear and helpful. Nice comments, like yours, are the only payment we seek or receive.

[@ericarndt8285]

Uncle Doug =Amp God! Thankyou, I had an uncle jack who taught me basics @ 9years old +/-.

[@themongoloid8944]

Uncle Doug is the best ain’t he

[@chasbodaniels1744]

@@themongoloid8944 Yes he sure is. Wow!

[@3kil0w4tt]

I totally agree and subbed after watching only 3 minutes of this video. Thank you, Uncle Doug!

[@mikemullenix6956]

Sir ! You are the absolute best electronics teacher I have had the pleasure to experience. Only a master of electronics can simplify the subject with such clarity!

[@UncleDoug]

Thanks so much, Mike :)

[@championincharge]

I agree. I would love to take an entire amplifier class or online lesson with you!

[@john-zw9rw]

Being a retired Electrician .......and a musician since youth..... This is as Perfect of an explanation of Tube Amps you could ask for.... Reminds me of sitting in class again, listening to my Instructor change my life forever...I didn't know it at the time..... What a fun career, made a great living in Santa Cruz, in the 70's , I got on neil youngs crew and did my electrical thing with full respect from the crew... Kid's , Electricians have fun lives.......keep a log on the fire young Bucks.... critics...find fault in your own pile......

[@UncleDoug]

Thanks for your kind words, and for sharing your story with us, John. We need to encourage young people to enter the field.....or else it will become a lost art.

[@peteleoni9665]

You are the best Doug. We are so blessed to have you for a teacher.

[@UncleDoug]

You are too kind, Pete. Thanks :)

[@villeh5612]

This is what internet should be used for!! Sharing and learning. Excellent information, perfect structure for educative video. Uncle Doug, your and Rusty´s videos are one of the most entertaining and also informative of any video available in www. Thank you for the time you have sacrificed for educating us. This particular video has been priceless for a dummy like me.

[@UncleDoug]

+Ville H You're welcome, VH, and I agree completely with your first statement. I would also mention the benefits of courteous, respectful interaction between viewers and with the author of the videos, rather than the mean-spirited, childish arguments that occur way too often on YT. I sincerely appreciate your very kind comments and the time you have spent watching our videos. I'm glad they were helpful :)

[@davidferrara1105]

This is gold. Went to engineering school and none of the teachers could be bothered to talk triodes

[@UncleDoug]

Thanks, David :)

[@jakeowsley6552]

I agree. I graduated in 1988, and I am surprised NONE of this was taught -- even in the 3 semesters of physics classes. I find this extremely useful background to any EE undergraduate.

[@gregpeterson4348]

Doug, @ 16:15 of your explanation: You seem to indicate that scopeing the center tap (which is hooked directly to ground) of the transformer will show you the bottoms of the AC waveform. I guarantee that scoping anything directly hooked to ground will only show 0 VDC and 0 VAC, unless there is something seriously wrong in the circuit. If you want to see the bottoms of the waveform, scope each plate of the tube. When it is reverse biased, you will see your waveform bottoms, which the tube is conveniently blocking for you. Scopeing the filament would show the positive waveforms from both halves of the tube, but you will see that waveform smoothed by any filtering capacitors on the B+ line. So it will be more or less a high DC voltage, with some ripple. You will not see the sum of the positive voltage waveforms, the filter caps will swamp that out. Pete

[@UncleDoug]

+Greg Peterson Very interesting and informative, Pete. Thanks so much for your knowledgeable input :)

[@gunsofsteele]

To clear this up, erase the pencil mark for -325 pointing to ground & have it point to the lower transformer wire.

[@montpierce424]

Greg is correct. The diode/rectifier action is like a switch, only letting the voltage flow in one direction. Basically what it's doing is turning on and off each half of the center tap coil. As the top coil voltage goes positive, the bottom coil is turned off (filtered out by the rectifier), then as the bottom coil goes positive, the top coil is turned off. So, only the positive power of each coil is allowed to pass through and the negative power of each coil is blocked or turned off. If you look at the top coil separately you would see +325v for half the cycle, then 0v for the other half the cycle. Looking at the bottom coil only, you would again see +325v for half the cycle, then 0v for the other half, but in opposite phase. With both coils in action, the -325v peaks of both coils are blocked or filtered out and the +325v peaks from both coils then produce the continuous stream +325v peaks with no gaps as you show in the rectifier output.

[@sharkskinboy]

@@montpierce424 Yes, this is spot on.

[@Rendon276]

Yes, I noticed this too.

[@sfgylk34u_57]

Wonderful! This has taught me faster and more than many books and videos, I have tried! Thank you!

[@UncleDoug]

Glad to hear it, E.

[@sfgylk34u_57]

@@UncleDoug You should continue teaching and explaining things!

[@UncleDoug]

@@sfgylk34u_57 OK, I will ;)

[@pstock49]

This is the best explanation and presentation of how a power supply works that I've come across. The world needs more of Uncle Doug.

