You are 120% better at teaching than any of my EE professors. A+

This video is excellent. That is the first time in my life that I have ever heard a satisfactory explanation of the difference between resistance and impedance. Thank you so much. I'm learning so much about valve amplifiers just from watching your videos. I'm very grateful that you have taken the time, care, and planning to share your knowledge with us.

I'm retired Industrial electrician and a ham radio operator for 40 Yrs but I learn something every time I watch your videos. In a word, they are brilliant. Many thanks.

I have to say, Uncle Doug, you are one of, if not the best, teacher I have ever encountered. Your explanations and accompanying diagrams are phenomenal. Thank you so much for all that you do. And please thank Rusty for teaching all of this to you. 👍🏻

Very good video. I have only one criticism: Please do not apologize for the use of math nor for getting into the numbers involved in calculating these concepts. That is exactly what's wrong with our generation is that people have become afraid of (or at least disinterested in) anything that requires exertion of mental capacity. If someone wishes to become good at audio electronics engineering, they'd better get over any aversion they may have of numbers. So sincerely, please do not apologize.

Uncle Doug, you are a national treasure. Thank you!

You explain things well enough that I (a math zero) have a chance, if I watch this over and over, of getting THE MATH! Thanks for your patience!

Thank you Uncle Doug! I wish we had more teachers like you around.

I have just found your channel in 2021 and I am having a great time going through the catalog. I have learned a lot and have had it on in the background of the shop for the past week. You are a great teacher!

Your videos are so important for future, and us current, generations. This is invaluable information! Thanks Uncle Doug.

This presentation is absolutely phenomenal. Simple, elegant, best verbal delivery to encourage learning and retention.

Uncle Doug, your contributions to KZfaq are priceless. Thank you!

I really appreciate you doing this. I'm watching and doing my best to take in bits in hopes that one day it will all come together and I can say, "Yes, I can build an amp. A dual 6L6'er."

Such a well explained article for electronic starters

WOW! Uncle Doug is the best teacher. Simply the best explanation of resistance and impedance. Wish I had found him a long time ago. Thanks.

A simple yet complete explanation of what could be a confusing topic! You're a gifted teacher Uncle Doug.

Uncle Doug you did a nice job covering this topic. There is one other small point that I have never heard anyone mention concerning the speaker impedance and that is this. While the voice coil is the main element involved in the speaker impedance we forget that this coil of wire in also located in a magnetic field. The location of this coil makes for a totally different circuit than if it were just an air coil as the inductance changes. This may explain why some guitar players say they like the sound of certain magnets in their speaker as well as a certain type magnets in the guitar pickups. Since the magnet type can change the sound of something do to the metals used in the magnets and the magnetic energy of the magnets. This could be something you may want to think about doing a video on. Since the magnet type can change the sound of something do to the metals used in the magnets and the magnetic energy of the magnets. Thanks.

What a gold mine of information ♥️♥️♥️♥️

Besides the perfect approach to the matter, being me italian, I do appreciate your always perfect and easy to understand english! Thank you very much!

It's 2022 and I enjoyed a couple of your video's now and the one thing that surprised me most: You apologized for the math! Hahahaha, thanks for all the effort! The knowledge and theory is getting banned from school more and more every year. Alle the basics are brought down to an absolute minimum, so your teachings are worth the minutes in gold!

Thank you. Very generous of you to share your knowledge sir.

Can you make your next video on the mains/power transformer please ?? You are the man!! I love all your videos !!

You are a gifted teacher, Doug.

You, sir, are a gifted teacher

Thanks for the lesson. Learned this stuff over 40 years ago, but forgot a lot of it. Btw...don't see em a lot with todays fancy digital meters, but I love the old Simpson 260 meters. Tough as nails and last forever! There's just something better to me to watch the needle than a bunch of numbers. Guess I'm old fashioned! And gettin old too! Lol☺

Excellent explanation!

The best explanation ever about the difference between resistance and impedance on KZfaq.

Thank you. I have never been able to get an explanation to so many questions in such a great way. I so much appreciate your time and knowledge.

An excellent transformer treatise. Thank you.

