What does the Choke in a Tube Power Supply do?

[@brucetaylor1753]

I know this is an old video but this is the best explanation I’ve heard on how a choke operates.

[@autonomousindividual7780]

Little chance that there were many new developments in the technology in the last 5 years so age isn't much of a problem. Great video.

[@andydelle4509]

As usual, great video. Well explained for any novice getting into electronics. One point I think we need to make here is just like the capacitor, the choke stores energy as well. And just like the capacitor, it releases that energy when the voltage feeding it falls. One reason chokes were used in tube circuits was cost. Today that seems absurd as a choke costs many times even a large high uf/high voltage capacitor. But it wasn't that way in the 1920s through the 1950s. Large caps were quite expensive if not outright unobtainable prior to the 1940s. A choke was actually cheaper to manufacture at the time. Solid state circuitry also made the power supply choke mostly obsolete. As SS circuits use lower voltage, higher current, the required size (Henry's) of the choke becomes impractical at 60hz. And by that time we fortunately mastered the dry electrolytic capacitor. But then in switch mode power supplies that are universal today, we once again see a choke power supply. This is because the high frequency AC at 50khz or higher is easily filtered by a small choke (very low Henry's, in fact just a few micro Henry's). So in a sense we have come full circle in power supply design basics. But also note in a switch mode power supply, the primary input rectifier filter is still a moderately large electrolytic capacitor typically in the hundreds of uf range. This is because at this point we are still at 50 or 60hz.

[@WallStreet749]

I dont know much about electronics but I have always had a great curiosity . You are a great teacher your digrams help greatly in understanding. Thank you for explaining.

[@soapboxearth2]

Amazing explanation. I'm a newb and am having a hard time wrapping my head around things. But this cleared up a lot of questions. easy to understand. Thank you

[@gregj.gotham4402]

Real nice explanation of why a choke is used in a power supply. Thank you for this information.

[@acestudioscouk-Ace-G0ACE]

Another great video, I'm not a sound guy but a radio ham... never the less, I'm learning loads and really appreciate you quiet, sensible delivery style. I might have to learn the guitar now! LOL

[@b97209]

I too was struggling with "choke." You earned a subscriber. Thanks.

[@SteveHacker]

My new hero!!! WHERE HAVE YOU BEEN all this time I’ve been trying to learn electronics?! Every other YT channel I’ve found shows but doesn’t explain, explains but doesn’t show, goes way under my current knowledge level, or goes way over it. You should have a million subscribers. BEST video explanation of this I’ve seen YET! Subscribing and watching ALL your videos! As an aside, I’d love to know how you learned electronics. I’m fascinated by discovering what got other people to where they are... If you haven’t already made a video about your background, PLEASE DO! Thanks! 😊😊😊

[@wellusee]

Excellent video well done , if only I was 40 years younger , these were used in florescent lights to stop flicker. lovely sound from old equipment.

[@Ten80pete]

4 minutes into this video, and you have already taught me (in a manner that I will remember!) more about tube amps than almost 6 months of reading books/blogs/articles and even watching other content creators. I mean Rob Robinette has a invaluable reference site, but it kind of assumes that you are already fairly familiar with tube amps and schematics. When you buy a B-52 AT100 that is already infamous for electrical issues sight unseen, and the seller swears up and down that it was working when he sent it, but the 20 year old masking tape has markings that highlight the one tube that shows scorch marks on the board... well, lets just say, I'm out of my depth after replacing 3 bad resistors, 2 blown fuses, all of the tubes. Still will not power on. I Love the B-52's, but I might as well have gotten a Mesa-Boogie for the amount I'm spending to repair a $500 amp.

[@Brenda-jf2pe]

This is one of the best explanations, I have ever heard in my 75 year’s . JohnBoyUtah KJ7TBR 🇺🇸😎🎙📡

[@TonePriest]

Thank you for doing this. It's great to see theory put into practice - and a nice, flat line of pure DC voltage!

[@jerkerfridh8189]

Great tutorial ! I started out watching D-lab and M.Caldeira which raised my interest but also raised questions such as the "choke". Visualizing the explanation helps out a lot for us who don't have english as the first language. Thanks ! And yes that is my real name, it's Swedish.

