Just so you know, I'm coming from 70 years of life, and my beginning in electronics with tubes started in 1965 working on TRF radios like Atwater Kent and RCA! I just love this video! I just love the low orange glow of that tube doing what its supposed to do! And that sound! Don't get me started!!
A good way to learn is buy books of amplifier builds from the 1940s and 1950s Heathkits and draw out the schematics and get a few bins and save up parts and build it’s a fun hobby I need to start selling
Great Work! Actually Fender used 68K input resistors but wired in in parallel when you plugged in the high impedance jack making it a 34k R, So when building a single input and still wanting to stick to Fender specs you would use a 34k (33k is closest) R.
Great video ! I've been building small to mid size transistor audio amps for a year or so and I've wanted to make a tube amp for a while . This is a big help to me . I also play guitar so It will be cool to build an amp to play through . Tube amps are so expensive this will be a rewarding and cost effective alternative to buying one . Thank you !
Every time I see something like this I am always curious what provokes these responses. TH-cam comment sections uses to be entertaining. Now they just delete all the offensive shit. Lol
This is the exact thing I've been looking for. Gonna attempt my first recap of a vintage Marshall and I really like understanding the circuity. This explains it so easily. Thanks!
I used to assemble tube Amplifiers years ago, using 6V6, 6L6, EL 84, EL 34, mostly in push pull for higher output. The cost was largely dependent on the requirements of the guitarist. I see that in your 6V6 grid, there is no grid leak resistor. Is that done on purpose or otherwise? I used grain oriented stampings, for the output transformer. Heavier bass response!! I am now running 80 years and this my obsession!!!! I now use 5200 and 1943 Toshiba Transistors. They are Heavy duty and give astounding Bass! Drives a 12 inch DJ speaker.
I have watched a TON of videos trying to understand signal paths in tube amps and they always start with an existing schematic with complicated preamps, etc. This was an extremely helpful 16 minutes! Thank you!!
Paul, I love the glow of tubes. It has been a very long time since I worked on a Fender amp. The Champ is a classic. I would use the feedback resistor, but put a switch in to take it out when you want or make it variable. Since you said the amp could be used with other input devices, I would recommend a blocking cap on a second input port to protect the input devices. I would hate to see any stray voltages get loose. I hope the dentist trip goes well and you have a safe trip there and back.
My father had a Champ that I used as a boy to amplify the minute signals from my home-built crystal radio receiver. The night I heard, from way down in Mississippi, the top-forty music from WLS Chicago got me hooked forever in electronics! That glow of those tubes in the Atwater Kent and RCA TRF radios I worked on was magic!
This is awesome! Wish I found it earlier. Simple and excellent tutorial. I have a tombstone radio chassis that I want to become a Bluetooth receiver and an MP3 or other type player. I have wanted to use a tube amp setup, I want a rich and not tinny sound. Yes I know I can buy one, but so much better to build. I'm retired from the aerospace industry, not an engineer but a builder for the engineers which included some electronics. I was certified in soldering. This is exceedingly helpful. Thank you.
With all due respect to everyone who commented that they learned a lot from this video, from the title I expected you to describe how one reaches the values of the components. Instead, all I saw was a schematic of pretty much a *copy* of an existing circuit, with no explanation for the selection of the values of the components. That's what I expected, based on the title.
Great video on showing just the signal chain but why doesn’t the grid of the output tube reference ground thru resistor like for the grid on 12AX7 but with a fixed resistor rather than variable resistor for volume control?
In my Champ 5F1 build I needed to change the value of the cathode bias resistor from 470 ohms to 750 ohms in order to reduce the plate dissipation to 12 watts from the 19 watts I got with the 470 ohm.
So all that did was shift you right along the loadline for that stage and decrease your quiescent plate current. Did you notice any decrease in distortion? It may have been more appropriate to adjust your load resistor instead.
You should always use a push-pull final, finals will be driven into non-linear regions and with a push-pull output odd harmonics will not be generated and it will sound more smooth and less harsh when strongly driven.
I've learned more about guitar amps from this video than anything else. I've been playing rock'n'roll for 40 years. COVID has me doing more stuff at home, including electronic projects. I'll watch the rest of these videos, but can you point me to a resource that explains *why* components are used? In particular, I'm curious as to why the capacitor is in parallel (?) with the pot. Thanks for this.
I appreciate the progress of design with application. I use pencil and earsing rubber. Although it is proper circuitry to make amplification , without any feedback and without possibility to adjust input signal the first stage which is likely to be overloaded. And mono. For music it is useless. . No tone controls, no phisiology correction ? Why to build with marvelous tubes something useless?
A minor point, just to stop any confusion, you labled the 12AX7 as T1 instead of V1, which made the 6V6 V1 (instead of V2), and the output transformer as T2 (it should be T1). Sorry. It's a bit pedantic I know, but having worked for many years (late 70's - early 90's) on design and repair of valve equipment I can get a bit like that. Again, sorry. Great vid.