We All Appreciate you Uncle Doug !!! Thanks . . . I'll keep watching !

The best information on the net about XL and transformers.

Uncle Doug, thank you SO MUCH for sharing your knowledge! I know I have said it before but, you have no idea how much you have helped me. AND, I am VERY MUCH enjoying my new hobby of working on tube Amplifiers!

all the years of using my Marshall major and my other tube amplifiers I never had the idea of why these negativities could happen here's why in the way you just explained it 🙏

Reactance + Resistance = Impedance. It's now so simple! Thanks so much Uncle Doug! I already knew about the winding ratio but finally I now understand impedance. Wonderful :)

Excellent video Uncle Doug! If only all teachers were as clear and thorough as you.

It's Amazing how smart you are Uncle Doug. God Bless you and your Family.

I am getting a better understanding of how amps work than I had just a month ago. You opened up a huge door into tube electronics for me. Don't let the hot rods distract you!

Great straight-forward information..the math is necessary for anyone entering the field of electronics....just gotta suck it up and get used to it! Go Uncle Doug..I'm loving it!

This channel is beyond incredible. I took my fair share of EE classes in college as a computer engineer, but never before has someone been able to truly explain what these terms are, and especially well by explaining why they are named as such! Amazing job. I just watched your video on the 5F1 yesterday for the first time as I'd been looking for an in-depth component by component breakdown of how that circuit works, and no one yet has described it better. What an awesome teacher you really are. Thanks Doug.

Incidentally, the VERY best electronics course on vacuum tube circuit design and operation was the ack section of the OLD RCA Receiving Tube Manual out of the 60's. A couple years of electronics education in a few weeks, and dead easy to understand. I just ate it up. Then I designed and built my own amp roughly based on an RCA circuit and I pushed my 6L6's for 100 watts of clean sound. I used a tiny resistor in series with a 100-watt light bulb connected to the 70-volt-line output tap (meant for use on disttibuted PA systrms) on my special output transformer. I put a speaker across the resistor to sample the power going to the light bulb. It was clean and the light bulb was hitting way over 100 watts. This is what you can do with proper design. I had chosen to raise the plate voltage and put a cooling fan on the tube though. And little resistors on the tube elements to prevent parasitic oscillations.

Uncle Doug, you are a INTERnational treasure. Thank you!

Again I have learned things I wanted to know for a long time. Some fifty years ago I built simple tube radios with only a wiring diagram. It worked well, but I did not understand everything. Now it getting clear, thanks to you, Uncle Doug.

You are a very good teacher. In the last 3 hrs, minus time away, I learned so much about a subject that was BORING in HS and college plus solid state was the latest thing (if it ain't broke don't fix it!)

Thanks' Uncle Doug.I was watching your videos' a few years' back, then stuff came up and I am now getting back to them!Really informative and some info that I wish I had,some years' ago.I hand-wound an output-transformer for a prototype amplifier that a friend of mine was building and we were doing a lot of guess-work,at the time!This explanation video helps' so many people to understand the "black-art" part of tube electronics'!Thanks' again for your generous offerings' and sharing your incredible knowledge with us!

Your teachings are some of the best on KZfaq. I greatly appreciate the time it takes to put together these videos. The more of these educational videos you make the better off we all are. Thank you so very much I know how time, effort, and energy it takes to put these together. With appreciation...

At 65, I am finally taking time to relearn what electronics I learned in grade 13 which was mostly tube circuits. Having forgotten most of that, it is a real pleasure to study with you. My interest is Stereo tube amps and they are so much like guitar amps that your teaching is right on. THANKS

Sir, I must declare you a living miracle-worker! You have actually managed to convey knowledge into my logic center which had previously been quite indecipherable!! Thats amazing! This is a great great vid thank you so much!

I am new to your channel and am very glad that I found you because nobody else is teaching this stuff and certainly not in the down-to-earth manner that you do which makes it very easy to understand and digest! Thank you for the excellent education!

Thanks Doug for a very clear explanation. I looked for this type of clarification elsewhere and couldn't find it. I was amazed however by how willing people are( who had no idea what there talking about) to explain it.

