I am a 62 year old vacuum tube lover both for my audio and guitar amps. For the first time in my life I started to understand how the tube amps function and what they do. You are a great teacher!!
this was fantastic pitched perfectly for me as a novice with electronics knowldge....love that you are so generous with your time and expertise...keep going! Mark
Your tutorials are very well done. I am a former electronic technician and watch your videos to sort of reminisce. I may have understood more if I had these tutorials back around 1960
Extremely good video and series for someone with basic electronics experience, but who wants to learn tubes in depth! Thank you so much for such great teaching.
Really useful. I was trained as an electronics engineer by the Royal Air Force in the UK 40 years ago. I haven’t worked in the field since 1992 so I’d forgotten most of what I knew. I have a Fender Prosonic tube (valve to me as I’m British lol) guitar amp head which was faulty so I did a search and found your videos. Everything came flooding back. Result, 1 new electrolytic capacitors and 1 resistor between two halves of a 12ax7 tube and a fully working amp. Cheers
Studied electronics in 70s - this brought it all back. Haven't touched a tube since then, but you've sparked my interest. p.s. I almost skipped watching this "boring" power supply episode because I'd always thought that if I cooked up an audio tube amp that I'd just use a solid state power supply. Glad I watched though since understanding the PS is necesary to understand a tube amp functions e.g. biasing, 5v and 6.3v filiments.
Your video on understanding Vacuum Tube Amplifier Schematics-Power Supplies is fantastic. I am a beginner and thank you for the walk thru, showing all the symbols and nuances with the circuits. I am learning a lot due to your patience and in depth analysis. Usually we get a string of letters, numbers etc. with no explanation--not with your detailed instruction. Thank you. I look forward to more of this type of basic training. Ron
Glad I took the time to look at this one. Never heard of a "death capacitor" before but it makes perfect sense. Reminds me of an old 50s era refrigerator that I bought for $10 off a friend during my freshmen year in college. One day I opened its door with one hand and touched a grounded metal shelf with the other hand and got treated to a full AC electric shock. I quickly realized that the old non-polarized two pronged plug it had needed to be reversed so did that and from then on got no more shocks, but it taught me that grounded outlets and plugs can be lifesavers. Even kitchen appliances can be shock hazards if you're not careful.
Hi Mark, I have been watching your videos and have to say you are stand-up guy. You share your knowledge and ideas like no other. I have learned quite a bit from you and just want to say thanks for being a great person!!
I love watching this seven part series and am on my third time through it. Very informative, and you did a fantastic job of explaining it to someone like me, a beginner.
absolute blast … binge watching your Tube Series .. didn’t make sense 40 years ago … and after watching your channel … clear as mud ! fantastic … also helps me out as i run Valve HF gear and my Guitar amp is Valve … learnt lots and in retirement , i might have to set up a work bench 👍. Thanks a million and i have subscribed !!! regards from Adelaide Australia
Most informative and educational video on this subject that I've yet come across. Explains it all in clear and simple terms, very comprehensive when you have a bit of basic electrical knowledge. Especially now that I'm looking at getting my Hot Rod Deluxe repaired. Grateful thanks to the poster.
From a fairly basic understanding of circuitry with my HVAC experience with schematics and wire diagrams i have tried for a long time to fully understand sound, tubes, and layout function when it comes to my music equipment but just couldn't jump the gap. Thank you! this little series in such a short time helped a incredible amount. Fantastic job covering not only image and symbols but their common combinations and sequence, sharing this with all my musician friends 🏆🤘
Really enjoying your channel ! Excellent series ! I wanna jump the gun and learn how to convert the schematics into or onto a board and how to etch ! I'm eatin this up ! I'm an ST70 Bottlehead ! Ya know I restored my first one way back in the early 90's before everyone sold all the kits and boards. I could follow the instructions and build it, but I was aggravated because I didn't fully understand how it worked ! I made one small mistake, I'd reversed polarity on one of the small caps on the driver board. Was using a Variac to do the initial power up. It popped and smoked about halfway up! I flipped it over and giggled when i figured out what I had done. I had another one, stuck it in there and it fired right up ! Thank you for what you have taught me!
wow this is quality info. Luckily I have an engineering degree but holy cow if I didn't have my knowledge from college, I'd be lost! College taught me a lot of theory but I'm seeing a lot of practicality here. Thanks
Thanks for this series, as others have said it strikes a great balance between being too basic and really dumbing it down without being too hard, I have been looking for something like this for a long time, looking forward to the rest of the series, I can imagine myself watching these videos again and again, cheers.
Best channel , best content. Not an easy topics for semi beginner so many many thanks for making those videos and sharing so many knowledge. Thank you !!
I have now watched the first two episodes of this series, and I have probably learned more about tubes than I have done for months trying to read the book by Morgan Jones - it's simply too advanced for me yet. Thank you for your very simple and clear explanations of how tubes work, I am in progress of watching through all your other videos now :-)
Great video ! ! Well taught with a great teacher vibe ! ! A beginners video with a shop tool list with electronic bench testing equipment included with suggestions as to which is best for two or three price ranges, electronic safety tips, basic trouble shooting techniques would be a great way to prepare for basic repair work.
