Tube Amp Power Supply Design 

The topics that you cover throughout your lecture are what I would’ve guessed electronics lectures would be like 60 years ago. Rectifiers and the things that are presently more esoteric. I’m really glad I’ve found your channel for this, THANK YOU very much!!

This was exactly what was looking for. I have been working on implementing VVR on my amp. Replace the voltage divider with a pot and there you have it. Thanks very much!

This behaved well in sim. Saved me a lot of time. Thanks for the video.

thank you for clear explanation for non electrical engineer tube builders!

chillaxing to watch, i learned a lot

Interesting stuff. As a novice tube amp DIY'er its interesting to hear some of these concepts explained. Like others have mentioned it would be even better if you would include how to determine the values of the parts and examples with values. But hey I'm already long happy to see new tube related content :) keep it up!

A calculated example would be the icing on the cake!

Nice video, explained everything in great detail, we will refer our students to this video. It contains all you need to know to build the regulator. I see some people complaining about a lack of values and calculations. If you can't compute the values for your requirements from the explanations in this video, you should NOT be experimenting with tube amps and power supplies like this.

Valuable clip, excellence

That was very enjoyable did I understand what you were saying NO! Yet I will watch it again and again it really was good!

I never had a rectifier tube go bad. Probably because our voltage was only 115 vac from the standard outlet. Filter caps usually went bad probably because of their age. My amplifier had a 5Y3 and the preamplifier stage used a 12AX7 wired for 6.3 volts, the power amp stage was a push pull 6AQ5. Good little amplifier made by admiral. I believe it would still be working if I still had it. I have a voltage reducer for my tube radios. Made by APC the same company that makes UPS for computers. I like to keep everything original they sound better as a tube amp. My biggest project will be restoring my dynaco st70.i bought all new tubes including the rectifier tube. The only thing on the dynaco amp that will be changed is the Selenium rectifier I have the diode that was recommended for that amplifier. 73

Awesome 👍👌

This is a series Voltage Regulator versus a Shunt Regulator, many prefer a voltage source feeding a Shunt Regulator for Audio Electronics as it is more stable to powers line fluctuations. A Shunt Regulator would have the Drain going to ground and the Source near the incoming voltage..

Nice!!!

If you enjoy this sort of stuff, go to your local community college and take some classes… maybe get an EETC associates degree.

Nice overview. Thank you for your time and effort! IMHO the title is a little misleading, though. I would expect calculations if "design" is in the title. Nevertheless, great video and hoping more of this type come out: subscribed!

The protection diode you added from source to drain in the fet is not required because it already exists as a function of how the fet is created, It is commonly called the 'body diode'... The zener diode you added as a dual purpose device to current limit the supply and protect the Gate of the fet can actually cause the fet gate to go overvoltage in the case of the input cap shorting out while the output cap is still fully charged. I strongly recommend using a bipolar transistor to sense the voltage across the current sense resistor with a series diode (1N4007) between the collector of the bipolar transistor and the gate of the fet which would allow the transistor to pull down the gate voltage to current limit, but not allow any current flow TO the gate when the output cap is charged when the input cap voltage rapidly drops to zero. You also need to add a reverse biased HV diode from the gate to the drain of the fet because of the reverse voltage pulse that can be developed across the resistor between the capacity multiplier input and the charged capacitor from the gate to ground. There are other ways of providing similar protections, but the one I described fits well into your design and provides a more accurate threshold of current limiting.

On your first drawing you should match the transformer resistance and min rectifier resistance found on your data sheet about 50-200 ohm add them and put in series a 10 watt or 20 resistors the added value should work very well…put the resistor right after the rect tube this puts a load on the tube and keeping current moving forward and not going back into the transformer and causing it to heat up saving the tube and transformer life many manufacturers did this in the 1960s also the choke inductor has a resistance from 150-300 ohms as well add these calculations in your circuit design 😀the inductor choke will lower your b+ also using a too large of a capacitor on the first stage could be bad again look at the data sheet of the tube after the choke have fun and put a giant one in but 50mf to 100mf should do plenty Also you can do a simple 5 stage filter with resistors and capacitors I personally would use a motor run capacitor for a hvac they are dirt cheap and on Amazon and are oil filled and have no esr and make perfect filter capacitors I have had very low ripple ac about .0031 at -90dbv and a standard ac ripple it will be dead quiet

For your final example where you suggest the idea of several zeners in series to add some voltage regulation to your circuit, I am recalling the use of tubes such as the VR-150. (Which we used to use.) Also, this brings to mind devices like the NE-2, as well. Just wanted to toss out the idea that one does NOT necessarily require the use of silicon zeners for this purpose.

This is the best explanation of a main power supply and filtering I have found so far. Is it possible to use a Mosfet after a rectifier tube or do you have to use a Bridge rectified B+ with a Mosfet only?

Bravo bravo bravo

Tube rectifier will be great for your tube amp.

Another question if I may: Because of horror stories I've heard about when using modern diodes in place of the old rectifer tubes and problems they can cause is that the reason for that RC time you mention ranging in the 15-30 seconds, is that to mimic the time the old tube rectifiers would also give .....as in, to help illuminate current surge and time for the tube to warm up before seeing full voltage on their plates ?

