Uncle Doug, you are an awesome teacher! Sometimes I have to go over your material several times to get it, but you explain things very well. I have run into a hand full of people in my life that I consider true teachers, you are right at the top of the list.I have been intrigued by capacitors since I began learning how guitar amps work. But I admit, some of it has been pretty much over my head. This series on caps has really opened my eyes to what's actually happening during operation. Thank you! You really are awesome man...
You're welcome, KV, and thanks for your extremely nice comments. Supportive words such as yours really make our YT channel a worthwhile and rewarding experience for both Rusty and me.
I'm probably repeating myself, but your videos are really great. That goes for all three parts in this capacitor series, and all other of you videos I've seen so far. I don't know a better teacher in this field. You explain not just "how" but also "why" in an excellent way. I have got so much use of the knowledge you share. Thanks, Uncle Doug!
Best mini-series on capacitors I've seen. 3D-animations? Fancy visuals? Nope, that's not necessary! All it needs is someone with profound knowledge and an unsurpassed talent to explain! ... oh, and 2 trustworthy sidekicks like Rusty and Jack. Gotta love the pet-interludes :D Great work, thanks muchly!
Hey Uncle Doug, Ich simply wanted to extend my huge thanks to you for keeping up your quest in explaining the functions of amplifiers to the simple-minded like myself. I recently finished my third amplifier build, a complete scratch build of an Orange Super Bass from the late 70ies, after starting out with a Marshall 18Watt Kit and converting an old Siemens Radio into a Vox style Amp with two 6BQ5 tubes, a 12AX7 and an EF86. All that would not have been possibly, without your work, so tahnks a lot and keep 'em conversions and scratch builds coming! Greetings from Germany, Phil
Thank you for all of your time, knowledge, and willingness to teach us the things you know, Uncle Doug! Your videos are the best teachings i have found on RU-vid... Easy to grasp the concepts, yet still very deep. Bless you sir!
I cannot get enough of your videos -- just the right tempo, and very thorough explanation -- you must have been a professor somewhere -- I taught math for 15+ years and know how tempting it is to just go ahead full speed -- you explain things thoroughly and also anticipate the questions that would come up...and Rusty is still deciphering the milk-bones,...Hang in there Rusty -- you'll figure it out..Thanks for these good videos..
You're quite welcome, Bill. I too was a math teacher for 17 years, and probably developed my video approach as a result of what I found to be a successful teaching strategy.
Hello Mr. Uncle Doug. I find your video's to be very informative and well explained. I'm new to these things, being a musician/guitarteacher all my life (55 now). I finally get to understand the working of tube amps which reduces costs on simple maintenance. The cat and dog intermissions always bring a smile on my face :-) Greetings from the Netherlands.
I have learned a great deal from these three videos. Finally I understand why caps are used in tone circuits. Very many thanks. I really enjoyed the biscuit test too. Thanks very much.
I really enjoyed this series on capacitors. I'm an old electronics buff but was in IT for quite a while during my career, so I've enjoyed the refresher. But I mostly enjoyed your videos of Jack and Rusty. Loved your comments especially the CAT scan one. 🤣
excellent once again! I loved the use of caps to get rid of unwanted visitors as well as the discussion on electrolytic caps! oh, and of course its good to see Jack coming out of his shell!
Great video series! Will there be some other series like this in future? So informative and clear and your drawing skills are so good! Great job, as always. Honor to you and Rusty, Uncle Doug! =)
Thanks so much, GW. We're going to take a little rest for a few days and then start looking around for new topics. Best wishes to you from all the gang at Chez Rusty.
Hey Uncle Doug I have been watching your videos over the past six months and have enjoyed every minute. I have seen most of them and using the information in my attempt to learn how to do some amp servicing for myself. I studied MET in college and had some EET classes as well and did well in those classes so I do have some background albeit long long ago. I am amazed at your knowledge of so many different areas and not only knowledge but apparent expertise. You are truly gifted sir. My question. I noticed you have recently stopped posting videos. I am saddened by this event and hope that you are okay. With the assumption that you are doing well, I am asking if you intend to produce anymore videos? I am hoping that you are just busy and that my message finds you in good health. Regardless of your intentions of producing videos or not, I sure wish you my best. My Best to you
Thanks so much for your concern, Scott. We've been sidetracked by some new hobbies and fully intend to continue making videos......hopefully in the reasonably near future. Until then, our best to you and yours.
