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
I got a kick out of this video. The nice part is that this is a proven, basic class A circuit and you can add anything you might want by adding a pot or different valve. Add a tone pot or tremolo circuit, how about a more powerful output valve with a different output transformer or more B+, the combos are endless and can be built with scrap parts or different valves you have on hand, that's the fun. Personally I like repurposing old electronic equipment and some of the amps that come out of that process are just crazy and built for practice and fun and some are standouts. If you like to tinker it's the hobby for you and there are many kids that need a practice amp to get their talents started.
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!!
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 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. UA-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.
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!
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.
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.
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.
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?
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
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!
Hello Paul! If I may make a suggestion, I really think that you should put a capacitor between the input and the grid resistor in the first stage. Especially if you want to use the amp as a HI-FI amplifier. It is a form of protection to you, and your equipment. Also, I hope that your dentist appointment went well! Stay safe and keep up the videos!!
Which is seperate from the output transformer. I know this is a 6 month old comment. I answered anyway incase someone else was wondering the same thing
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. ua-cam.com/video/d9O7oZEYALI/v-deo.html ua-cam.com/video/D5N82Qr6k78/v-deo.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 ;).
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.
If you don't have a resistor from J1 to gnd when you unplug the input grid will collect electrons and shut off completely so that when you plug in the input again there will be an almighty crack as that voltage is discharged to ground. Also without a resistor from V1 grid to ground, V1 will shut off allowing only the peaks of the incoming signal to get through. Typically the grid to ground resistors are 1M to 10M. And BTW you will never get a true HiFi amp using valves.
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 ?
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.
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
The input grids of valves should be connected to ground (0v) otherwise the operating current of the valve cannot be controlled. The purpose of the resistor from the cathode to ground is to apply a negative voltage on the grid wrt the cathode. Check your valve data book for details, every valve is different.
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?
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
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.
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.
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.
@@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.
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
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.. : )
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.
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.
Use Ohms law to solve for the current through each component. You know the voltage, you know the current you want, so you solve for the resistance. As for the caps, different caps for different frequencies.
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.
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-
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?
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!
Hmmmm what if you don't connect the B+ at the output transformer but instead connect the B+ between the output transformer and the output tube, then use a capacitor to block DC from going to the output transformer which will be grounded where the B+ would normally be connected. My thinking is that since no DC current will be present on the output transformer, it wouldn't reach saturation as early as it would had it been connected the way which you are going to do... Yeah it's a little unorthodox but I don't have the means to test my theory, my understanding is that the fact that you have D.C. across the output transformer and also the Ac signal when the amplifier is working, the transformer goes into saturation very easy which is why the output transformers are so large! If my theory is correct, you can either get away with a much smaller output transformer or get much more power at the output... I know that someone else tried to use a smaller output transformer but he was still connecting it the traditional way which just saturated it... I plan to try it out one day and hopefully soon..
Missing resistors from the plates of the triodes to the hi voltage. The other end of the transformer to be connected to the hi voltage. Pin 6 of the triode to 6.3 volts
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.
There needs to be a resistor from pin 5 on 6v6 to ground About 470 k . That gives you your negative bias on output tube , Otherwise the tube may cherry plate and distorted sound.
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?
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
Ignoring the plate load resistors is a significant omission as they determine stage gain and are an essential part of biasing each stage.
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.
I got a kick out of this video. The nice part is that this is a proven, basic class A circuit and you can add anything you might want by adding a pot or different valve. Add a tone pot or tremolo circuit, how about a more powerful output valve with a different output transformer or more B+, the combos are endless and can be built with scrap parts or different valves you have on hand, that's the fun. Personally I like repurposing old electronic equipment and some of the amps that come out of that process are just crazy and built for practice and fun and some are standouts. If you like to tinker it's the hobby for you and there are many kids that need a practice amp to get their talents started.
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%
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 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. UA-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.
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.
The most helpful video I’ve ever watched for a novice
Where would the tone stack go?
Between the pre and power amp sections
do you plan to heat the 12axy as a 12 volt filament [pin 9 not used] or a 6 volt filament?
How do you determine the values of the resistors and caps?
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!
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.
Where (or in what date range) can I find the next video in this series? I don’t see it in the playlists… Thanks!
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.
Fantastic. Anybody knows what software was used above?
excellent video, hours worth of learning in 16 minutes.
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.
That is an iconic way to start a video
Excellent! What programme did you use for the schematic?…
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?
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
Is there a part two to this video. It was one of the best. I’m finally understanding and this confirmed it.
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
The anode resistors are also part of the signal path, otherwise there is no gain at all my friend...
i was thinking about taking out the feed back loop in my amp to get more gain,,you dont need it ,,correct
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! :)
Hello Paul! If I may make a suggestion, I really think that you should put a capacitor between the input and the grid resistor in the first stage. Especially if you want to use the amp as a HI-FI amplifier. It is a form of protection to you, and your equipment.