[@mikoschannel6413]

The best explanation. Thanks for posting this vid.

[@MikeWest_W]

Outstanding tutorial

[@bondsongmusic]

Awesome explanation. Thank you very much!

[@raymondmenard5444]

Man oh man that was well explained ! Thank you for sharing your knowledge with us. Merry Christmas and God bless.

[@green95gt]

YOU TUBE GOLD...as far as I am concerned...! Thank you so much...now I don't have to search some university library for a EE textbook to sort this out...! Very cool tip with the duncan amps software as well...! Thanks again...!

[@audiorick841]

Excellent explanation. I learned something today. Thanks!

[@jeremytravis360]

You took me back to 1969 when I went on an evening course called the fundamentals of electronics and i built a TRF or Reaction radio. My tutor never went into so much detail, so thank you.

[@dogpoundoatthetube7756]

Just want to thank you for sharing your knowledge once again, you are a good teacher and easily understandable.

[@TheDecguy]

Great video explanation of how a choke works to filter the circuit. Thank you.

[@Eric-uf8zx]

Nice video, thanks. I find it helpful to add a load when testing for ripple. Switching between 2 loads can also help provide details on what kind of output impedance you can expect from your power supply design.

[@dayradebaugh]

Enjoy your videos. Nice job; very clear and helpful.

[@anthonykettle2039]

Thanks so much! Learned an absolute ton.

[@JesusIsLordofMybeing]

Awesome explanation and lab test showing in real time!!

[@romannumeral5547]

Great explanation and demonstration! Thanks. 🤗

[@edwardhannigan6324]

Awesome explanation, and demonstration..! Learned loads off this vid..😀

[@mvaron2546]

That's a really good demonstration and explanation. I would have also liked seeing the effect of the capacitor that follows the choke. It looks like it's shunting an even higher frequency to ground to smooth out the plate voltage even more. Thanks again.

[@EJP286CRSKW]

Marty Varon It is shunting the same frequency, to form a third pole of the filter, which is now 18dB/octave.

[@David-zu9op]

Excellent video, thanks for this. Just what I wanted to know.

[@harryshector]

The voltage of the high voltage secondary of the xformer is 780 VAC RMS. The P2P voltage will be 1074.8 V. The P2P voltage of each half of the secondary will be 537.4 V.

[@halbertking2683]

I replaced all the filter caps in a customers 70s Fender Twin Reverb guitar amp. The amp still had more hum than normal. The problem was a shorted choke. I've probably had maybe 5 or 6 chokes fail in 30 years of servicing tube guitar amps.

[@Slugg-O]

Very informative video that answered a question I've had for a very long time, and thanks for the PS software tip.

[@djfrank59]

Many early radios, and guitar amplifiers used the speaker's field coil as a filter choke for the power supply. Including the early 31H Leslie speakers.

[@TheGuitologist]

Great tutorial.

[@Blueglow]

Thanks for watching Brad. Check out my video I'm posting tomorrow, it has a shout out to you :-)

[@xnotx2]

Good explanation and showing it on the scope is great. Wish I had the cash to follow this build along with you.

[@hissst69]

Wow, that was amazing, Best explanation I have seen, thank you.

[@georgecampolo9948]

Nice videos. I'm a ham operator who plays with old AM "Boat Anchors" and have found a lot of overlap with your toys. If you are not already you should think about getting a ham ticket and getting on AM with some old tube gear. I will be watching. Thanks, George

[@mikesimmons1307]

Basically, a choke cleans up the signal right? How would I go about getting a ZZ Top or Led Zeppelin sound (tone) from a tub amp?

[@jp040759]

Great explanation. Thanx for putting time into the demo. Great job.

[@fifanoob2990]

Excellent explanation!