Uncle Doug deserves a medal of honor! Always professional in depth of things explained.🎖 Also I stuck into some thing called vintage "dual can capacitors". A high voltage elektrolytic can cap with multi capicity tags in in case I got dry out one in circuit I want to replace this thing. The last thing I want to do is ask some stupid question. I doubt in what way it opperates in the circuit. The diagram shows... power transformer(secundair 320VAC>rectifier>Capacitor 16+16+16uF(MFD) 400VDC (outher can is negative) The 3. 16uF tags are connected with resistors and each tag has a different lead for function. I wondering is this thing parallel or series inside constructed? I ordered 3 separated axial capacitors with equal vallue (3x 16uf/400VDC) with the purpose of replacement. So series or parallel is to essential to choose. Hope Uncle knows because he knows best. I can show diagram if required 😊👍🏼greetings
The three capacitors are separate within the can.....just like the three separate capacitors you bought. They are not wired in series or in parallel. Each one connects a different point in the power supply to ground......just like it shows in the schematic.
Uncle Doug Thank you so much Uncle Doug allways much appreciated. I think I was thinking too complicated. When the 3 positive lugs of that old can cap connect with each other with a 2.2k resistor from lug A(feeding VDC)>B followed by 4.7k to lug B>C. I was a bit confused.. i meassure a doubler in capacitance and its old, its dangerous, certainly working with high voltage capacitor. Better ask before harm or die 😊 👍🏼thanks and greetings from Netherlands
I find these to the point explanations nice and soothing, though I knew most of it already. Nice to hear them in the context of a tube amplifier. About the cat: there is a Dutch saying "Omwille van de smeer likt de kat de kandeleer" or "Because of the grease the cat licks the candelabre" so I think the waxy nature of the condensators is the attraction.
We're happy to hear that you enjoy our videos, Roeland, and enjoyed your rather unusual saying. You may be right.....perhaps the wax has an appealing odor.
I definitely have to send your videos to my college professors, so they can learn how to explain complex subjects easily and passionate the way you do! I just love your videos, full of information + a very easy english to listen and understand. Greetings from Brazil!
I'm very flattered that you feel that way, AM. Thanks. Like you, throughout my formal education, I had some really good teachers......and some really lousy ones.
Maaaan uncle doug .. guy must've really pissed you off .. had a flash cap knock me off my feet once when I was little so I guess the guy wasn't so badly hit :))
After watching this series, I then went back thru them again to take notes. I write really small, I took 10 pages of notes. Now I see why you didnt recommend a book on this subject.. You are "The Book..." lol So much knowledge you hold and I'm blessed to be able to learn from you. Thank you Uncle Doug. I will become a Patron member and show you much support as this virus stuff winds down. Now off to the Resistors 101 class you have.. stay safe and God Bless.
you worked for NASA didn't you? It's ok. We still love you. What I love the most is the story of how we talk to space ships millions of miles away. Like breaking the speed of sound, some helped design a circuit that could adjust for the time shift a million miles away and make it look easy. That is what you do. With out guys like you we could not see what Pluto really looks like today. thank you.. just sayin' you are a bad a** teacher. You make it easy to be smart.
I really like your approach to teaching, factual and clear explanations how things happen within components.........the speed at which you move forward and length of lesson is spot on. Those of you from the "Electronics Generation" have an amazing ability to explain things in High detail, yet simply..........please please please keep doing this sort of thing, or the true skill of the Electronics Tech will be lost in this generation.........the age of the IC has taken away the basic principals of how things work in the "Engine Room" of electronics. I am going to refer new players to both your and Elpaso's channels for learning aids.......Bringing your wonderful old dog and cat into these is a brilliant way to wake people up and refresh them into paying attention.....plus its great fun......you are a master educator , and I thank you for taking the time to pass your knowledge on.
Thanks so much for your very nice comments, HE. Rusty, Jack, and I really appreciate the fact that you appreciate what we do. In return, we wish you the very best in all your endeavors.
Your channel has inspired me to try and build my first tube amp from scratch. Im a web developer who has been rewiring guitars and fx boxes for years but never an amp. with the dangers in mind, building a 15watt tube amp could be so much fun for me. Any suggestions for a model/schematic? I realize something like a 5e3 is better for beginners but id like to gave something that uses el84s (2x) and results in 15w.
Greetings, Luke. It's great to hear that you are ready to build your first amp. My preference would be the 5E3 Deluxe, but if you are more inclined toward a DE amp using EL84's then perhaps a kit like this would be of interest: www.ebay.com/itm/Classic-British-18W-18Watt-Chassis-DIY-EL84-Amplifier-Tube-Guitar-Amp-Kit-/252385890210?hash=item3ac35f0fa2:g:avQAAOxyrUZRyqIs If you want to build completely from scratch, then download the schematic of a DE EL84 amp you like, make up a parts list, and order the components from Antique Electronic Supply. You will probably have to fabricate your own chassis, however, if you go the scratch-built route. Good luck.
