How Tube Amplifiers Work, Part 2: The Pre-Amp and Power Amp
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- เผยแพร่เมื่อ 14 มี.ค. 2014
- In this Part 2 of a two-part video series, we will follow the +325VDC current as it flows to the tube plates. Then we will study the nature of the guitar input signal, and apply this signal to the grids of the tubes, following it through several stages of amplification until it reaches the speaker voice coil. The presentation is primarily conversational rather than technical and utilizes analogies and basic language to explain the chain of events that occur within the amplifier circuit.
CORRECTIONS: My voltage and power values for the secondary of the output transformer are incorrect. The voltage should be around 4.5V and the output power should be around 2.5A, resulting in secondary power output of about 11.2W....matching the primary winding power. In reality, due to heat losses in the OPT, actual output power from a single 6V6 tube to the speaker would be in the 6 to 8W range.
Components such as coupling capacitors, output transformers, speaker voice coils, etc. will be encountered along the way, and will be discussed, as will concepts such as plate voltage, plate current, and output tube biasing.
If you enjoy watching videos featuring classic vintage tube amps, jukeboxes, exotic electro-mechanical devices, and simple, basic technical presentations, then please subscribe to my channel. You will gain immediate access to almost 100 videos, and (if you activate the service) you will be notified each time a new video is posted.
Thanks for watching !!! - เพลง
I wish I had found Uncle Doug years ago. I've learned more here in 21 minutes than I have in the last 10 years. What a fantastic teacher!
Wow, thanks, Red. We really appreciate it :)
My thoughts exactly!
This is why some teachers get boxes of dog treats, cat toys and capacitors... and some don't :p
Excellent! First instruction video I did not have to stop or rewind to understand. 👍
Brilliant explanation indeed!
Man I wish I had teachers like you 40 odd years ago in high school. Very well presented.
Thanks, P3 ;)
Same. Realize as you get older bad teachers are usually bad because they dont understand it fully themselves.
When you know it you can express it with meaning and accuracy.
@@luminousfractal420 Oa
THIS is what youtube is for!
Thanks, Tom. Please see all our other videos :)
@@UncleDoug love this!!
Yes, I agree. Super nice!!!
This must be where the name comes from...You TUBE :). great videos Doug thank you!
EXACTLY! THIS is definitely what TH-cam is for!
Uncle Doug you have made two principles very clear, 1) How vacuum tube amplification works and 2) The importance of having high quality educators like yourself. Much thanks.
You're welcome, Paul.
@@UncleDougDon't forget the value of living with the dog (Rusty) who taught Chuck Berry how to play!
@@edwardebel1847 Chuck insists that HE taught Rusty.....but we all know better :)
This was better explained than 95% of what I have seen.
Thanks, Sarge. We're glad to hear it :)
I've read several books on tube, radio, and amplifier technology and came no where near the clear understanding I got from watching these 2 videos. You should be teaching teachers.
Wow....thanks so much, Jack. When I am learning a new subject, an essential part of the process is to break it down into basics that make complete sense to me. These videos are a (hopefully clear) presentation of those basics. I'm glad to hear that you found the videos to be helpful :)
and teaching amp book authors how to write lol
I have serviced many many tube amps like Fenders and Marshalls etc. And now I understand exactly how they work. Do any of your videos explain phase? Absolute polarity?
This is exactly what I came here to say.
god bless you sir. i can't thank you enough.
Since I started watching Uncle Doug, Rusty, Jack and the stray cats I can browse a tube manual and make sense of what I'm reading. My father would be pleased to know you guys are helping me take care of his collection of electronics repair equipment from his career as an electronics technician. He passed in 2015. I kept all of his gear.
That's great to hear, CR. We're glad to be of assistance :)
Awsome man ..I hope my son takes care of these guitars and amps I've been building...
Rip
My first time here.. I truly appreciate your presentation. I am an electric guitar player for may decades. Life diverted me away from my love of 'tubes'... But, as a 25 year engineer for Boeing and Lockheed Martin. Your ability to present complicated reality that cannot be seen, to the level that all can understand is remarkable..
Thanks so much for your very kind words, Don. We're glad to hear that you enjoy our videos.
As I sit here watching this I keep thinking "this is absolutely brilliant". I've learnt more from these two videos that from anything else I've seen, mainly books. You have an incredible knack of explaining things in an easily understandable manner. I can't wait to see the rest of your videos.