😄 This just reminded me that, many years ago, when first learning about electronics, I saw an American circuit where the valves were labelled T1, T2, T3, etc. I could not understand what the "T" signified. In the UK, "tubes" are called valves and that's what my theory books called them. There was no Internet in those days to quickly look things up. It was only later, when I came by an old American ham radio book, that I realised valves were referred to as vacuum tubes (T for Tube). I still can't decide which term I like best - vaccum tube nicely describes what it is, whereas, valve describes what it does.
Should there be a capacitor between the input and the tube/valve to prevent DC getting to the grid? If you put any pedals between the Guitar and the amp, there will be DC voltage on the input in addition to the AC signal from the guitar.
@@learnelectronics I would vote for the negative feedback.. it will make it much more Pedal friendly. You might consider adding a master volume and effects loop. I have been thinking on building a tube amp and this might be the project!
Any reason why a tube head wouldn't switch from clean channel to distortion channel ? Bought a used blue voodoo 60. Had no sound but fixed that, second problem it won't switch channels
Thanks for the video! A minor advice: you could give some more in-depth info for us newbies about the actual purpose of the caps and resistors added to the construction. I know that there are tons of videos about tube amps, but none of them seem to give enough explanation about the purpose of the individual parts and their values, just "a capacitor here, a resistor there, and you're good". You could also make a video about the characteristics graphs in tube datasheets and how to use them. That's a topic I've been interested in for a very long time, but never found a good video about making sense of those graphs.
Hello , ive been fallowing the channel since forever , i dont subscribe nor like any video or anyone , so jsut because im not a subscriber doesn't mean i dont fallow . Whati want to ask is this a Hi Fi preamp , i want to build it and use it as a preamp for now , latter with a power stage , Would this bee a good design ? I got 220 to 240V AC Transformer that i plan to use for it , it has 7v output as well . On a 2x 12AX7 tube as a stereo pair
There's nothing wrong with using a tube amplifier for music, but a Champ circuit will not produce a "HiFi" music amplifier. I suppose that this depends on your definition of "HiFi", though . The reason that these old circuits are so desirable for guitar amps is *because* they add tons of color to the sound; they are not neutral. For music reproduction, we generally want uncolored amplification. There are no rules, though, so if someone likes the sound of music through a guitar amp then they go right ahead. I just want to let people know they will not get a distortion-free amplifier if they build this project. They will get a simple Fender-like amp design that is great for classic guitar sounds. This is a relatively affordable tube amp to build due to the minimal parts count, but it will add color/distortion to your music at high volumes, the bass may be "flabby", and the sound may vary widely from speaker to speaker. Impedance matching is critical for tube amps. Many modern speakers have low efficiencies and need lots of wattage to get loud, whereas this circuit will produce up to 5 watts. Distortion *will* be audible at 5 watts, however, so really this is probably a sub-1-watt music amp. I recommend a solid-state amp based upon a proven IC for a beginner-level music amp project; it will much be less expensive and less dangerous to build and provide cleaner sound with tighter bass. th-cam.com/video/d9O7oZEYALI/w-d-xo.html th-cam.com/video/D5N82Qr6k78/w-d-xo.html But I love tubes and tube amps, so build this project anyway if you already know what to expect. If nothing else, this Class A amp will make an attractive room heater ;).
@@Songwriter376 they are determined by some calculations from the tube datasheets. the tubes have graphs relating the anode current at a specified voltage. These passive components determine what the quiescent current and voltage is and determines the amount of signal headroom.
Hey, I am having huge difficulty with op amp circuit used in TA7642 radios, I cannot figure out how to attach the lm386 chip to have a gain of more than 200 (10 u cap between pin 1 and 8) if I give it too much signal in 50 k ohm pot then the radio just makes a farting noise. My problem is that I need to figure out which lowpass or highpass filtrations between the speaker pin 5 and the 470 n capacitor and which resistors I need to reduce the hissing noises without any distortion or clipping when I try to make it louder
Moist Andy The gain cap for an LM386 is 200. To remove the distortion, you either need to cap the gain at a level below 200 by using a fixed resistor in series with the 10uF cap or adding a gain pot. You’ll need a 1k pot for a smooth transition. Check out the datasheet! Also, for the Zobel Network from pin 5, the resistor-cap to ground, the datasheet recommends 10ohms.
Do you have any videos that speak to the different caps, and depending on where in the circuit,and the preferable cap materials that better handle sonics vs just being a workhorse. I hear different interjections on this subject but haven’t found a good explanation of except when folks rave about bumblebee caps in the Paul’s. Maybe I’m. It searching correctly. Fantastic walk through. Cheers-
Just a suggestion, but you glossed over the bypass capacitor requirement. i think it's important to understand the requirements for DC biasing resistors etc and it's affects on feedback, hence the need to bypass them for the AC signal.
