Phase Inverters....for the Common Man

This video describes the purpose and design of three different common phase inverter circuits: Split Load or Cathodyne, Paraphase, and Long-Tailed Pair. Simplified diagrams are used to explain how each circuit functions, and then then these circuits are demonstrated within schematics of classic tube amplifiers. The language is basic and simple analogies are utilized to clarify concepts.
If you enjoy videos featuring classic vintage tube amps, jukeboxes, home-built electromechanical marvels, and clear, concise technical presentations, then please subscribe to my channel. You will gain immediate access to about 100 additional videos, and (if you activate the service) you will be notified each time a new video is posted.
Thanks for watching !!!

[@zeerust2000]

The great thing about Uncle Doug is that he tells you what you need to know and not what you, right now, don't need to know. I wouldn't be surprised if he's got a teaching background of some sort, because these videos are so well done.

[@UncleDoug]

Thanks so much, ZR. Yes, I was a classroom Math and Science teacher for many years.

[@mrwolfsang]

@@UncleDoug If I had a science teacher like you, I would have fell in love with it and became an engineer of some sort. Thank you so much for the video, I always learn so much.

[@UncleDoug]

@@mrwolfsang You're welcome, Wolfsang.

[@franky2shoes660]

@@UncleDoug Was going to say "all day long, uncle Doug has some kind of teachers degree". Thanks for everything, I have built a bunch of SE. Amps after finding an old line op. Westinghouse console and your youtube. Nice hotrod you have as well....PS attempting my first P/P amp today.

[@UncleDoug]

@@franky2shoes660 Thanks, Franky. Good luck with your project.

[@jimviau327]

26:00 - Uncle Doug , I am an engineer myself and would like to let you know that, apart from some minor complicated details, your analogies are quite fine. In my opinion they are 98% accurate, which is quite remarkable. I think your best quality is to be able to represent some very complicated electronic concepts in a simplified way so that the electronic beginners could grasp the essence of it and start to understand. If a student pushes further his study, then the hidden details are going to reveal themselves anyway. Kudos buddy. Keep the good work, we like it.

[@UncleDoug]

Wow, thanks for the nice comments and excellent observations, Jim. I agree completely that the presentation to beginners has to be easily understood, then they will have a foundation to move on to higher levels of understanding.

[@danweston6109]

My god man, i've been searching for this and you. Finally someone who understands what is going on and can explain it in a way normal people can understand. You're a rare breed Doug.

[@UncleDoug]

Thanks, Dan. I hope you enjoy all our videos :)

[@keithcoltron3171]

As an electronics engineer I still found this fascinating, Your description and explanations are just simply superb, I have tried on many occasions to 'teach' others but I'm afraid I just can't explain it like you, you just seem to explain things in a way that I'm sure anyone could understand, I knew what was coming next but still enjoyed it so much, it's the way you put things that makes so much difference and for people that want to learn it's an absolute must, being able to picture the process in your brain should turn anyone's light on! really well done and thank you for all you do, it's invaluable, if you haven't done any teaching in the past then we've all missed out! You're a star in a somewhat dark and otherwise confused universe.

[@UncleDoug]

Wow, thanks so much, Keith. I was a middle school math and science teacher for many years :)

[@keithcoltron3171]

@@UncleDoug Hi Uncle Doug, all I can add is lucky pupils, if you taught like this back then they would've had no complaints, at Uni the standard between lecturers was at times glaring, some were as bad as me (and that's bad!) It's just not my forte, some teachers just have that extra something and it makes learning an absolute treat so I hope things continue, I for one won't miss any as it's just so enjoyable, even if one already knows it's still a pleasure to listen, I hope that others will find you and your channel continues to prosper. There is unfortunately so much rubbish on KZbin which can have a negative effect and push people away, I just wish I could have a magic wand and do some frantic waving, I'm 74 now but still (given the right teacher!) love to learn new things, some may not stay embedded now though :-) but it's still fun, our profession is I think great to be involved with. From many more I'm sure here in the UK thanks again for all your time, effort, wisdom and patience, long may you reign, I'll have a quick word in her Majesty's ear and who knows a Knighthood could be just around the corner :-) Take care and stay healthy.

[@edwardkujawa]

you engineers all alike dont fix the stuff just design it maybe your different lolololol

[@JTM45100]

Your videos are a pure joy to watch. I'm addicted to them. I say this as someone who has probably 100 builds under his belt of various Era 100 watt Marshalls. I feel like I have a better understanding of push pull amps and the Phase inverter. Before I just knew what voltage should be, what my signal should look like, and trouble shooting methods.

[@UncleDoug]

Wow.....thanks for the very nice comments, JTM. Coming from someone with your experience, they mean a lot. I'm really glad that you find the videos to be helpful :)

[@nevenante]

JTM45100 , isn't great to actually understand the reasons behind our activities? For me it is hard to obey rules without understanding the reasons behind them :-)

[@UncleDoug]

Yes, I've always been very curious about how things "really" work, and very hesitant to accept most explanations......without some personal experimentation to verify them.