Wow, thank you, FK. We're glad it was helpful.
Wow, what a tutorial. You’re an excellent teacher and your analogies are actually really good. I learned so much from these two parts about tubes.
That's great news, AD. Thanks so much :)
God bless you Uncle Doug. I learned more from these two videos than I learned in two years. I've had a Pilot 232 stereo tube amplifier sitting on the shelf that I've been picking away at restoring for about 2 years now, but I kept shying away because I didn't quite understand it. You've given me the confidence to saddle up and finish the project. Thank you.
Thanks so much, SJ. We're glad the videos were helpful, and wish you good luck with the repairs.
Uncle D, you sir are an international treasure!
For the first time ever, I've heard someone tell what a "coupling capacitor" in language that is easy to ingest. I couldn't say how many other sources I've encountered that just throw the term out there and assume that I know what that is.
That is just one of many brilliant expositions that your videos contain. I am not an EE student, nor ever will be, but I have built microphones, effects pedals, and such from "paint-by-numbers" kits. You have helped me understand what those circuits are actually doing at an electrical level more than any other source I have encountered.
I feel like I actually understand simple tube circuits well enough now to actually try my own hand at a build. Other videos of yours help ease the fear of high-power tube circuits, and how to deal with them safely.
Thank you Uncle Doug. Your approach to teaching shows a love for the topic, but more importantly, a love for sharing the topic. Thank you.
You're quite welcome, Kevin. Rusty and I sincerely appreciate your very kind appraisal of our methods and philosophy. Best of luck with all your ventures and projects.
Perfectly executed in parts 1 & 2. And on a side note, I am a huge fan of the way you present yourself through vocabulary and diction. So many guitar / gear channels are either nonstop foul language or paid ads. Thank you for keeping it classy and thoroughly educational while more interesting than any other explanations I've seen. 👍👍
You're welcome, Oq.....and thanks for your very nice comments :)
Uncle Doug,
Your videos and the way that you thoroughly explain EVERYTHING is extemely detrimental to my approach of self taught electronics.{i can tell you have a lot of experience teaching and your methods are very sound and helpful} I can not thank you enough for your posts and the time that you spend making them. It has given me the chance to go in leaps and bounds instead of baby steps. you are truly the patron saint of electronics teaching. Thank you for everything .
RONALD
Thanks, Ronald. Did you mean to say "beneficial to my approach" ? ;) Regardless, we're glad the videos are helpful.
Mr. Uncle Doug, you taught me more about tube amplification in 20 minutes than I have learned in all my 67 years. As others have said, if you weren't a teacher, you missed your calling. Your voice is clear and pleasing and your diagrams are excellent. Thanks much for sharing your knowledge.
Hearing from great viewers, like you, makes it all worthwhile, sir. Thanks so much, from a descendent of Scottish ancestry.
@@UncleDoug Best description of tube amp basics I've ever heard.
@@stefmaster1 That's great to hear, S1. Glad you enjoyed it :)
Ditto-squared
Just absolutely the best explination of a complex piece of equipment I have found. The tube amp has been an enigma for me until I found your chanel. Love your clear and concise explanations and thank you so much for taking the time making these vids! Could I make a suggestion on a couple of topics I would love to here your input on and I feel would really be useful for us newbies. One I think would be great is for you to go through how you work on your amps safely and the precautions you take to make sure you do so. secondly, would love a vid on your tools and mainly your meters and just the essential tools a beginning ampurologist...lol...would need to get the job done. Thanks again uncle Doug!
You're welcome, Dean. Thanks for your nice comments. If you check my video list, I think you will find that the topics you requested are all included in currently posted videos. They may not be the main topics, but they are discussed.
+Uncle Doug Ok, thank you I'll look for them. I was just thinking that a safty vid was important enough to deserve its own stand alone vid. Also your such a good teacher I would have complete confidence in all you had to say on this very important issue.
Actually the Shock Hazards video was a stand-alone......check it out.
+Uncle Doug Geez I found it, I dont know how I missed it but I did. Thanks again Unk.
You're welcome, Dean.
What an amazing instructional video, clear and concise with real world examples. Thank you so much for all your effort making these!!