[@UncleDoug]

Wow....thanks so much, Paul :)

[@timmyv694]

You're one heck of a teacher . Thanks for making both these videos. Everybody that wants to get into building tube amps like I do needs to watch these. Any monkey can assemble parts but it's so nice to be able to understand just exactly what's going on inside the amp and tubes. It's genius! I'm going to save these videos for future reference

[@UncleDoug]

Thanks so much, Tim. Rusty and I really appreciate your kind words. Best of luck with your amp project :)

[@MuminovicGoran]

the future came

[@danlampton]

"Making the simple sound complicated is commonplace; making the complicated simple, Awesomely simple, that's creativity." -Charles Mingus

[@UncleDoug]

Thanks so much, Dan. It's good to know that I'm on the right track :)

[@philpembroke5373]

As with Charles Mingus brilliant music, after a few minutes, i have to go back to the beginning and listen again - to take it all in

[@ian-c.01]

I am an electrical engineer with over 30 years of experience and find this fascinating ! I have always wanted to know more about how valves work but never really had a need to, you just don't come across them very often and even when you need to repair a device that uses valves, it's usually not the valves that are the problem, 9 times out of 10 it's a bad connection, bad control pot or bad capacitor. Those are usually very obvious and easy to eliminate, then if there is still a problem it's easy to take the valves to someone who can test them and then get replacements if necessary. In all my experience I have only had to repair 3 items that used valves so I have never really need to know how they operate. I really like your explanation style, a bit repetitive but easy to follow, so I'm looking forward to learning more from this series.

[@UncleDoug]

Thanks so much, Ian. Rusty and I really appreciate your nice comments, which are all the more meaningful due to your experience as an EE. We're glad the videos are helpful :)

[@mayito714]

Ian, what kind of electrical engineer gets to repair connections, bad control pots or bad capacitors on devices? Sounds very interesting yet quite different from design work...

[@larrybrusso1815]

A lot of EEs work in small design shops, and frequently do repair work along with design to pay the light bill. David Jones, an EE in Australia runs the EEvblog channel, and his lab does almost as much repair work as development. Didn't mean to hijack Doug's channel with info about David's, just say'n, a lot of EEs do repair work.

[@UncleDoug]

No problem, Larry. Thanks for the input.

[@wellusee]

Where were you 50 years ago when I needed you? You must be the best teacher yet.

[@UncleDoug]

Thanks, W. I wish I could have been there for you.

[@jesperdahl1486]

Thank you for taking the time to conceive, film, and post these videos. Due to my age (55) I have never had any training i tube electronics, prior to my formal education, I had years of electronics training (night school) but only using semi conductors, in my formal education as electrician (which is a three and a half or four year education, where I live (Denmark)) I was taught plenty of now, obsolete technologies, but with your videos, I can understand, and work on tube amps, which will give me great pleasure. Thank you.

[@UncleDoug]

You're quite welcome, Jesper. Best of luck with your interest in tube technology.

[@natsubbu]

Hi Uncle Doug, You are a phenomenal teacher. The video was very educative. Big thank you. Regards.

[@UncleDoug]

natsubbu Greetings, Nat. Thanks so much :) Glad you enjoyed the video.

[@deathside216]

Doug, your videos are really helping me a lot. There are some videos on KZbin that help, but your breadth of knowledge on the subject blows them away! Thanks, again!

[@UncleDoug]

You're quite welcome, Greg. I'm glad the videos are helpful. Rusty is quite impressed by your icon....a handsome pup indeed :) ^. .^

[@francisxavier7403]

Hi Uncle Doug, Learnt a little about this 40 years ago and now have vaporised. Thank you for your very clear description.

[@UncleDoug]

You're welcome, Francis.

[@MasterRayX]

This is my first time learning about these kind of circuits. Your teaching style makes this so easy for me to comprehend, thank you!

[@UncleDoug]

You're welcome, Daniel. Glad the videos are helpful.

[@Vicwing6-87]

its been 9 years since these videos were uploaded...why I didnt find them before is beyond me. Highly appreciate the lecture and the didactics. Tech talk on guitar & amps have been growing on me for a while and these suit the case perfectly. As the guy Jason just mentioned. You're an KZbin asset no doubt. Thanks Uncle Doug : )

[@UncleDoug]

Thanks so much, Caio Glad you found us.

[@UncleDoug]

Note to Beer Magic.....I'm not ignoring your comments. I am simply unable to reply due to your privacy settings. Please alter them if you would like me to respond to your input.

[@Tinybench]

Thank you so much! Big hug!

[@patricialawson6749]

Very good description for the vacuum tube rectifier. The "Correction" note at 16:56 has corrected a very series error in the explanation. I have tested radio tubes for about 20 Years at Tungsram in Hungary and I have immediately realized the error about the negative 325 V pulses going to ground. This is incorrect. Best regards, Patricia

[@UncleDoug]

Thanks for your input and confirmation of my correction note, Patricia :)

[@slyrez]

Very cool! As a guitarist I find this very interesting as to what is really going on in there. Electricals are quite fascinating.

[@giulioluzzardi7632]

Thank-you, it's begining to make sense at last!

[@UncleDoug]

Keep at it, Giulio :)

[@julesl6910]

Doug, I can't thank you enough for sharing all of your insight. I have been absorbing as much as possible over the past year. It has been an absolute pleasure. Below I provide my basic understanding of AC and DC, for future students so that they might better understand. Alternating current (AC) and sound waves share a fundamental similarity in that both are oscillatory in nature. AC changes direction periodically, creating a wave-like pattern of voltage or current that can be represented as a sine wave, similar to how sound waves oscillate in pressure as they move through a medium like air. This oscillation allows both AC signals and sound waves to carry information. For example, audio signals can be represented by AC, with the frequency and amplitude of the current corresponding to the pitch and volume of the sound. This is the basis of the term analog, where the oscillation and behavior of the electrical waveform is analogous with with sound wave to a high degree, achieving its final point of accuracy when reproduced by the speaker creating amplified sound waves that are analogous to the source. The peaks and troughs in a vinyl record's groove are also analogous to the sound wave being reproduced, for example. The output of an amplifier is alternating current. In contrast, direct current (DC) is constant and unidirectional, meaning it flows in a single direction without oscillating. Physically, DC power doesn't have a wave-like behavior in the same way AC or sound waves do. However, you can think of steady or constant phenomena as parallels to DC. For instance, the steady flow of water in a river or a consistent breeze can loosely parallel DC, as they both have a singular, unidirectional flow rather than the oscillating, wave-like nature of AC or sound waves (think waves at the beach). If you have a hydroelectric generator, you want as constant a flow of water as possible in order to design a mechanism that generates electricity. With a wind turbine generator, you want to aim it at a relatively reliable direction where you'll get steady, direct wind flow. DC is like cash on hand, good for making things to happen reliably. AC is like money in the stock market, it goes up and down and you want to cash it out into DC (rectification) so that you can use it. The output of a power supply is direct current.