You Sir are the cool old Uncle some families have that does all the cool stuff with all the cool knowledge you've obtained from a cool life!! Uncle Doug = Cool Yoda!

Dear Uncle Doug, the power of knowledge is zero if it's not shared and passed on. You are doing exactly that - sharing knowledge. I've seen few videos of yours, and the way you are explaining, the tone of your voice and the drawings you're using - are all together making things easier for dummies like myself, eager to learn about tube amps (because they are sick and tired of transistors and op-amps, ha!). Thank you form the bottom of my heart and keep up the good work!

THANK YOU SIR. Finally an explanation that is simple and clear. Radiotron Handbook was driving me crazy. 🌠

After 43 years on this earth, 15 of which I have been a professor of electrical and computer engineering, I finally understand what speaker impedance mismatch means. Thanks, Uncle Doug!

These are great video's, thanks for them. I'm a retired Electrical Engineer who's hobby is guitars and old amplifiers. I find your video's informative and fun.

Wonderful video! Not only does a great job of discussing the basics of output transformers, Doug also clears up the confusion for me regarding resistance vs. impedance. Thanks Doug!

I feel smarter after I watch your videos. Thanks uncle Doug

It seems that the best teachers are on KZfaq and you, my friend, are certainly among them. I hope this wasn't already asked. I looked for it, but 1397 comments is a daunting task, so please forgive me if I'm being redundant. Thanks to this episode, I now understand why my multi-meter always produces a value lower than the spec sheet, when I attempt to measure the impedance of a speaker using my shiny new multimeter. With that being said, what is the best way to determine a speaker's impedance, since it cannot be accurately determined with a multimeter?

Finally, someone who knows how to teach! I have never found a better explanation of tube and transformer characteristics and there application than this. Thank you! new subscriber

Have to say Doug you are an amazing teacher. The smoke clears every time you speak. Greetings and best wishes from Yorkshire UK.

I wish you'd been my electronics lecturer, "back in the day". You have the knack of taking a complicated subject and making it seem simple, enjoyable and intuitive. Come over to Australia and let's build an amp together!

Without doubt ,this is the best way to learn about circuits. I'll be back here a few times yet. Well done. ( Subscriber )

Once again, this is a fantastic video. I busted out my old RCA tube manual and looked up a 6V6 and saw the 6600 impedance and got giddy because I finally understand what that number means. I have a box of transformers, tubes, sockets, caps that are all going to finally become tons of small amps. Thank you so much for all the time you put into these videos.

Time for more honesty here... I worked for a pro audio company with an owner who claimed to be an electrical engineer (I've often doubted whether or not he graduated). He could not explain how any of this worked. I took a high enough level of physics in college to know the guy was full of beans. It is all finally starting to get clear. AWESOME videos.

I highly appreciate any of your KZfaq Land videos. So much to learn and allways using the correct terms. Makes it so much easier to understand. What I want to say is that using the right terms is ways much more better than prattling about which is so often seen on other channels. Like the car's stuff too.

Hay Uncle Doug! You have really helped me remember my electronics coarse in High school. mid.70's. we had a great teacher who was a radar tech in the 2nd. WW. he really tried hard to help us understand all this amazing stuff. Its been many years since i felt such a strong disire to dive in to this amazing stuff again. But i plan on finding some time soon. Your a very good teach! Blessings

This was the most informative‌, most right to the point, and most useful video on the topic! Not only you covered the theoretical aspects (which I came for) but it also showed practical aspects (which were bonus for me). I cannot thank you enough! Really!

I watched this the first time a month ago and learned a great deal, but what I have used most since is the phrase "I invite you to try because it's one of life's great disappointments when (insert impossible idea here)". Thank you for all this great content and specifically that phrase. 19:50

Great video. I'd also like to add, for the benefit of others, that there is a direct correlation between the impedance of a device and the frequency of the A/C signal applied to it. For example... You have an 8 ohm (impedance) speaker. If you measure the resistance with an ohm meter, your reading will be about 6.2 ohms. The way that a manufacturer determines the impedance is by using an A/C signal of (typically) 1KHz. At 1KHz, the speaker presents a resistance of 8 ohms. With that in mind, using a lower frequency, the resistance will be lower. Using a higher frequency, it will be higher. This is why we measure the resistance of inductive devices (transformers, speakers, chokes, etc.) in terms of impedance. When referring to the 'impedance' of something, we are differentiating that we are not measuring the D/C resistance, but rather the A/C resistance at a specific frequency. I tried to make that as short as possible, so I hope it makes sense. Thanks!

