Power Supplies, Part 4: The Voltage Doubler 

I watched this, then immediately fixed a 2× 50L6 record player that had 2 selenium rectifiers understand completely why it began humming. World's greatest electronics teacher right here on RU-vid. So grateful for you.

Your educator skills are far beyond that of a teacher. You are a naturally born mentor and absolutely responsible for the majority of the knowledge and understanding I now possess for tube amps and complex control circuits circuits. As a note, I am a retired public educator for electrical technology and maintenance from which I learned and honed my instructional skills and mentored many high school and adult students into their own careers in the electrical field. After I retired I then took on a second career as a Nuclear Electrical Maintenance Training Specialist at a dual unit Nuclear plant in the NE from which I am now retired from. My knowledge of electrical theory is very strong and secure although my knowledge of vacuum tube and transistor amp circuits was in need of the guidance of a superior mentor. While searching and educating myself online, there you were and I haven't let up yet. You Uncle Doug are an amazing presenter of knowledge and the immense skills you possess. Since finding you I feel as though my knowledge acquisition is supercharged. THANK YOU for everything I am on a journey that lives in the fast lane. One last thing, I am also a musician and motor head. Been playing in bands for 40+ years and wrenching even longer. Built a couple sweet street rods over the years and still have an ongoing 44 year love affair with my 73 Big Block Z/28. Again thank You for everything. Mark

The best professor ever! Thanks Uncle Doug!

I love that you left in the error with the positive negative

Hi Uncle Doug, I'm a huge fan! I've since employed this method in a (dual) Altec 1566A mic preamp clone, which was on the Ricktone website. I also built a Trem-O-Drive into a large guitar pedal. Many thanks for your expertise! Your videos have been and continue to be an invaluable resource and reference.

I have learned more, watching a few of your videos than I learned over the past 3 years combined! Thanks!

Blathering, especially yours, is cherished and gratefully accepted. Blithering, from others on subjects like high voltage is not. Thanks again, can't wait for the next installment!

Still getting value out of these in 2018! I’ve just reviewed Power Supplies Parts 1-4. Thank you again, UD.

Uncle Doug, this has been a really fine group of videos about Power Supplies, transformers, and rectifiers, better than any class or course or general study that I've done. You really did good! Buddy

That was really cool! Can't wait for the term/overdrive unit!

Hi U D , I love your straight forward explanations . I wish all people in the world could get along as well as your Voltage Doubler does .

Thank you Doug! Excellent video and explanation. You really make this easy to understand! So useful.

After reviewing your past videos, which in my opinion, brilliant, I would like to request a topic of great interest.The in-dept explanation of the output section of a double ended guitar amp. You have explained how to bias the output tubes and a further look at the circuit components before and after the output tubes and their function. If you have already posted such a video, I could not find it. You are the #1 person to do this kind of analysis. Thank you for your sharing. Thankz

Very much enjoying these videos. :)

Fantastic Uncle Doug. Before this vid i couldn't understand my measurements on the power supply of my fender champ 12. Turns out that its a voltage doubler. I fully understand now my measurements and how it works.

wonderful concept and very useful!! Rusty once again shows his street smarts. Thanks UD!

You explain everything so well it makes it simple. Thanks for sharing your knowledge.

im learning so much from this series... THanks Doug!

* Voltage Doubler Note*: If you keep the 4 diodes from the full bridge rectifier, all you need to do is add a switch and an extra filter capacitor to make a voltage doubler. The capacitors are connected in series between the rectified positive and negative rails. One side of the switch connects to one of the AC secondary terminals of the transformer. The other side of the switch connects at the center point between the two capacitors. When the switch is closed the voltage is doubled. Alternatively, if the switch is closed and the center point of the capacitors is connected to the load, this will create a dual polarity supply from a secondary without a center tap. I haven't played with the dual polarity configuration yet but I believe the ESR of the caps can become problematic in this configuration when loaded. Thanks for the upload :)

This was a life saver for me. You showed a very convenient way sir. Thank you

Has anyone already said that you have a supperb diction?? Your english is very easy to understand even for me and I am not a native english speaker. We in the third world feel gratefull when you bring saving money solutions like this one.

Here we have a rare look at Uncle Doug's fingers. Again, well done, sir. Thank you!