Excellent video. One suggestion. If you can have another video where you could explain how do we arrive at those resistor & capacitor values & the reason or logic to use it. In fact that’s the fundamental aspects of circuit design. Thanks for uploading wonderful videos.. Keep up the good work..
This is to do with the tube characteristic curves, these determine how anode voltage and current behave for a given load. vrps.org/documents/TubeTheory/TubeTheory.html The curves for a given tube are the key to determining the values for the cathode resistor and anode resistor. On another note, the coupling capacitors and grid leak resistors have to be chosen carefully as they act as a high-pass filter and the wrong values can lead to them lopping off the lower frequencies of your signal.
How did you work out values for the resistors and caps? Whats your operating point etc? Why are you Not using a plate resistor? How will voltage be carried to next stage by just 1 capacitor? Did you actually build this?
He isn't covering power supply design in this video. IMO, plate resistance is part of the amplifier stage, not the power supply, but it isn't my video. The capacitor blocks the DC plate voltage and allows the audio frequency to pass to the next stage.
subbed 👍 I've been repairing amps for a number of years simply off experience of years using amplifiers with basic knowledge of components and the components purpose. however the actual signal path and wiring has been such a mystery and you have taught me more in 15 minutes about that then I've learned in the last 5 years. I believe this is because I do not know how to read schematics and do not have electrical background but your tutorial did not require that and it tied so much up in my understanding thanks a lot bud great video!
Pak bos saya mau tanyak tube vacum tipe EZ90 yg deket sama trafo input itu klu putus atau tiba2 mati mendadak apakah bisa menyebabkan kerusakan pada yg lain kah
Thank for sharing knowledge! Could someone ecplain what c1 is for and if r1 ist just current limmitation or something else with the cap in parallel. Thanks in advance
Excellent video, I've studied electronics on my own for a bit, in the schematic I'm assuming that the electrons are coming from the GROUND and feeding into the cathode in order to get the electrons going via cathode-grid-anode ? Thanks............Jay
Yes, you can. But, to do that you would need one tube to use as a phase inverter, and you would be losing a gain stage so you might want to add another tube.
I never fiddled with tubes but have had a lot laying around many years ago. As I always wondered and when you say that the grid thus the voltage of it, is that the negative or positive voltage of it? If it's the positive this must make it 180 degrees inverted, right? since then the electrons will stop there instead of continue to the plate. If it's the negative then why even leave the cathode as it "won't see" the plate as much as it's being choked by this grid.
Well THAT I know, lol, as I asked the it's the negative part of it or the positive. Think of it as if I probed it as if the input was just one short digitized pulse and in that moment it was sampled it was either positive, negative or zero, all the values AC can be. Sorry... as you see on my name, English ain't my native language so... Hope you understand what I mean with this.
Question: how do I take a 5 watt circuit like demonstrated in the video and bump it to 15 watts? What kinds of changes are needed? More tubes? Different (more powerful OT? & if I can raise the wattage, do I need to change the caps/resistor values ?
i recently took apart a 1950's lemco model 45 ignition coil/condensor tester that uses a ken-rad 6-48 4 pin vacuum tube but cant find info on specs but the heater is ok @ 5.0-5.5v. i dont know tubes very well but im wanting a vacuum tube tesla coil. could I use it for a vttc??? any info would help .thank you paul!
I know this is an old video and you probably won't see this comment but I'm really curious about the program you're using to draw your schematics. You do see this will you please tell me what it is and where you got it. Thank you
With no bypass cap, there is a signal at the cathode which works in opposition to the signal at the grid, reducing the gain of the stage. Adding the cap removes the signal at the cathode, allowing the stage to attain its maximum gain.
was never really into tubes but thats coz i never seen them explained before. i know they can do loads of stuff like, transistors, op amp's, diodes, amplifiers, im sure voltage regulators & current too, and much more.. what im trying to say is i think!! NO!!! i know i like them now!! thanks again Paul.. : )
I see a problem in your schematic and it may not actually be a problem but you are missing the anode load resistors which would go between your b+3 voltage to the ax7 anode. That resistor is necessary to determine your load lines and to find your cathode bias. From what I saw on your diagram your cathode resistor is normal for that tube but its a little ambiguous to see how you determined that value without the load resistor. Also depending on how you are drawing the schematic ltspice might be a better tool for initial design. Using ltspice you could then simulate the circuit and determine your overall frequency response as well as feed a .wav audio input and actually listen to a simulated output. Also you are missing grid leak resistors.
Maybe someone has commented on this but I didn't read all of them. Shouldn't there be something like a 1 meg resistor from the tip connection of the jack to ground?