[@steveelliott4132]

i'd like to say thanks like the other guys i've been following along for a while and tonight it was nice and quite around here and i understood quite well about the single tube amps finally and was not sure about even trying to learn about the push pull amps but decided to go ahead and watch the videos anyway and i'm so glad i did it must have been my night and a little bit about the way you explained things (LOL) but i got it. It made perfect since to me finally man do i owe you dearly thanks a million keep it up cause without your explanations i dont know how long or if i would have gotten it and i know now i don't have to start with the smaller champ style amp i can go ahead and build the larger push pull amp witch is more what i need anyway your explanations are very clear and straight to the point if someone is strugelling i sajest they keep on watching the video's and it will come to them as i don't believe anyone could make it any clearer . again Uncle Doug thanks one more thing do you know of anyone who can be as clear on RF tube amps i know there are some differences and want to learn that end as well???

[@steveelliott4132]

p.s. for those of you strugling i sajest pay close attention to the rules one that helped me greatly is ac and dc can be walking down the same road over and over and never bother one another want affect each other at all one can go through some doors the other can't and vica verca but they can both share the same path at the same time without hurting the other and that amazes me but that is the one rule that blew it wide open to me thanks again Uncle Doug (pay no attention to my spelling or you will get no where guys)

[@AndJusticeForAll...1985]

I totally understand it, with basic electron flow understanding. I haven’t seen it explained so easily.

[@UncleDoug]

We're glad to hear it, TG.

[@JagStar]

I watched this when you first put it out and did not get the long tailed pair at all. For years I just couldn't understand the workings of the long tailed pair, so I just trusted that it worked. I watched this again today and I totally understand it now. Interesting how years of doing can assist understanding. I think what a lot of people don't get, and this was my case, is that you can input a signal to the cathode. We are so used to seeing signal input to the grid that we have a block to understanding that signal can be input at the cathode too. Kind of like the old joke, "you can't get there from here". Thanks Uncle Doug!

[@UncleDoug]

You're welcome, JS. It's great to hear when a seemingly complex concept suddenly becomes clear. You made our day :)

[@JagStar]

😊

[@danielcrook9504]

In the words of the late great Tom T. Hall...faster horses, younger women, older whiskey and more money ! Great stuff as usual from the Master !

[@UncleDoug]

Thanks, Daniel. I would add "more horsepower, less nagging, and unlimited amp wattage".

[@andypendlebury6445]

Thanks Uncle Doug, I love watching your presentations. They are some of the most detailed and clearest examples I have found anywhere. I've read books, watched lectures, but I've learned the most from you. So Many thanks for that, it is well appreciated. Your'e a real hero for amp lovers. Best wishes!

[@UncleDoug]

Wow....thanks so much, Andy. That's great news :)

[@stevefiorito5379]

Excellent diagrams and clear instruction. Thanks.

[@utapandgo]

Flip me daisy - that was so awesome learning - I pulled my amp out and want to start fixing it myself. thank you so much.

[@UncleDoug]

Glad to hear it, U......be careful !!

[@edwardkujawa]

he is a great technicial love him God Bless him wish he was around back 25 yrs he would make it soooooooooooo easy kudos to him

[@UncleDoug]

Thanks, Ed. I was around 25 years ago......also 50 years ago.......and 75 years ago......

[@markbunch5062]

Gosh, I've spent such a happy weekend with some of your videos. They are beautifully paced and pitched at exactly the right level for me. Thank you.

[@UncleDoug]

That's great to hear, Mark. You're quite welcome :)

[@baronsaari9878]

Thank you so much for these videos. I truly mean that. The fact you took the time to do all these drawings and have a clear easy to follow plan is just amazing. My hats off to you. Now if only I can find someone like you to do this on mic pres I'd be set. Thanks again.

[@UncleDoug]

You're quite welcome, Baron. Getting such nice feedback from viewers (like you) makes it all worthwhile. Rusty and I wish you the best !! ^. .^

[@EricDobsonTV]

I’m going back and watching all the tech videos in order. They’re so insanely good. So clearly explained. They’re connecting a whole lot of dots I’ve picked up over the years from other sources. Thank you for making these!

[@UncleDoug]

You're welcome, Eric. We hope you both enjoy and benefit from the review :)

[@matthewmartin9313]

Still coming back years later for a simple explanation. Also, im always impressed by your drawings

[@UncleDoug]

Thanks so much, Matt. In my early years, I wanted to be an architect.

[@charlesshaw9090]

Hi Doug. Another very informative video for the DIYer. The size of the tail resistor in a long-tailed pair determines the basic gain of the phase inverter, PI. A large tail resistor gives a low gain PI but the inverting and non-inverting triodes would be balanced so could then have equal plate resistors. A small tail resistor will increase the gain of the PI but will introduce an imbalance in the triode gains. The inverting triode will have higher gain, 5%-10%, so to balance the triodes the inverting plate resistor is lowered to lower the gain, so restoring balance. 82k is usual but it actually lowers the inverting triode gain too much and so introduces its own, but opposite, imbalance. The distortion introduced by imbalance is very pleasant so equal plate resistors or 82k/100k both have a positive benefit. Some amps used 91k which balances well but sounds sterile. I hope this is useful.

[@UncleDoug]

Thanks so much for this very informative input, Charles. I, and other viewers, really appreciate it.

