Impedance Ratio: The Easiest Way to Decipher Output Transformers
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- Опубликовано: 20 окт 2024
- Output transformers (OPT's) serve a critical purpose in tube amplifier circuits. To function properly, their primary winding must match the impedance of the output tube(s) while the secondary winding must match the speaker impedance. By determining the Impedance Ratio of an OPT, we can quickly determine its suitability for use with any combination of output tube and speaker impedance......using math so simple it can be done mentally.
This video will explain how to quickly determine the Impedance Ratio of any OPT, even if it is unmarked and has no available specification data. Then it will demonstrate how the Impedance Ratio can be utilized to quickly determine which output tubes and speaker combinations the OPT can be used with. It will also show how to determine the impedance for all output tube(s) using readily available data.
In addition, we will get an update on the 1930 Ford ratrod and the furry musical trio: Jack, Ollie, and KC.
If you enjoy advertising-free videos like this one, please subscribe to our channel and consider becoming a Patreon patron at / uncledougsvintageamps or making a PayPal donation to dldcam@aol.com. Also, you can contribute any tube amps and gear, working or not, to be used as subjects for future videos. Thanks for watching !!!
Uncle Doug might be the coolest cat on RUclips.....And DEFINITELY one of the best instinctive teachers. Thanks for another informative video, sir.
You're welcome, Eli. Thanks !!!
He surely is the coolest can in the clowder! And a fine clowder he has there! 😸
Man ain't THAT right!
I hope you mean "cat", Damian :)
He sure is. My electronics instructor at the voc I went to in late the 60s was pretty good.... but his circuit explainations were lame compared to Uncle Doug.
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.
Wow.....thanks so much. I really appreciate the very nice comments.
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
Thanks so much, ATL. This was actually the third version of the video......I discarded the first two, thinking they were too pedantic. Hopefully, it will successfully convey the concept to a broad audience.
@@UncleDoug "Pedantic"?!!! I resemble that remark.
It's my "big" word for the day, Carl :)
pedantic......never used that word before, but I'm a sucker for unused words and phases. Uncle Doug you are no pedant. A wonderfully explained way to further one's knowledge, in a precise, logical manner, is not pedantic! It's just the Uncle Doug way! Thanxz
@@UncleDoug Allow yourself one for each project and we'll be standing by with out dictionaries and the google. This is random, so please delete if inappropriate, but I found this cool short video comparing LDR vs. bias wiggle trem using two very nice Fender clones and some very tasty licks. Thought you and your viewers might find it of interest. ruclips.net/video/bYX4qPqcFv8/видео.html
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!
You're quite welcome, Ik. Thanks for your nice comments.
you're awesome Uncle Doug you always seem to put out something that helps me understand a project I am currently dealing with.
...As an old Norwegian saying: Good things cannot be said often enough - you are the best teacher ever.. Thank you :-)
Wow. I really like old Nowegians.......and their sayings, Patrick :) Thanks so much. You're welcome.
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.
Good luck with your measurements, F1. I hope you find some useful OPT's.
"if this sounds interesting...", well, you haven't disappointed yet. Another great and useful video, thanks Uncle Doug!
Glad you enjoyed it, Ben.
Dude, I love your channel, your literally handing down the knowledge of tube amps to people. I've repaired a few amps off you sharing your knowledge, thank you so much!
You're quite welcome, Andrew. Keep up the good work.
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.
Glad to hear it, DL. It is our intention to be clear and helpful.
I must say I have never seen or heard an explanation of the easiest way to Decipher the impedance ration of an Output Transformer as you have today. You made it very easy to understand. Thanks Uncle Doug all my best to you and your four kitties. You really did some phenomenal work on the Ford hot rod Uncle Doug. Hope you got it for a decent price with all the work you have had to put into it.
Thanks so much, Larry. These old hotrods are all investments for me, so I have to buy them right or risk losing money.
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!
Thanks so much for your very kind words, S. This is exactly the news I love to hear. We need "new blood" to keep our hobby alive.