Ok, but no connections made to the HV side of the tubes, which I believe is thru resistors?, I think you should included that in part one, otherwise its confusing to have a circuit with no HV connection).
Awesome video explaining everything & it's purpose clearly. So far the best fundamental explanation video I have found thank u for clearing up a ton of things for me. I am now a subscriber
Good to see you doing tube stuff, not too common nowadays. But if this was the whole designing part, hadn't it been good to also include a explanation to how you got your component values and why they are needed?
Amp design is actually pretty difficult. To explain why some values are chosen can really amount to a lot of just trial and error. I'm an electrical engineer and I find tube amps can be pretty challenging to build because every small change effects another part of the circuit. Its really hard to explain the selection of a lot of these components without going deep into tube behavior. If you really want to know though go research tube characteristic curves and loadlines, they are the key to how tube amps work.
Good job. You would want to use a 33k input R rather than a 68K with only one input. Fender's 68k's are in parallel when youre plugged in to the jack so your actually going through 34k ohms rather than 68k.
It's also a good idea to reduce the value of the input grid stopper resistor to reduce Johnson noise as well as place a capacitor to ground forming a low pass filter to filter RF
After watching 75% of your video, the question in my mind becomes: since you are essentially using class A amplification, why would we need negative feed back? What would be the purpose in this stage?
Nice video! Can you tell me what is the purpose of the bypass capacitors which connect in parallel to the ground resistors? And how can you determine capacitance value? Thank you.
I got a Weller soldering iron for Christmas and now I have to figure out what to do with it! This video is such a great introduction, but way over my head! I'm going to subscribe and thumbs up to help your channel! Any suggestions for a good beginner project? I have a couple dead speakers. Any suggestions? Thanks again!
@@learnelectronics thank you, is there another circuit diagram one for the power supply/distribution to all tubes? I might be being blind but I can't see it?
Hi. Thanks for the video. very helpful. Are Capacitors C1 to C5 coupling capacitors or electrolytic capacitors? Also are 2 watt resistors power rating sufficient for all of the resistors in the design? David.
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Just so you know, I'm coming from 70 years of life, and my beginning in electronics with tubes started in 1965 working on TRF radios like Atwater Kent and RCA! I just love this video! I just love the low orange glow of that tube doing what its supposed to do! And that sound! Don't get me started!!
yes great another old schooler
Please make a part 2 to this! I'm down the rabbit hole on amp builds and this is so helpful!!
A good way to learn is buy books of amplifier builds from the 1940s and 1950s Heathkits and draw out the schematics and get a few bins and save up parts and build it’s a fun hobby I need to start selling
I am engineer and this 16 minutes video was the best master class in tube amplifier
No you are not.
Great Work! Actually Fender used 68K input resistors but wired in in parallel when you plugged in the high impedance jack making it a 34k R, So when building a single input and still wanting to stick to Fender specs you would use a 34k (33k is closest) R.
Great video ! I've been building small to mid size transistor audio amps for a year or so and I've wanted to make a tube amp for a while . This is a big help to me . I also play guitar so It will be cool to build an amp to play through . Tube amps are so expensive this will be a rewarding and cost effective alternative to buying one . Thank you !
@Gerald Fisher stfu
Every time I see something like this I am always curious what provokes these responses. TH-cam comment sections uses to be entertaining. Now they just delete all the offensive shit. Lol
Have you built your tube amp yet? How did your project turn out?
This is the exact thing I've been looking for. Gonna attempt my first recap of a vintage Marshall and I really like understanding the circuity. This explains it so easily. Thanks!
I used to assemble tube Amplifiers years ago, using 6V6, 6L6, EL 84, EL 34, mostly in push pull for higher output. The cost was largely dependent on the requirements of the guitarist.
I see that in your 6V6 grid, there is no grid leak resistor. Is that done on purpose or otherwise?
I used grain oriented stampings,
for the output transformer. Heavier bass response!!
I am now running 80 years and this my obsession!!!!
I now use 5200 and 1943
Toshiba Transistors. They are
Heavy duty and give astounding Bass! Drives a 12 inch DJ speaker.
I have watched a TON of videos trying to understand signal paths in tube amps and they always start with an existing schematic with complicated preamps, etc. This was an extremely helpful 16 minutes! Thank you!!
Ben, I agree 100%
Paul, I love the glow of tubes. It has been a very long time since I worked on a Fender amp. The Champ is a classic. I would use the feedback resistor, but put a switch in to take it out when you want or make it variable. Since you said the amp could be used with other input devices, I would recommend a blocking cap on a second input port to protect the input devices. I would hate to see any stray voltages get loose. I hope the dentist trip goes well and you have a safe trip there and back.
My father had a Champ that I used as a boy to amplify the minute signals from my home-built crystal radio receiver. The night I heard, from way down in Mississippi, the top-forty music from WLS Chicago got me hooked forever in electronics! That glow of those tubes in the Atwater Kent and RCA TRF radios I worked on was magic!