[@UncleDoug]

P.S. Your explanation is one of the clearest and most concise that I have ever seen. Thanks again.

[@silasfatchett7380]

It is possible to calculate the value of the inverting triode’s plate resistor which results in perfect balance in a long-tailed pair phase inverter (LTPPI). When the LTPPI was first introduced in the 5F6 Bassman with its 100k plate resistor on the non-inverting triode, this calculation resulted in 84k for the inverting triode, so Fender used the closest preferred value of 82k. The tail resistor was a relatively low value of 10k. As the value of the tail resistor is increased, it not only reduces the available output signal swing of the PI but also results in the ‘ideal’ value of the inverting plate resistor becoming closer to that of the non-inverting plate resistor. If the calculation is performed for the AA864 Bassman with its 22k tail resistor, it results in a value of 92k (which is closer to 100k than 82k), so 100k/100k would result in closer balance than 82k/100k, and 91k/100k closer still. As Charles points out, an unbalanced phase inverter encourages (pleasant sounding) second harmonic distortion in the output stage, so an amp designer can choose his preferred amount of imbalance, or simply copy the traditional 82k/100k combination (which is often the case).

[@perlgawker]

Hi Doug, Thank you for posting all these videos, sharing your knowledge and taking time to making these videos. I'm a guitar player and I want to know more about tone. Your video's about amplifiers and how they work are a very valuable resource for me as they provide great insight about what goes on in these tube amplifiers. Some day I hope to design and build my own amplifier. I know I am a long way from it because I don't fully understand everything yet (and therefore am rightfully fearful of getting zapped, or bit in my ankles by Rusty if he finds out i'm tinkering with high voltages without enough knowledge) but I feel you videos help me a lot in getting closer to achieving my goals on this subject. So once again: Thank you very much.

[@UncleDoug]

You're quite welcome, Niels. It's great to hear that the videos are helpful and informative. I encourage you to consider building your own amp....and I applaud your safety concerns. No one should "tinker with high voltages without enough knowledge" (very well stated), but that knowledge can be acquired through diligent study. Thanks for your very nice comments and best regards.

[@ramsaybolton9099]

Sir, you are a genius. Finally I understand why the signal is inverted at the plate when the control grid is driven. Thank you.

[@UncleDoug]

Thanks so much, I WA. Glad the video was helpful :)

[@mikkabrightheart2268]

This helped me figure out why the channel volumes on the 5e3 are interactive. I built one recently and everyone on the internet basically says "these knobs interact and nobody knows why" ... Theres a rudimentary nfb loop thru the preamp stage on the unused channel... The cathodes are linked directly and the plates become more so as you turn up the volumes so the in phase signal on the cathode of the uses channel becomes the in phase signal on the cathode of the unused channel becomes the in phase signal on the plate of the unused channel and creates phase cancellations with the out of phase signal on the plate of the used channel I made a breakthrough in my understanding of amplification this morning and had to tell someone lol ... Everyone in my life goes all glassy when i start talking about amps... Also thanks for making this info available, your channel is an invaluable resource

[@UncleDoug]

Thanks for sharing your insights and joy of learning, Mikka :)

[@Dan79istheman]

"I am such a fan!, cause' Uncle Doug is the Man!"

[@UncleDoug]

I thought YOU were the man, Dan.....but Rusty and I are very flattered. Thanks so much !!!

[@tubical71]

A cool shirt logo as well, may be on the back sinde of the -hopefully- ;) upcommin (!!) shirt, from the Tube-professor (next cool shirt name!) Uncle Doug!

[@jeffbrooks7246]

Thank you for "common man" explanations! Although I have a good understanding of electricity and electronics it seems any books dealing with tube amps and theory that I have acquired assume an engineering level of understanding and even if they start off with basic theory they seem to jump from that to the very complex too fast and I find myself either lost or bored from trying to piece it all together and not understanding why. Keep up the good work!

[@UncleDoug]

Jeff Brooks Thanks so much, Jeff. Rusty and I are glad our videos are helpful :)

[@ianbarker2599]

Hi Uncle Doug. You have just blinded me with the light shining from this video. Top bloke, Ta. Ian across the murky pond.

[@UncleDoug]

That's good to hear, Ian. Glad the video was illuminating :)

[@78tag]

These videos are perfect for people like me. I will never build or repair (some minor repairs) an amp but this goes a long way to satisfying my curiosity and will keep me from letting my lack of knowledge from overloading my butt when I do attempt any work on an amp. Just in case you are concerned about my skills, I know this much - use a wooden stick to touch components when checking for loose connections and don't trust anything to not have a charge if you don't want any nasty surprises :) :) :) Thanks again for your interest in helping all of us guitar fanatics. EDIT: I forgot to mention that you picked the perfect example for me, the Princeton Reverb, as that is the only tube amp I own or need.

[@UncleDoug]

Greetings, 78. It sounds like you have a good grasp of two very important safety rules :) I agree, the PR is all the amp that just about anyone needs.