Uncle Doug are you aware of YT channel called Mr Carlson's Lab ? He has built some really useful measurement tools that cannot be found anywhere else and for reasonable cost. Nifty time saving devices. Just thought I'd ask and maybe some of those test boxes could make your consignment estimates/repairs more cost effective (I'm thinking of that recent hacked Fender nightmare you set straight likely at great cost to you in additional time spent). His channel is highly addictive just so you know. Keep up the fantastic work !
Yes, I am familiar with Mr. Carlson, Peete. I like his manner and his work.
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
Thanks so much, Demian :)
I have several old air conditioners. Don't know there actual working condition, but a couple of em have York 210 compressors. That thing would be slick and cool.
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
Thanks so much, RJ. Although I are always excited to discuss tube amp theory, apparently it is not evident in my voice ;)
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!
Wow, thanks so much, Ana. Welcome aboard :)
@@UncleDoug Seriously, though. Here I was thinking maybe I wasn't smart enough after seeing so many arcane, byzantine and even cryptic explanations and you made it all click. That's another wonderful talent of yours. Can't get enough of this channel, so please do keep them coming! Sincere thanks and congrats!
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.
You're welcome, BM. Always good to hear from a fellow Texan.
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
Thanks for the very nice comments, William. Will do ;)
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!!!
You're welcome, Q. Thanks for the nice comments.
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
You're welcome, Kevin. The output tube impedance divided by the impedance ratio must equal the speaker impedance, so all three factors must be in agreement and each one affects the other two.
It’s not the impedance of the secondary that’s in play here. It’s the impedance of the speaker that is reflected through the transformer by the square of the turns ratio. This is the effective load seen by the tubes. This should be matched to the tube output impedance.
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
You're welcome, Gary. I hope it's helpful.
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!
Our pleasure, Ace......glad it was helpful.
@@UncleDoug It certainly WAS! I am most greatful!
All that work on the car, I am most impressed with the wheels. Great idea
Thanks, Dirk :)
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!
Wow, thanks so much, Mark. We're always here for you in your time of need, and look forward to hearing more from you in the future :)
I couldn’t say any better. It’s a wonderful day in the neighborhood ! With those gems of dry humor, it’s always an enjoyable visit c Uncle Doug !
💔💔
Uncle Doug your a great teacher, that is a rare gift these days. You really have a way about you that makes leaning fun.
That's great to hear, Jeff. Thanks !!
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.
You're welcome, Matt. I will :)
Once again Uncle Doug, you make it plain as day. A master.
Thanks, Chris.
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
Thanks, Prince. I always feel obligated to explain every detail and then reiterate key points, which takes some time, but generally works well with beginning and intermediate students. I'm glad you found the information helpful.
@@UncleDoug - Would you believe I've built valve circuits for decades and only late last year learnt Ohm's Law. Everyone says its so tough but, errr, nope! Once again thanks for blowing my mind - I really had not the first clue that the secondary impedence was in any way linked to primary coil voltage or valve resistance, these are transformers after all! LOL :o)
Glad i Just became part of the Family Uncle Doug. You are a Life Saver.....
So are we, Stuart. Welcome aboard :)
@@UncleDoug I do try to work on amps. Found a 1978 WEBB 6-14 E in the trash. Inside the back of the amp was a old Peavy 705-18771 transformer. Surprised the old Peavy sticker was still intact. Its in a complete metal casing 4" tall 6" across. I'm gonna dig into this amp but apparently there somewhat rare. I can't believe someone threw it in the trash, could've at least parted it out. Thank you for sharing your knowledge, think I got 1 extra IQ point👍
@@stuartewoldt1513 You're welcome, Stuart. Best of luck with your project.
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!
Glad it was helpful, Elmo. Thanks so much :)
I don't know how I missed this video. This was genius. Thanks Doug!
You're welcome, J&K :)
Dude you are living the dream! Thanks for the hot rod addendums - definitely adds color. Oh yes, the transformer tutorial was great too!
You're welcome, Curtis. Thanks !!!
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!
Thanks so much, G. I'm glad the video was helpful.
@@UncleDoug Not at all sir... thank you!