For whatever reason, I guess it is just "my time" to watch all these videos. I have not fooled much with electronics in many years. Some of this information was taught to me years ago. However, I am at a point where I can really absorb it. REALLY appreciate this stuff!
32:17...if you're gonna try to "reform" an old electrolytic capacitor, you'd BETTER apply a variable DC voltage! If you're gonna use a variac to control the applied voltage, you'd BETTER have a RECTIFIER in the current path- otherwise, you'd be applying AC voltage across the capacitor.
Thanks for the VERY educational and entrertaining video. @20:06, how do we carefully choose a value for the capacitor to achieve the result we are looking for? Thanks! You have a very valuable "Cap-sniffer" You could make a lot of money offering Jack's services to hobbyists all over America! Cheers.
By using formulas related to phase shifting, Bongo, or by experimentation using values that are known to work in oscillation loops (i.e. look at schematics). Jack already makes more in a week than I make in a year, mostly working for the DEA :)
Back in 1973 I first separated from the US Army, following 3 years service, one of which was in Vietnam. When I got to my home town I was immediately hired by the Police Department now I was not hired because of my experience in the Army, I was a pole jockey and also cross trained as a teletype operator. It was, however, the simple fact that I had served in Vietnam at all. You see the City had a grant from the FED that if they hired a Vietnam Vet, the Fed would pay all my salary for 1 year, and 1/2 for the next, 1/3rd for the following. A tremendous bargain for the City. At any rate, the most despised part of that job was the destruction of unwanted pets that had been caught by our dog catcher (in reality it was one old drunk who could catch a few, and we police officers who could just open the back door on the squad car, the dog would love riding, usually just jumped right in!) We were to take the dog to the city dump, dead animal pit and shoot them in the head. Most of us had several dogs because it was just, well horrid killing perfectly friendly dogs, our families got used to the pitter patter of the little feet at 3AM. Why, you may ask, are you telling this tale to begin with? Well one night I hit the dog pound to pick the do be destroyed only when I opened the outer door, this beautiful blue healer jumped over the dutch door bottom and licked me on the face. Now I am kind of sentimental, they tell me that was one of the things that made me a great cop, and I just could not shoot that dog, or the 5 puppies she had with her. Well I loaded all six of the dogs in my squad car but instead of going to the dump grounds, I headed to the farm that I was renting on the outskirts of our fine little town, and that dog was named Lady, she stayed with us for the next 20 years till she had a stroke and died in my arms. One of her puppies looked exactly like your dog! Ah the things we used to do.
Hi Uncle Doug, what are your go to brand/series of capacitors to use in preamp and poweramp sections of an amp. I'm looking at doing a cap job on a bass amp and would appreciate your recommendation. BTW keep up the excellent videos, I'm always eager to watch. Thanks.
I use good quality but economically priced capacitors from Antique Electronic Supply, Declan, such as Illinois or Mallory metalized polypropylene tubular resistors. I also like Sprague Orangedrop caps for a vintage look.
I still didn't learn why electrolytic caps exhibit a polarity effect. Also (in your tone stack video ) you never explained how the resistor effects the frequency of the R/C network. This as I understand it, is because when a cap becomes saturated it conducts less at all frequencies. Without some path to ground, the cap remains charged Thus the greater the resistance the longer the discharge rate and is this which effects the frequency of an R/C network. Am I correct in this?
The frequency response of capacitors depends on the speed with which they can charge and discharge. Low-value caps can charge and discharge very quickly, so they will allow high frequencies to "pass"......and vice versa. The resistor's value alters the charge/discharge rate of the cap and can create finely tuned thresholds of pass or fail (RC filters).
As usual, an absolutely brilliant series of simple yet effective explanations. The only thing I'm left wondering is who are the 16 jackasses that disliked it.....
Has Rusty now replaced Mighty Manfred as the official wonder dog? Not that he doesn't deserve it, but you may receive a 'cease and desist' notice soon from Tom Terrific's attorney...:)
It appears that the voltage lags the current in capacitors in the AC circuit and as it relates to the oscillator you show in the schematic and your own drawings. Is it the current that is being sent back a head of phase or the voltage lagging the current that is being sent back to the other grid of the 12AX7? I hope the questions aren't so ridiculous. Thanks for answering my questions up to now no matter how silly they may be.
The current leads the voltage in capacitive circuits, so the phase is negative. To me, it's because you first apply current to a capacitor and then the voltage builds. Perhaps this diagram will clarify the relationship: hyperphysics.phy-astr.gsu.edu/hbase/electric/phase.html
So to properly understand the dielectric being only on the anode means the capacitor has a preferred polarity? With regards to the voltage rating i assume the electrolyte can pass charges so doesn't it effectively short the isolation and hence voltage rating. That is, its like bringing two high voltage cables closer . Re the caps leaking : it is a massive issue with circuit break downs , i would have thought they would have a much better construction by now since the 70s..
