Impedance Ratio: The Easiest Way to Decipher Output Transformers 

Uncle Doug might be the coolest cat on RU-vid.....And DEFINITELY one of the best instinctive teachers. Thanks for another informative video, sir.

I learn more from Uncle Doug than any electronics instruction source. His smooth voice, combined with "down to basics" approach are just great. The levity of adding in a current cat status here and there are just great. I could listen to him all day, and have learned so much. He goes into technical aspects effectively, and doesn't insult as he goes way back to basic concepts to ensure he's grabbing all audience members regardless of their own knowledge base. These are just great.

This is the best hands down the best video explaining impedance ratios, in a way that an idiot (me) can understand it. I can tell you are a teacher in your profession. Thank you!

A very "in depth" look at OP transformers. This is a tried and true method of matching unknown transformer tubes to speakers, but it was not well known, until now! Your presentation was easy to understand, although nothing about impedance matching is easy, you did an excellent job of explaining it all. You truly are a wonderful teacher! Whether your students knew it or not, they were extremely lucky to have had you as their teacher! You did what I would have done with the Rat Rod. Painting the wheels did not take away from the Rat Rod's over all look. The mods you did were spot on! You are almost ready to start racing it. Thanxz

you're awesome Uncle Doug you always seem to put out something that helps me understand a project I am currently dealing with.

"if this sounds interesting...", well, you haven't disappointed yet. Another great and useful video, thanks Uncle Doug!

Bless you Uncle Doug for sharing your wisdom with us!!! I have some organ transformers from a yard sale and did not know where to start. I also have some organ tube chassis with large transformers on them.

This is the tube amp video that I needed......I have seen this referenced many times on forums, and couldnt wrap my head around it.....Thank you

...As an old Norwegian saying: Good things cannot be said often enough - you are the best teacher ever.. Thank you :-)

Uncle Doug, thanks for the inspiration! I am on my 3 vintage amp build thanks to you. Been a blast learning from you and my clones have received rave reviews. Thanks for providing the knowledge that moves beyond duplication of a circuit and comprehensive understanding of a circuit. You are a good dude!

Fantastic video Uncle Doug! This has been a huge mystery to me for years and you found a way to teach it in less than an hour. My overall understanding of amplifier circuits has just gone up a notch! Thank you sir!

This channel really is a WEALTH of information! Really great video!

Thanks Uncle Doug. My grandfather left me a box of used tubes and output transformers. Now thanks to this video I will be able to properly give life to vintage amplifiers. Thank you very much for sharing your knowledge and your work. It is amazing and impeccable as always

Once again Uncle Doug, you make it plain as day. A master.

I don't know how I missed this video. This was genius. Thanks Doug!

So useful, I can't thank you enough for posting this Uncle Doug.

UD that was a brilliant explanation! Clear concise & easy to understand! Love that exhaust tone can't wait to go on a ride along! Thank you Sir!

Thanks Uncle Doug! This is a jewel of information. Totally clarifies a lot about both tube and transformer selection. Your videos are just awesome.

Definitely, there should not be many people as calm as Uncle Doug explaining in detail the details of technical areas as specific as is the case with transformers. This is undoubtedly needed by all of us. Thanks for the explanation, Uncle Doug. Stay safe! Macedo Pinto Portugal

UD has Legendary Teaching and communication skills.. THanks for this great video Doug!

As soon as I saw this video title, I thought of how I use a pair of 6V6GT's for my 1484. I pair an 8 ohm 15" speaker with the 4 ohm tap. Interestingly, that means I can push the 6V6's to a good amount of power with less worry that I might damage that little OPT! Thanks for covering an example that is close to my heart!

All that work on the car, I am most impressed with the wheels. Great idea

Every time I have a question that needs answering about tube amps, the first thing I do is search for one of your videos. 9 times out of 10 my question will be answered in a way I can understand. Thank you for sharing your time and knowledge.

The knowledge you give is priceless. Thanks for sharing!

Excellent Tutorial Uncle Doug! I've always wanted to figure this stuff out ...and your explanation has been the most logical & easiest to understand that I've come across thus far! Keep the videos coming!

There's so much useful info in this video. I tried to like this video so many times, because I thought that it was a totally different video with new info. You're a treasure trove Uncle Doug! Btw I just repaired, retubed and biased my first Marshall amp much thanks to info that you've shared on your channel. Thank you Uncle Doug!

Ohhhhh boy! My favorite subject! Thanks Uncle Doug. People NEED to know this stuff for repairs/modifications/scratch builds. Give the kitties some pets and treats for me.

Cool stuff, Uncle Doug!