Hi Doug, I really enjoyed this and liked the way you walk through the circuit from something basic that is understandable, and slowly make it more complex. Each time explaining really intuitively the improvement. I did have one question. I really like the way old amps like Plexi etc briefly sag when hit hard. And I also really dislike hum! Do you think we can get the best of both worlds with a design like this? For example something quite saggy, momentary voltage drops across the board, and also low ripple? Just wondering if you have played around with that?

Nice job. you're Very talented at making videos. stay frosty x3

Great Video found it really useful, would you mind explaining further the job of the resistor on the output after the source of the Mosfet.

Any reason that the source follower circuit won't work with a full wave rectifier (not a bridge)?

New to the channel and am very impressed! So have you given any more thought to a real live with values example video on this? And if I may ask....what are those depletion type Moffetts you've spoke about in the other comments? Thanks!

Can I use the tube power supply with a solid state mini amp I just built?

i Like your psu design. I wanna use/have 2 x 15 Volt (1.5 Amp) transformers back to back, to get around 210 V ac ( a bit of lost from 220 V ac). after i rectify that i have like 290 V dc. the circuit i wanna build has 3 12AX7 an 1 6AQ5A tube, both have a max operating voltage of 250 V. What output voltage of your psu would you choose? the schematics says 275 V dc. i saw your example circuits and taking "p7", what resistors, zener diode, Mosfet, capacitor (appart from the 4700uF, next to the rectifier) would i take?

What about negative feedback to make it regulated?

Excellent video. And passive components for high voltage? Suppose I am building a transmitter with an RF vacuum tube needing 800Vdc plate voltage. What capacitors and inductor can I use? And where do I get them? Oops. I did not watch the whole video. At 16:00 into the video the inductor is replaced with an N channel MOSFET. I wonder if I could use P channel for negative supply?

Really nice job and great explaination of how things work. I see the link to Circuit examples is broken . Do you still have circuit examples avaiable ? I'm building a power supply for a BC-348. It is an HF receiver from a B17 Bomber. I think the regulated version fits the bill to replace the Dynamotor.

Why not put an inductor in-line before the final mosfet circuit? Get the best of both worlds? Would be interesting to see how much ripple makes it to the final circuit under load. Nice vid, thanks for making it. I stumbled in here looking for a regulated DC power supply made with just vacuum tubes. Yeah, I know, I'm a glutton for punishment :)

Would love your comments on how tube rectification SOUNDS.

Good explanation of the different supply options. How does this final circuit differ from "capacitance multiplier? To my untrained eye it does not. I'll try the last one out. Is it necessary to filter it further with an inductor or can I pass it straight to plate?

Certainly interesting, although I have my doubts. This looks more complicated as it needs to be - in my reading of tube systems schematics I've never seen anything similar. In a lot of modern tube power supplies LC filter is simply replaced with RC filter (respectfully series of them). Also, you have said it wrong, most of the times OT primary is connected directly after the rectifier (on very first cap) and after the choke comes the second node, going to the screens. But surely a similar circuit would be quite nice to provide a bias supply (even eliminating the need for a separate bias winding). I think you are also wrong about the CT PT with two diodes being in any way inferior to the bridge rectified configuration, I suspect it is much easier on PT and eliminates half of the rectifiers needed.

Hi Doug - can you tell us how to compute the components value for a 320V output? 250VAC PT? Many thanks!

14:20 You messed up the diode bridge description - opposite sides of the bridge diamond are conducting on each half cycle.

if a thermistor was put in the power supply ahead of the transformer wouldn't it help to protect the rectifier tube

With the Zener regulator you show at the end, if wall voltage drops and the zener drops out, does the circuit go back to being a capacitance multiplier?

See ELECTRONICS FROM THE GROUND UP by Ronald Quan, P 499

Wuld you please make those old wacum tube baterry charger circuet diagram? Im surching for some thing similar that can by used for magnet alternators I like wacum tubes but dont know how the automatical current cutt out circuet shuld look like with wacum tubes is it posibel useing those old external voltage regulators or those old external regulators for dc generators for cars with wacum tubes. Honestli told Im indead afraid to use it in car so was curriuse can that by some sort of cloosed loop system?

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cap choke filter

Aren't you significantly raising the power supply impedance with that current resistor at the output?

@14:26 directions of returning currents are wrong. They are returning at the other end of winding than they are entering the circuit.

I built an LM386 small amp, can I use a tube power supply instead of a battery?

Just some silly idea is that inductor there by any chance replacebel for exampel dc commitator or armature to by preciseli what wuld the result by dc generators use wave and lap windings expeciali Im refering to Amplidyne and Metadyne generators . So Im cinde of interested how those old gasoline electric trains operated exactli no one hase rewive video about them on youtube . So wacum tubes are reali cool devices

Dude, do everyone (including yourself) a favor and write a script. Its really hard to watch and understand your videos with all the "uuhh" and "uuummm" in that monotone. The content is cool, the execution is rough.

Yes, nice, but fairly useless, so far. Not one calculation. How do you build power supplies with no calcs, by "feel"?

hi sir my name is mohammad..in the past we talk together..but sir i have a problem,, i have a otl circuit with 6080 vaccum tube ..this is my question :: who must i calculat the anod resistor??? because i have a power suply with 230volt on output but i need to 170volt on the anod!!!!!! now i need know how can i calculat anod resistor????? and i dont want change anod current just i want change the voltage .....if you need to know more detail,, you just tell me and i will send for you my email ...... pleas lead me and i am realy thankyou.......