[@UncleDoug]

To Jay Blue: Your inquiry did not have a reply capability, so I will address it here. Hopefully you will see it. This is an example of the Paraphase Inverter, and is virtually identical to the inversion circuit discussed in my recent Rickenbacher Model 59 video. The signal leaves the plate of the upper 12AX7 stage, through the .05uf coupling cap, headed for the grid of the upper 6V6, but some of the signal passes down through the 220K resistor to the grid of the lower 12AX7 stage. In addition, some of the signal is leaked to ground through the 28K resistor, so that when amplified by the lower 12AX7 it will be of approximately the same amplitude as the upper signal, when it finally reaches the grid of the lower 6V6. I hope this all makes sense. Thanks for your kind words regarding my videos :)

[@sinecure45]

Ah yes, I do see the common structure to the two amps, though I note that you were first leaning toward a LPT interpretation. One wonders why such complications are introduced into a design--perhaps the design process is really just trial and error. Since I am planning to build a DIY of the YBA-2, I wonder if I could simplify the whole PI and power section without sacrificing tonal characteristics. Perhaps the gain in simplicity would pay off in improved performance. Would you care to comment on this proposition? Incidentally, I hope to use a power transformer from a Delta Blues for the DIY, but have yet to settle on an output transformer. The folks at Hammond have offered some suggestions in this regard. Any advice would be appreciated. If this is too off-topic feel free to shift the discussion elsewhere.

[@UncleDoug]

I wouldn't consider it a complication, Jay. It's a fairly standard style of phase inversion that was quite popular back in the late 30's and 40's. In my video on phase inverters, I featured it as one of the three types discussed. For some reason, perhaps fatigue or the fact that I hadn't seen one in a while, it took me a few minutes to pick up on it (in real time) in this video. If you want a simple PI, go with the cathodyne. All you need is the second stage of a 12AX7. Simplicity, however, does not necessarily equate with improved tone. You might want to watch my Phase Inverter video for some insights. Re the output transformer, the parameters are quite clear cut. You match the load resistance of the 6V6's, which is about 8K ohms on the primary side, and the secondary matches whatever speaker(s) you will use, 4, 8 16 ohms. Naturally, the primary must be center-tapped. I get all my transformers from Triode Electronics. I have also posted a video on Output Transformers that you should watch. Good luck with your project.

[@sinecure45]

Uncle Doug Many thanks for your comments. Right after the pole dance show I'll head into the transformer room for further enlightenment. Actually, I am much impressed by the logic of the long tail pair, and would probably consider switching over from the paraphase, at the very least in order to gain a tad more gain. I assume this would not upset the overall balance of the system. I guess it could be turned into a Deluxe as you show in the video. I too have sourced from triode for a champ project, and will check their offerings. Hammond may have something to offer, however. I just finished your expose of tone stacks, which was quite illuminating. Any chance of a discussion of active tone control?

[@UncleDoug]

The LTP is generally used in more powerful amps, like the Fender Bassman and Concert, and does provide additional gain, while the 5E3 Deluxe uses a cathodyne PI, and the 5C3 Deluxe uses the paraphase. Since the 5E3 came later, it's interesting to speculate if Fender considered the cathodyne to be superior.....or just slightly easier/cheaper to build (?) I had not really thought about an active tone stack video, primarily because the vintage tube amps I deal with are all passive, but it might be interesting. I recently encountered an ATS HiFi amp, as featured in my Garage Sale Bargains video, but it's been repaired and is long gone.

[@sinecure45]

Uncle Doug Given that the YBA-2 project is for a bass amp, I think that it would be desirable to extract maximum gain from the circuit, e.g., by switching the preamp 12AU7 to a 12AX7 and coaxing extra gain out of the phase inversion. Hence also my interest in active tone stack design. I suppose it depends on how much I am willing to risk on modding. After watching your rectification video I realize too that the YBA-2 does not have bridge rectification so the power transformer requires a centre tap. I suppose some efficiency might be gained by changing the rectification method.

[@jlucasound]

If you are not, I hope this is taken as a complement. I am sure you know who he is. Master.

[@TheDudesdad2000]

Once again I am pleased to have this video as a visual aide to identify the PI in a circuit. I have a new project with a rare Orrtronic Company tube amplifier, which was designed to amplify from four sources (tuner, TV, tape, phono). I presume it's rare, because there are only photos, and no other info, of this exact unit online from it's seller. It has a tube compliment of a 5Y3 rectifier, a single Mullard 7025, and two 6AQ5's in push pull. After thoroughly examining the schematic (lucky it was attached to the cabinet), and watching this video a number of times in the past and now, it looks like a long-tailed-pair phase inverter. Now time to dig in and get this one playing again. Thanks again Uncle Doug. Note: I was able to learn that J. Orr was responsible for the introduction of modern cassette tape material to the rest of the world, via German WW2 prisoners who had been developing the technology before and during WW2. But other than that, not too much to find online about this obscure amplifier.

[@UncleDoug]

You're welcome, Ted. Best of luck with your Orrtronic amp.....and thanks for the historical info.

[@chrisgehlen1]

Thank you for this magnificent channel, where your wonderful teaching makes knowledge flow to our brains, just as electrons flow from the cathode to the plate. Thank you very much!!!