[@julesl6910]

Part 2 of my Doug addled brain: I envision amplification as so: When I was a kid, my brother and I would lay in our beds before going to sleep and play with flashlights. In the dark room, we'd put our hands in front of the filament of the incandescent flashlight and we'd amplify the image of our hand onto the ceiling. In other words, we'd shine a flashlight at our hands and it would cast a far bigger shadow of our hands, and we could play around before nodding off into the glittery galaxy of sleep. This is the basic idea of amplification. You take something small (your hand) You find a method to modulate something technically bigger (light in this case) Now your hand is shaping the light beam, and you are amplifying your hand. In the same way, the cathode is like the start of the flashlight beam, and the plate is the ceiling in your room. The grid is where you pass the AC signal (your hand), and the current flowing through the tube is modulated by the grid. Realistically let's change your hand to a very small current produced by the transducer in your turntable cartridge. The needle passes over the analog waveform recorded in the grooves, and the mechanical energy is converted into a small electrical current that we need to amplify. So we pass those wires, that current, to the amplifier tube's grid. Now that very small electrical current is shaping the much higher electrical current passing through the tube. Now out of our plate we get a signal that is analogous to the very tiny initial electrical signal, but much higher current and voltage. This is amplification.

[@julesl6910]

Lastly, the hand projection analogy has one final point - it's a negative image of the hand, and we want it to be positive. Phase inversion.

[@saddle1940]

Wooow, hold up a second. I was taught the 120V value is the RMS voltage. And the peak voltage for this on one half of the waveform is actually 170V. If you look at it for positive and negative with respect to neutral, the voltage from an AC outlet is actually 340V peak-to-peak.

[@UncleDoug]

You are correct, Stephen. We cover this in detail in later, more sophisticated videos. This one is simply an introduction, for beginners.

[@jakeowsley6552]

Yes, @saddle1940, but US outlets are single phase 110/120 VAC rms, so only 155/170V P-P. You would be correct with European or if plugged into a US "240V" outlet, where the split phase has two 120VAC rms phases. It is easier to think of all 1° and 2° voltages as RMS until they are rectified (then it gets more complicated). The DC voltages' average value depend on filtering used, i.e. the size of capacitors & chokes used downstream, but safe to use 325VDC in this case.

[@carld]

Thank you Uncle Doug for all the explanations. It's easy to understand and well explaned with simple words for a non english person like me. Merci beaucoup! ;)

[@burntreynolds5701]

WOW!!! YOU REALLY UNDERSTAND THIS & ARE TAKING THE TIME & HAVE TAKEN THE TIME TO WORK OUT HOW TO TRANSLATE IT TO US DISTRACTED IDGITS!? THANKS! You're the Tone Professor! My AMPS=( BROKEN!!!! I'm nothing without them & my wah. I need to shut up & listen again. I gave up after I didn't try! r X( POW!!! THANKS THOUGH. INTIMIDATING. 2 THOSE BEING IDIOTS & TEXTING INSTEAD OF LISTENING.

[@UncleDoug]

You're welcome, Wyatt. We're glad the videos are easy to understand.

[@guitarpilot]

Fantastic explanation, been playing on tube amps for 40 years. This is the best explanation I've ever came across. Thank you!

[@UncleDoug]

You're welcome, Britt. Thanks for your nice comments :)

[@TroyMira]

You are a natural teacher = clear, modular units + excellent visuals + comfortable pacing + macro/micro lens + layman’s level fundamentals - jargon/formulas. Feels weird to say this but, thanks Uncle Doug!

[@UncleDoug]

You're quite welcome, MR. Thanks !!!

[@christophertstone]

0:50 No. AC voltage is not the total distance from top to bottom, and your +60 to -60 isn't even close to 120VAC. AC is measured against the absolute average voltage from neutral; 120VAC hits about 170V in each direction, that's +170V and -170V.

[@UncleDoug]

You're right. This error was corrected in the video with notations that are not visible on all viewing devices, Christopher. For a much clearer, detailed explanation of peak voltage vs RMS please see my more recent video postings.

[@musicproducer27]

Awesome, Uncle Doug! Thanks so much. I enjoy your videos and you have really furthered my understanding.

[@UncleDoug]

You're welcome, Jamie. It's great to hear that the videos were helpful.

[@UncleDoug]

Dylan, your question did not have a reply capability due to your YT Privacy Settings, so I'll answer it here. The +325VDC output has passed through the diodes of the rectifier tube. The diodes, due to their alignment, only pass positive voltages. The -325VDC was rejected by the diodes (it was not allowed to pass through) and goes to ground. Think of the power supply as a 325VDC battery, with a positive output (from the diodes within the rectifier tube) and a negative output (from the ground).