[@johnfkiii]

Really concise and informative explanation. I’ve always wondered what the chokes did in my amp -thanks

[@cobar5342]

Thank you for a well presented video

[@oldricky]

Great video. Thank you for the excellent video. I have a question or two. I noticed in your schematic the neutral is switched. In my jurisdiction that is not allowed. The neutral must NEVER be open. Only the line side of the AC. When the neutral open the chassis is always live with a potential of 120v to ground and the could be you if the earth-ground (green) is not, for whatever reason, present. All fuses/CB must be on the line side for this reason. Again, that is my local code but maybe not yours. Next, I have a few old original Dynaco ST-70 amps. One was functioning perfectly when I decided to install a three-pronged "earthed" plug. The green went to the metal chassis. When I plugged it in the resistors on the rectifier board exploded, I assume due to high current ground as this amp has one lead from the power trans to the star ground along with the electrolytic capacitor can tab and other leads from the rectification board. I'm just in the process of replacing the caps and the board, I have read other have earth grounded that chassis w/o issues other than some hum (which makes me crazy why the chassis should have ever had anything to to with carrying current). My first thought is that it/s a polarity issue. Any thoughts would be greatly appreciated. Many thanks.

[@danielthomas3057]

Nice video explaining the power supply and purpose of filter chokes. Why does Paul Carlson refer to them as reactors? On your schematic L on the IEC connector is shown connecting to the 2 amp fuse and then to the transformer primary. N is connected through the switch to the other end of primary. Switch should be on L side between fuse and transformer.

[@alexreeve]

"Reactor" is an older term, it refers to the effect of "reactance". But it was always ambigious because reactance is not unique to coils, it also happens inside capacitors (capacitive reactance/inductive reactance), so it was never clear wether you are talking about an inductor, a capacitor (or sometimes also combinations of both were called a "reactor"). Paul Carlson seems to use the old terms on purpose when he talks about vintage gear.. you also hear him saying "megacycles" or "kilocycles" very often ;)

[@EJP286CRSKW]

Daniel Thomas Both switch and fuse should be on the hot side.

[@danielthomas3057]

@@EJP286CRSKW Yes, that's what I was saying. His schematic shows the fuse on the hot side however the switch is on the cold side.

[@Kalkaekie]

Appreciate the good explanation ! Helped a lot !!

[@jacobdykstra8499]

Great video but I must politely point out a small yet important detail you missed. All the voltages you refer to in this video are RMS and those are not the same as peak to peak. For example common household voltage is well known as 120 V but that is RMS, the peak of this sine wave is actually the RMS voltage multiplied by the square root of 2 which turns out to be around 170V peaks. This is important as this peak voltage is what is actually rectified and stored in the capacitor which is why your DC voltage is higher than the RMS voltage when rectified. Same for the transformer secondary voltages. The rectified voltage will be 380 times square root of 2 or 1.71

[@garybevis8691]

Hi Jacob, the square root of 2 is 1.414 not 1.71, hence the 380 volts RMS when rectified becomes 537 volts DC. You are correct about house peak to peak voltage in North America is very near 170 Vpp or 120 x 1.414. :-)

[@jacobdykstra8499]

@@garybevis8691 You are right! I don't know where I got that number from. I think I was thinking of root 2 and root 3 simultaneously root 3 is about 1.73. I use root 3 more at my job for 3 phase conversions.

[@davidfuller581]

To be clear, wall voltage is more like +/- 170VAC P-P, 120V (ish) RMS.

[@stevenstewart5980]

I'm glad you posted this David Fuller. You are correct. I'm really surprised how many people have worked in electronics for years and don't know that the 120 VAC (or 117 or whatever) wall voltage is RMS not Peak to Peak. It makes me wonder if they have never looked at the wall voltage on an oscilloscope.

[@kgsalvage6306]

I think most of the time, the person explaining something don't want to confuse viewers about it or just skip it. Most probably know.

[@misterhat5823]

Why aren't there center taps on the rectifier filament windings? The connection of the load to one side, as is common, introduces significant 60Hz ripple.

[@vincentrobinette1507]

In filament rectifiers, the filaments in the 2 halves are in parallel. You can choose either pin 2 or 8, and there will be no difference in plate voltage due to filament voltage.(5Y3, 5AU4) If you have a unipotential rectifier, it is necessary to draw positive from the pin #8, which is connected to the cathode sleeves.(GZ34, 5AR4)

[@markstewart1807]

Thanks so much for your excellent video and explanation I have learned a lot from it.