[@UncleDoug]

You're welcome, Chris. We're glad you enjoyed it :)

[@idogepgyar]

Nice explanation, really like you videos! Will you make a basic video about how to "decode" a schamatic step-by step? I mean how to read it, how to follow the audio signal and such. Thanks, András

[@tubical71]

For 12:40 You Nailed! Another side effect is that the output impedance of the cathode and plate circuit is not the same, in fact the cathode output impedance is much lower. So if you want to drive big tubes or some in paralell you need some extra driver stages, or you amp end up in doing "funny" things at high output levels...

[@UncleDoug]

A good point, TC. Thanks for bringing it to our attention.

[@brettni5698]

Good point, can you add some resistor to the cathode to match the impedance?

[@silasfatchett7380]

@@brettni5698 No, because the cathodyne requires equal plate and cathode resistances to produce equal (but out of phase) signals for the output tubes.

[@aaronatwood9298]

There are a few tricks to fix it, but then the simple cathodyne becomes way more complicated.

[@phildiegidio4658]

Uncle Doug:............You have awaken the old Air Force tube jockey tech in me. I lost my way in the Solid State world and do very well to fix these types of Amps. Minus the high density stuff and multi layer boards that are impossible to desolder. Anyway......we are a breed from the past and will be missed. I am heading to retirement and am fixing amps to give them and the kids a second chance. Ebay is a great source of broken amps that don't take much to fix. Especially the Solid State stuff. You are my hero, and I greatly appreciate your no nonsense method of explanation. Thanks for bringing back my interest in tube amps. I still like the better frequency response of Solid State............but the harmonic presence of tubes is the real magic. You are the man. Phil from Philly.

[@UncleDoug]

Thanks so much, Phil. Rusty and I are honored by your kind words, agree with your comparison of SS precision vs tube "magic", and wish you the very best with your rekindled interest in tube amplification. Indoctrinate all the young people you can......so this art does not die out (with us).

[@kungfooo]

Doug: This is the first time someone explained the paraphase inverter in a way that I understood properly and now I get how this works in amps with two channels, one feeding the one side of the paraphase while the other channel feeds the other. I could not understand this before, but now it's very clear. Thank you.

[@UncleDoug]

You're welcome, KF :)

[@kcrmson]

Don't try using "Let me center tap your output transformer" as a pickup line on the ladies, I just did and got slapped. ;)

[@UncleDoug]

+kcrmson I guess that's better than offering them a chance to see your ground lug :)

[@kcrmson]

+Uncle Doug hahaha, you win, you win

[@hippiekarl7]

+kcrmson That line caused a spike in ~resistance~

[@gyrgrls]

+kcrmson You want to insert your pole piece into her voice coil? Shame on you. That woofer really pumps...

[@oneofthemodels]

kcrmson hahaha that's pretty damn funny dude I'll have to remember that one!!!

[@robotsongs]

Dang, Uncle Doug. I've been watching your videos for years and years, and I've started and stopped this one several times in confusion. But I just came back to it again after another couple years and more study under my belt, and it made perfect sense and explained succinctly everything I wanted to know. Thank you so much for this gift! You're awesome.

[@UncleDoug]

That's great news, RS. It's always best to revisit troublesome topics and work your way through them :)

[@SeanLewismd]

You're awesome, uncle Doug! Everything I need top get my amp worked out! Keep doing what you're doing! Super inspiring!

[@UncleDoug]

Sean Lewis Thanks so much, Sean. Rusty and I are glad the videos are helpful :)

[@annomaus8386]

At last! Now I know why it's called a cathode follower. This is the first video or article in 3 years of searching that bothered with that very useful fact. Thanx Uncle Doug!

[@UncleDoug]

You're welcome, Chuck. We're glad the video was helpful :)

[@HHTTRRNN]

I really appreciate this common sense explanation of a process that easily escapes understanding. Excellent presentation! Many thanks.

[@decsnspace]

Another great video Uncle Doug! Extremely informative and in less than a half an hour you've explained some difficult concepts on phase inversion that I've been trying to wrap my head around for over a year! Can't say enough about how much I've learned watching your videos! Thanks again!

[@UncleDoug]

You're quite welcome, Dec. I tried to keep the video as clear and focused as possible. I'm glad to hear that it was helpful. Thanks for the kind words :)

[@mister60066]

Uncle Doug, you are amazing! Thanks for all the information, I redrew all the schematics in all your video's so far, i love them!

[@UncleDoug]

+sirmarcou You're welcome. I admire your dedication, and really appreciate your very nice comments.

[@harveyellis6758]

Great video. Yes, I know more than before watching. Always a pleasure to visit your channel to learn!

[@UncleDoug]

Thanks, Harvey. Mission accomplished :)

[@framusburns-hagstromiii808]

Fantastic stuff! Great explanations. Thank for going through examples of the three most common types of audio circuit tube phase inverters, finally cleared up my confusion!

[@UncleDoug]

It was our pleasure, FBH :)

[@nicky5185]

The horse analogy is brilliant. It made me understand the concept perfectly. Perhaps that is what makes your videos different and more attractive than those others who adopt a more academically correct approach.

[@UncleDoug]

Thanks, Nicholas. I'm glad the use of analogies helps to clarify the more abstract principles.