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?
It depends on what you consider to be "reasonable", Kenneth. I can tell you that shipping it both ways, combined with parts and labor will cost more than double your local price......so you might be better off seeking local help. One final suggestion: Most European amps made for 230VAC also have primary winding leads for 115VAC. Before you spend a fortune, check the power transformer to see if there are one or two extra (generally black) wires not connected. You might still need some help, but at least you won't have to buy a $150 power transformer.
This channel really is a WEALTH of information! Really great video!
Thanks, DW :)
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.
You're welcome, Buzz. I hope it sounds great !!
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
Thanks so much for your very nice comments, Bart. We're glad the videos are helpful.
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 !.
Thanks so much, Pete. The cops can't ticket what they can't catch :)
@@UncleDoug Ha-ha.. How very true...But our lot are equipped with helicopters & 'stingers' (spikes that are placed on the road to puncture all your tyres (or should I say tires !) when you dive over them) .. They're about to get commercial drones , no doubt equipped with cruse missiles, ha-ha...
Uncle Doug, a real renaissance man. Great video about impedance matching and great job on your rat rod. You have skills. 😊
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.
We're glad the videos are helpful, Arn.
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!
You're welcome, Britt :)
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! 👍🤗
You're welcome, Lee. Glad you enjoyed it :)
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!
You're welcome, Paul. Thanks for all the very nice comments.
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!
You're welcome, DS :)
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.
Thanks, so much, Mark. Yes, with different speaker combinations, you can achieve all sorts of odd secondary impedance values.......but I didn't want to complicate matters by delving into a separate subject. Most viewers probably use a single speaker and would be best served by learning how to match it to their output tubes. I too like fat back tires and have a nice pair of 12" x 10.5" Ansen "gasser" wheels that will bolt right up to the rear end and make it look like a steamroller......but for now, I'm going with the 17" red wheels and brand new Coker Excelsiors (not cheap) :) Maybe when these tires get some wear.
Fantastic stuff UD! This was a bit of a mystery to me, but I now completely understand it.
That's great news, Rachel :)
This was just great uncle doug. The explanation was very clear. Another great video.
Thanks, Rohan :)
@@UncleDoug I recently completed a 100-watt plexi kit amp and had some trouble with it. In the end, the problem was a mislabeled output transformer. By modifying the procedures you presented in this video, I systematically tested the transformer to determine the common, 4, 8 and 16 ohm wires. Now I know the common was yellow, not white. To be safe I compared calculated the effective load resistances with a similar Hammond unit. Thanks for the video.
*As usual - a pleasure to watch.* I love the perfect balance between serious information an subtle sardonic humour.
Keep it up sir ;-)
.
Thanks, DQ. We will :)
I don't think I'd want to meet the person who would down vote you. Thankfully there are very few of them. Great job!
Most of them are probably confined to psychiatric hospitals, Stuart, so there is little chance of encountering one out in the real world :) Thanks !!!
Thank you - people on forums make this very difficult to understand. Now i’m going to go re-test all of my mystery transformers
Good luck, F.
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.
You're welcome, Troy.
Another awesome and highly enlightening video. Many thanks! And the rat rod is super cool too!!
Thanks so much, SB :)
On my bench I still sit my coffee on an old RCA tube manual ... another great vid !!
Thanks, Bob :)
Another great and informative video...thanx!! That Rat Rod looks and sounds awesome!!
Thanks, T2 :)
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!
You're welcome, James. Thanks !!!
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
You're welcome, Chico.
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
I would be honored to view your first homebuilt amp project, Frans. Just provide a link and we'll be there for the premier.
@@UncleDoug Thank you! had some technical problems yesterday when i wanted to put part 1 up so we'll try again later this evening and if it works this time
i'll drop the link!
@@UncleDoug
Hi Uncle Doug, i finally got the first video of my project up, this narating videos is much harder than people think so it took me a while to do the best i can but i think you'll like it very much, or at least i hope so.
ruclips.net/video/UOULuILu50I/видео.html
That's the link, i gave you a little shoutout at the end, hope that's ok.
