now we are starting to get in to the really cool stuff!!! thank you so much for not slacking on the math and continuing to show everything by equations and then visual representations. i believe this is where many electronics tutorials fall apart. now, what are the chances that you'd like to do one of these for an RF amplifier as opposed to an audio amplifier? getting into the equations behind the voodoo black magic that is RF electronics would be AMAZING!

Wow, another super-great video!!! Thank you!!! You just set the bar to a new high mark. Your best video of your best series, yet!

What a fantastic video, Tony. Being new to understanding this stuff, I could easily follow along with the logic presented and understand the concept entirely. Well done!

love this new series, thank you.

Down to earth and easy to understand! Enjoyed watching. Thanks!!

A very useful episode in this series, as I’ve been trying to figure out how to test a suspect audio output transformer for one of my repair projects. Thank you, Tony.

I really like this series of vids! Nice that you do the math and back it up with visual measurements. Hope you do a series like this on AM/FM tuners along with alignment using basic equipment. The Sansui manuals always refer to some off the wall equipment. So today I learned size does matter, concerning transformers🙂.

Oh, this is cool, I have a dats and I have never considered measuring an output trafo with it, thanks Tony! You rock!

Thank you for a helpful series

Tony - a very informative video with lots of great information. Thank you for sharing your knowledge and experience with us. Best, Don

Very informative, Tony, very much enjoyed this video.

As always, nice video. Slow and very clearly explained like we all are complete id*&%$#s and never ever heard about output transformers. Thank you Tony for everything you're doing for the community. Those who need FFWD expert videos are free to go visiting other channels. I learn from your every single video some small bit and piece. Some here, some there. If only all teachers at school or at the Uni were like that. Slow, clear and with real world examples. Noone has been born into this world an expert. Thank you for taking your time and doing these.

Just found your channel and I'm subscribing because I'm learning a lot from you! I'm new to tubes and I'm about to build a hybrid tube amp consisting of 2 lm1875's and 2 jy6 (I think) tubes and I didn't realize the power supply was a 18v plus or minus AC power requirements which I have never heard of till now soooo I'm trying to figure all of this stuff out lol

Great taste in calculators. I have a DATS V3. It's much more robust and more versatile than previous versions. Like TubeDude mentioned, Parts Express has them and you can see all the specs there.

Great video. Thank you for sharing what parameters to look for in a transformer per application.

I have v.3.0 of the DATS...love it. I per-ordered 1, so I got a heck of a deal on it! Got it from Parts-Express.

thank you for making this video

I'm so glad I found this video.

great videos tony

With your oscilloscope that has a bode plot mode you can do a similar measurement(perhaps with less accuracy) by measuring the applied voltage to the transformer and the voltage over a shunt resistor(as output input), and if you set your current scaling according to your shunt value directly get the correct values on screen. This is useful for those of us that don't have an specific instrument to perform those measurements. You need to have a scope that allows you to use the difference between channels as a bode plot "channel" OR a differential probe(Micsig has some cheap ones) OR you can get creative and take advantage of the isolation of the transformer and the turns ratio if you dont have any of the previous options. Also you could use a current transformer(pretty cheap but only for AC) or a current probe, but until recently those were always really expensive.

After 3m13sec, there was some missing activation-sound !!.. Thanks for videos Tony :-) ..Always looking forward to them when you have time to make&share (..specially when schematics&talks is involved)

Great video and love the math…

Xraytonyb, I learned something by watching your video, now I see another way to find impedance of an AF transformer. The way I was doing it was to use an AF Generator at 400 - 1000 Hz to feed through a series potentiometer into the primary, with the secondary loaded with a resistor of the rated secondary impedance. Read the generator voltage and adjust the potentiometer to read half the voltage at the primary. Then measure the resistance of the potentiometer and you have the impedance of the primary.

Xraytonyb your information on electronics part 8 the out put transformer is cool

Like to see how those McIntosh auto formers do the impedance test

This was super interesting

I noticed no load on the output transformer. Shouldn't you at least have a good dummy load to not burn it up? Thanks for sharing.

A pair of 6AQ5s or 6P1 will sound fine if it is 5K. I have done it before single ended as well as PP. Typically as you know 6AQ5s, 6V6s, EL84s are optimum between 6 and 8k depending on plate voltage. But I have a couple of SE output transformers that came from a Sony R2R which had 6AQ5 output tubes and the OT was 5K to 8ohms, So Sony designed this tape recorder with those tubes and an OT with that impedance. I used one with an amp and it sounds good with 6L6s and 6V6s. Also, I have a Kodak Projector amp which came with PP 6L6gb's and the amp also sounds great with 6V6s. As you know a 6AQ5 is a 7 pin 6V6. Tubes are very forgiving.

interested in the pt31 as that is the one recommended in a thread about 8000 series magnavox units not very promising alternatives ? THANKS