Yes, it appears that the polarity is based on which plate has the Aluminum Oxide coating. Current doesn't pass through the electrolyte, its ions dissociate to create an opposing charge on the plates. Yes, DC leakage is a big issue, especially in coupling and filter caps.
Not sure if a Cat Scanner (named Heath, short for Heathkitten) is actually cheaper, long term, than a high end capacitor tester. The wife has a different opinion on the selection criteria. -Joe
Thanks again Uncle Doug. Maybe you should write an in-depth book about how amps work, I bet it would be one of the good ones out there ...Dang! I already want to buy it!! ;) Cheers! EDIT: how about an Amp Design Analysis series explaining and comparing the design of famous amps? like the tweed deluxe, the tweed bassman, tweed twin, princeton reverb, etc... That would be so friggin' awesome!
You're welcome, N&C. I'm not sure how many people would pay for a book when the contents were available for free on the Internet.....but it's an interesting suggestion.....as is your second idea. I will keep them both in mind. Thanks.
+Uncle Doug it is not about just the content, it's about "what" content and "how" you put it together. Besides, it's kind of tiresome to read from a screen, I prefer paper myself ;) ...AND you are an awesome teacher, I love your videos. Have a great week!
Are tremelo caps polarized electrolytic s ? Where in the amp sections are polarized electrolytic used - and where in the amp sections are non polarized, non electrolytic s used.?
I've been binge watching your vids since I came across them a couple weeks ago. This is amazing stuff. I have an electrical engineering degree, but I've been stuck in the world of software for the last 20 years. Your videos have rekindled a love of circuits that I'd almost forgotten about. And your delivery and wit are just icing on the cake. I just finished this series because I was hoping to find out how to determine which type of cap to use based off of a schematic. When building an amp off of schematics where should one use polar vs non-polar caps. Orange drop vs electrolytic? Do you have a video that I might have missed (or not yet gotten to) that covers all of this?
Welcome, HW. Thanks so much. Electrolytics are used exclusively for power supply filtration (usually 10 to 50uf @ 450 to 500V) and as cathode bypass caps (usually 25 to 50uf @ 50V). All the remaining (tone and signal) caps are non-polar, i.e. Orange Drop, polypropylene, etc.
Excellent vid again Doug. Very thorough explanation of reforming electrolytic caps and the balance of phasing. Thanks as always and tell Rusty and Jack that Carl sez hey.
Muchas gracias por toda la data, tus videos son sumamente claros! estoy viendolos uno tras otro. Incluso siendo en ingles se entienden perfectamente, saludos desde Argentina!!
De nada. Estamos contentos de que disfrutar de nuestros videos. Aunque somos de diferentes países, compartimos un interés común en la electrónica de tubo. Los mejores deseos de Rusty, Jack y tío Doug.
Uncle Doug, Thanks for these great videos. Questions about testing and reconditioning electrolytic capacitors using the "variac method". I am working with power supply caps in the 10 to 100 MuF range. Can you apply an AC 60 Hz voltage to recondition them, or must you use a DC (or pulsed DC from a rectifier) to do this? (I think the answer is DC only.) I tried using a gradually increasing AC voltage using a dimmer switch. I put the test capacitor in parallel with a lightbulb and brought the voltage up with the dimmer switch. Fortunately I put a 2 Amp fuse in my circuit. I found that I quickly blew the fuse with a 100 MuF cap. Using the equation for Xc when C= 100 MuF and f=60 Hz gives Xc=26 Ohms. That means that I would blow my 2 Amp fuse at 52 volts. V= i Xc = 2 x 26 = 52 Volts. It seems like it blew at an even lower voltage! Anyway, I quickly realized that I must be doing something wrong here. Can I recondition my caps using an amp circuit? If I have an amp with a solid state rectifier, can I plug the amp in to the dimmer switch with no tubes in it and then bring the voltage up slowly with the dimmer switch and thereby gradually apply a pulsed DC signal to my filter caps for the B+ power supply? This is probably too many questions, but perhaps you could make a video about this. Thanks!
You can only re-form electrolytics using gradually-increasing-voltage DC, Cosmo. They are a dead short for AC......hence your experiences with it. Nowadays, with high quality capacitors readily available at very reasonable cost, it makes better sense to simply replace the caps.