[@thierryhanot7610]

Crystal clear ! So many thanks

[@lawrencehudlin]

Straight forward and easy to understand. AAA☆ video

[@dryzoneau]

Great explanation, thank you.

[@JoleenHurley]

Kudos ur schematic is very good in order for ur choke to do its job thebinput C should be relatively low and the C after the choke should be 20 or so times higher good power supply design

[@jacknewton3150]

Hi so i just watched your video on how chokes work and was hoping you could come with a answer for me. I'm building a amplifier that is going to use 6 KT88 tube witch will draw around 842 ma and 6 smaller preamp tubes that will draw around 2 ma so lets just round it off at 845 ma I'm going solid state on my power transformer using 8 N14007 and this will be a filter input not choke input amplifier. the capacitors will be 50uf @ 500v the first 2 at the power supply wired in series parallel followed by 2 at the screens of the kt88 also wired in series parallel and 4 more cap in the preamp section all 50uf @ 500v. I'm having a power transformer made that will be 500 0 500 at the H.T how many hennery do i need ? I've gotten different answers like from 4-8 hennery but o more than 10 also would you know how many ohms it would be thanks Jack

[@jimhenderson2308]

Just to be clear are not these voltage waveforms you reference only valid when there is a load resistor present on the output side of the power supply? It looks like the output is open circuit.

[@cocosloan3748]

Beautifully explained..Thanks!

[@MichaelLloyd]

Also called a Pi filter? The choke opposes a change in current by storing and releasing the energy in an electromagnetic field. The capacitor opposes a change in voltage.

[@Panuwatboy159]

Watching this with my DIY tube amplifier. One question, suppose I have an unused supercap (1.2 mF 400 V), is it OK to connect it parallel to the rectifier output and eliminate the use of a choke? Since a bigger capacitor will smoothen the ripple even more as well.

[@stephenneff2926]

Thinking about a using an inductor on my next supply. Thank you!

[@jimcatanzaro7808]

Can you tell me what is a acceptable ac ripple voltage after my capacitor and choke I read .9vac

[@1Dcorace]

This was a really nice, informative video. I would like to mock something like this up so that I can add a choke to an amp that was not originally designed with a choke. I've added a choke to a Princeton Reverb and had to install a lower than spec resistor after the choke to drop voltage to the next node in the chain. The choke alone dropped me 3v., I needed to drop 20v. I'd like to add what you did to a build board. Do I need a load on the power transformer to do what you just did? I always put a 4, 8, or 16 ohm load on output transformers to run diagnostics so I don't have to listen to signal coming out of a speaker. Does the same methodology apply to power transformers? Can they be powered up open ended?

[@Dumdadum76]

Great video! Maybe you should put the fuse and switch inline in the L channel of the power input though. As a best practice, because whether the fuse goes or when you switch, in both cases you want the live input connection to be interrupted, and not the neutral.

[@amrkoptan4041]

great video, great effort !

[@primedirective00]

Do you recommend actually switching to "boutique" capacitors or is that just marketing BS? Would love to hear your technical description of this

[@jimcatanzaro7808]

Best capacitors are oil in paper u can use motor run capacitors for hvac systems u can use ac capacitors there voltage ratings are 1.4 x of what they are rated at at ac voltage and they are cheap and long lasting

[@evankolpack]

Great video. A couple corrections, VAC peak to peak is not the same as RMS. Line voltage in the US is about 340VPP (+170/-170) which translates to about 120VAC RMS. You might think this is pedantic, but if you're ever using a function generator to run appropriate signal through a circuit, you'll need to know the difference or stuff can go poof, or get calibrated incorrectly. Also, caps by themselves aren't low pass filters, they're high pass filters. You can put them in a circuit so they pass HF to ground, thereby creating a LPF, but by themselves, they're HPF. Also, not a correction but worth mentioning, in modern gear, voltage regulators are also often used to smooth out ripple current....of course you won't see these in oldschool tube circuits, but they're still pretty neato ;)

[@buildstoys]

Thanks for the explanation!