[@ncnoman]

hi Doug, im not sure if we had the same question but was wondering why if diode output is +325vdc and ground is -325vdc, why when we look at the amplifier stage it doesnt have +650vdc going to the output transformer with ground as a reference voltage of 0v? when looking at certain components like filter caps connected to ground and the rectifier, will they need to be able to handle 650 or only 325v? thank you for the video!

[@UncleDoug]

This is an ancient video, NC. The voltage readings on the diagram reflect the readings you would get if you first measured the voltage between the B+ and ground.....or if you measured between the B- and ground. If you measure the voltage potential between the two secondary output wires of the PT with no load, it will be approximately 700VAC before rectification. After rectification, since only the B+ is sent to the center tap of the OPT (and the filter caps), the output tube plate voltage(s) and the filter cap voltages will be 350VDC to ground. All of this ignores losses due to heat, inefficiency, and the boosting of the smoothed DC to peak voltage.

[@ncnoman]

@@UncleDoug where is B-? i was assuming B- IS the ground.

[@UncleDoug]

No, ground has zero charge. It depends on the bias of the rectifier diodes. I you take the HV from the cathode (as in amp HV circuits) you will have B+ if you take the HV from the plates, you will have B-. You need to watch my videos on power supplies and rectification.@@ncnoman

[@ncnoman]

@@UncleDoug will do!, thank you for the answers. your videos are a tremendous resource. i appreciate your time. im hoping to learn about this, maybe build a few amps for educational purposes, so i can one day be able to help people in my area with tube amps. ive got an EE degree but i ended up going into networking. thanks again Doug

[@dogdive]

I just wanted to reiterate what other have said. This is an excellent video. I learned more in the first 5 minutes than anything else I have done. Your video is exactly what makes KZbin the great thing that it is. Thanks.

[@UncleDoug]

You're welcome, Jeff. Thanks for your very nice comments.

[@johnjoyce]

Hands down best explanation and delivery I’ve ever seen on tube/valve amps. I am especially glad you used a paper circuit diagram and not something graphical. Very refreshing and traditional and WAAAAY easier to grok than the RCA manual. The considered callouts on windings in transformers and tube/valve voltage are great reinforcements of critical fundamentals that are much tougher without a practical example. Bravo.

[@UncleDoug]

Wow.....thanks for your very nice comments, じょいすじょん . We really appreciate them and hope you continue to enjoy our many other videos that have varying levels of technical complexity.

[@bullthrush]

Very clear explanation.

[@UncleDoug]

Thanks, Andrew. I'm glad you liked it :)

[@Flumphinator]

Wildly easy to understand! Love your teaching style. Could I feasibly substitute in rectifier diodes for that tube?

[@UncleDoug]

Yes, diodes can be substituted for a tube rectifier. Weber makes "Copper Cap" Diode Modules with tube bases that you simply plug into the empty rectifier socket. It allows you to change back and forth from tube to solid state rectification without altering the circuit wiring. There are different modules to replace specific rectifier tubes.

[@Flumphinator]

Uncle Doug I'm very interested in trying my hand at building one of these. I've watched some of your other videos and some by others, and I think I understand biasing, basic tube physics, and the fundamental electrics. Is there a benefit from using a rectifier tube over a plain diode? Planning the project, I'm also wondering if I can wind my own transformers and achieve a good result. If I'm asking too many questions, where can I do some further reading?

[@UncleDoug]

Many people feel that rectifier tubes provide a more "vintage" tone, while diode rectification is simpler, cheaper, and provides a cleaner, sag-free sound. It's really just a matter of taste, I guess. Re the hand-winding of transformers, I would advise against it, especially on a beginning project. You would probably be better off building a few amps with purchased transformers, gaining some experience first, and then perhaps you could delve into the mysteries of transformer design and construction.

[@AtomicElectronCo]

Thank you very very much for this. Fantastic.

[@UncleDoug]

You're quite welcome, Chris. It's great to hear from you. Please enjoy the other 97 videos while Rusty and I work on the next new one.......

[@tomrybak3074]

I have watched and read a lot about tube amps but never found as clear an explanation as you presented here. I am subscribing to your videos. Thank you for taking the time to make this available.

[@UncleDoug]

You're welcome, Tom. Thanks for subscribing and watching :)

[@tomrybak3074]

I have also watched a few of your other vids which are right up my alley. I have several of the same amps you do. I have an old Davis amp similar to the 2 you fixed. I also have a B&H projector amp. Also I have a bunch of old Wollensak R2R machines & Muzak amps I modded for guitar which are both great sounding. I however am a novice. I really know very little about electronics but have managed to avoid electrocuting myself. Your videos are just what I needed. Keep em coming! I love your little aside comedy breaks with your dog & cat. Great deadpan!

[@UncleDoug]

We're glad to hear that the videos are helpful and informative, Tom. Best of luck with your current and future projects.

[@rileypowis5319]

The way you explain things is so easy to understand. Thank you so much!

[@UncleDoug]

Glad to hear it, Riley.

[@mdhsabh]

The narrative at 7:45, adding the two 6 volts, isn't correct. The two 6 v heater elements are powered with the same 6 v.

[@UncleDoug]

Sorry to disagree, but two 6V filaments in series add up to 12V, just like two 6V batteries in series would. Otherwise, the 12V filament tube could not function properly.

[@silasfatchett5693]

mdhsahb is correct, in that the filaments are connected in parallel, each powered by 6V. However, you are correct, in that the filaments could be connected in series and powered from a 12V supply.

[@cbcdesign001]

@@UncleDoug you can disagree but you are wrong. The heaters are in parallel.