Thanks, Z1. You're welcome :)
Probably the best series on guitar tube amplifier circuits there is
Wow....thanks so much, SP :)
This two videos about the the tubes are the most magical explanation about the most magical part of electronics that I have had the luck to see. Just beautiful.
Thanks, Luis. Glad you enjoyed it :)
Great playing and amazing and simple explanation! Thank you sir.
You're welcome, Mike.
If you enjoyed this advertising-free video, please subscribe to my channel, and consider becoming a Patreon patron at: www.patreon.com/uncledougsvintageamps or making a PayPal donation to: dldcam@aol.com . Thanks for watching !!!
Thank you for the videos. I'm getting back into music, and with it the guitars and amps are getting some work in an effort to not sound terrible.
My electrician trade school and navy electronics courses are coming back, it's been many years. You use a concise format for your videos, starting with the basics and slowly (and comprehensively) building to explain the bigger picture - for those with or without electrical backgrounds. Awesome stuff.
Love you videos made it clear to me, I have a Tubes and a half Lafayette receiver and amp I wish I knew how to make them into a guitar amp they appear to be all original although I haven't looked under the bottom of the chassis.... Sorry my screen is cracked so I can't really type in this microphone on the smartphone doesn't pick up everything exactly it's hard to go back and fix the Spider-Man screen on my phone love your work thanks for the great videos!
Hello Uncle Doug, I just became a Patron because I value you and your great educational videos, also to show my appreciation for answering my technical questions.
Best regards always !
Sincerely
Michael Kent
Thanks for your superb explanation videos, I now have a much better understanding of tube amplifiers.
Learned a ton. How you describe the way tubes function makes it very easy to understand. And now I know why vacuum tubes are also referred to as "valves!" Thanks.
I'm glad the video was helpful, Devon :)
Thank you Uncle Doug for leading me out of the darkness and into the light.
You're welcome, Shim. Glad to hear it :)
OMG not only are you a great communicator but the way you explain it is so easy to understand. I only wish I had come across your channel much sooner.
Thanks so much, SB. Welcome aboard :)
So many little pieces of knowledge that I couldn't before connect are now coming together. So incredibly satisfying and motivational Uncle Doug, such an amazing teacher you are. Thank you! Go Rusty go go go
That's great to hear, Kent. You're quite welcome :)
Won't be the last time I watch this series, thanks much UD!
I hope you enjoy it, P3 :)
What an absolutely fantastic instructional video together with part one. They are without doubt the best that I’ve ever seen on TH-cam on whatever subject I’ve watched. They are explained so well, with the analogies, that it makes it so understandable. I wish that I had found them years ago.
Wow.....Thanks so much for your very high praise, Martin. We're glad to hear that our videos were helpful :)
The black art of the amplifier revealed ..... thanks
My new favourite human being. He's the "This Old Tony" of guitar amps.
Thanks so much, Ezra.....I guess ;)
Fantastic presentation. Should be part of the standard high school curriculum.
Thanks so much, Will.
As an electrical engineering student and a guitar player, I must say this is just what I was looking for, thank you very much sir
You're welcome, Sal. We're glad the videos are helpful.
Uncle Doug, I got my BS in marine engineering 30 years ago. I work in power and heat transfer now and am no stranger to the topic of electricity.
These two videos gave me a better understanding of tube amps than I’ve had in 50 years.
What a service you’ve done for all of us who enjoy music, electronics, guitars and dogs.
I’m now a subscriber.
Thank you brother.
And thank you Rusty for that wicked Chuck Berry impression.
Thanks so much for your kind words and for subscribing, Winston. We're glad you found our channel and wish you the very best.
OMG!
More pieces coming together in my brain!!!!
This really helped me better understand how they "actually" work....
Great JOB!!!!!!!!!!!!!!!!!!
Despite having dabbled in the past, I'm a beginner in electronics and especially to tubes / chassis. Your videos made it finally click for me in how the latter work by breaking things down to easily understandable chunks. Thank you!
That's our goal, Dennis. You're quite welcome.
This is the best, clearest explanation of amplification I’ve ever heard! Awesome! ✌️😃🎸
Thanks, Mac. Glad to hear it :)
Rusty really gets down to it on this one. How does he make those bends without thumbs? Just amazing.
Rusty passed away several years ago, so I guess we'll never really know his secret.
Thanks a lot Uncle Doug, sure enjoyed the great tutorial. Rusty sure plays some mean guitar!