[@richardkice2113]

hi ! really cool bench-top prototyping stuff going on at 13:55 or so . . . where can i get that green tube socket thing shown ? thanks !

[@billwilliams6338]

BLUEGLOW ELECTRONICS Is the Chokes storing current like a reservoir like the filter capacitors or is the Choke doing something else to the AC ripple, not sure if the Choke is regulating the current? Most Power tubes 6L6,EL34 use a B+450vdc on the plates, if you increase the B+ to +600vdc would this increase the AC ripple but why would it increase the AC ripple? i would think it would decrease the AC ripple because more B+ voltage mean less current draw from the power tubes. When you're biasing the power tubes in an amplifier circuit how do you bias the compression of the power tubes the 1dB compression point of when the power tubes start to compression? because its say to bias tubes at a 30mA bias current per tube to be safe but how do you know when the tube is compressing?

[@larryshaver3568]

In a stereo amplifier how does the B+ get divided so the anodes don't cause crosstalk?

[@jon4715]

Any thoughts on Schiit's new choke-based Tyr power amp?

[@zeb4128]

It looks that you mix peek to peek and RMS values. It is not the same.

[@eugenepohjola258]

Howdy. Chokes try to uphold the current. This causes the anode voltage to drop in suddent current demands. For instance a kettledrum is hit. When the current demand goes down the anode voltage will rise. This can cause a pumping effect on the sound. Chokes were used earlier when there were no large high voltage capacitors available or they were crazy expensive.

[@luisbosch9433]

Excellent explanation but the modeling experiment even better. Would you provide a schematic and parts list for your test? What did you use for a load on the rectifier circuit?

[@ronwebb9249]

How do you have 5v and 400v on the same line ?

[@dedskin1]

Choke filters the Ripple like Capacitors , but does so much better because magnetic field is a lot stronger then Electrostatic that is weak , good only for Voltage , no current , while Coils are good for current no voltage . So that is why combo of those is the way to go

[@DonBonin]

Hi Mark, why not just two electrolytic caps in the CLC? What's going on with that Solen cap as the first filter?

[@MrAudiophile101]

thank you maestro 😘😘😘

[@harryconover289]

I have been using the 1N4007 for a replacement for tubes for ten years now I know of and have dealt with are flash over and the turn on transient the coil stuff is fight on

[@thomjmoore]

Are you familiar with Matt Renaud's power supply design article where he uses a 2 stage filter scheme using 1.5 H chokes instead of a single stage using the 10 H. Better ripple figures and a lower cost. Very interesting topic. Thanks for your video.

[@vincentrobinette1507]

Such a scheme will also result in lower resistance losses, and higher core saturation currents, allowing the power supply to handle higher peak current, with less voltage drop. It just means a few more components to mount, despite their smaller sizes.

[@David-nu8qc]

Thank you. Question is there and issue using a larger uf capacitor (32 or 50 in place of a 20uf) for the power filter?

[@silasfatchett7380]

A tube rectifier has a maximum capacitance specified by its manufacturer which can be found on its data sheet.

[@silasfatchett7380]

@Kevin Counihan Thanks! I stand corrected.

[@kevincounihan6120]

silas fatchett. You're welcome, no problem. Just trying to clear up the misconceptions here on the 'tube. 11-06-2019.

[@littlejohnny1498]

Good video.Thanks.

[@alfonsolarcinese8926]

Nice video. Do you know a good place where one could find sockets for tubes and rails for point to point soldering elements in a tube circuit? Thanks!

[@jackallen6261]

Ebay

[@joellandry8407]

Thank you. I didn't know that.

[@williamsquires3070]

Actually, it’s 760 RMS from one end to the other, ignoring the center tap, as all the other specified transformer voltages are RMS. Therefore the P-P voltage is twice the peak voltage, which is: 380 (V RMS) times sqrt(2), or roughly 537 volts peak, so the P-P is twice this, or roughly 1,074 volts peak-to-peak. This is important, as you need to make sure the capacitors have a higher voltage rating than the pulsating, full-wave rectified DC peak (here, 537 Volts), so the 630 volt rated, 10 uF capacitor is good!