A video from learnelectronics about a guitar amp? Auto-like! :)
The most helpful video I’ve ever watched for a novice
Where would the tone stack go?
Between the pre and power amp sections
Ignoring the plate load resistors is a significant omission as they determine stage gain and are an essential part of biasing each stage.
This is awesome! Wish I found it earlier. Simple and excellent tutorial. I have a tombstone radio chassis that I want to become a Bluetooth receiver and an MP3 or other type player. I have wanted to use a tube amp setup, I want a rich and not tinny sound. Yes I know I can buy one, but so much better to build. I'm retired from the aerospace industry, not an engineer but a builder for the engineers which included some electronics. I was certified in soldering. This is exceedingly helpful. Thank you.
Excellent! What programme did you use for the schematic?…
how you get values for components could be nice to know...but great approach, keep up the good videos!
There are thousands of amplifier designs
@@jimcatanzaro7808 I meant specifications, references like frank.pocnet.net/sheets/049/1/12AX7A.pdf
Old circuit designs not too hard just keep trying
excellent video, hours worth of learning in 16 minutes.
With all due respect to everyone who commented that they learned a lot from this video, from the title I expected you to describe how one reaches the values of the components. Instead, all I saw was a schematic of pretty much a *copy* of an existing circuit, with no explanation for the selection of the values of the components. That's what I expected, based on the title.
Great simplified discussion.
do you plan to heat the 12axy as a 12 volt filament [pin 9 not used] or a 6 volt filament?
Is there a part two to this video. It was one of the best. I’m finally understanding and this confirmed it.
Great video on showing just the signal chain but why doesn’t the grid of the output tube reference ground thru resistor like for the grid on 12AX7 but with a fixed resistor rather than variable resistor for volume control?
How do you determine the values of the resistors and caps?
This video was very helpful, thank you! I’m looking for part 2 now but not having any luck, do you have a link by chance?
That is an iconic way to start a video
Where (or in what date range) can I find the next video in this series? I don’t see it in the playlists… Thanks!
Fantastic. Anybody knows what software was used above?
In my Champ 5F1 build I needed to change the value of the cathode bias resistor from 470 ohms to 750 ohms
in order to reduce the plate dissipation to 12 watts from the 19 watts I got with the 470 ohm.
So all that did was shift you right along the loadline for that stage and decrease your quiescent plate current. Did you notice any decrease in distortion? It may have been more appropriate to adjust your load resistor instead.
You should always use a push-pull final, finals will be driven into non-linear regions and with a push-pull output odd harmonics will not be generated and it will sound more smooth and less harsh when strongly driven.
The anode resistors are also part of the signal path, otherwise there is no gain at all my friend...
I've learned more about guitar amps from this video than anything else. I've been playing rock'n'roll for 40 years. COVID has me doing more stuff at home, including electronic projects. I'll watch the rest of these videos, but can you point me to a resource that explains *why* components are used? In particular, I'm curious as to why the capacitor is in parallel (?) with the pot. Thanks for this.
I appreciate the progress of design with application. I use pencil and earsing rubber. Although it is proper circuitry to make amplification , without any feedback and without possibility to adjust input signal the first stage which is likely to be overloaded. And mono. For music it is useless. . No tone controls, no phisiology correction ? Why to build with marvelous tubes something useless?
A minor point, just to stop any confusion, you labled the 12AX7 as T1 instead of V1, which made the 6V6 V1 (instead of V2), and the output transformer as T2 (it should be T1).
Sorry. It's a bit pedantic I know, but having worked for many years (late 70's - early 90's) on design and repair of valve equipment I can get a bit like that. Again, sorry. Great vid.
i know Paul is not a guy who take affiance to what you pointed out. he's one of the nicest guys on YT.. FACT!!
😄 This just reminded me that, many years ago, when first learning about electronics, I saw an American circuit where the valves were labelled T1, T2, T3, etc. I could not understand what the "T" signified. In the UK, "tubes" are called valves and that's what my theory books called them. There was no Internet in those days to quickly look things up. It was only later, when I came by an old American ham radio book, that I realised valves were referred to as vacuum tubes (T for Tube). I still can't decide which term I like best - vaccum tube nicely describes what it is, whereas, valve describes what it does.
Why would you want negative feed back ? Will it suppress osculations or ? ???
It creates more "headroom" so it doesn't go into distortion at lower volumes
You are correct, the negative feed back will make the amp more stable, and less likely to oscillate.
Dude thank you for this video. Really into wiring up stuff and you helped me understand how those paths work and why they work a little better.
Should there be a capacitor between the input and the tube/valve to prevent DC getting to the grid? If you put any pedals between the Guitar and the amp, there will be DC voltage on the input in addition to the AC signal from the guitar.