@@UncleDoug Thanks for the confirmation Uncle Doug! I love your videos. I played with tube stereo amps with a friend in college. Both of us became engineers (mechanical and bio, not electrical). My dear stereo friend is dead and gone and now another old friend has got me interested in tube guitar amps, as he is a great guitar player who has just discovered the magic of tubes. I am a tinkerer and he has brought me an old Alamo Fury to play with. Despite the advantages of buying new caps (which I will likely do, eventually) I am still interested in the reconditioning process. If I have an amp with a solid state rectifier, can I recondition the caps right there in the amp by bringing the voltage up slowly by plugging the amp into a variac (or dimmer switch)? Is it better to do this with or without the tubes in? Could I build my own reconditioner using a dimmer switch, power transformer, and a solid state rectifier? If yes, could you suggest a circuit layout for this? THANKS SO MUCH FOR YOUR FAST REPLY! You are currently my favorite "Professor" of the University of RU-vid!
When rolled up, would'nt the anode and cathode be able to exchange electrons directly because of touching or close proximity without paper between them?
No, they can never touch, Philip. The entire basis of capacitance is that the two plates can never touch......if they do, it creates a short circuit, possibly to ground, which would be disastrous.
Great video. Do you have a series on which type of capacitor to use in different areas of a tube amp. For instance, where is it appropriate to use or not use a silver mica, a ceramic, an orange drop. It would be a helpful (pt 4 perhaps) video to explain that to us. I am currently rebuilding an HH Scott 299C and they have quite a few inferior ceramics including a few in the early stages of audio path. So again this would in my opinion be a great addition to this series, explaining what where and why. Thanks..
From my experience, M-100, the type, brand, or cost of capacitor has little effect on tone. I have removed (inferior) ceramic caps and installed relatively expensive caps.....with absolutely no noticeable effect on tone. I suggest that everyone try their own experiments in this area, but meanwhile I stand by my conviction that money spent on boutique caps is money wasted. You would be far better off taking the difference in cost and applying it where it would have obvious beneficial effect: speaker and possibly tubes.
Thanks for the reply Uncle Doug. I mainly use orange drop 716 series in audio path. What I was really curious about is the appropriate use of Ceramic/Silver Mica for bypass and where in a circuit not to replace a ceramic with a silver mica.. the Following is a quote from a friend that has a lot more experience with theory than I do. Just wondering if you would comment on it. quote = Remember that subbing micas for ceramics isn't always a good idea. Read up on dielectric materials and their optimal uses in audio. Micas always replace micas. Ceramics need to stay ceramics for screen bypass positions. Signal path ceramics swap to film/foil. Tone circuitry ceramics can go to mica or film. Film caps swapped only with film, and never to ceramic.
You're welcome, M-100. As previously stated, I obey none of these rules. There are probably excellent theoretical reasons for them, but from my own experience, the effects are neither audible nor worth the trouble. Like you, I tend to favor polyester and polypropylene caps such as Sprague's and use them liberally in all positions except where electrolytics are required. To me, correct value and good quality is all that really matters.
Could you explain why everybody says caps pass ac when current can not actually pass thru a cap, they don't conduct. In an ac circuit they just charge and dis-charge at a rate equal to the frequency This allows current to flow thru the circuit but never actually passes thru the cap. I see you at least put the word pass in quotes. Might be a good vid as most people thinking that audio signal goes thru them is why they would sound diff. If you understand how they work you understand why diff. types can't sound diff. It's all the value. Mostly people hear the tolerance diff. Found your channel the other day, very entertaining, I've been involved in electronics since H.S. Won't say how long but graduated in 72. OOPS.
You're a youngster compared to Rusty and me, Brad, we graduated (from high school) in 1964 :O Your point is well made. Although current does not run through a cap, for all intents and purposes it behaves as if it did. I discuss this in several other videos and am careful to avoid the "pass through" terminology, or at least put it in quotes, as you noticed. I also agree with your stance on "boutique" capacitors. I have never seen a study based on legitimate experimentally-derived data (as opposed to opinion) that could demonstrate ANY difference in tone between caps of equal value but different construction. Even with his exceptional hearing, Rusty agrees that no such difference exists......and his opinion can't be bought, except maybe with some dog cookies :)
Cool, haven't seen that one yet, but after my post I thought maybe you had discussed it. Like your videos. And yes when you understand how a cap works it is not feasible that the cap material could affect tone. Oops I hear you discussing it in the video playing in the message box. OK, take care.
Hi uncle doug, glad to see you back ive enjoyed all your video's i have learned so much more watching them. Sad to hear about rusty .Regards Bob parker England
One has to wonder why UD has depicted current flow as a sine wave, when in fact the current flow would be instantaneously at maximum at Tzero in this context, then tapering off in an inverse of the curve UD has depicted. Further, one has to wonder why the voltage across the capacitor would decline at all while the power supply is still attached.
One also has to wonder why a "genius" would content himself with nitpicking videos created to provide basic understanding for beginners and intermediate tube amp enthusiasts.......rather than blessing us with brilliant insights on his own channel.