Arjun Kaul You're welcome, Arjun. Glad you liked it.....and enjoyed Rusty's guitar solo :)
Yes I'm going to build my first tube amp
Best of luck with your project, Arjun. Please let us know how it turns out.
Thanks Uncle Doug! Yes I sure will (y) Do lListen to my rocknroll album, its a tribute to classic rocknroll. You might like it. Have a great weekend!
Likewise, Arjun.
Thank you for this excellent break down of amplifiers! I've worked on music row in Nashville and for years with a high end AV company and this is the most thorough explanation of amp operations I've seen on TH-cam! Cheers!
Thanks so much, 38M. We're glad the videos are helpful :)
Super teacher, has to be one of the absolute best explanation I’ve ever heard.
Thanks, WW. Glad it was helpful :)
Great Video. Doug explains the workings of the amp in a very understanding manner. I will certainly be watching your other videos. John
Great video series. Thanks for breaking it down for us.
You're welcome, Greg. We're glad you liked it :)
Thank you. I did valve + amp theory in 1970 when I was 16. Transistors were just on their way in at the time. So, never ever got to grips with thermionic valve theory. After all these years yuor videos have cleared a lot of it up.
That's good to hear, Joe. We're glad the videos have been helpful.
most people dont do such a great job at explaining things like this on youtube. thanks.
Thanks, Dj. Please watch our other videos for all sorts of interesting presentations.
I love the way you explain, the way you separate the whole thing into tiny pieces and then you slow down before a difficult concept. Great teaching, Great video!! Thank you so much.
Great explanation Uncle Doug, your sharing of your wisdom is most appreciated!
You're welcome, Eric.
Really well explained. Easy to understand for everyone with no formulas and maths involved.
Thanks, EG. Glad you enjoyed it.
Amazing what you teach us in just 2 lessons, my father was an amp technician and i wish i payed more attention to what he teached me .
but now i have found the same teacher online i'm so grathefull you have the same kind if passion in teaching
so now i have an uncle online after my father died 30 years ago you even sound like him
Thanks so much, RD. I appreciate the kind comparison :)
Rusty! You are really rocking out there dood. Must be time for a treat after that performance.
Man, I wish this existed back when I was trying to teach myself how to build an amp. This was a GREAT little series and you really provided good analogies to what's going on, especially with some of the finer detail of why, where and how. Thank you for doing this! I'm looking forward to biasing, phase inverters etc. :)
Nice to see Rusty again, I always feel everything's under control with him around :D
Greetings, Sarcast, and thanks for your kind appraisal.....glad you enjoyed the videos. You're right about Rusty, his high energy and work ethic are always inspirational :) ^. .^
Just brilliant! - came across my first valve amplifier at someone's house the other day and was so fascinated I had to know more. What a fantastic 2-part explanation. Thanks.
Glad it was helpful, Nodge. Please watch our other videos for additional insights.
Uncle Doug, 4 years and 4 months later and this video series is still teaching rubes like me basic electronics (well, for me it's advanced) so thanks for that. I understand that since this video's inception Rusty has passed, sorry for that. After watching these 2 vids over and over I think I have a much better grasp of the subject and am getting closer to one day being able to construct my own stereo tube amp. Thanks again
You're welcome, Jim, and thanks for your very nice comments. It's great to hear that the videos are helpful. I have made quite a few videos since this one that go into much greater detail on all of the sub-units of tube amplifiers. Best of luck with your project !!
Perfect detail, Thank you for all your time !
You're welcome, NF :)
Simply put, these two videos were "a moment of clarity"! Great working definitions and understandable paths, filter caps, coupling caps, rectification have never been clearer. Thanks for picking tubes with a straightforward nomenclature to boot. Keep up the great work!
You're welcome, Brett, and thanks so much for your very favorable evaluation. I have other videos covering these components in greater detail, if you have the time and interest to see them. Thanks for watching.....and commenting :)
This is by far the best instruction video I have ever seen! Thank you!
Wow....high praise indeed, Joseph. Thanks !!! Glad you enjoyed it.
AC and DC can travel on the same wire. That’s the biggest piece a novice can’t forget. Thanks Doug.
Yes, they coexist, like ice and water, but never mix.