That was a excellent explanation of a voltage doubler. Read about them but never put one together on the bench. Will have to do that for some fun. Thanks as always. Kudos to Rusty on his math exam. A student. Carl

thank you uncle Doug, your videos are the best, best speaking, best demos, best pets always ready and willing to help you

I am going to need a 12 step program to get off these lessons..nah..these are great..very addicting..im loving every one..cheers

Please indulge me another comment. Love how your ideas have so much applicability to amp building concepts combining practicality of weight reduction without any compromises to tone. This is fun to learn too.

I looked almost all of your videos . thank you very much Uncle Doug!

Very nice tutorial on voltage doubling! Thanks!

I can't resist, I just hit like on every video of yours ! Ty so much for the great work.

I made an isolation transformer for my workshop only yesterday using a couple of old hi-fi power transformers back to back. Works great.

I am a commercial electrician and I hate trying to read schematics I am a visual learner I appreciate you going out to the workshop and putting it into action I just learned something new, this isn't learning for work though what I'm trying to do is hook up a couple transformers in series from the secondary so I can get a stepped-up primary to use as a AC stick welder because I've been needing one desperately

Fantastic explanation of a concept that I never really fully understood. I have a 70VAC transformer I was wondering what to do with, now I know how to calculate what I can do with it. Thank you!

Love the + and - symbols on your fingertips/fingernails ! Very nice idea! Love your videos!

Been planning on a champ circuit recently! The transformers for the generic power/output have been really nicely priced, but this definitely allows me to use some of my spare 12v transformers for sure! However, I do want to get into adding some lower voltage IC preamp elements, and I'd love a video about how to convert those high B+ voltages into reasonable audio IC voltages, if you wouldn't mind! Love the stuff you do! Very palpable and understandable! keep doing what you're doing!

Another great, crafty and very useful video!

Hi Uncle Doug & Rusty, Very informative power supply series, great explanations and demo's. Look forward to next part. You are the tops in Amps. I hope all doing well. A really great channel you have, learning a lot. Take care, C.

Hey Uncle, thank you very much for your excellent and very clear videos with clear explanations for all of us to understand! Keep up the great content!

I am waiting for next video, because I so want to build that tremolo, I learn so much from these videos

THANKS UNCLE DOUG, EVERYTHING SEEMS TO BE TWICE AS GOOD!

Shared 😸! Really, we can be called amphollic or "amp addicted" Thank you for another great video master!

this was a great series of videos. thank you

Greetings from Australia! Keep up the good work mate, really enjoying these videos. Cheers, Dave

Rusty is such a smart good lookin boy :P really like your stuff, waiting for the postman to give me my EL34 kit.. love to hear all your tips&trick

Howdy. Really nice walk-through. My experiences: My location is Finland, Europe. The mains voltage is 230 V 50 Hz. In my 4 x EL34 PA I use a 230 V / 115 V 350 VA transformer. With a tripler I get abnout 500 V anode voltage running idle and about 460 V at full power. I made sure the item complies with Protective Separation. Voltage multiplying is usable up to maybe 4 or 5 times. No more, because as the voltage climbs, so will the impedance do squared. For filaments I use a separate 12 V 50 VA transformer. This also powers another tripler circuit for biasing the tubes. I use individual fuses for both transformers. This way there will be complete overcurrent protection. The transformer is a SELV item. A hybrid transformer will not provide full overcurrent protection in case of a partial short in the filament circuitry. The 3 phase voltage here is 400 V 50 Hz between two phases. There are 400 V / 230 V transformers easily available intended for floating control voltages in 3 phase switchgear with no Neutral. I use a 450 VA piece connected backwards in my 4 x KT88 PA. Because the inherent loss compensation now works backwards I only get 395 V AC for the anodes. Full bridge rectification and filtering yields about 540 V running idle and just a little over 500 V at full power. Regards.

Love to watch your videos. First you deliver a lecture then a practical demonstration. That is the hallmark of an experienced educator. So I get a two fer when I watch, my interest in electronics and pedagogy are both covered. One question: why don't you use a breadboard for your demos?