[@DavidMFChapman]

With respect to Uncle Doug, those heaters are wired in parallel with a 6v supply. If you had a 12v supply, you would wire them in series across the transformer, no central tap. In either arrangement each heater would carrying the same current through the same resistance so the power (I^2 R) would be the same.

[@StimulatingPresence]

@@wildbob If you are going to be white knight a least be sure you are right. It is not a matter of thinking he is wrong he is absolutely for a fact wrong. He has clearly drawn the filaments as parallel with 6 volts, and it's not a simplified drawing as you call it, they could be wired in series on a 12 volt supply just fine but that's not how he has drawn it. And to rain on your parade this isn't the only error in this video, there are several.

[@TheCherryUrban]

Ron Swanson :)

[@UncleDoug]

Michael Gutierrez I hear that a lot, Michael. I guess I'll have to contact this Swanson guy and ask him to quit imitating me :)

[@andrewcsteen]

Fantastic 2 part series. If you were not a teacher, you should have been!

[@UncleDoug]

Thanks, Andrew. I was, for many years.

[@LarsonGuitarPlayer]

Ten years later I watch this and part two multiple times at reduced speed and make an almost twenty sides dokument. This will be the basic knowledge of understanding the guitar amplifier. Thank you!

[@UncleDoug]

You're welcome, LGP. I hope the information is helpful.

[@humbleskeptical8249]

Thank you so much for your videos. Your explanations are so clear and concise. And taking people through the whole diagram/schematic step by step is EXTREMELY helpful. If you weren't/aren't a teacher as a profession, you should've been. Awesome work and thank you so much again!

[@UncleDoug]

You're quite welcome. I was a teacher for many years. Thanks for your nice comments.

[@KC-cl1vr]

Uncle Doug, wish I had a mentor like you back when I first explored a career in audio. The good news is that you are here 30 odd-years later. Thank you

[@marklowe7431]

We all wish we had someone like yourself as a mentor. Maybe this video is a million times more effective. Couldn't have explained this better. Zero resistance into my brain.

[@UncleDoug]

Thanks, Mark. We appreciate your nice comments.

[@AtomicElectronCo]

This is one of the best videos on KZbin for those learning about tubes and tube amps. Hands down.

[@UncleDoug]

+MAN CAVE NO.1 Thanks, MC :)

[@m1l268]

What a fine video by Doug and Friends. Old school, clear, concise, and generous. Thanks for all you do. Greetings from KZbinland

[@UncleDoug]

Thanks so much, M1. You are quite welcome :)

[@taifromyea]

Thank you so much for this series! I've watched and read several explanations of how tube amps work (pretty much always looking at the 5F1), and never got anywhere until I watched this. I think the difference is that all the others I've encountered focus on the signal path, and treat the power supply as an afterthought. So what I see is that the signal goes into the amplifier, and then it goes into a magical forest of tubes and capacitors and resistors, and then music (or in my case horrible noises) comes out the other end. Your videos have demystified that magical forest, and for that I thank you.

[@UncleDoug]

You're quite welcome, T. We're glad it was helpful.....and loved the "horrible noises" part :)

[@mp-ov9dh]

Doug, hands down best video I have seen. I have been into electronics (as a hobby) since I was 8 and i am over 40 now. I have built several tube amps, the champ being one of them, and countless guitar effect pedals. With that said, when building these projects it is just hooking up wires from a picture and you dont have to know everything about how the parts work. I am no expert for sure and have tried to educate myself along the way but always had blanks in the information. For me you have filled in a lot of blanks and for that I thank you. Keep posting!!

[@UncleDoug]

+mp224 You're welcome, MP, and thanks for the very kind assessment. Rusty and I are glad the videos are helpful and informative. We have posted over 120 other videos you may find equally entertaining, so please subscribe to our channel and become a member of our YT family. Happy Holidays !!

[@sixstringlove8242]

Uncle Doug, I have learned sooo much from you in such a short amount of time. It is so refreshing to find a well spoken and knowledgeable person who is also very smart. Thank you for taking the time and posting these videos.

[@UncleDoug]

You're quite welcome, 6S, and thanks for the very nice comments. Rusty, Jack, and I really appreciate them and wish you the best.

[@sixstringlove8242]

Uncle Doug Yes, Rusty is quite the musician. In the following video he really tears it up with the demo. Does he use a pick. or play "clawnail" style?

[@UncleDoug]

It's hard to tell because his paws are moving so fast, but from what I can see, he's using his paws, nails, and dewclaws simultaneously......not an easy task :)

[@richardobannon6301]

Thanks so much for this two-part video. I am an old retired plumber that has always been fascinated by electronics and how they work. To be honest I always thought it was above my head. You explain it so comprehensively and simply that I now know that it was my own stupid fear that kept me from learning something I really enjoy thinking about how it works and how to make it do what I would want it to do. Maby I can have something that I really would enjoy doing in my later years. Thank you from the bottom of my heart.

[@UncleDoug]

Wow.....thanks so much, Richard. You really made our day with your nice comments. Bless you and yours.

[@silasfatchett7380]

I'm an old retired truck driver and I build guitar amps. If I can do it, then so can you.