This blew my mind. I never considered the impedance of the output tubes impacting the impedance of the secondary of the output transformer. Furthermore, I was about to rewatch your transformer videos to see if I could figure the secondary impedances of the mystery output transformer I have for my next build, then I get a notification for this video. Uncanny timing. lol Excellent video my friend. Thank you

Amazing, I was just today researching how to calculate the transformer impedance of two unknown toroids I have - and then this pops up in my playlist! Thank you sir for your, as always, very interesting and educational videos! 🙂

As always, thanks for sharing. That will be one more trick up my sleeve. Great information.

Life can be terribly difficult sometimes... and when I need a healthy dose of calm, and a review of some of the principles behind our love of music and old amplifiers... I pull up a chair at Doug's place. That soothing voice... those famous quips... and the patient knowledge... and I'm all better and ready to face another day in our convoluted world. There will never be another Uncle Doug. Thank you sir! You are a saint... and greatly appreciated!

Aha! once again you've made it perfectly clear. I'm very appreciative of your knowledge! Thank you!

Watching this over Chritmass hols and want to say all the best for the new year from Portugal. Living a shoestring , delux shanti,off grid(ish(got 220 volts pluss donkeys(future transport hopefully) and setting up a small workshop to fix my amps and guitars, used to work on a valve stuff in late 60s in the Navy (FAA uk)Aircraft then had racks with Nav computers (analouge) comms transmitters recievers radar gear.,etc all driven by mini valves. At 71. now its so nice watching your vids and learning and being awakened by you,a truly gifted teacher your kindness comes over, what a softy with the critters❤ as well as your mischievous side (cars😊) thanks and hang on to the kid in you

Perfect timing UD! This is very handy. Thanks!

Once again THANKYOU! I have finally bought a 5F1 kit and making the cabinet etc. You have taught me and I think alot of others so much.

Very Excellent instructor!... Way better than my old HS Electronics theory AND shop instructors (who were just obsolete GE engineers)! You've opened up and are KEEPING ALIVE... the ART of old school tube design. I've got over 40 yrs in electronic design and now have grand kids interested in the way things used to be done (when they asked about vinyl records, and one building an amp)... so, just so you know... you have some YOUNG new fans too!!! Thanks for helping NEW generations keep the old school arts alive!

Another great and informative video...thanx!! That Rat Rod looks and sounds awesome!!

Great episode UD! thanks for sharing,nice ride!

Thanks, Uncle Doug - I learned something from your video, as expected. You made my day!

Brilliant presentation Doug.. Years ago I learnt about TX's whilst doing my Ham Radio exam, but here we are 50 years down the line and I'd forgotten most of it. I'm pleased to say I got your quiz correct which is down to your laid back, detailed & precise teaching,. Nice to see the cats & the Hot Rod as well. If you tried driving that on UK roads you'd be arrested, ha-ha !.

Dude you are living the dream! Thanks for the hot rod addendums - definitely adds color. Oh yes, the transformer tutorial was great too!

Having always wanting to design a guitar amp, the one think I've always known is the closer one matches the OPT to the tubes being used, the better the frequency response. This video is priceless for exactly that reason and so are you Uncle Doug! Thanks for all you share with us 'whippersnappers". I hope to do you proud with my amp design one day. EDIT: That Ford is looking rude! Great work!

I'm into ham radio and want to learn tubes so I can build my own AM transmitter. I am learning more from Doug about tune technology than I am about any tube radio guy on the internet. Thank you Doug!!!

Uncle Doug You gave it away when you had the color order written down. LOL!!!.. Still Your the BEST online Mentor I've ever come across.. Thanks from Austin Tx.

Thank you for the video, Uncle Doug, very clear and informative.

Excellent information Doug. Watching your videos takes me back to my VOTEC electronics classes in my high school years. I had some great instructors that really knew how to make the material interesting as well as being able to present it in a way that made learning it easy and made you want to learn more. Thanks for all of the work you put into these videos.

Thanks so much Uncle Doug! Just what I needed to check out some unknown spec OTs I have sitting around! I do love your restauration videos and repairs but I also think these educational theworetical ones are superb and so well explained! Awesome!

Thank you - people on forums make this very difficult to understand. Now i’m going to go re-test all of my mystery transformers

Another awesome and highly enlightening video. Many thanks! And the rat rod is super cool too!!

Fantastic stuff UD! This was a bit of a mystery to me, but I now completely understand it.

Best video I've seen in a while, thank you very much for your work. Wonderful car too!

Thank you so much for this uncle Doug, I’ve been waiting to see a video with this kind of info

This is exactly what I needed, thanks Uncle Doug!