I remember doing this kind of stuff when I was very young, actually did it the first time I got some spare tubes to play with. Actually remember the first tube which I used to experiment a lot as a kid was an EBC91 made by Phillips, which I still have, though it seems to be pretty much dead. Placed two trasformers back to back, though back then I didn't use a voltage doubler. I just rectified half of the wave, which gave me a cap with about 120 volts. It was enough for my first experiments with vacuum tubes. You can also feed the secondary of one with an oscillator driven by a 12V battery. You could power tubes with low voltage sources, not unlike old car radios did.

Great vids Doug. Reminds me of when I used to know all of this stuff...and Rusty is a great feature! Good boy! Good Boy! Please give him an ear scratchin' for me!

OK Doug I appreciate Your experience

Very cool! It would be awesome to see some videos about output transformers as well. It seems to be an often overlooked aspect of tone, and expensive part of the amplifier.

Hi Doug. Very well explained has always. If you get the time I would very much like a series on Watt's,Amps,mA's and uA's Thank you for this great series. I am looking forward to your next video. All the very best. Bobby&Molly.

OK working my through your awesome lectures and i have 2 old transformers. I think I will set them up ad you show and just do the math and hook up a scope and practice all this stuff. 300 VDC out is amazing. And then ad the bid cap to smooth it out. I am so excited thank You Doug. Hope the Hot Rods are still chugging along too. Dennis

Fantastic, de-mystifying videos, looking forward to the ongoing valve, inductor and output transformer circuit videos! (Hopefully!)

I miss your valued and informative videos. Please come back to us.

Thanks for these videos.

Careful, Uncle Doug- if you keep this up, I might become edumucated... Great way to explain the theory here!

Your videos rule. Thank you for making them. Also, am I the only one that yells "Hi Rusty!" When he pops on screen!? Lol cheers!

thks a lot for the advice Mr doug

Incredible!

again an educational video Thanks. Bertus

Wow great review of voltage dubblers Doug, thanks 4 sharing, and Rusty must have taken intro to math when he was a puppy! Smart dog, but he knows we don't develop film anymore and does not care how much room you have left, also,a bright move. haha

I fondly remember visiting the local Radio Shack ( or Tandy as it was branded in the UK) for the electronic kits with the spring connectors

Superb video uncle!

Clear, Concise...

awesome vid UD

Спасибо!

I like the isolation concept using two transformers, you can experiment without tripping the breaker

Thanks again Uncle Doug. Just Subscribed. Could you and Rusty please do a vid about using the oscilloscope to check audio signals, such as a sweep. Something simple for people like me.....

Sorry to be so verbose here, Uncle Doug; but this circuit interests me quite a bit, since I used it in my own circuit designs over the years, using lower transistor voltages and transformer windings for transistor guitar power amps. In my case I used the 4 diodes in a full wave bridge configuration and massive power filter caps (4000 uf) to serve as the voltage/current source for the power transistors. However it was not configured as a voltage doubler supply but instead as a bi-polar supply, using the centre tap of the power transformer tied to chassis ground. At the junction of the two (stacked) power caps it was 0V (ground. The negative side of the diode bridge and the cap provided the Minus voltage (-40v) for the collectors of PNP power transistors, and the positive side of the diode bridge and the filter cap, provided a positive voltage(+40v)for the collectors of the NPN power transistors when referenced to the centre tapped ground. This type of power stage was labelled full complementary with the power signal taken between the emitters ( of the centre point of the O/P power transistor set) and ground.

All of the other videos on RU-vid parrot or mimic what they seen they can't answer a simple question. Uncle Doug understands, he gets it.

Hey Uncle Doug. Great video as usual. I think I may know why the sine wave on the output was a bit flat. The term is called clipping. It's trying to suck out more current then the transformer can push out. Maybe a load can be added to the 12volt filament line to make the first transformer to produce more current so the second transformer can rob from it. Honestly I never tried this form of a voltage doubler so I might be wrong but from what I have read in text books on power supplies this sounds like the first transformer isn't pushing out enough current.

Спасибо! Понятно даже без знания английского языка ,или я учу английский язык по вашим видео. Очень хорошее дело. Построил, с вашей помощью 5f1.ремонтирую ,,champ 12,,который имеет подобную схему power simple. Это видео очень помогло понять как это работает. Продожайте пожалуйста. Интесно как самому расчитать power simple имея трансформатора без имени. Привет с Украины

It's a great alternative to get rid of hum with cleaner DC at the end. Unfortunately you'll need some space on your chassis to install them.