[@southjerseysound7340]

Doug,I just found your channel and want to say thanks for putting these videos up.I truly look forward to watching and trying to learn what I can.That and I could use a break from Mr Carlson's videos.He's also a great teacher and has amazing videos in case anyone is wondering,

[@UncleDoug]

You're welcome, SJS. We're glad you found us and hope you enjoy our videos. I agree that Mr. Carlson's videos are top notch :)

[@zummliller]

Doug, you have demystified, clarified, given your wisdom generously un-defy-ed and have teach-i-fied this stuff marvelously!!! Oh, the books and websites that I have checked out and have picked up bits and pieces of good stuff but nothing like you have un-academicized and summarized, demonstrated-ized and put together in these two videos. I have a beautiful but sad '68 bassman head waiting to be loved on and restored to it's beautiful condition and I think this stuff is my inspiration THANK YOU, THANK YOU, THANK YOU!!! Shall I go on??? OK! You are the best-est 'youtube'/vacuum tube teacher around... Eatin'it up! Blessings, Joe Jach

[@UncleDoug]

Wow, Joe, you just made my day....and you're quite welcome. Nothing makes me happier than knowing that the videos have been viewed, understood, and appreciated. Thank you so much for your very kind appraisal :)

[@momsazombie1]

I've been wanting to understand this stuff for a few years...this is the first time, heard or read, that I've understood the explanation. Plus your dry sense of humour makes it very watchable. Thank you Doug!

[@UncleDoug]

Greetings and thanks for the very kind words, MZ. It's great to hear that the videos are helpful. As a Walking Dead fan, I definitely like your screen name :)

[@The_Absurdistt]

I was an electrical engineering student many, many years ago. My teachers did NOT explain tube theory and principles a fraction of how Uncle Doug has done here. Masterful instruction. Many thanks.

[@UncleDoug]

You're quite welcome. Thanks for your nice comments.

[@Sandman2879]

You got a new subscriber. Best explanation of circuitry I've ever seen on KZbin. Not even half way through the video and paused it and decided to comment.

[@UncleDoug]

Thanks so much, SM. Welcome to our channel.

[@MrArchonta]

I wouldn't think of a better introductory presentation of a world we love so much. Thanks, Doug.

[@UncleDoug]

You're welcome, Mr. A. Thanks for your very kind comment.

[@bristolfashion4421]

I'm in my sixties and been playing around with guitars & amps all my life - it's great to finally sit down and listen to the story of how they work! Brilliant - thank-you so much !! regards, from Bristol, England.

[@UncleDoug]

You're quite welcome, BF. Welcome to our channel :)

[@moparac902]

Brilliantly explained, thank you so much!

[@UncleDoug]

Thanks, Mo. You're welcome.

[@KeithMcConchie]

I just out of the blue decided about two weeks ago that I was going to learn how to fix and build amps. Of course, I have no experience whatsoever, but that's never stopped me before. I can't believe how lucky I am to have found your videos! They are clear and concise, and chock full of incredibly useful information. Thanks for making them available to us!

[@UncleDoug]

You're welcome, Keith. I'm glad to hear that the videos are helpful and informative. Please be very careful and observe all the safety rules when you work on a live chassis.....Rusty and I only want the very best for our viewers and subscribers. Best of luck !!

[@KeithMcConchie]

Uncle Doug Thanks for the warning! I'm not planning on putting my hands inside an amp until I've learned a bit more. For now I'm reading a textbook on electronics, watching videos, and setting up my bench.

[@UncleDoug]

Sounds good, Keith. I hope all goes well for you.

[@crawdini7641]

Uncle Doug, you are a fantastic teacher. If I had you as a teacher in High school, I would be somebody now. Great video !

[@UncleDoug]

Thanks so much, David. Don't sell yourself short :)

[@edfrench6503]

God bless and keep you safe... Thank you Uncle Doug for saying it plainly on KZbin once. I never tire of review, because I'm old and prefer to review regularly, call it work ethic, good habits, or old age, I keep coming back to the fundamentals to see if I missed anything.

[@UncleDoug]

You're quite welcome, Brian. Likewise on the blessing :)

[@ronwisman1767]

I studied this 60 years ago, thanks for the refreshing lesson. You would have been a great teacher. I do love this old stuuf. Thanks for sharing.

[@elmadouf]

I've been looking for explanations for months. But I always lacked basic knowledge to really understand everything and I would get discouraged. But this is just the right thing. None are as clear as yours. Thanks Uncle Doug !

[@UncleDoug]

You're quite welcome, Fancois. I sometimes receive criticism for keeping my presentations so basic, but I really believe there is a big demand for educational videos that can be easily understood by those without a lot of training and experience in electronics. Thanks for your kind appraisal and best of luck :)

[@elmadouf]

Uncle Doug I don't know about other people, but after understanding the fairly simple circuit of the champ, I could use a video like this to explain the circuit of the 5E3 step by step. I haven't found anyone able to explain what the "push-pull" system is about... At least no one able to explain it clearly and in simple terms like you did on that 5F1... might be an idea for a video ;) Thanks again !

[@UncleDoug]

You're right, Francois. I have not yet explained the output stage of double-ended amps....and it would indeed be a good topic for a video. I will give this idea some serious thought. Thanks for watching and for your excellent input.

[@technicsummse2350]

This is finally the first video i could find, explaining how exactly the amplifying of the base signal works! Thank you so much!

[@UncleDoug]

I'm glad the video was helpful, TS.

[@frieddo]

wow ... if only i had found this video sooner ... it would have saved me HOURS. Thanks a LOT Doug, this is a perfect teaching time, really appreciated.

[@UncleDoug]

You're quite welcome, Fred.

[@craigkeller]

Wish all educators were this gifted. Thanks uncle.

[@UncleDoug]

You're welcome, Craig. Thanks :)

[@braddraper2013]

This is by far the best explanation of how a Tube Amp Circuit works I have ever seen ! I have read tons of books and watched various videos before but nothing like this. Uncle Doug, you are the best and I love how you use the schematic to walk thru the circuit with complete detail. I can't wait to go through the rest of your videos and continue to learn from you ! Thanks for all you do Uncle Doug, You Rock !!