Hands down the best tube explanation out there. thank you
Hello Uncle Doug! :) Once again, you've opened new doors for the young folk that is willing to learn about a technology that has made a tremendous comeback and is here to stay for many moons. There is so much vacuum tube equipment being manufactured again--now and over the past 15 years; and the numbers keep going up...from guitar amplifiers, to professional recording equipment (including condenser microphones) and even in the digital world, there are radio/TV broadcast transmitters that still use tubes for the final RF output stage.
I occasionally teach vacuum tube electronics courses in a local vo-tech school (once a year), but one of the issues I've had which took me a while to get use to was, realizing that I'm talking to new kids on the block, and not a room full of techs. So, my explanations tend to be too far advanced for these kids to comprehend, You've honestly given me an eye-opener for my next course, and that's to use what I would call "Household Analogies" to make theory of operation a lot more comprehensible.
With some careful planning, I may even be able to create analogies using ghetto terms that the kids today seem to understand (more than I even do) (Ebonics is grammatically a disaster; but it may sink in better with some kids). Either way, I would love to show some of your videos to the kids...They just keep getting better, I teach these courses for free to possibly give a kid the opportunity to have a future, keep them off the streets, learn something constructive, and out of trouble...PS: I never knew rusty had such great chops on the guitar! ;)
Greetings, Frank. If you think any of my videos would be helpful with your classes, then feel free to use them. Yes, Rusty is quite the little musician :)) ^. .^
I think there should be a TH-cam king. And I nominate Uncle Doug! Out of the thousands of video's I've seen on TH-cam, he's my favorite!
Wow.....thanks so much, Tim :)
I really wish I had watched this before I built my home-brewed Champ. It took me a couple of tries to get it right. Thanks, Doug!
You're welcome, Aly. Glad it was helpful :)
Best 40 minutes I've ever spent!
Thank you so much for those two videos, you're the best, man!
You're welcome, Emil, and thanks for your very nice comments :)
You are an outstanding explainer!
+oscar arevalo Thanks, Oscar.
This series is the first instance in 50 years of banging my head to understand what always has been black magic to me. THANK YOU, Uncle Doug (and Rusty for keeping Uncle Doug in line), for this series. Golden!
Thanks, John. We're glad the video was informative.
Fantastic, clear explanation. Plus a talented dog. My standard, Frodo, played blues on his guitar, and he used to sing the most soulful, sad lyrics, you ever heard; he would sing when I played my guitar, or piano too. Poodles are so clever.
Indeed, Paul, animal musicians are underappreciated.
Thank goodness for Uncle Doug. I really appreciate you sharing your knowledge in such an understandable way. d;D
Uncle Doug I second what 'cuda says. You are a wonderful teacher. My stepfather is an electrical engineer and i cant get even the smallest things explained without him starting some rediculous arguement. Thank you so much for your time and knowledge. We need more people like you in the world. And more rock n roll dogs too! :) Maybe you can teach us how to build a race hemi engine next time? Haha. Mmmm Mopars!!!
Thanks so much, Brian. As you can probably tell, I never received "school training" in electronics, but picked it up over the years via self-study, experimentation, trial and error, etc. I too have difficulty assimilating input from (vastly more knowledgeable) EE's, and really try in my videos to keep the explanations grounded (no pun intended) in common terminology that makes sense to those of us who were not "classically" trained. I catch some heat from time to time for this, but the vast majority of comments have been appreciative and supportive. Thanks again :)
Another fantastic video, even a lay person like me can have fun and understand your explanation in extreme clarity - Thanks again U Doug and Rusty
You're quite welcome, Mudy. Rusty and I really appreciate your kind assessment of our work :) ^. .^
Uncle Doug :)
I've owned tube amps for twenty years and never even knew how tubes worked or what they did. Yesterday I read the owners manual for my mesa boogie amp and it had a section on tubes that used drinking irishmen going to the bar as an analogy for electron flow in a tube. Pretty funny. That led to a few other videos and then this one. It's satisfying to finally have at least a working idea of how a tube amp works now. Beautifully explained. Thank you Doug!
You're quite welcome, Torrey. We're glad the videos are helpful.
seriously, what a resource!. 40 mins and I have a much better understanding of the tube workings!. Sub well and truly earned!.
Thanks so much, F :)
Excellent video. Great explanation. I've been reading about tube amps but this video makes them easy to understand..Thanks.