That's one well behaved dog! Or you're feeding him way too much :-)) Anyways thanks for another great video Your stuff deserves a wider audience !!

Connecting up the secondary of one 12 volt transformer to the 12 volt secondary of another will work as in your example BUT there are some hysterisis and laminate core losses as the winding wire guages were designed for more efficient current operation if the primary has the higher voltage applied to it,. Normally it would be a much thinner gauge of wire. So in reversing the winding functions, the voltages will not be the same as in a normal ac connection, but as long as the output ac voltage is not critical, it serves the purpose. The current requirements at the primary only serves to energize the laminated core magnetic field, which the secondary thicker guage winding is wound around in a conventionally wound transformer. The exception would be an auto transformer.

Ebay is probably the best bet for surplus transformers as today, a lot of these old surplus shops in my area are out of business..rents and other operating costs are too expensive today for a surplus electronics shop to make any profits. Years ago, back in the 70s, that wasn't the case, and you could get a lot of surplus or even NOS at these stores at cut rate prices. I bought a lot of stuff at these stores including VTVM kits and nixie tubes. Radio Shack used to sell electronic bits and pieces and while they were convenient, they were expensive. They would package two resistors in blister pack and sell them for $1.99 or 10 of the same kind for $3.99...somebody was thinking that was a good business strategy for RS I never bought any parts from RS because to build from scratch, you would need many resistors, capacitors and other active components like transistors. To build even a simple electronic project like yours, it would cost 10 times more than if you bought it already made. No wonder they got out of the electronic component business years ago no serious experimenter could afford their prices.

Appreciate your videos very much, and I LOVE dogs. Have a cattledog mix myself named Yoda. I do have to say that I think your mistaken in your interpretation of dog behavior (at least in this case) however... I speak dog. :O) First (being an older dog, and rudely awakened from his nap), when he came over to please you, and you were asking him which he preferred (when what he really preferred was to be taking a nap, and being overweight didn't really need the biscuits), what he was saying was, "Dude, I'm not even awake yet, this is what you bothered me for??? Let me think for a minute and stop rushing me." Eventually after being pressured to make a decision, he went with the 1 1/2 biscuit option (not necessarily knowing whether he had to choose or not, since he probably figured he could eat the other biscuit later), mainly because being an old dog with old teeth (and being smart), he recognized that there was less chewing involved (since they were already broken). He's no dummy! Rusty looks pretty old here, and again I deeply love dogs, so I hope he's still with us. If he is, I respectfully *urge* you to buy him a bag of Missing Link food supplement ASAP and add to his food (it's a powder, just sprinkle on top), it's absolutely amazing... over 1,000 reviews on Amazon with a 4.7 star rating last time I checked. It will add to his quality and length of life, absolutely, and I have no financial connection to the company. I just love dogs, and older dogs need a boost (contains high quality nutrients not found even in good dog foods), so I feel an obligation to tell every dog owner I meet about it, if they have older (or sick) dogs. I'd recommend trying a 1 pound bag of Ultimate Hip and Joint formula, though the Senior formula would work also, very similar but a few different ingredients. You can get this on eBay for a little less if you look around, usually... and follow directions on the package, giving him a little less for a few days until he adjusts to it, then the regular amount (probably around one teaspoon/day for him or so). If you try it (and trust me, if you love your dog you'll be glad you did), make sure you get "Canine", they make it for cats, horses, and birds now also. Please try one bag (which will last about two months), and see if you don't see a change for the better in his over all well being, and anything he might be dealing with (including arthritis, it contains Omega 3 oils and other great ingredients). It can only help (and improves energy level, digestion, and skin and coat also)... and read some of the reviews if you have any doubts about it. Thanks again for the videos, and best wishes.

Uncle Doug, the core flux may reach saturation levels during peak moments of the AC sinewave cycle. If this happens, the voltage induced in the secondary winding will no longer match the wave-shape as the voltage powering the primary coil. In other words, the overloaded transformer will distort the waveshape from primary to secondary windings, thus, maybe causing your not so good looking sine wave on the output. That is, I think you may be operating in the saturation regions of your transformers. To test this, maybe try using a potentiometer and play with the values to see if the output waveform gets better for higher values of resistance..........or, perhaps try bigger transformers with higher flux density capabilities. Or, even yet, try adjusting your frequency (higher) to minimize the possibility of core saturation. Just my two cents.