[@starsighter13]

Another great tutorial on amplification from Rusty and Doug!! Well done, keep them coming you have a lot of very appreciative fans!! Thanks for the time, effort and thorough yet straight forward explanations !!

[@UncleDoug]

You're welcome, Jim. We're both glad to hear that the videos are helpful :) ^. .^

[@douglasRbrown]

I've been watching your videos for years and find so much info and enjoyment from them. Thank you Sir.

[@UncleDoug]

You're welcome, Doug.

[@Shadowcruise99]

Just ran across this particular video, Doug. I think you did a phenomenal job of explaining practical phase inversion. Thanks so much for posting this!

[@UncleDoug]

Glad you enjoyed it, SC.

[@petermayonejr.3420]

Excellent, captivating, educational, substantive, information on all the intricate operational features of tube amps; The BEST on the web! TY.

[@UncleDoug]

Wow.....thanks so much, Peter :) Please see all our other videos. They provide a gradually increasing level of complexity to the basic foundation laid in this video.

[@stevenstewart5980]

Another great informative video! Thanks for covering this topic, Uncle Doug!

[@UncleDoug]

You're welcome, Steven.

[@ColettaHughes]

I'm grateful for how simply you explain things on your channel, it helps me to understand electronics a lot better. You give enough information to understand the basic build and enough information that leads one to dig deeper if they so desire to know more. Thank you :)

[@UncleDoug]

You're welcome, Coletta.

[@jwan148]

Thank you, Uncle Doug! Your videos are so easy to understand! I wish my lecturers could explain as clearly as you! Please keep making these videos!

[@UncleDoug]

+Jason Wan You're welcome, Jason. Rusty and I are glad our videos are clear and helpful :)

[@wildbob]

Thanks for this video. I don't think anyone else could have done it so well. Valuable resources.

[@UncleDoug]

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

[@carvingbone]

Fantastic videos, really well explained, first time I understood the phase inverters and their differences! I also really like your respectful style, a rarity on youtube and the net... something to treasure!

[@UncleDoug]

Thanks so much, CB. I'm glad to hear the videos are helpful. I also appreciate your comment about being respectful, which we could definitely use more of....both in life and on KZbin. I definitely try, and it pays off when the vast majority of comments and responses are pleasant and supportive, as is yours. Farewell and best of luck !!!

[@marsattacks7071]

Thank you very very much Uncle Doug for those explanations ! I've been trying to understand that for a couple of years now and you made it clear for me. You're a great teacher !

[@UncleDoug]

You're welcome, Eric, and thanks for your nice comments. We're glad the video was helpful :)

[@treborheminway1196]

Anytime you get an electronics lesson combined with a Horse analogy from UD, you know that 1) its a good day. 2) your much less likely to forget the lesson. What a great teacher!

[@UncleDoug]

Thanks so much, Trebor :)

[@newtechgs7471]

Doug thankyou so much for all your videos, by far the most comprehensive ive ever watched

[@UncleDoug]

+NewtechGS You're welcome, NT.....glad you like the videos :)

[@stevenkimsey7039]

I find this fascinating. It's an older lecture, I understand. Professor Doug is always worth a curious person taking a look at older videos/lectures. Thank you Doug for sharing 👍🍺

[@UncleDoug]

The pleasure is ours, Steven. Thanks !!

[@zopilotesky3014]

Another outstanding explanation, this time regarding tube phase inversion. Books are filled with potential knowledge but there's no substitution for a good teacher. Thanks!

[@UncleDoug]

You're welcome, ZS.

[@MrUbiquitousTech]

Very good, clear and easy to understand descriptions. Really appreciate it!

[@UncleDoug]

Thanks, Shy. You're welcome.

[@tgirard123]

You totally hit your target audience. this made more sense to me than all the other videos I've watched. In fact, now that I understand this better I can watch those other videos and really have a clearer understanding as some of those videos go into deeper concepts. Thanks again for all of these

[@UncleDoug]

Thanks, Timmy. That was our goal :)

[@buntafujiwara3586]

I haven't watched this video for years. It was worth watching again. Thanks, Uncle Doug.

[@UncleDoug]

Glad you enjoyed it, Bunta :)

[@bondsongmusic]

The best explanation of this subject I've ever seen. Thanks a lot!!!

[@UncleDoug]

You're welcome, BSM :)

[@chrismitlyng1411]

Great information and explanation Uncle Doug!! I am new to the BYO community and I am lucky enough to have a great friend who is helping me build my own tube amplifier. Your videos are perfect for me at my level of understanding and I am greatly appreciative of all you offer. Thanks so much for your time and dedication to the craft!

[@UncleDoug]

You're welcome, Chris. Thanks for your very nice comments and best of luck with your project.

[@UncleDoug]

Alice Lane: For some reason, YT will not allow me to respond directly to your question. If you are referring to the 0.1uf @ 200V cap in the Fender schematic, according to Randall Aiken, it is a coupling capacitor for the lower grid and it works with the 500pf coupling cap (to the upper grid) to enhance bass response in the phase inverter stage.