+jim mcdowell You're welcome, Jim.....glad the video was helpful :)
I appreciate these videos and your channel so much. Thank you thank you
You're welcome, KB. I'm glad the videos are helpful :)
Thanks Uncle Doug. I know I'm late to the party but good stuff. I learnt a lot.
Glad to hear it, Wayne :)
I’ve wanted to understand how that worked for over 40 years. Thank you sir!
You're welcome, Greg. Glad it was helpful :)
8 year old video... Extremely relevant info! Thanks Uncle Doug! You've cleared up a while bunch of questions and fog I had about amps and audio in general. Lotsa pieces just feel into place! 🔉👍 Nice guitar work from Rusty! (probably gone now but never forgotten! 😔)
Glad to hear it, KL. Thanks so much :)
Thanks for the time and effort you put into your video's they are excellent,.
Clive Mayo You're welcome, Clive.....glad you enjoy them :)
Uncle Doug, You are the best. You explained the subject very clearly. Thanks a million.
You're quite welcome, James. Glad you enjoyed it :)
Great job ..I knew this over 40 years ago but never used it. Trying to pick it all back again at 68 years old . Thanks
You're welcome, Frank.
Rusty, the NEW Chuck Berry!
Great lesson sir!
It would be great a complete course and how distortion occurs in amplification process!
Thanks uncle Doug I finally understand tube amp electronics....you must be a professional teacher...you do an excellent job!
You're welcome, Paul. I was indeed a classroom math and science teacher for 17 years.
Great video series, finally I get it. It just amazes me that none of this was taught in school, if I would have had a Science teacher to teach this, and a Math teacher to teach the formula's, I would have been a lot more interested. I got my 1st guitar in 5th grade back in the 80's, although I work as a heavy equipment mechanic sometimes a lot of searching for shorted wiring, or a dead accel pot, or a dead brake pot, or a controller issue (controllers turn DC voltage into AC voltage). I was never able to make the jump with understanding how tubes work, and I understand what the capacitors are doing now because in systems trucks you have 36v 1000a battery but AC drive motors and AC hydraulic pump motors. absolutely great video. I've bought books on building guitar amps but none have explained what is happening inside or why its happening inside of a tube (tube amp), as good as this video series has. THANK YOU SIR!!!!!
The explanation of ripple current alone gave me understanding into something I had always heard of but had no clue what it meant. Thanks.
You're welcome, RB. I'm glad the video was helpful :)
Finally somebody says in plain English how this works. I have so many people turned off by electronics because of the elitist out there who make things way more complicated than need be. I have been doing audio for 50 years plus and it is a breath of fresh air to see you explain so beautifully how an amplifier works. Well done. By the way I think I can get Rusty a record deal.
Thanks so much, Vincent. I'm glad you enjoyed the video, and Rusty's finale :)
What ingenius clever minds these people have who harnessed the functionality of electricity this way. I would have never thought of this on my own. Not in a million years would I have developed the capacitance to get there. And this presentation....simply the best....clearly, precisely,.... well done.
Wow...thanks so much, Rusty :)
You do a very good job of explaining the technical parts of the components and there relationship to each other and you do it without sounding like a arrogant Richard Cranium what a guy
Thanks, Terry. I simply try to explain things in a way that I too can understand.
Good job. Actually, excellent job. Thanks for taking the time.
Best explanation ever ! I work on amps as a hobby/be-able-to-play amateur. and had a couple of aha moments. Greetings from Denmark , I love all your videos , highly appreciated. BTW , my yellow Lab sends kudos to Rusty !!!
Thanks so much, Soren. It's always great to hear from international viewers. I'm glad to hear that the videos were helpful.....and Rusty is glad to hear that he has a fan in Denmark. :)) ^. .^
These are gold! Thank you for creating these!
you've recharged my batteries and have begun to look for used amplifiers and tube radios to service. I have a lot of my digital testing equipment from my early computer servicing days so this would be a great hobby to get into. You have a dedicated fan here and I love the way you present the material.
Thanks so much, John. Best of luck with your new hobby :)
David Stanley, your comment came without any reply capability, so I'll answer up here. The AC signal would indeed pass back up through the 150VDC wire.....if it were not for a 100K plate resistor (that you can see in the original schematic at the beginning of this video). I will post a video in the near future explaining it in detail, but for now, just consider the plate resistor as a sort of 2-way dam that controls how much DC reaches the plate and also forces (by its resistance) the signal AC to go to the next stage, rather than to ground. I left the PR off of this diagram to keep it as clear and simple as possible.