Great video Mark! You helped me understand the filter section after rectification, it was a little confusing before. I really hope you get back to this and continue this series!
I have something to add on the multiple OHM taps starting at 27:15 I am sure that most people know this already , but in case some folks don't know here it is , you can add switches on the back of the amp near the speaker jack and label them 4 ohm , 8 ohm ETC ETC .... The most commons are 8 and 4 ohms for band amps .... Guitars and such....A lot of small 4 watt amps power a separate speaker box..... Larger amps like Peavey and Marshal's have the speakers built into the amp box .....
Nice tutorial. One additional note, Howard Sams Photo Facts schematics were actually independently derived by actually ringing out products with an ohm meter. In a nut shell, most manufacturers that provided a schematic, provided the, "As designed document" Sams provided the more valuable, "As built" document. In fact when ever a manufacturer changed the revision level of a model number, Sams would re-evaluate and if necessary produce a new schematic.
Hi, just thought that I'd comment on your video. I find these kind of videos of yours and uncle Doug's videos extremely interesting and very informative. I would give anything to go to an electronics school to learn amp building from a guy like yourself. I'm a musician for years and I would love to have the knowledge to fix my amps. Thanks Michael Newell from Niagara Falls, Ontario, Canada
Thanks, nice overview ! You asked for input on subjects: I would really like more a indepth review of looking at feedback loops, and the effects of resistor and capacitor values in this. Why this affects the output impedance. And causes and remedies for oscillations.
Please cover the 1964 Scott 200 Integrated tube amp schematic; I have one, and I am sure there are places to upgrade, etc.... This little gem of an amplifier, is one of the best sounding ever made for a push-pull vintage piece... Mine is completely restored and I love it!
If building your own tube amplifier from scratch, May I suggest you cover load lines, choosing bias resistor's and calculating output transformers. Power supplies Schematic would be nice If you can cover that.
In your discussion of transformers, you implied that an air gap was required because an amp operates in Class A. However, it is because the amp is single ended (which of course means it must operate in Class A) that the air gap is required. DC current is constantly flowing one way in the primary which means that an air gap is required to prevent core saturation. It is possible design a double ended amp to operate in Class A, but since DC currents flow in opposite directions in the center tapped primary they induce magnetic fields of opposite polarity which cancel so that no air gap is required.
I know this video is ancient in internet years, but a step by step series, or one in-depth video on the Marshall 1959 Super Lead circuit would be incredible
could you make video going in more detail into all typical capacitor application patterns to consolidate and give a few examples of solid state as well as valve amps using this patterns. eg pattern 1 Resistor and capacitor in input transformer... purpose making DC curve of B+ as constant as possible. pattern 2 coupling capacitor from plate output to grid input... etc capacity in cathode biasing circuit... there seems to exist 100 different patterns for using capacitors . typically seems to be always a game of let ac pass fix dc etc ... many thanks for the great video
One thing I've always wondered is why (at least in these circuits) the rectifier heater isn't 6.3V like all of the other tubes'. Seems like a little $ could be saved by not having that extra 5V winding.
Very well explained. You have a lot of patience going through all of this. I would like to ask if you can elaborate on how exactly a tube rectifier works. I am used to solid state diodes, I simply don't see how AC in a tube becomes DC. Another big mystery to me is how a "choke" works. How can a coil filter a ripple ? I always thought this is what capacitors are supposed to do.
A tube diode, just like a solid state diode, will only pass current when its plate (anode) is positive with respect to its cathode, when it is said to be 'forward biased'. An AC voltage applied to its plate will result in pulses of current at its cathode during the positive excursions of the AC. A transformer with its center tap connected to ground produces AC voltages which are 180 deg. out of phase, i.e. one voltage is positive while the other is negative and vice versa. If these out of phase voltages are fed to the two plates of a rectifier tube, each diode will conduct during the period that the other is not conducting, resulting in a series of positive pulses of current at the cathode. Each dropper resistor in the B+ supply not only reduces the voltage, but acts as an RC low pass filter in conjunction with the following capacitor, reducing ripple. A choke is an inductor which has a property known as 'reactance', a resistance to AC that depends on its frequency. The Hammond choke in example circuit #4 has a reactance of 7.5k at the 120Hz frequency of the ripple current but only 82 ohms of resistance to DC. This means that it can, in conjunction with the following 100uF capacitor, efficiently filter ripple current while allowing the majority of DC voltage to go to the rest of the amp.
Interesting and nicely made but I seem to be missing an essential point on the diode operation: where does the magic B+ (400 or 500V) comes from? I undertand that for the diode to operate, the plate (anode) voltage has to be higher than the cathode. But how does one establish what the cathode voltage is from those diagram? You state this as if it was the most natural expectation but does not come as such to me. Is there another video that I haven't stumbled upon yet to establish this basic fact.. Thanks anyway for an otherwise very accessible material!