[@henryburt72]

Once again you came through! I am a newbie with 1 5E3 build and each time I discover another part of the amp that I have no idea about - I search for one of your videos. Thanks for demystifying more of the magic.

[@UncleDoug]

You're quite welcome, Henry. Best of luck with your projects.

[@lextrip123]

So great! All your videos! Thanks Uncle Doug!

[@UncleDoug]

You're welcome, Lex.

[@michaelmiller-ce4du]

Doug, you are the most informative teacher on YT. Some can relay information but the best teach in a way that gives understanding on the listeners part. You're one of the best and much appreciated. I have spent hours pouring over Fender circuits. Now I understand how they work. Thanks! You're awesome!

[@UncleDoug]

+michael miller You're welcome, Michael, and thanks for the very nice comments. Rusty and I sincerely appreciate them.

[@r.charbon2028]

What a splendid video. The horse analogy is one for the books, clear and understandable. Thank you again Uncle Doug.

[@UncleDoug]

You are very welcome, RC.

[@josquinmingus]

Terrific content. I watch your videos to understand radio circuits. Your explanations and illustrations are easier to follow than any radio-oriented video I've come across (and I've watched many). Thank you, Uncle Doug!

[@UncleDoug]

Thanks for your very nice comments, Jos. We're glad the videos are helpful.

[@waynejohnson6594]

Thank you so much for making these videos. I have learned so much from them. I just bought a champ clone kit for my first amp build, & am looking forward to building it.

[@UncleDoug]

You're welcome, Wayne. Good luck with your project.

[@nickvictor7398]

Thank you uncle Doug for all of your information and teaching ability. I have learned much from you.

[@UncleDoug]

You're welcome, Nick

[@richclayton5785]

I was referred to you and this vid by a bunch of great folks at the Marshall Amp Forum. Thanks for making muddy waters clear for me.

[@UncleDoug]

You're welcome, Rich. Glad the video was helpful.

[@joneoo73]

Loved the explanations in this video. You made it much easier to understand the use of other components in the circuit and how they are related to each other. And like you said, you can always repeat or rewind to se if you missed something. Definitely I'm a dedicated fan

[@UncleDoug]

Great to hear, John. Welcome to our channel :)

[@George.Andrews.]

Thanks Doug . Very easy to keep up with you . I know more now than a little while ago. Mission accomplished.

[@UncleDoug]

You're welcome, George. That's our goal :)

[@sixstringmarauder]

Once again ,splendid job uncle Doug, I love the visualization you bring with things like the horses pulling in the same direction, being a mechanic for the past 30years it helps when I can visualize the inner workings of these systems.

[@UncleDoug]

Thanks, David. I think that providing "mental pictures" of abstract events really does make them easier to understand. Like you, I've been a mechanic most of my life and this approach just seems like a natural progression.

[@tonyhills2112]

As usual, Doug’s tutorials ring clear as a bell. Superb!

[@UncleDoug]

Thanks so much, Tony :)

[@russellsmith4615]

Great stuff, Uncle Doug. Really have enjoyed your presentations. You've presented these all videos with simple, direct, concise explanations that have made it easy for someone like me (who has just enough electronic knowledge to be dangerous) to be able to understand the theory and concepts. With your tutorials (and a few other How-To videos) I've been able to replace old worn out components and update my '72 Fender Princeton Reverb & '77 Vibrolux Reverb amplifiers so that they are now up to the specs they had when they were shipped out of the Fender factory. They now run clean and quiet, and the tone in both these amps is stellar! Well done! And additional thanks to your four legged assistants! Cheers

[@UncleDoug]

You're welcome, Russell. We're glad you were able to put the videos to good use.

[@MC-bu6ez]

Thank you for such a great explanation of phase inversion, a subject quite complex for non specialists to follow, great tutorial.

[@UncleDoug]

Glad it was helpful, Mario :)

[@bullthrush]

It's all so simple...now! Thank you for another excellent explanation, and a well done to Rusty's camera work!

[@UncleDoug]

You're welcome, BT. Rusty was also holding the pointer.....since my hands were required to act in several scenes :))

[@joeseefeldt8192]

Wow. Simply the simplest and most understandable explanation of phase inversion I have encountered. Thanks Doug. I know so much more now!

[@UncleDoug]

Thanks, Joe. That's our goal :)

[@sweetharddussigut5619]

What a fantastic explanation! Thank you so much for your videos. It's like having a library of knowledge. All the best with greetings from Europe!

[@UncleDoug]

You're welcome, SD. Likewise :)

[@thechangee]

Great information and thanks for taking the time to post it. Look forward on your next videos.

[@UncleDoug]

You're welcome, TC. I'm glad the video was helpful :)

[@jessecripps7830]

I agree with most sentiments on here...I've been trying to digest this information through studying schematics for many, many years and this video has finally delivered me unto a basic understanding. I'm very grateful and excited to move forward with my projects.

[@UncleDoug]

Thanks, Jesse. That's great news :) We're glad it was helpful.