What I have covered this far is the exact signal path of the Fender 5F1 circuit.
@@learnelectronics I would vote for the negative feedback.. it will make it much more Pedal friendly. You might consider adding a master volume and effects loop.
I have been thinking on building a tube amp and this might be the project!
Thanks this is great
Finally someone explains this clearly
i was thinking about taking out the feed back loop in my amp to get more gain,,you dont need it ,,correct
Any reason why a tube head wouldn't switch from clean channel to distortion channel ?
Bought a used blue voodoo 60. Had no sound but fixed that, second problem it won't switch channels
Thanks man. You helped explain a big part of what I wasn't understanding
Thanks for the video!
A minor advice: you could give some more in-depth info for us newbies about the actual purpose of the caps and resistors added to the construction. I know that there are tons of videos about tube amps, but none of them seem to give enough explanation about the purpose of the individual parts and their values, just "a capacitor here, a resistor there, and you're good".
You could also make a video about the characteristics graphs in tube datasheets and how to use them. That's a topic I've been interested in for a very long time, but never found a good video about making sense of those graphs.
This is just the first part of this series, lots more information will follow.
@@learnelectronics Thank you, can't wait! :)
I want to make it 60 amps instead of one amp. Do I just use a bigger transformer or do I have to change the tubes?
You will need to change your output transformer, probably add two more preamplification gain stages, and two more power tubes.
Hello , ive been fallowing the channel since forever , i dont subscribe nor like any video or anyone , so jsut because im not a subscriber doesn't mean i dont fallow .
Whati want to ask is this a Hi Fi preamp , i want to build it and use it as a preamp for now , latter with a power stage ,
Would this bee a good design ?
I got 220 to 240V AC Transformer that i plan to use for it , it has 7v output as well . On a 2x 12AX7 tube as a stereo pair
There's nothing wrong with using a tube amplifier for music, but a Champ circuit will not produce a "HiFi" music amplifier. I suppose that this depends on your definition of "HiFi", though .
The reason that these old circuits are so desirable for guitar amps is *because* they add tons of color to the sound; they are not neutral. For music reproduction, we generally want uncolored amplification.
There are no rules, though, so if someone likes the sound of music through a guitar amp then they go right ahead. I just want to let people know they will not get a distortion-free amplifier if they build this project. They will get a simple Fender-like amp design that is great for classic guitar sounds.
This is a relatively affordable tube amp to build due to the minimal parts count, but it will add color/distortion to your music at high volumes, the bass may be "flabby", and the sound may vary widely from speaker to speaker. Impedance matching is critical for tube amps.
Many modern speakers have low efficiencies and need lots of wattage to get loud, whereas this circuit will produce up to 5 watts. Distortion *will* be audible at 5 watts, however, so really this is probably a sub-1-watt music amp.
I recommend a solid-state amp based upon a proven IC for a beginner-level music amp project; it will much be less expensive and less dangerous to build and provide cleaner sound with tighter bass.
th-cam.com/video/d9O7oZEYALI/w-d-xo.html
th-cam.com/video/D5N82Qr6k78/w-d-xo.html
But I love tubes and tube amps, so build this project anyway if you already know what to expect. If nothing else, this Class A amp will make an attractive room heater ;).
Thanks for the video, could you go a bit more in depth about what the passives around the tube are doing?
Keep watching the series...
It would be great knowing how the values were figured out too.
.
@@Songwriter376 they are determined by some calculations from the tube datasheets. the tubes have graphs relating the anode current at a specified voltage. These passive components determine what the quiescent current and voltage is and determines the amount of signal headroom.
zacboss467 Thanks for that answer!
what schematic program are you using? is it free?
Hey, I am having huge difficulty with op amp circuit used in TA7642 radios, I cannot figure out how to attach the lm386 chip to have a gain of more than 200 (10 u cap between pin 1 and 8) if I give it too much signal in 50 k ohm pot then the radio just makes a farting noise. My problem is that I need to figure out which lowpass or highpass filtrations between the speaker pin 5 and the 470 n capacitor and which resistors I need to reduce the hissing noises without any distortion or clipping when I try to make it louder
Moist Andy The gain cap for an LM386 is 200. To remove the distortion, you either need to cap the gain at a level below 200 by using a fixed resistor in series with the 10uF cap or adding a gain pot. You’ll need a 1k pot for a smooth transition. Check out the datasheet! Also, for the Zobel Network from pin 5, the resistor-cap to ground, the datasheet recommends 10ohms.
Do you have any videos that speak to the different caps, and depending on where in the circuit,and the preferable cap materials that better handle sonics vs just being a workhorse. I hear different interjections on this subject but haven’t found a good explanation of except when folks rave about bumblebee caps in the Paul’s. Maybe I’m. It searching correctly.