Great lesson. The impedance of your teaching was a perfect match to my brain.........

Thank you-Funny I ran across this video when I did. I was just looking at 3 output t. f.'s in the ao-33 and trying to figure them out about one hour before this popped up on my you tube feed. I was practicing studying the amp for practice before I start one myself. It has two treble and one bass circuits in the amp and guess I could use the same layout as each stage and same tubes to use those transformers? But, now I can figure them, thanks to your help. Don't know what I would do without your knowledge!!! Thanks again.

Terrific vid.Even “i” understood the numbers.And that is saying something.Normally anything like that, and my brain shuts down.But this was great.Thank you.

I understood all of that, and I did the art school thing, so the sums are simple! And just when I was thinking, hey, you could get a winding ratio from resistance that idea was shot out of the sky... But now I know why. Clear as a bell, sir. Thanks.

Seven years a sparky, it's been a good education on how to be safe with electricity. A few months ago, I revisited theory fundamentals, I've been so amazed by learning I'm not sure if I'll ever get to actually work on anything. I picked up a Hammond aurora 8200 for free on craigslist last week. It's a solid state system, I took it apart so fast I didn't document the connectors on the amp, signal inputs, supply outputs, whatever reverb driver means, output transformer connection. I looked for hours and couldn't find any technical information on it, or even a good old amp teardown on youtube. I'm still so fresh with electronics I look inside the amp and I can tell there's gonna some gratuitous groping in the darkness without some relevant information. I'm going to have to table this and find a simpler project. I picked up a Juliette record/8 track player for a dollar and the balancer pot plays both speakers on the right side and nothing on the left. I have chopsticked all around in it. Could it be as simple as the pot is shorted, open, ungrounded or that it's designed this way somehow? Thanks for any help and much love.

Best explanation of resistance vs impedance I have heard!

Doug, Nice layman's terms explanation! Harp players seem to love a mismatch like a 16 ohm speaker on an 8 ohm tap. Putting a 4 ohm speaker on an 8 ohm tap is a great way to burn things up. I have seen a shorted voice coil running at 1.2 ohms on an 8 ohm tap. Thankfully, all I got was a really good light show! I own an old ESI Teague LCR, but the Variac dialed to 1 volts secondary works fairly well, but RMA, NAB etc generally used 1000Hz as their test freq. You will have to use a lower B+ and the 6L6 pair won't deliver much more than 30 watts, but it will be a nice amp. At 5200 ohms you will get 60 watts from a pair of 6L6GCs, 5881s, 7581s, KT66s etc. When I went to college there was a discussion of teaching ohm's law for DC as AC theory with a 0 degree phase angle. Let's face it, going from DC to AC theory was a major learning curve for most people! NEVER say you are sorry for the math! NEVER! That math is what keeps us from screwing up more often than we do already!

You are an excellent teacher, thanks so much for all of these KZfaqs.

Thank you so much for shedding light on an area that as a musician and collector of old amps I am interested in but have always been shy of investigating. Very clear delivery.

As always, excellent info here for everyone. You have given the gifts of your time and knowledge. Say hi to Rusty if he’s still around.

Love, love, love your work and teachings... I have a few friends struggling to understand electronics, I am sharing this video (among several others) to help them with the heavy lifting, falling so far out of audio'fool'dom. Doug you are a master teacher... Thank you for the effort!!!

WOW Such a great explanation and the math wasn't too hard to comprehend either. Thanks so much for this. This video gets saved straight to the reference library of other useful videos on Valve Amplification

After using your method and Mr. ElPaso's method, I determined which were the primary leads. Also, the ratio is approx. 5500 to 1 for a 4 ohm load. Your videos are most informative.

I am SO glad I watched this series of videos! You have explained Impedance in a manner that I actually understand. Thank you!!