Ty so much I am new to tube amps and I am fascinated by your wealth of knowledge. I want to build the Sansui Q-50 Tube Amplifier Monoblock 50 Watt 117v push-pull. Can you go over the schematics if you can Again Ty
Hi Mark, Very good information.. Maybe you could do a video on actual formulas to arrive at a desired voltage on a tube plate, or screen.. For instance, if you were building your own amplifier and not following a schematic exactly. I know most amps are basically laid out the same (as shown in this video) but what if you wanted to use different pre-amp tubes which required more or less voltage? There must be math formula's for this. Thanks, Tom
Just found your series on the single ended amp build and now schematics. Thanks so much great info. I recently repurposed a Conn organ console with surprisingly nice results. I actually began with AM tube radios and have always struggled with the concept of ground. Especially when a chassis is not directly connected to ac source or line third wire ground. Any clarification would be greatly appreciated.
In an amp with a three wire power cord, the chassis is connected to the safety ground (or earth) at the wall socket. The negative side of the power supply is also connected to the chassis, which makes it the 0V point from which other voltages in the amp are measured. In a vintage amp with a two wire power cord, or if the amp is battery powered, the chassis is still the 0V point in the amp, and is still referred to as ground.
Very good information! I was wondering about center taps. I understand they can pull current off of the transformer but am not clear on why they can be grounded without causing a short. My guess is that grounding it is not a short and instead nulls the CT? But why not just cap the lead? Also, when using a CT, wouldn't that reduce the current from the other legs? Sorry if I am using current where I should be using voltage. I'm going to take a break from these videos and go learn about ohms law and do some breadboarding to further my learning. It has become clear I need to understand that before I can move ahead.
What purpose does the CT of the 6.3V have? -- if the replacement X-former secondary doesn't have a CT for the 6.3V, is there a class of tubes' filaments that wouldn't work?
Great series. Would you elaborate on the AC/DC in the schematics? Most schematics do not indicate AC/DC component which was the biggest confusion for me when I was learning. For example, a 5u4 tube, the 5VAC from the transformer is connected to filament and it is also where the 5U4 output B+ (high VDC voltage). For future videos, please consider the topic of tone circuits, rolling off high or low frequencies, or a narrow band boost or cut in frequencies, RIAA equalization for vinyl, NAB, IEC playback equalization reel tapes in a preamp, sharp cutoff tubes used for signal compression, the challenges for using small signal tubes, SRPP circuits, using voltage regulator tubes OA2, OD3, and solid state rectifiers using Schotky diodes. how to generate negative voltage for bias if you don't have a separate winding, capacitor bypass vs diode, LED. What do you think of the new dual triode Nutube from Korg? Thanks.
LOL, you want a 4 year degree in electronics via a youtube video. Hold tight, I'm sure over the years, I'll cover all that. I will hit the AC/DC thing soon.
I understand that when the tubes are installed in an amp that load in conjunction with the internodal resistors in the power supply is what defines the voltage at the nodes and i know that when you pull the tubes those voltages go up but why do they not all come up to full b+? If the ps isnt referenced to ground thru the tubes to define the voltage drop why is there still a voltage drop and how do the volts know how much to drop?
Learned a lot, clarified a lot. Thanks. Questions: How does using DC regulated five volts on the filament of the 5U4 or 5AR4 change the output ripple if at all? Would there be any benefit to feeding the rectifier filament from a separate transformer; does using a separate transformer for filaments take some of the load off the main transformer? Does the power supply program you used allow you to substitute dc to the filament?
Ok Thanks for the Video was informative for me. The Inductor symbol section cleared up the types of materials used for their cores and the symbol representation, Can I assume that ferrite core is also referred to as powdered iron??. - I did not know that they wound transformers in both directions on the same unit and that the dot was a representation of the direction, I do now. - The CLC & CRC filter thanks for explaining that. - With the Dynakit amp the bias tap and the diode orientated in that way would represent a negative bias feed?? and would this mean by adjusting either of the 2x 100R resistors that this would also alter the bias of that particular tube even though it has a resistor on the cathode and a pot to adjust the bias ?? - Thanks for the duncan's app and explaining it a little should be able to get some value from that.
Thanks for the nice videos. However I don’t think your explanation in the video at around 19.40 is not accurate enough. The transformer core tends to saturate because of the constant quiescent plate current in the class A I think.
Great video, I have a heathkit w5 amp that is having what I think is a tranny problem( 5r4gy red plating). Have not did any measuring. Where would be a starting point?
Hope your still taking,requests I am very new trying to,absorb all I can I have several older tube radios and feel I have enough parts between tubes resistors transformers etc.. Could you do a scabbed together with what you got thanks your series is very informative
What would you do in my situation? I have received some old vacuum tube equipment some that are military others possibly handmade and I haven't a clue what they are or to be used for despite searching the internet .