Uncle Doug, am i right in thinking when AC is fed into one side of the cap and AC then flows from the other side it has not physically jumped the gap but induction has taken place across the gap a bit like a transformer but without ant voltage change, and like a transformer it does not work when DC is applied?
Exactly, George. Neither AC or DC can actually "cross the gap" between the two plates. AC stimulates the creation of an equal charge on the distal plate, so it "appears" to have crossed over, while DC simply charges the plates with no current exiting from the distal plate.
Sorry if my question should be obvious. I've wondered whether the grid was being presented with voltage or current and if it is just voltage where does the current go or is both current and voltage seen as one thing that goes to the grid? I'll try not top ask anymore questions
The grid is a dead end, Robb, so current really can't flow. Instead, the grid is charged positively and negatively (voltage) by the music signal. Recall that voltage can exist without current.
Congratulations mr. Doug. I am a teacher of electricity and electronics and, like you, I lived the age of tubes and I love this world, and I make this world my weekend hobby. I often refer to your videos, and I watch your videos for inspiration and find ways to teach my students in a simpler and more efficient way. Thank you for sharing your knowledge.
Well I'm speechless. You gave all ampoholics a chance to build their own tube amp. You and Rusty made a remarkable job. You play with electrons just the way you play with nature's instincts. Thanks UD!
Hi Uncle Doug, that’s for the great explanation. One question that I hope is no too silly: if a capacitor blocks DC in a circuit where it is functioning as a coupling capacitor, is the DC voltage that is “felt” on circuit after the capacitor “effectively sent to ground” via a resister? (Just checking if I have the correct understanding). If my question does not make sense, feel free to just tell me to rewatch the series. That is a perfectly fine response. I do not expect you to explain the error in my thinking in your response. Thanks!
Your question makes very good sense, Zoltan. A small portion of the blocked DC is absorbed and stored within the capacitor. The rest passes through the plate resistor to ground.
Hi Doug! Great educational series. I'm watching them all for a second pass! Something I can not get my head around - I get how electrolytics are used to smooth the DC, but on the other hand, capacitors do not pass DC? I'm stuck. Can you help?
The DC does not pass THROUGH the electrolytic capacitors during the smoothing process......it passes BY the positive lead of each cap, where smoothing of the post-rectification ripple occurs.
@Uncle Doug thank you so much. This had been tickling my brain for too long. It now makes perfect sense. Thank you for all of your great work Uncle Doug!
Love you Doug, Im trying patreon, but what does" $177 per Subscriber and Viewer Donations....if and when they see fit" mean? Can we donate in smaller amounts? Sorry, it's not clear to me, but i want to help support.
Thanks, NF. The $177 is the total of all pledges. Most individuals pledge between $1 and $5. When I post a video, you will be asked to pay your pledge, and can refuse if you wish......thus the "if and when" part.
Oh great, thanks, I thought the $177 was the minimum hah. Sending some money your way; I sincerely appreciate your efforts, and enjoy you and the granimals "company". Though I'm afraid to ask about furry kitty (beautiful cat). But Jack is stellar as well:) Hope you are havin fun! Do you do car videos too?
Jack is doing quite well, Jeff. He's only 2 years old, so he has a great career remaining in amp repair :) We intend to feature some vintage trucks in our future videos.....which should be posted in the near future. Thanks so much for the pledge :)
I'm confused that capacitors block DC but also smooth out a DC signal. That seems contradictory. I would think that smoothing out DC would involve letting DC pass through.
Tothna1 capacitors do not allow DC current to flow through. The capacitor does charge DC on the initial plate, but it does not pass through. Remember that audio signals are basically always AC. The signal coming from a record player, guitar, or microphone is AC. The signal going to speakers is AC.
I'm sorry Uncle Doug, I don't get it. The electrolytic caps have two sheets of aluminum foil, and they both use aluminum oxide as a dielectric. What distinguishes one from the other to establish polarity? I understand these cathodes are usually grounded to the can, but it doesn't sound like you'd have to make them that way. Are there two types of aluminum oxide?
Yes....the sites I used as references never identified the specific type of oxide on the cathode, but they showed aluminum oxide only on the anode plate.
so ac voltage after the full wave rectification process is dc the rest of the way through the amp. the ac you are referring to is the vocal or input(ie electric guitar) the only ac? thank you!
Yes, exactly. The amp operates on DC, but the music signal is AC. The primary circuit that supplies electricity to the power transformer is also AC from the wall receptacle.
@@UncleDoug I was thinking of how easily the annoying visitor can complete the circuit with the different package types ;) I've started collecting parts for my my first build. Got the valves (that what we call tubes downunder) and an OT and choke. About to order all the smaller stuff - I'm going with Mallory 150 series caps for coupling and tone circuit. I've watched these older videos of yours several times. Your work has given me the inspiration and confidence to do it!!! Thanks bloke!!