Fantastic walk through. Cheers-
Good to start again after many many years
Just a suggestion, but you glossed over the bypass capacitor requirement. i think it's important to understand the requirements for DC biasing resistors etc and it's affects on feedback, hence the need to bypass them for the AC signal.
This is just part 1
hi sir thankyou for this beautiful video...sir i have a question what is name this software .???
What software were you using for making the schematic?
Yes put in the negative feedback...thank you for doing this I hope the next video is coming soon...
Nice explanation, thanks brother from India.
Excellent video. One suggestion. If you can have another video where you could explain how do we arrive at those resistor & capacitor values & the reason or logic to use it. In fact that’s the fundamental aspects of circuit design. Thanks for uploading wonderful videos.. Keep up the good work..
This is to do with the tube characteristic curves, these determine how anode voltage and current behave for a given load. vrps.org/documents/TubeTheory/TubeTheory.html
The curves for a given tube are the key to determining the values for the cathode resistor and anode resistor. On another note, the coupling capacitors and grid leak resistors have to be chosen carefully as they act as a high-pass filter and the wrong values can lead to them lopping off the lower frequencies of your signal.
Hello, what software do you use for drawing the schematics? Is it freeware? Does it have all the elements in the library?
How did you work out values for the resistors and caps? Whats your operating point etc?
Why are you Not using a plate resistor? How will voltage be carried to next stage by just 1 capacitor?
Did you actually build this?
He isn't covering power supply design in this video. IMO, plate resistance is part of the amplifier stage, not the power supply, but it isn't my video.
The capacitor blocks the DC plate voltage and allows the audio frequency to pass to the next stage.
how did you determine the values of the resistors and bypass caps?
subbed 👍
I've been repairing amps for a number of years simply off experience of years using amplifiers with basic knowledge of components and the components purpose. however the actual signal path and wiring has been such a mystery and you have taught me more in 15 minutes about that then I've learned in the last 5 years. I believe this is because I do not know how to read schematics and do not have electrical background but your tutorial did not require that and it tied so much up in my understanding thanks a lot bud great video!
Pretty simple and easy to understand, thank you.
Great video, I guess you can have a switch for negative feedback for (on or off)
Thanks..............
Pak bos saya mau tanyak tube vacum tipe EZ90 yg deket sama trafo input itu klu putus atau tiba2 mati mendadak apakah bisa menyebabkan kerusakan pada yg lain kah
Thank for sharing knowledge!
Could someone ecplain what c1 is for and if r1 ist just current limmitation or something else with the cap in parallel.
Thanks in advance
Excellent video, I've studied electronics on my own for a bit, in the schematic I'm assuming that the electrons are coming from the GROUND and feeding into the cathode in order to get the electrons going via cathode-grid-anode ? Thanks............Jay
Yep
@@learnelectronics Thank you , I've always thought of ground as a positive source--you cleared that all up for me....
Great video - what software are you using there?
Could you use the two sides of the 12AX7 to handle the left and right channels of a stereo signal?
Yes, you can. But, to do that you would need one tube to use as a phase inverter, and you would be losing a gain stage so you might want to add another tube.
I never fiddled with tubes but have had a lot laying around many years ago.
As I always wondered and when you say that the grid thus the voltage of it, is that the negative or positive voltage of it?
If it's the positive this must make it 180 degrees inverted, right? since then the electrons will stop there instead of continue to the plate.
If it's the negative then why even leave the cathode as it "won't see" the plate as much as it's being choked by this grid.
The signal is AC
Well THAT I know, lol, as I asked the it's the negative part of it or the positive.
Think of it as if I probed it as if the input was just one short digitized pulse and in that moment it was sampled it was either positive, negative or zero, all the values AC can be.
Sorry... as you see on my name, English ain't my native language so... Hope you understand what I mean with this.
hi I have old circuit maker software. I'm interested to refresh again. is this a free?
Yep
Question: how do I take a 5 watt circuit like demonstrated in the video and bump it to 15 watts? What kinds of changes are needed? More tubes? Different (more powerful OT?
& if I can raise the wattage, do I need to change the caps/resistor values ?
A pair of 6V6’s or EL 84’s make 15 watts in amps like mini-Marshall’s or the EVH 3. Likely in a push-pull configuration.
i recently took apart a 1950's lemco model 45 ignition coil/condensor tester that uses a ken-rad 6-48 4 pin vacuum tube but cant find info on specs but the heater is ok @ 5.0-5.5v. i dont know tubes very well but im wanting a vacuum tube tesla coil. could I use it for a vttc??? any info would help .thank you paul!
what would negitive feedback do?
I know this is an old video and you probably won't see this comment but I'm really curious about the program you're using to draw your schematics. You do see this will you please tell me what it is and where you got it. Thank you
EasyEDA
I'm a beginner at electronics, and I was just curious, what does the cathode bypass capacitor do?