[@jacknewton3150]

Hi William can you help me I'm building a amplifier that is going to use 6 KT88 tube witch will draw around 842 ma and 6 smaller preamp tubes that will draw around 2 ma so lets just round it off at 845 ma I'm going solid state on my power transformer using 8 N14007 and this will be a filter input not choke input amplifier. the capacitors will be 50uf @ 500v the first 2 at the power supply wired in series parallel followed by 2 at the screens of the kt88 also wired in series parallel and 4 more cap in the preamp section all 50uf @ 500v. I'm having a power transformer made that will be 500 0 500 at the H.T how many hennery do i need ? I've gotten different answers like from 4-8 hennery but o more than 10 also would you know how many ohms it would be thanks Jack

[@LandMineFX]

Is that an Edcor?

[@bblod4896]

Thanks for the informative video. Where did you purchase the lazy Susan tool caddy?

[@BT-iy3fb]

Mark, where did you get the tool caddy, that is on your bench behind your chair ? ( it looks like a desk organizer ). Thanks b. Toth

[@Nihil1st1347]

I wonder: is there no short circuit in your scematics from the rectifier tube? I am a scholar, always learning.

[@giovannicirlincione3803]

The circuit with the respective load of el34 has been simulated on multisim, with the choke and with the gyrator and actually seems that the choke and the gyrator identical same

[@RitusG]

I wish you would have swapped out the choke with a resistor and showed that on the scope. Still a great video.

[@drew945101]

Do nodal resistors basically do the same thing that the choke is doing? I believe that's what they are called, but they are basically votage dropping resistor(s) that go in series in-between the filter caps. It's something that you'd typically see in a guitar amp.

[@silasfatchett7380]

An 'internodal' resistor serves two purposes. It drops DC voltage and also works in conjunction with a following filter capacitor to form a low pass RC filter to reduce ripple. A choke, due to the low DC resistance of its coil, has little effect on the DC voltage but it forms low pass LC filter in conjunction with the following capacitor which reduces ripple more efficiently than an RC filter.

[@countryhamop4580]

Liked most of the video but the rectifier doesn't "flip" half of the waveform negative to positive. You have two diodes alternately conducting around a common center tap. Each diode adds its pulse when its side of the HV winding goes positive with respect to the center tap.

[@JelckedeBoer]

I came across a place that sells lots of transformers and Chokes that are relate to tube amps. Often there is no writing on them. Could you make a video on identifying such components? Especially estimating or measuring the current limits of these hunks of metal... Thanks !

[@McSlobo]

Maybe the name "choke" comes from the fact that you push all the current needed by the amp through this component while wanting to ensure there's enough steady breathing material available for the amp.

[@kgsalvage6306]

Question about current in the choke? Chokes always say working current rating. Higher current you'll have less inductance and lower you'll have a higher inductance. Is the current rating the maximum rating, or can it be exceeded some? Thanks again!

[@countryhamop4580]

Determined by the gauge of the wire. Not a good idea to exceed ratings- wire will get too hot.

[@tibortruba]

Magnetics, inductor, gap, storage of energy, hysteresis?

[@Nah-kh]

Is China brand choke any better than Japanese made?

[@kd5ozy]

you said at the begining of your video ac household voltage is around 120v ac "RMS or P-P" is p-p and rms the same thing. You made it sound like it is?

[@Blueglow]

Sorry 120v, would be RMS, I was pointing out the Peak to Peak waveform in the diagram. P-P would be about 170v

[@EJP286CRSKW]

Blueglow Electronics No, that would be peak. P-P would be double that. 120VRMS/0.7~=170VP X 2 = 340VPP.

[@kd5ozy]

I love watching people learn.

[@kd5ozy]

doing a video is a good way

[@ivandoe8496]

Which simulating program is that you use ?

[@kimhansen6384]

PSU Designer II from Duncan Amps: duncanamps.com/software.html, and it is for free.