This was just great uncle doug. The explanation was very clear. Another great video.

Uncle Doug, This was a great and easily understandable video. I hope that you do more for us tube amp newbies, before we ruin an old amp. And please keep us up to date on the ratrod too!

I'm so Happy! I WATCHED THIS, followed along, with my trusty calculator & actually understood this ~ I feel like I regained the knowledge I missed by not paying attention, when my father tried to instill this info in me when I was 12 years old. Thank you, Uncle Doug! Much appreciated!

*As usual - a pleasure to watch.* I love the perfect balance between serious information an subtle sardonic humour. Keep it up sir ;-) .

Uncle Doug your a great teacher, that is a rare gift these days. You really have a way about you that makes leaning fun.

UD, great looking Rat Rod, I like it a bunch.

This was long but worth every minute - its obvious you where a teacher, nice slow, even tempered pace which is easy to follow but goes in. I have a mountain of output transformers that this will be essential for - bless you sir! :D

You made that very understandable that was the first time I could comprehend how to come up with the impedance and our relates to the use of vacuum tube and speakers by varying voltage

Well presented Doug - great informative video.

Thanks Uncle Doug, a very good tutorial on measuring transformer characteristics through its impedance reflection (conservation of power). This can be a real head scratcher to newcomers and this video clearly shows the process of working it out. Very nice. Cheers, - Eddy

Great video uncle Doug! Love the pop quiz and the rat rod looks awesome! Than You

Thank you! You are a very good teacher! And you are so kind to share your experience and wisdom to explain these things in such a simple way! 👍🤗

Merci beaucoup M. Doug !!! Great video.

What a wonderful Video !! Many thanks !!

Thank you so much for this video Doug. It helped me reverse-engineer an amplifier I have. And I finally have a clear understanding of output transformers!

Amazing, I love your explanation. Great teacher.

I love your restos and rebuilds, but this is the stuff that initially drew me in to your channel. As a novice amp builder/modder myself, this information as extremely valuable. Thanks for doing it. If I may make a suggestion...do something similar with a power transformer when you can. I'm still in the dark about deciphering and adding up amp-draw requirements and stuff like that.

No single thumbs-up button is enough for the gratitude I'd like to express for a clear, concise, BS-free explanation. Thank you, Uncle Doug. Subbing immediately!

Love that 34. And your. Tutorial on impedance ratio was 😃 great thank you

Great video always learn something from them & you have some cute cats

Hello Doug, I just wanted to say Thank You for this video, I learned so much! I followed your set up and it worked great. I have been watching all of your videos and taking notes along the way. I watch a lot of other electronic channels and I have to say that your style of presenting (teaching) is unparalleled. Say hello to the kitties for me. Bart

This really explains it well. Thank you for this video.

Man, thank you so much!!! This is basically pure gold, thanks for sharing ❤

Great explanation. Finally i know how i can use a transformer that have been lying in a drawer for many years. TIPS. I used a 240 - 12 Volt AC-AC adapter made for AC guitar pedals.

Outstanding teacher!

Sensational! Super useful!

Glad i Just became part of the Family Uncle Doug. You are a Life Saver.....

That was awesome!

This video is extremely useful, I used this technique on a project I am working on and characterized the O.T.. Then in researching the tube characteristics found that the bias used, FIXED or CATHODE also changes the plate to plate output impedance.

This is great. Thanks for doing this! I learned something (actually a lot of somethings) today!

This is fascinating stuff!

Great video again! Love your car, well done.

Thank you so much for this excellent information. I have a few transformers that are not marked. This video is going to be saved in my files! Love the rat rod and thanks for sound check! Music to my ears! Great work on the rod, she is a beautiful car Thanks again!

Thank you very much on clearing up the speaker impedance schooling us on the formulations on the making us look smart to our ladies ! Super neat "rat rod" and the innovations you did on the sweet ride showing all ideas to soup our own rides and Fender amps ! Chico-Detroit

Thank you for creating this. You are amazing!