This video was extremely helpful - Great Job and thank you so much for the effort and time you put into these video's. I've been studying tube amp circuitry for the past year and the fog is finally starting to lift!

If only you had been my math teacher in 7th grade...I would have actually learned something. Thank you for all your great videos.

What a spectacularly amazing video lecture. This is a must-watch for anyone from an audio & DIY enthusiast all the way down to high school and college level students who are studying electronics. All in all a fantastic watch!

Hey Uncle Doug. I am finally getting around to learning tube amps. I just want you to know that you are an amazing teacher. I am a HVAC tech and have an understanding of basic electricity and you explain things in a manner waaaay better than any tech school teacher ever did. I am not sure if you are still making videos or not not, but please keep it up if you are. Thank you thank you thank you! Ryan Wham

Love this video explaining the impedance Z (Xl) and ohms... great technical information you have broken down into terms that most can understand.

@ 19:23: I often do it this way - hooking up the variac at the Lo-imp-side of the OT. This is a good way to test OT´s for shortcuts etc (as you can easily compare voltages between center tap and both plate-taps or also screengrid-taps for their symmetry). What I do in this case: I put another transformer inbetween. It works great this way: variac -> primary of a tube power transformer / 6.3V (or 5V) tap´s of this power-transformer -> secondary tap of the OT / -> primary OT taps -> probes of your multimeter. Then tell Rusty your values, and he´ll tell you what to do with this transformer!

Thank you for such an illuminating video! You have a great talent for passing on technical information in an accessable yet scientifically rigorous way. Many thanks 😊

This is the best video tutorial on OT's I have ever seen. Thank you for this uncle DOUG!

The best explanation about speakers and impedance, ever!

Hi Doug and Rusty; Thank You for Your Patience with me.. And Thank You for Your Great Answer.. A little while ago I found Dennis Carter, and His Video's give me, even more of what I am looking for.. Not so much in Output Transformers, but the Rest of the Set, which is even more of where I need Help... The Front end is where I am having the most trouble, and the Questions I have asked You was to complete what I needed to know for the Amplifier or Back End.. Thank You for doing such a Great Job !! THANK YOU Marty

This lesson is pure gold! Thank you Uncle Doug!

Just watched this video and I have got to say, you explain this with fantastic clarity. It has been a pleasure to watch, thank you.

Thanks Doug, this helps me...I am not afraid to tackle my Hot Rod Deluxe...worst case scenario, I strip it down and do a hand wire job using said chassis, speaker, and cabinet. Thanks for all your knowledge.

I built two 'World Audio Designs' K5881 Power Amplifiers back in 199something and have been very happy with them driving a pair of Tannoy Definition D500 speakers. A keen electronics armature I did not manage to destroy the equipment, or myself! BUT I could not follow what the narration of the designer when he prattled on about how 'wonderful' the Output Transformers were. I did not have a "Scobby Doo" what he was describing. YOU have just explained it all. Thank You. p.s. In Scotland "Tubes" = "Valves".

Uncle Doug thank you you are a great teacher.

A few months back I was working as an electrician in a warehouse by an import and shipping dock, removing old wiring from the ceiling to free up space in the cable trays, which were overflowing and tilting from the weight of the cables. At the end of one of the lines (most of them had been cut in various places prior to my arrival) I find a really old PA speaker (which was completely covered in many decades of fork-lift soot), mounted on the wall. It's made to be used with a 50 or 100V signal, and has a transformer built into it. So an idea strikes me: what if I were to use this speaker, and the built-in transformer to build some kind of gnarly franken-amp? Certainly would make a fun project. Well, after many months of collecting even more dirt in the corner, you've helped set me on the right path to getting this thing started, so thanks a whole bunch, Doug!

This video is just great! I wasn't expecting you to go into the Resistance vs Impedance, so that was a lovely surprise as I was needing to study up on this. Thanks again!

Thanks for this video. I used this video and one by D-Lab, to check two output transformers from a Fisher X-100C that I purchased off eBay. I originally thought I had bad output transformers, but after using your test method, I was able to verify that they are both good and also determined their winding ratios.