[@UncleDoug]

Wow.....you're quite welcome, Brad. Thanks for your very nice comments. I hope you enjoy and benefit from all the remaining videos.

[@braddraper2013]

I certainly am enjoying your channel and have been binge watching all of your videos trying to learn as much as possible. Just starting buiding an 18 Watt Marshall Kit this week and I know that these videos will greatly help with this and future tube projects ! BTW, would love to donate to the cause if you can send me a link...Thanks Again for all you do !

[@UncleDoug]

You're quit welcome, Brad. Nothing makes me happier than hearing about viewers who are going to put the new knowledge to good, practical use. We have posted over 160 videos, and I'm sure that many of them will help you with your Marshall project. You can become a Patreon patron and make a small donation when each new video is posted: www.patreon.com/uncledougsvintageamps , or you can make a single donation via PayPal to [e-mail]. Thanks !!!

[@UncleDoug]

You're welcome, Brad. Best of luck with your Marshall project. You can become a Patreon patron at www.patreon.com/uncledougsvintageamps and pledge a small amount for each video I post, or make a one-time donation through PayPal to: [e-mail]. Thanks !!

[@StevenRiseNYC]

I can't thank you enough for your videos, I went from knowing zero about tube amps to building my own amp from scratch just from watching your channel. You explain everything very clearly and your channel is an incredible resource for anyone wanting to learn.

[@UncleDoug]

Thanks so much, Steven. It's great to hear that you put the video knowledge to good use.

[@dannyyorri2345]

Thank you very much Uncle Doug, clearest and simplest teaching of complex workings of transf. tubes and electrons I am making a comeback after 40 years, I think that I learned with your vids. more then in 2 years of electronic courses in my teen years!!

[@UncleDoug]

That's good to hear, Danny. Thanks so much :)

[@whatyoumakeofit6635]

Doug you have done a fantastic job here. Best I've seen anywhere. Be it a book, video, internet,.....etc. you have done a great job !!! Thank you so much for your effort

[@UncleDoug]

You're quite welcome, Bryan. Thanks for your very nice comments :)

[@Rightnow0101]

Uncle Doug, you produce the best informational and educational content on tube circuits. Done in an understandable and clear manor. Uninterrupted by commercial advertising! I love this!! I'm learning to use and service my collection of vintage gear. Much appreciated.

[@UncleDoug]

You're quite welcome, CR. Good luck with the maintenance of your gear collection.

[@thomvogan3397]

For the first time in many frustrating years of not being able to grasp the subject I can finally shout the words : I GET IT. Thank you Uncle Doug. Your videos should be required watching in schools

[@UncleDoug]

Thanks, Thom. It's great to hear that the videos are helpful.

[@DennisMurphey]

Just found this you tube video as my Solid State Amplifier is in the shop so I bought twin 6V6 Tube amp to play on in the meantime. But i wanted to understand why there are so many wires and components on the Tube Amp while the Solid State amp has so few but has many more effects built in. This is OUTSTANDING TROOP! I did get a little drowsy once in a while but I am pretty old and just had lunch. You diagram and explanation was quite understandable and very informative. I am more awake now and want to see part 2. Thank you for sharing your talents. well done.

[@UncleDoug]

Thanks, Dennis. I'm glad the video was helpful. Don't feel bad about getting drowsy, it happens to me all the ti......zzzzzzzzzzzzzzzzz.

[@turiddu9]

Dear Uncle Doug, I've been intently watching Mr. Carlson's Lab, Blueglow Electronics, ElPaso Tube Amps, ElectroBoom,and just about everyone else to understand how tube amps actually work and your analogizing explanations on this series and your Phase Inverting video (especially your emphasis on the fact that AC and DC can coexist on the same circuit thus giving capacitors inductors resistors and transformers a reason to exist!!!) finally solidified basic electronic concepts in my head......finally! Sincerest thanks for your efforts in these videos, you are a KZbin goldmine and I am forever in your debt!!

[@UncleDoug]

Wow, thanks so much for your very nice comments, Sal. It's gratifying to hear that our videos are both helpful and informative. You might want to add the Guitologist to your video list......he's a very knowledgeable fellow and excellent musician.

[@wseeback]

Wow, your metaphor of; "the frying pan (Filament) cooking popcorn (Electrons) thats negatively charged, being sucked thru the chain-linked fence (Grid) to the positively charged Plate, and you can change the porosity of the fence (Grid)" ...is the best way i've heard to explain it. It actually helped ME more fully understand how they interact. Thanks for making these vids.

[@UncleDoug]

You're welcome, WS. When I was a classroom teacher, I found that making analogies involving common, familiar things often made the understanding of abstract concepts much easier. I'm glad the video was helpful. I would only add (just to be thorough) that varying the "porosity" of the grid is accomplished when the input signal varies the negativity of its charge (since a varying negative charge will repel more or less of the negative electrons passing through it to the plate).

[@wseeback]

Ahhh....AHHHH!!... ok, so, the guitar signal actually varies the grids negative charge. And the amount of negative charge the grid has in the first place, (controled by the...cathode resistor?) actually really repels the electrons rather than "let's them pass"?

[@UncleDoug]

The grid can have a negative charge for different reasons, depending on whether the tube is grid or cathode biased. This is needed to reduce the current flow from cathode to grid.....like a faucet that is 50% on. The input signal then varies the grids charge (more or less negative, but never positive) as if you varied the faucet from 25% to 75% (for example).....producing an output signal that is many times greater than the weak input signal.