Good

I came across some Stancor P-8364 transformer that have three secondaries each at 12V 0.5A. I was thinking that two secondaries on the first could be series wired making 24V and then fed into two secondaries on the second transformer in parallel for even current distribution. It might be enough to run a preamp without a voltage doubler. The dielectric strength si 1500VRMS.

Great, how Rusty mastered the quiz. My cats start eating before I'm able to explain the test... Somehow clever:)

Snazzy!!!

Voltage doublers: Fender used them in their extremely high watt tube amps (of the '80's?), the 160 watt PA amp, 300 watt 300PS, and the 400+ watt 400PS amp. All of these had 700 vdc B+ voltage and used 6550 power tubes.!

Heyo Doug! As always, still really enjoying your videos! How about tearing apart some old and unused transformer-based 12v wall-warts for their transformers? Super cheap and plentiful at the local thrift shops!

6:34...another thing to remember, is once the rectifier tube filaments are connected to the 12 volt winding(s), the output on the right transformer is going to be even LOWER.

another great video, thank you. btw, what voltage value did the 2 x 10uF caps have?

Nice Video, I think the flat spots on the input sine wave could be caused by core saturation. Those aren't the highest quality transformers.. and/or, 2 transformers close to each other could be magnetically reacting with each other.. I know they are tiny. but, ya never know..

I recall old bw. Tv had a doubler not using a xfmr for isolation .don't remember the circuitry.but a 200uf cap was common.failure part dead set.

Wow! Very good. Rusty seems a little smarter than Jack....

Thanks for the video, Uncle Doug! A question: I am building a Lectrolab R203 (the schematic is online). I don’t like the fact that the circuit for the fillaments is on the primary side of the PT, so I would like to have a separate isolation transformer, and am interested in applying the concepts of this video to save money. The circuit of the filaments are in series, and it goes: 130 ohm 5W resistor, the filament for the 35W4, the filament for the 50C5, the filament to the 12AU6, and finally back to the PT. If I make a voltage doubler as in this video as a separate transformer set for this filament circuit, what are the minimum current requirements the two transformers need? Can I get by on the 1 amp ones, or would I need to purchase a pair of 2A or 3A ones? Thanks!

Mr. Delon would say "...Thank you..." :)

This is exactly what I needed! How do you determine the value of electrolytic capacitors for the voltage doubler assembly?

Hey Uncle Doug! Happy New Year! Do you have a vid on how to make and use a capacitor discharger like yours?

Very neat! I'm excited (pun intended) to see the tremolo / OD, even though I have 4 ODs on my pedal board now. :))Is this the drive that appeared in the "Elvis amp" video? Rusty looked too sleepy to make snap decisions.

Forgive me if this question has been answered elsewhere. I wonder if a similar doubling operation can be performed with 2 output transformers, such as one might find on an old stereo hifi? Thanks for a great exposition Uncle Doug.

I have a feeling Rusty knows you are filming and he likes to toy with you. LOL! Great video on power transformation. I still get stuck on sizing capacitors. I can understand the voltage part of them... Match it to the voltage it will be handling, but I don't understand how/why to choose larger or smaller uF capacities.

Nice video Doug. How much current will the 12 volt taps take? Presumably they go to the cathodes?? Is that a lot of current through those 12 volt windings? Interesting mod.

Thanks for idea, Uncle Doug. I made high gain preamp with 2 transformers and voltage doubler. It works perfect and very quiet. No hum. Should secondary transformer 12v CT be grounded?

I am curious how the tremolo-overdrive circuit will work. I looked at the schematic of the princeton and figured out, that the level of amplification in the powertubes is modulated by an ac-voltage, but i got no idea how to create this oscillation with a single triode. I guess it is filling and draining a capacitor? Also this voltage doubler circuit is very nice. Could it be used to create a envelope follower for an audio signal, for example to link the speed of the tremolo to the dynamics of the guitar?

EZ....The Best

One more question Doug; It If use a 24 volt secondary with 5 amps to a 24 volt and 3 or 4 amp as a second transformer will I get enough total power to use a Harvard amp head? Yes, I will have to reduce the voltages to the filaments, that should not be a problem. I intend you use this amp as a keyboard amplifier.