Enjoy and if you have any tips or advice on the project that would be greatly appreciated.
Best regards, Frans
UD has Legendary Teaching and communication skills.. THanks for this great video Doug!
You're welcome, CD. Thanks so much :)
Love that 34. And your. Tutorial on impedance ratio was 😃 great thank you
Thanks twice, William :)
Great video uncle Doug! Love the pop quiz and the rat rod looks awesome! Than You
You're welcome, Prof. Thanks !!!
Man, thank you so much!!! This is basically pure gold, thanks for sharing ❤
You're welcome, Federico.
Awesome video Uncle Doug. Glad to see the cats are keeping the lines of communication open. I know your pain on the rat rod. Once you start to unravel the ball of twine that is under a car, you are obligated to touch just about every component before you finish up.
Thanks, Greg. It is an endless project.....but that's exactly what I bought it for......and hopefully, I can sell it for a profit when I tire of it.
Aha! once again you've made it perfectly clear. I'm very appreciative of your knowledge! Thank you!
You're welcome, Greg.
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!
That's great to hear, Carl. Thanks for making our day :)
As always, thanks for sharing. That will be one more trick up my sleeve. Great information.
You're welcome, Daniel.
The knowledge you give is priceless. Thanks for sharing!
You're welcome, Vince. Thanks for the acknowledgement.
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!
You're quite welcome, Merc. I hope the video is helpful.
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! 🙂
You're welcome, HB. I hope the video is helpful.
2:54 re testing an output transformer that is already installed in an amp - many tube amps (especially Fenders) have the output jack wired so that the tip shunt throws the transformer's output to ground if there is no plug inserted; for this reason, measurements are best taken by inserting a plug in the output jack and attaching the test leads to the tip and sleeve contacts of the plug. If the test leads are connected to the jack contacts inside the amp with no plug inserted, you'll be reading a short. I'm sure you (Uncle Doug) know this, but a lot of your viewers are noobs, and it's been my experience that if there is a way to screw up, a noob will always find it. ;-) 3:20 re "standard" wire coloration - the primary red/blue/brown convention doesn't apply for Brit (and some other) transformers, and on old Fender tranny secondaries the common lead is usually black, with the positive lead being green. If there's more than one impedance (rare) the third lead is usually yellow. This is a great vid - I haven't thought about this stuff for probably 30 years. I have a Fluke 289 which can resolve .001 ohm, so I do most of my mystery-tranny ID tests by ohming the windings. After the amp is built, I do power testing with a scope and a testload to find out what kind of tubes I can use with it. But I'm a dangerous kinda guy...don't try this at home, noobs. ;-)
Thanks for all your excellent suggestions and input, Willie. We really appreciate them.
@@UncleDoug Aw, shucks, ;-)
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!
Thanks, Daniel. We will :)
Thanks Uncle Doug! This is a jewel of information. Totally clarifies a lot about both tube and transformer selection. Your videos are just awesome.
You're welcome, PF. That's great to hear :)
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
That's great to hear, Sean. Keep up the good work.
Thanks, Uncle Doug - I learned something from your video, as expected. You made my day!
You're welcome, CM. That's good news.
"Tennessee"! I see what you did there, Uncle Doug! Since Mr. T is a Tuxedo kitty-kitty, he's named after one of my favorite early '60s cartoon characters (Voiced by Don Adams, who went on to become Maxwell Smart in "Get Smart"). "Come on and see, see, see... Tennessee Tuxedo..."
And remember, "Tennessee Tuxedo... will NOT fail! Right, Mr. Whoopie?"
I learned a HECKuva lot from you and this video! Thank you. (LOVE the Rat Rod!)
As usual, you're right on the money, Dave. That's his name.....Tennessee Tuxedo. One of my favorite penguins. I guess the next cat will be named Chumley :)
Nice video U.D....I'm not ashamed to say that I'll have to watch more then once...
I'm flattered that you would want to do so, Lee. Thanks.