[@edwardkujawa]

trying to understand whats on paper sometimes not the same theory versus practical application and what instruments t ue to diagnose problem in circuits some . instruments better than others{ I mean Test Instruments}

[@UncleDoug]

@@edwardkujawa Thanks for sharing, Ed :)

[@matieupizil424]

Thanks, so much. This is actually sinking in. My word, you must've been a wonderful teacher to study under. See ya again, real soon. Staying safe with tubes

[@UncleDoug]

You're welcome, Matieu, and thanks for the very nice comment :)

[@ianbrereton4783]

Thanks so much for this, your analogies are great! The 'horses with tails tied together' gives a great visualization of whats actually happening across the output transformer. You've got a real talent for communicating these rather abstract things into plain english!

[@UncleDoug]

You're quite welcome, Ian, and thanks for your kind words. I'm a firm believer that, when presenting a complex concept for the first time, simple analogies are much more effective and palatable than scary equations involving Greek letters, terms like EMF, and unfamiliar words like Reluctance and Flux Density. Once the foundation has been established, those embellishments have their place, but not before.

[@PrinceWesterburg]

Thats crazy, it all makes sense - for 35 years I've carried the idea that push pull amps have a 'phase splitter', that one valve pushes and the other pulls with half the waveform sent to each - I always wondered why there wasn't a gap in the middle where diode lag killed low voltage signals! D'oh!!! All my amp builds are single ended as a result of not understanding this - except for my Marshall and the Radford STA-15 in my living room. Thanks for that, its all making complete sense at last!

[@UncleDoug]

I'm glad to hear that the video was helpful, Prince, and that your concept of double-ended amplification is now clear. Let us know how your first DE build turns out.

[@sachmostaub1990]

Beautifully explained. I enjoyed every minute. Never had any idea of how tubes functioned. Thanks

[@UncleDoug]

You're quite welcome, Anne Marie :)

[@Rodedog55]

Thanks Uncle Doug ! I Love your Videos and Teachings here ! Keep Preachin' and Keep Teachin' !!! Your videos are valued highly !

[@UncleDoug]

Thanks so much, RD.

[@BoHunter2010]

Awesome presentation. Thanks again for all you do!

[@UncleDoug]

Thanks, Bo. It our pleasure :)

[@philipdonovan6510]

Very informative and well explained video. I'm ramping up for a build starting with a Princeton reverb but giving it a long tail pair inverter. This makes it make sense! Thank you.

[@UncleDoug]

That's great news, Philip. Best of luck with your project.

[@williambiddle5683]

Doug you are a huge help to us and a fantastically gifted educator. thank you Sir

[@UncleDoug]

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

[@Ricksworldtv]

Thanks Uncle Doug for explaining how the signal amplitude is compensated for in the phase inverters.

[@UncleDoug]

I'm glad you enjoyed it, Rick.

[@cmguitar50]

Doug Thanks again for a great video and it answered my years long question about the 82k/100k load resistors. I never thought they were double purpose until I looked at phase inverters and your explanation!

[@UncleDoug]

You're welcome, CMG. I'm glad the video was helpful.

[@LEANDROID14]

Excellent video! Very clear explanation with useful examples, UD you are the man!!!

[@UncleDoug]

Thanks, Leandro. I'm glad the video was helpful :)

[@therugburnz]

I'm watching again. You explained it well the first time but I'm planning on making some hybrid(gasp) amps as a study in my Old Compactron TV Tube project. Your language makes it easier to explain to others what I'm REALLY doing. Thanx

[@UncleDoug]

I'm glad the video is helpful, RB. Best of luck with your project.

[@DaBadger354]

Thanks Uncle Doug you've done it again for me, really great video hope you continue to make many more in the future.

[@UncleDoug]

You're welcome, Steve. We will definitely keep trying :)

[@patthegunsmith]

Thank you so much. An absolutely clear, logical presentation and an exemplary occasion of what teaching should be.

[@UncleDoug]

You're quite welcome, Pat. Thank you for your very kind appraisal :)

[@mp-ov9dh]

Doug, I am very impressed with the videos. I have watched so many others on the subject and was always left with more questions at the end. I have a much better understanding now! Give Rusty an extra bone for the good work..

[@UncleDoug]

+mp224 I will, MP. Thanks for your very kind assessment of our work :)

[@whynotme5926]

Great stuff. You make things simple as they can be. Thanks.

[@UncleDoug]

You're welcome, WN :)

[@themarcoharder]

Finally, an explanation of phase inverter principles that I can understand, particularly the LTPI section. You really have the mark of a great educator, Uncle Doug. Thanks!

[@UncleDoug]

+themarcoharder You're welcome, Marco.....glad it was helpful :)

[@daveschings828]

Thanks for the clear explanation for phase inverters! You teach tube theory better than it was taught to me in the Navy Electronic Technician School back in the early 70's. I'm just learning guitar but for some reason I keep looking at tube amplifier schematics, I guess I just want one 😃

[@UncleDoug]

We appreciate your very kind words, Dave. I hope you get a nice tube amp in the near future :)

[@DetroitWrecker666]

Uncle Doug, as you know, the past few days, I have been taking a crash course with your videos. I am learning SO MUCH!!! And using the Schematic for my amplifier, to follow along. Everything is becoming clearer! Thank you!

[@UncleDoug]

That's great to hear DW. Best of luck with your continued education.