How Tube Amplifiers Work, Part 1: The Power Supply
836,642
Published 2014-03-14
NOTE: There are two ways to look at an amp circuit, based on where the electrons are.....and where they aren't. "Charge" is based on this. Where the electrons ARE is "negative", and where they AREN'T is "positive". In effect, the power supply is an electron pump. It pumps all the electrons out of the circuit and into the chassis, so the circuit (i.e. tube plates) have a positive charge and the chassis is negative. At this point you could say that the circuit has a charge of +325V compared to the chassis at 0V, or that the chassis has a net charge of -325V compared to the circuit at 0V. One or the other. It is the accepted standard, however, to say that the circuit is +325V compared to the chassis, which is at 0V.
My diagram was meant to convey this, but ended up being confusing for many people. Hopefully, the explanation above makes sense. If not, here is an analogy: If you drive 50 miles away from home, there are two ways of describing your position: You are either 50 miles from home, or home is 50 miles from you. One or the other. You can't add the distances and say you are 100 miles apart. Either you or home have to be set at zero distance.
PLEASE NOTE: I have made some changes to this video to update it's accuracy and improve the content. Whenever the notes contradict the narrative, especially during the rectifier portion, please heed the notes.
ALSO: I have since released an updated and much more comprehensive video describing this topic. Here is the link: • Power Supplies Part 2: Full Wave Rec...
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Link to Part 2: • How Tube Amplifiers Work, Part 2: The...
All Comments (21)
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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!
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I cannot overstate what a tremendous asset you are to the YouTube, 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!
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After playing with VFD displays I was recommended to watch this. Very interesting. You explain it very good. Thanks
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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!
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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.
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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.
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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.
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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
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"Making the simple sound complicated is commonplace; making the complicated simple, Awesomely simple, that's creativity." -Charles Mingus
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This is the best video clearly explaining not only "what", but "why" and "how" as well, as I've ever seen.
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Im a graduated mechatronics enginner, did my job only for few years and now Im a commercial pilot now for 10 years but I was always curious about tube amps as a guitar player. I was never taught this well unfortunately. Thanks for the amazing video.
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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.
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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!
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Hi Uncle Doug, You are a phenomenal teacher. The video was very educative. Big thank you. Regards.
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Doug, your videos are really helping me a lot. There are some videos on YouTube that help, but your breadth of knowledge on the subject blows them away! Thanks, again!
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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! ;)
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Very cool! As a guitarist I find this very interesting as to what is really going on in there. Electricals are quite fascinating.
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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.
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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
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Sir if I rated your teaching ability on a scale of 1 to 10, I would rate you at 12. Excellent job!!!!!