Howdy. May I be so bold trying to clarify things ? Firstly. The magnetic induction depends almost entirely on voltage, frequency and number of turns. Current has little effect on magnetization other than the 90 degrees shifted inductive magnetization. Second. The core does not convey or transport anything. The core only serves to keep the flux concentrated for tight induction. Third. What heats up the transformer is almost entirely ohmic losses in the windings. The oscillating flux generates some heat. Yes. But that is almost negligible. Fourth. The core size must be chosen large enough to accomodate wire gauges thick enough not to generate too much heat and to be able to dissipate the heat without causing the bobbin and wire varnish to melt and be a fire hazard. The core and winding outer surfaces do the heat dissipation into air. Fifth. There is a rule of thumb that says that the core cross section in cm2 should be about the square root of the power in watts. But this rule is empirical only. It is not derived from laws of physics. Sixth. How do we then understand the illusion of power conveying? Induction generates voltage over the secondary. This voltage starts driving current through the speaker. This current also fights the induction. The primary observes the induction going down and compensates by drawing more source current until the induction is restored. Regards.

A very good demonstration to determine the impedance of an audio output transformer . What software do you use to check linearity of the transformer's impedance. Thank you.

I like the MATH! That's what I wanted to learn ! When you know the math, you can actually design it !

Could you please provide link to software being used on this topic of transformer frequency response. Thx

I'm get readings of between 4 and 9 megaohms when I connect between the primary and secondary windings on a suspect output transformer. So I assume thats the problem with my amp? Massive amounts of humming and no sound from speaker?

How does running a single power tube in a push/pull cathode biased circuit effect the output transformer? Does it damage the output transformer?

One little trick that a high school classmate pulled on us when we were in grammar school was to bring an output transformer and a D cell battery to class. He would put the battery on the speaker side of the transformer and have one of us hold the input leads. The second he touched that battery we got a big jolt! It wasn't until years later that I finally understood how a dc voltage could shock you using an ac device. Had he touched the wires to the transformer BEFORE we touched it, nothing would have happened but by doing it the way he did he momentarily created a current flow in the coils and we got zapped! Since he was on the "low" side it meant that he was amplifying the voltage that we got. Modern transformers are too small and don't have the potential that those old tube type transformers did so it wouldn't work otherwise. Some have argued with me about it until I did the same thing and it made believers out of them. The current flow is of very short duration so if you hold on to the leads after the initial jolt, nothing else will happen.

Be fun to see the size of the Xray components in comparison.

You didn't try to dazzle us by drawing load lines on the tube data sheets so I don't think there was too much maths in this tutorial ;). An interesting tid bit is that the primary transformer impedance connected to the pentode is not selected for maximum power transfer but for minimum distortion (pentodes are awfully non-linear).

Yes we love math

Hi Tony Great video. what if my speaker impedance is rated at 6 Ohms. 👍 Thank you.

Tony, you may want to note to your viewers to look up “maximum power transfer theorem”, if you don’t have a video on that already …

I wish this kit was designed for EL84/6BQ5 push pull. It seems like it's so close to that, but not quite there.

How can I convert a vintage Yamaha CA-1010 transformer from 110V to 240V, from Japan to European standard.

Howdy. Nice. About getting laminations for OPT:s. Check eBay for Line Transformer or Audio Line Transformer. One will get several hits. I settled for Parts Express. They have 100 W 70 V items for about 30 dollars a piece. I ordered two and rewound them. The laminations are good audio grade steels. Regards.

Hi Tony, first of all..great videos! Very well explained stuff! My question: many times you hear people say that a tube amplifier produces a more warm sound than a solid state...is that because of the behaviour of the output transformers and if so, what causes that difference?

I've seen this impedance ratio video over and over on different channels. Why not just put an LCR meter on the primary, measure the inductance and use the formula Inductive Reactance (impedance) = 2 * Pie (3.14) * F * L? I believe the standard frequency (F) used is 1 Khz. Would that not save a little effort? Thanks!

is it possible to ID mystery winding voltages with only one multimeter?

Is not the max voltage on the Anode of the 6P1 rated at 250 volts and not 275 volts

Hi Tony. Something doesn’t make sense here: Why would a higher-power amp (which, presumably, would need a higher B+ voltage) need a lower impedance of the primary? That seems like it would be equivalent to saying that “if I can safely put a 10k resistor across the 120 volt mains, then I should be able to put a 5k resistor across 240 volt mains).” But, of course, you’ll just end up with a burnt 5k resistor if you do that. 🤣😂

Maybe its a se tx?

you are wrong. it is a 5k transformer meant for Class A Amplifier. and we know Class A modifies impedance downward. more precisely Push-Pull Class A. you do not measure that "5k" or "8k" at the output, you measure it at a single section of the primary, when it delivers nominal power signal, not music, but tone, full power. how you do that?