I didn't see the original question, but I think this is exactly the answer I was also seeking...
The AC guitar signal would want to traverse the 150V DC lines at the 12AX7, but the plate resistors prevent the signal from passing...
I also assume that the AC traverses on the 320V DC line coming out of the 6V6 back towards the branch for the 12AX7 plates - but the filter caps and resistors would eliminate this signal / "ripple" :). Is that a reasonable assumption?
This series was fantastic. Thanks so much for the excellent explanations. (Glad I saw in comments on other channels to check out your content!)
Kickass!
I have to send you some $. This is just too good not to be rewarded. Amazing teaching, never experienced anything like it. I've learned more about valves in 15 minutes than the last 40 years of being into electronics. Absolutely brilliant. Such a good circuit to use as an example too.
Thanks so much, Mark. I'm glad the videos are clear and helpful. I have links in every video description to enable contributions, if you so desire.
This was great. I learnt all this at university 50 years ago. Haven't totally forgotten it all, but needed your refresher! Great way of thinking about it all. My university lecturers took a really intellectual approach to it all, really doing all the design stuff of working out all the resistor, transformer and capacitor values, etc. But your rather down home explanation hit the spot with me. Keep it up. Your latest fan.
Thanks so much, Evan, and welcome to our down home channel :)
Back To The Future, Rusty - Go Baby Go!!!
I loved this so much. Very easy to understand. You are a great teacher. Do you think you could ever explain a Neumann U67 ?
Rusty B Goode! I really appreciate that video. As a young sailor in the US Navy I was trained in the BE&E school as an Electronic Technician some 40 years ago. But life took me in a vastly different path, not using my knowledge very much at all. But I did play a LOT of guitar. This was very interesting to me and jarred my memory of "trons" so many years ago. You're much better than the dry military method my instructors used!
Thanks, Ken. Glad you enjoyed it :)
Best explanation I've ever see of how a guitar amp does what it does.
Thanks, Don. Please be sure to subscribe and watch all our tech-related videos.
Wow I was never told AC and DC can share the same wire. Thanks
Greetings, TJ. Rusty and I love the cat icon. Yes, they can happily coexist within the same wire.
Uncle Doug I’ve been running separate lines for dc signals; now I can save all that time and material.
Well technically they combine into offset AC signal. So if you have 1V amplitude AC going about 0V and you feed in 5 volts DC its going to go back and fourth between 6 and 4 volts, as if 1 V AC going about 5V DC.
It would be a 1v ac peak (2v peak to peak) signal offset from zero by 5v.
@Gregster DC offset AC.
Zac Volmer, your comment had no reply capability, so I'll answer up here. The standard input jack on all guitar amps is 1/4", but if you're building the amp yourself, you could install a 3.5mm input jack instead. However, I'm not sure if a tube amp would be the best bet for phone or computer input, due to impedance differences between solid-state device output and tube amp input. I think you might be better off with a transistorized amp for your purposes.
+Uncle Doug I know I am coming at this late, but I found this video series to be amazing, and all of your videos are so well explained. I have often wondered why a tube amp isn't really used that much for a "digital performer", someone using a computer or such.
Thanks, Chris. I guess musicians who favor the clean sound of IC circuits and transistors aren't looking for the warmer tone you get from tubes. It's all a matter of taste, I guess.
Yeah, I figured it was a taste thing. I play synth processed by a computer/ipad and really enjoy mixing it up with tube amps at the end. Gives it a fun quality.
There's no reason not to play a synth through a valve amp. Consider that early synths are valve operated and all that amplification would be valve driven. I further note that some of my relatively modern synths have a distortion or tube simulator effect that can be engaged. I have a Roland D10 amongst my toys, and despite being tedious to program it does some interesting things, but it's quite thin and sterile sounding. Warmer moogish or just plain mashed up sound can be extracted by the use of a guitar amp. Sometimes I need a transistor buffer (a clean boost, eq, or similar pedal or just a buffered bypass pedal in the bypass mode) to get a good result.
Outstanding! Doug is now my favorite uncle. Excellent explanation.
Thanks, Mark. Welcome to the family :)