Hi Uncle Doug, fist i apologize for the long story..... second i'm a long time subscriber, have commented on numerous videos which most always got replied to in a friendly manner and i just wanted to let you know how grateful i am to one such as yourself in helping us understand valve tech a lot better. Also you inspired me to start my own video series of a cool tube project soon, will be uploading a video of it later today or maybe tomorrow but i think you will really like it. It's a 1950's Hohner Electronium amplifier originally intended for Accordeon that's going to be a guitar amp but the catch is the tube pre-amp is in the accordeon in the original combo design and i don't have that so all i have now is a 2xel84 power amp. It works fine with a pre amp pedal that boosts about 6-10db and a speaker so i won't be changing anything on the original amp but i will need to build a pre amp with parts i intend to scour from other stuff as much as possible, in the original design the pre amp tubes are fed off a cable running from the amp (yeah b+ from amp to something you hold in your hands...) and the socket is still there on the chassis so i hope to find a plug and build a Fender Exelsior type separate pre amp. Sadly i don't have the original cabinet but what i do have is easily just as or maybe even cooler, an old RCA400 Deluxe suitcase speaker cab covered in dark green/brown Croc skin tolex with a metal grill screen. I intended to just gut the amp for parts because i wanted to build a Marshall style head and cab instead of a combo but when i went to pick it up the guy also had this cabinet laying around and i decided to buy that too and build this combo. Anyway .... long story short I hope you'll take a gander when i put the fist video up and again thank you very much for teaching and inspiring. Best wishes, Frans

That was nerdelicious. Thank you, Doug.

Great Video. You are a great teacher.

Hello Uncle Doug, I happened to stumble upon your channel I have absolutely no interest in electronics repair however I couldn't stop watching your videos I was very impressed with your knowledge. Anyway, the reason I'm writing is I have a Marshall Class 5 tube amp that I bought used without a power cord so I couldn't test it first. After buying a power cord (plug-in type) I plugged the amp in to test it and nothing happened. Upon closer inspection where the plug plugs in I noticed it said "Mains Input 230V" So apparently this amp was made to be sold in the UK not here in America. I spoke to Marshall via email explaining the problem they said I need a new Mains input for 110V. After making numerous phone calls I can't find anybody in my area who fixes amps without charging $200 just to look at it. I could probably do it myself but I've heard it could be dangerous if you touch the wrong capacitor so I don't want to do it. Do you repair amps or just restore old amps for yourself? If I mailed you my amp could you repair it for me at a reasonable cost?

Uncle Doug, Just bought an old tube amp made by Alamo, the Texas company you mention in your videos. The model is an Embassy and it's been serviced by one of those Mickey Mouse guys you warn about. It works and the sound is okay. Got it cheap from a guy for twenty five bucks. He said the tubes were worth more than that. You should see the "modern art" paint job on the thing! You talk about little white paint drips? This thing looks like it was attacked by the Dutch Boy Paints kid! Can't wait to play it with some volume when I jam with the guys, I live in an apartment and don't want to piss off the neighbors. Thanks for the videos, Uncle Doug, I've learned a lot.

Thanks for this. I got one of the questions wrong but quickly figured out my mistake. I was looking at the wrong column in the tube manual (AB2 instead of AB1)!!! All good now. Learned a lot

Great info for peeps like me with numerous unknown vintage output xfmrs laying around.

Great video, thank you for your time!

Uncle Doug once again imparts the benefits of his years of experience (not to mention wisdom) to us lowly mortals...and we are humbly grateful indeed... When are Jack and Ollie going to release their Josie and the Pussycats tribute album? The world is waiting...

I just love it when you teach, if I would have had you as a math teacher in school maybe I would be better at math. Thank goodness there are a ton of electronics calculators online or I would be sunk. I did come up with a speaker combination resembling something that you recently worked on, not exactly but close, that would work for the 6L6GC at 450 VDC Plate voltage and that transformer. Six 4 ohm speakers in series-parallel (2 parallel sets of 3 speakers, 4 ohms each in series) would give you 12 ohms impedance. But other than Silvertone you don't see a lot of 6 speaker cabinets. Probably be cheaper to buy a different transformer rather than six 4 ohm speakers unless you just happened to have some laying around. Just had to give you a little grief, I was the kid in the back row saying ”but teacher what if you did this or that”. Another great video, I really like the rake that you added to the Rat Rod, very classic stance now. I would have probably put N50/15’s on the back. But I am a 70’s wide back tire kinda car guy. I do usually prefer to see some side wall though. Not a fan of the 20’s and 22’s that look like a super heavy duty caster wheel, or a 1920’s solid rubber Truck tire, all wheel with about an inch of sidewall showing. Oh and the header baffles sound great, sounds a bit like a 3/4 cam in that engine, a little lope at idea then smooths right out with a few RPMs. Very good and informative video.

Thank you for your fantastic great tutorials on all things tube amp, Uncle Doug. Not many have that smooth ability to teach in a thorough and concise, yet very pleasant and clear and enjoyable manner as you. That '34 hot rod Ford and your vintage tube amps make it worth for Jeff Beck to pay you a visit :-))