Also, I hope that your dentist appointment went well! Stay safe and keep up the videos!!
10:18
How do the 12AX7 plates get B+ voltage?
From the power transformer
Which is seperate from the output transformer. I know this is a 6 month old comment. I answered anyway incase someone else was wondering the same thing
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.
ua-cam.com/video/d9O7oZEYALI/v-deo.html
ua-cam.com/video/D5N82Qr6k78/v-deo.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 this is great
Finally someone explains this clearly
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.
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?
how did you determine the values of the resistors and bypass caps?
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.
Can you tell me the purpose of the bypass caps and R1?
can i use one cathode bypass for two cathodes?
If you don't have a resistor from J1 to gnd when you unplug the input grid will collect electrons and shut off completely so that when you plug in the input again there will be an almighty crack as that voltage is discharged to ground. Also without a resistor from V1 grid to ground, V1 will shut off allowing only the peaks of the incoming signal to get through. Typically the grid to ground resistors are 1M to 10M.
And BTW you will never get a true HiFi amp using valves.
Great simplified discussion.
What about the anode voltage for the 12AX7 tube
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.
what would negitive feedback do?
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.
what schematic program are you using? is it free?
Thanks man. You helped explain a big part of what I wasn't understanding
what wattage should the 1 meg pot be?
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.
Nice explanation, thanks brother from India.
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
Where can I find part 2?
4:32, what is the drawing software you are using?
hi I have old circuit maker software. I'm interested to refresh again. is this a free?
Yep
The input grids of valves should be connected to ground (0v) otherwise the operating current of the valve cannot be controlled. The purpose of the resistor from the cathode to ground is to apply a negative voltage on the grid wrt the cathode. Check your valve data book for details, every valve is different.
Forgot to say, the input grid is connected to ground via a large resistor, typically 1 mega ohm, not directly connected to ground!
Pretty simple and easy to understand, thank you.
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.
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....
what simulator are you using?
Please tell me the software you use to build the schematic
Easy eda
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.
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.
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.
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!
I enjoyed this video! Great job!
Can't find part 2 l, does it exist?
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
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 was getting comfortable to use this to build my 5F1, but there is no conclusion. I am thankful though.
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.
What program were you using?
What schematic software do you use that supports valves
Easyeda
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! :)
Hi sir, can you send links for the next part of your video
aren't you going to put a coupling capacitor in the path of the speaker?
No need, cause already coupled with transformer
This will be fun. I've never seen how to design and build with vacuum tubes. Stay safe.
Hello, what software do you use for drawing the schematics? Is it freeware? Does it have all the elements in the library?
How do you determine the needed values for the resistors and capacitors?
Use Ohms law to solve for the current through each component. You know the voltage, you know the current you want, so you solve for the resistance. As for the caps, different caps for different frequencies.
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.
Hi, is there a part 2?
Don’t put neg FB. But what CAD are you using?
I think that was Diptrace
Good to start again after many many years
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-
wath program is it?
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.
What is the software you are using to draw your schematics?
Easyeda
Thankyou@@learnelectronics
Welcome
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!
What value did the potentiometer go with it?
Most likely a 1 Megohm logarithmic pot.
Hmmmm what if you don't connect the B+ at the output transformer but instead connect the B+ between the output transformer and the output tube, then use a capacitor to block DC from going to the output transformer which will be grounded where the B+ would normally be connected. My thinking is that since no DC current will be present on the output transformer, it wouldn't reach saturation as early as it would had it been connected the way which you are going to do... Yeah it's a little unorthodox but I don't have the means to test my theory, my understanding is that the fact that you have D.C. across the output transformer and also the Ac signal when the amplifier is working, the transformer goes into saturation very easy which is why the output transformers are so large! If my theory is correct, you can either get away with a much smaller output transformer or get much more power at the output... I know that someone else tried to use a smaller output transformer but he was still connecting it the traditional way which just saturated it... I plan to try it out one day and hopefully soon..
what software is that??
Like your work and thanks for the help . What computer program do you do the designing on. Richie
Great video, I guess you can have a switch for negative feedback for (on or off)
Thanks..............
You miss the plates of the triods to be connected to the hi voltage trough resistors!!
Missing resistors from the plates of the triodes to the hi voltage. The other end of the transformer to be connected to the hi voltage.
Pin 6 of the triode to 6.3 volts
what program are you running for the schematic design.
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.
There needs to be a resistor from pin 5 on 6v6 to ground About 470 k . That gives you your negative bias on output tube , Otherwise the tube may cherry plate and distorted sound.
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?