Thanks for this clear explanation in the capacitor series! I think in a short time you'll end up brightning up all the black spots in amplifier circuits on this channel. Maybe it should feature a playlist(s) for more advanced proceeding through on this topic where you organize your videos, more like an online textbook or something.
You're welcome, Andras. A playlist is available for subscribers, but it it organized chronologically rather than by topic. I will keep your suggestion in mind. Thanks :)
Love these video's and the supporting cast. Have have a question about old un used filter caps. I bought a large amount of spragues about 10 years ago and never used them. I am starting to rebuild some of the amps in my collection and wonder if these caps can be used, refreshed or thrown away?? thanks, john
They're probably just fine. If you have a DC power supply, bring them up to operating voltage slowly (i.e. over several minutes). If not, and you use them in an amp, use a Variac to bring them up slowly. If you don't have either, then build a Current Limiter and use it with the amps they are used in. I predict no problems at all.
Thanks, that is great news. I am re watching most of your video's in preparation for some rebuilds......I think I am starting to make a transition from a mechanic to one who understands why it works.......You have a great style of explanation in a clear way. thanks!!
Uncloe Doug, thank you so much for your videos. I'm starting my journey in electronics , so far I build small guitar preamp (with lots of satisfactions) and I watch your videos one by one discovering it all. Your approach to explain is not too shallow nor too deep , just perfect. Thanks !
I’m a little confused about filter capacitors. If caps block DC voltage, How then do they smooth a voltage to fundamentally make it more DC? I understand the concept that they charge and discharge slowly, thereby providing smoothing, but this seems at odds with the concept of blocking DC. What am I missing? Is it dependent on the values of the caps in relation to the 60 Hz signal? Thanks as always for your videos and assistance!
The DC does not go through the filter caps, it goes past them. You can see this when you look at a schematic. As the DC leaves the rectifier with some ripple, it passes by each filter cap, which charge during the ripple peak and discharge during the trough, "filling in" the trough so that the ripple is smoothed to its peak height.
Hi Doug, I have an 80's Hi Fi amp that hasn't had power connected to it in ten years and was wondering what is the best way to power it up again. Regards from Australia
I always suggest plugging it into a current limiter, to prevent any internal damage due to short circuits. I have posted a video showing how to build a current limiter. Good luck.
with regard to the capacitors, how long does it take for the ions to re align if they haven't been used for a while and will the current limiter be enough to do this or would lowering the voltage be advantageous in this regard. cheers.
If the amp is transistorized (solid state) the filter caps will not have much time to reform, and you might want to use a Variac (check Internet sources for info) to slowly warm it up. If it has a tube rectifier, then the Current Limiter will probably suffice.
Hi, Uncle Doug! Could you tell us the difference between the bias modulation tremolo and harmonic vibrato? For example, maybe in another video, could you explain to us how the harmonic vibrato from fender vibrasonic 6g13-a (and vibrasonic 5g13) works? Thank you!
I believe that Harmonic Tremolo is a more accurate term, Emanoel, since its basis is primarily a volume rather than frequency modulation. This effect was used in several large Fender brownface amps: Super, Pro, Twin, Showman, and Concert. I demonstrate the effect in a BF Concert amp (see my video). Here is the best site I have ever seen for a clear explanation of the difference between the harmonic trem and the other versions of tremolo: www.strymon.net/amplifier-tremolo-technology-white-paper/
I have an old solid state guitar amplifier that has a loud sound like fine gravel sliding down a corrugated metal roof.It gets louder as i turn the amp volume up ,and in reverse quieter down to not being heard at all,at lowest volume.There is hardly any volume from my guitar. I have just replaced the filter caps,as there was a loud hum.please help. regards.
Greetings, Andrew. Although Rusty and I only work on vintage tube amps, we can say that any noise that responds to the volume control must arise from a part of the circuit that precedes the volume control......so focus your attention to the input, VC, and pre-amp sections of the circuit. Good luck.
@Uncle Doug Dear Doug its blindfold test time, maybe for Rusty. Llast night here in Halifax we set up our guitar player with his Franken Tele, a Traynor tromp box amp - accepts an 8 ohm speaker load - and my University alnico 12 loudspeaker, mounted in a plywood long-scale bass guitar case (I was on my way to make a Dano imitation amp-in-case, and stopped - although this particular guitar and amp would fit inside, as is) My observation - tube amps must sound the way they do in part because their speakers cannot handle what (little) they produce, RMS wise - this little transistor thing last night, with chip verbs & tremolos, not even hollow body intrument, sounded funky, played unmiked to a room of 2 levels and 180 seated, the speaker stands about 3 foot 4 inches - IE above backline normal. Let's try Rusty on a transistor amp with different vintage spkrs, then tube amp with heavy ceramic ones - and see which one barks best.