WOW! finally the penny has dropped! and I understand some of the output transformer matching theory. Thanks Uncle Doug for explaining it in a way I can clearly comprehend. I have now discovered that the new output transformer that I have fitted in my amp should have the 16 Ohm speakers connected to the 8 Ohm taps on the transformer wires. Not the wires marked 16 ohms because the EL84 tubes need an input impedance of 8K. Many thanks again Doug........keep up your great work.
You're quite welcome, Ian. I'm glad you were able to put the information in the video to good use.
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.
Yes, it does, Scott. You have to factor in all the variables when determining the plate impedance.
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...
Thanks, C7. They're in negotiations with MGM for an album/movie deal.
Best video I've seen in a while, thank you very much for your work. Wonderful car too!
Thanks twice, Amity.
Thank you for the video, Uncle Doug, very clear and informative.
You're welcome, SE.
Once again your teaching style was so much more than wonderful so thanx so
very much... this great vid just happens to coincide with my own inner querying
about the use of different output tubes in low to medium powered amps
(6L6's and 6CA7/EL34's in 20ish watt amps)... and 'though your rat's color scheme
is still qualifying as "ratty" with flat primer black/rust splotches etc. I suspect
(and hope) you'll move on to the land of cherry with uh maybe a super dark olive
("ooo I can see myself") ...but that's just me. Plus I wuz really tickled pink when
you goosed the gas and she momentarily tipped to the right... that was So cool.
I really dig the 'mechanicky' theme where things are all well thought out and yet
somehow not cheezy or gooey... like the look of the silver finned drums... just
perfect. Just love how things are comin' together. Thanx again Uncle Doug.
Hey we almost caught a full on shot of you reflected in the baby moon!
Thanks, Jonny. I hope the video is helpful. Glad you enjoyed the ratrod tour. I went for the "steampunk" look, with gauges and controls strewn about......and hope the baby moon reflection didn't reveal too much :)
So useful, I can't thank you enough for posting this Uncle Doug.
You're welcome, GS.
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
You're welcome, Eddy.
Great episode UD! thanks for sharing,nice ride!
You're welcome, SG :)
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.
You're welcome, SA. Thanks so much :)
UD, great looking Rat Rod, I like it a bunch.
Thanks, Gary :)
Terima kasih paman Doug, pengertian dan pengajaran tentang trafo sangat menginsirasi saya yang baru belajar tentang trafo output untuk amplifier tabung...
Sama-sama. Saya senang videonya informatif.
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!
Thanks. We will, Bob, in both regards :)
that is really, neat, uncle Doug~ your neighbors will know that it is You~
Thanks, Jay. Trust me, they know ;)
Perfect timing UD! This is very handy. Thanks!
You're welcome, FWR :)
Ah HA so i can tell from my pile of stuff if anything is worth using for output!!!! Great.! Excellent tutorial thank you so much. D
Glad it was helpful, Dennis. Good luck.
Impressive that you have the Library available with all the Tube parameters of the different Tubes. Good and easy to follow explainations to a very interesting and important subject because Output transformers are very important Devices in Tube Amplifiers. And a really good prove that mathematics works. And by the way, from an engeneering point of view, an impedance is a very complex arrangement of different parameters. Greetings from Germany.
Greetings to you, Roland. Thanks for your kind and supportive input.
Great info for peeps like me with numerous unknown vintage output xfmrs laying around.
That's good to hear, Dave.
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!
Thanks so much, CB. Viewer numbers drop when I post technical videos, but I still do it, because the technically-oriented viewers, like you, really seem to appreciate them.
This really explains it well. Thank you for this video.
You're welcome, M01 :)
Merci beaucoup M. Doug !!! Great video.
You're welcome, Mathieu :) Thanks !!!
Well its good to see the Darf Vador mobile has been transformed into something a little more respectable, I don't think you will need the bullet proof glass now, people won't be afraid to see you coming. Great job.
Thanks, Hack.
This is exactly what I needed, thanks Uncle Doug!
That's good to hear, Tommy. You're welcome :)
Thank you so much for this uncle Doug, I’ve been waiting to see a video with this kind of info
You're welcome, Tim. That's good to hear.