With no bypass cap, there is a signal at the cathode which works in opposition to the signal at the grid, reducing the gain of the stage. Adding the cap removes the signal at the cathode, allowing the stage to attain its maximum gain.
was never really into tubes but thats coz i never seen them explained before. i know they can do loads of stuff like, transistors, op amp's, diodes, amplifiers, im sure voltage regulators & current too, and much more.. what im trying to say is i think!! NO!!! i know i like them now!! thanks again Paul.. : )
Dude thank you for this video. Can you tell me what kind of program you are using. Thank you
Esy EDA
This will be fun. I've never seen how to design and build with vacuum tubes. Stay safe.
Can you tell me the purpose of the bypass caps and R1?
I see a problem in your schematic and it may not actually be a problem but you are missing the anode load resistors which would go between your b+3 voltage to the ax7 anode. That resistor is necessary to determine your load lines and to find your cathode bias. From what I saw on your diagram your cathode resistor is normal for that tube but its a little ambiguous to see how you determined that value without the load resistor. Also depending on how you are drawing the schematic ltspice might be a better tool for initial design. Using ltspice you could then simulate the circuit and determine your overall frequency response as well as feed a .wav audio input and actually listen to a simulated output.
Also you are missing grid leak resistors.
Maybe someone has commented on this but I didn't read all of them. Shouldn't there be something like a 1 meg resistor from the tip connection of the jack to ground?
Yes. A 'grid leak' resistor is essential to its operation, and in this circuit would be 1M.
Unlike AC circuit math, I get this. What class amp is it? Could it handle a 1.2v input signal. My Icom 7610 generates little volume.
Ok, but no connections made to the HV side of the tubes, which I believe is thru resistors?, I think you should included that in part one, otherwise its confusing to have a circuit with no HV connection).
Hopefully your Dentist visit went well. Take care and save
I was getting comfortable to use this to build my 5F1, but there is no conclusion. I am thankful though.
Hi sir, can you send links for the next part of your video
Awesome video explaining everything & it's purpose clearly. So far the best fundamental explanation video I have found thank u for clearing up a ton of things for me. I am now a subscriber
Good to see you doing tube stuff, not too common nowadays. But if this was the whole designing part, hadn't it been good to also include a explanation to how you got your component values and why they are needed?
Amp design is actually pretty difficult. To explain why some values are chosen can really amount to a lot of just trial and error. I'm an electrical engineer and I find tube amps can be pretty challenging to build because every small change effects another part of the circuit. Its really hard to explain the selection of a lot of these components without going deep into tube behavior. If you really want to know though go research tube characteristic curves and loadlines, they are the key to how tube amps work.
he's pretty much copying the values of a fender champ, this is just a simplified version of the amp and would probably sound like shit.
What computer program are you using
Great video. What schematic software are you using? Thank you, Dave
I think Paul is using EasyEDAa
EasyEDA
Good job. You would want to use a 33k input R rather than a 68K with only one input. Fender's 68k's are in parallel when youre plugged in to the jack so your actually going through 34k ohms rather than 68k.
It's also a good idea to reduce the value of the input grid stopper resistor to reduce Johnson noise as well as place a capacitor to ground forming a low pass filter to filter RF
can i use one cathode bypass for two cathodes?
what simulator are you using?
What about the anode voltage for the 12AX7 tube
A great easy to understand video you have a great teaching method. Thanks for your instruction.
After watching 75% of your video, the question in my mind becomes: since you are essentially using class A amplification, why would we need negative feed back? What would be the purpose in this stage?
Negative feedback loops are to reduce distortion at higher volumes.
Nice video! Can you tell me what is the purpose of the bypass capacitors which connect in parallel to the ground resistors? And how can you determine capacitance value? Thank you.
As per my knowledge , the capacitor is used for better frequency response as well as gain.
I got a Weller soldering iron for Christmas and now I have to figure out what to do with it! This video is such a great introduction, but way over my head! I'm going to subscribe and thumbs up to help your channel! Any suggestions for a good beginner project? I have a couple dead speakers. Any suggestions? Thanks again!
Nice, simple and elegant. Tubes are so nice to work with.
Excellent!
Great video exactly what I was looking for! Looking forward to part 2!
The whole series is there
@@learnelectronics thank you, is there another circuit diagram one for the power supply/distribution to all tubes? I might be being blind but I can't see it?
@@learnelectronics I cannot find part 2?
Great video! I was wondering what circuit diagram software you are using. I really like that it has tubes as an option!
Hi. Thanks for the video. very helpful. Are Capacitors C1 to C5 coupling capacitors or electrolytic capacitors? Also are 2 watt resistors power rating sufficient for all of the resistors in the design? David.
C2 is a coupling capacitor. The rest are bypass capacitors, and their values pretty much dictate the use of electrolytics.