Uncle Doug: On the schematic for the Fender Champ/Bronco AB764 there is a 330 pf cap across pins 5 and 8 of the 6V6. I've read a few articles in which it was referred to as a "stability cap". Can you tell me what the thing actually does? My guess from what I've read is that it has to do with HF roll off but the explanations are not all that clear, in fact some folks take the thing out. The AA764 does not have it. Best regards always. JC
I honestly have no idea why you would want a low-value cap between the cathode and grid, Joey......unless your guess is correct. Only high frequencies could traverse it.
@@UncleDoug Many thanks as always. I'm learning this simple circuit before moving on to the Twin Reverb. You remind me of a professor I studied under at Rutgers many years ago who always said, among other things, that brute memorization might prove worthless in the long run, and that we needed to truly learn the subject backwards and forwards. He was the single finest teacher I've ever had and through the years he became my mentor and friend. Please take care of yourself and stay safe. JC ( KC2OUG)
Another quick story: Years ago, before I became an educator, I used to work in printing. For a while, I was in digital services for a branch of a large copy store chain, for which I did a lot of hardware support. Basically, this wasn't really my job, but my manager knew I could fix stuff faster than the "real" hardware guys could get there to do it. One day I come in and she tells me there's Mac that won't boot. So I pull the thing apart, and take the cover off of its 12-volt DC power supply to find that one of the caps has blown itself up. I didn't know nearly as much about caps as I do now, but these are large, cylindrical caps, electrolytics I assume, probably much like the filter caps you find in a tube amp, only bigger. Manager wanted to know what had gone wrong, so rather than showing her the scorch marks on the inside of the case, I told her to close her eyes and sniff. There was a distinct and unmistakable aroma of sulfur. I would wager that this has something to do with Jack's ability to cat-scan for bad caps.
Excellent. Enjoyable. When I was 13 I thought I was extra dumb because this was so hard for me to understand. Now 55 years later, I know for certain that I am dumb but it's comforting to know I understand. I was an electron in my former life and now have a love affair with physics. Thank you Rusty, Jack and your human.
Hi Uncle Doug, Rusty & Jack, A most excellent series with great explanations, graphic's and appearances by Rusty & Jack. Seems Rusty is teaching new tricks to Jack. You are a really good teacher, Thankyou. I hope all is good. Take care, C.
I've been working with electronics for years, and could never fully grasp a lot of the concepts I "learned" in EP courses-- until your videos. Thank you so much for these. I got my interest in electronics from modifying my (brother's) guitar, but ran into some speed bumps while taking traditional EP courses in the Air Force. I think the key for me is your practical approach in explaining amps, etc. Keep it up!
This is really informative Doug, thanks so much for creating this series. Excellent stuff... truly..... thank you very very much. Not sure if you have ever done this but do you have any theory on how to select the proper resistor when creating a circuit ( aside from hunt and peck) ? A formula perhaps ? Thank you Doug. - regards, Ron
You're welcome, Ron. Resistor values can be calculated based on the current and desired voltage drop, as explained in my Ohm's Law videos. After that, you can experiment to fine tune the values.
Will check that out... thanks Doug ! I am building amps these days in part due to watching your videos and learning. I have a few series on my channel of that process.. lots of learn as I go along stuff.... would be honored if you would check them out. Many thanks. Ron
Uncle Doug, I was schooled on tube and associated electronics while being trained as an electronic tech to work on the HAWK Air Defense Missile System while in the Army in 1966. With my recent interest in tube amps I was frustrated by my failure to remember after 50+ years. Lol. Watching your instruction has taken me back. Thanks for helping me to begin my journey back. You are a top notch teacher and much appreciated.
Hi, uncle Doug and helpers.! Your comment about charging up a cap. And giving it to a pest.!, reminded me of a time many years ago when I was an electrician in a factory. An office member who had an easy job not doing much, would wonder into the electrical shop to waste a bit of time., he would mess about and pick things up to look at.we charged a capacitor up that had two screw terminals on the top with a discharge resistor across which we had disconnected and left on the bench. Sure enough in he walked picking things up getting in the way, suddenly there was a Yelp! And dropping said capacitor he disappeared without a word. He didn't come in very much after that ...cheers from England. Hugs to assistant rusty. Love all your easy to watch informative videos on valve amps. my old 1963 vox AC30. Is in For service as we speak. Cheers Rob.
Greetings, Rob, and thanks for your very nice comments. I guess the joke might be on us if our intended victim touched each of the cap leads with a separate hand and was electrocuted.....but until that fateful day (and prosecution), the old "charged cap" trick definitely rids the work environment of unwanted pests :)