[@patprop74]

i have no wants to build one or to ever repair them, However, the in-depth explanation is more than perfect and useful for other things! very very happy you made this video! Thank you !

[@UncleDoug]

You're welcome, Pat :)

[@whitelion7976]

After playing with VFD displays I was recommended to watch this. Very interesting. You explain it very good. Thanks

[@UncleDoug]

Glad you liked it, WL.

[@grahamamorrisonsr1135]

For the FIRST time (I’m ‘69 and getting back into electronics in my retirement), I think I understand tube amplification. I have looked high and low for an instructional video like this that makes sense. GREAT JOB of explaining these circuits. After seeing this video, I looked at some tape deck schematics (old tube type) and actually recognized portions of the circuit and what they were doing. Thanks VERY much!!

[@UncleDoug]

You're quite welcome, Graham. We're glad you have found our videos to be informative :)

[@nimbly1693]

My older brother restores and collects old radios. I recognize all these components but never bothered to figure out what every thing does. I have enjoyed your videos so far.

[@UncleDoug]

Thanks for watching, Nim. We hope the videos are informative.

[@elitalbot-minkin8608]

Uncle Doug, thank you so much more your diligence in explaining these circuits. You are a natural teacher. Learning a lot here and enjoying myself in the process!

[@UncleDoug]

Thanks, Eli. That's great to hear :)

[@bobrowlette4143]

Having studied electrical engineering in school long ago, I find it truly amazing what an excellent job Uncle Doug has done here presented this subject matter so clearly and concisely. Thank you very much!

[@UncleDoug]

Thanks so much, Bob :)

[@groovee63]

Thank you so much for your instruction... as a musician I'm trying to learn more about my equipment. I watch your vids on a daily basis. You are an awesome teacher

[@UncleDoug]

Thanks so much, Greg.

[@gabry4354]

You are great!!!you explain in very good way. Even I m not english mother tongue, I understand completely everything.Thanks to share your knowledge!!!

[@UncleDoug]

You're welcome, Gabe :)

[@richhowell5873]

By far the best amplification lesson I have ever seen! Your post-annotations during the video demonstrate your thorough knowledge of the subject and commitment to teaching it accurately. Well done!!!

[@UncleDoug]

Thanks so much, - - , I really appreciate your kind words.

[@milosmil]

You should write a book. Rare gift to beautifully explain things and pass the knowledge and personal experience to others. I really enjoy watching your videos. Thank you!

[@UncleDoug]

Miloš Milosavljević You're welcome, Milos. Rusty and I are glad you enjoy our videos. Nice comments like yours make it all worthwhile :)

[@barrywuthrich8530]

I first saw this video years ago and blew it off because this tech talk always seems to go over my head. But having listened to the whole presentation and taking notes, I think I get it. I going to go check out part 2. I have had such bad luck with tube amp 'techs', the more I know the better off I will be. I currently own 8 tube amps and I have nobody that I trust to work on them.

[@UncleDoug]

That's great to hear, Barry. I feel the same way and as a result, I do EVERYTHING for myself from plumbing to auto repair. After al, there is only one way to be sure the job is done right ;)

[@mohamedbenzemam1251]

Hello. Sorry for my poor english. i am french. Thank you for your great explanations. This is the first time i understand the concept since 5 years ..... I think the concept is the same for audio amp . It is very nice to build an audio amp and understand what we are doing. Hello to your dog and have a nice day. Thank you.

[@UncleDoug]

Greetings, MB, and thanks for the very nice comments. Rusty and I are glad you enjoyed the video. No need for an apology.....your English is much better than my French :)

[@C0smicV0yager]

Few minutes in to the video, I had to pause to subscribe. This is gold!

[@UncleDoug]

Thanks so much, COVO. Welcome aboard :)

[@fosterjaml4]

You are one of the best teachers on you tube. Very clear and effective demonstration of a interesting subject. (like the saying "may you live in interesting times").

[@UncleDoug]

Wow....thanks, Eric. I really appreciate your kind words, and am delighted that you enjoy the videos :)

[@windmillarchive8181]

I am a senior electrical engineering student and this is a such a perfect, concise, and practical explanation of tube amps. Thank you so much!

[@UncleDoug]

You're welcome, WM. Please watch our many other, more advanced videos :)

[@ron4jon]

Thank you for your explanation on how a tube type guitar amp works..! I was a digital circuit design engineer for over 40 years and I didn't know much about tube circuit design. This KZbin explanation was Awesome so now I understand every bit of it. Your explanation was extremely helpful..!!!! I will watch your other videos too..

[@UncleDoug]

Thanks so much, Ronald. We hope you enjoy all our videos :)

[@kevinjmcmahonjr1970]

I have multiple books and DVDs on tube amps and tube amp repair and this two part series is hands down the most clear and straight forward explanation I have ever seen regarding tube amplifiers. It randomly popped up in my suggested videos today and I wish I had seen this video years ago. Although the other content I've purchase is much more detailed, this is just so clear and I wish I had seen this first before diving into other material. I anticipate rewatching these again. The way this is presented really made a lot of things just click for me. Especially how AC and DC can exist on the same wire in the Power Amp stage. You made this make perfect sense to someone who is merely a hobbyist on the matter with very basic electronic knowledge. Absolutely amazing!

[@UncleDoug]

Thanks so much for your very positive assessment of our videos, Kevin. They are indeed intended for beginners who simply want a basic understanding of how amp circuits function. For those who wish for more detailed understanding, I have produced subsequent videos that build upon this foundation, offering increasingly complex insights into the function of each of the sub-units of the circuit.