Just wanted to say that I teach an undergraduate electrical engineering class about electromagnetism, and I showed this video in class. The students loved it.
I just finished building my tube theremin. I looked up the article in EI 1961 and I remember seeing it back in the day. I chose to build mine in an LMB aluminum chassis box about 12 by 8 by 2 inches high. I used the dual OA2 regulators and added better filtering than shown in the article. I built it stage by stage and tested each circuit as It was assembled. The hardest circuit to get working was the 6AN8 resonant amplifier. My antennas form are still up in the air, but i chose a simple vertical 14 inch whip and a half loop for audio level. It works pretty good. Now I am going to attempt the sold state version.
Thank you so much! @1:37 I am weeping. Yes I am old and sentimental. Now forwarding this to my friends. You sir are one of my mentors. Your enjoyment is contagious!
Wonderful job. Figuring out the circuits and sourcing the parts.
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I discovered this channel yesterday, searching what components are worth desoldering and came across with this channel. Intro hooked me in, personality is fine AF, and i genuinely think this channel should be more popular because there's real passion here.
A company called PAIA makes a kit called theremax out if Oklahoma. I recommend it highly as I used that kit for my stydenrs in high school to build. You can buy the entire kit or buy it in sections as you can afford to. They even have a knock down cabinet you can build and finish off.
Tanner, that's an amazing accomplishment - building a Theremin. They are difficult to bring into alignment and difficult to play well. The addition of the regulating tubes helps greatly to stabilize the device. Personally I might have built it into a metal chassis instead of wood, but it appears to be working well as is.
Your fascination with analog is like an old soul reincarnated. Your theremin volume response direction is reverse of what is considered the standard today. Volume control your way does make the most sense but skill developed backward will prevent you from playing most other theremin models. Another great video in your fine collection.
V5 really needs a separate filament supply, as you are relying on the cathode heater insulation, which at red heat is likely to leak slightly, which can result in a heater cathode short circuit. Normally the transformer has a separate 6VAC winding, that is well insulated, to provide this supply, so the rectifier cathode can float at the HT rail, so that it will not short out and blow the tubes from a massive heater current spike.
Wow what an amazing video! It's so hard to find a video of a real Theremin build! Is there a big difference in sound quality etc if it's built using semiconductors instead? Cheers!
Thanks, Tanner. That's a really interesting tube circuit. The volume oscillator interference affecting output bias was obviously the result of a creative mind in the analog paradigm of the time. Tubes are inefficient, distorted, and suffer a plethora of other weaknesses, but they're awesome anyway .
Thanks for that very fine work, the investigations and explanations! Looking on the FFT signals there are side bands beside each of the overtones. That could be due to hum modulation.
what are the differences in Theremins you can buy (build)? amount of different sounds? clarity of sound? volume? ... I know some can switch from linear to non-linear. (is that possible to diy?)
Absolutely awesome video Tanner! Theremin's are wild, wild instruments, and the circuit is super interesting. You did an awesome job man, such a clean build! Out of curiosity, where did you slot your two 0A2 regulator tubes into the circuit, since they aren't included on the original schematic. Also, the 6BE6 oscillators are really interesting. The first 6BE6 looks to have the second control grid tied to the first grid through resistor R1. If I'm not mistaken, this effectively turns the 6BE6 into a fancy pentode (since the two grid potentials are essentially moving up and down at the same rate). I wonder if they did that to use the first 6BE6 as an amplifier for input into the second 6BE6, where the actual signal mixing occurs. That also raises the question of whether that could be shrunk down into a single 6BE6? The 12AU7 is a really interesting setup as well. They're both set up as cathode followers, which means there shouldn't be hardly any amplification of the signal coming out. It looked like you were feeding the audio jack into an amplified speaker? It'd be fun to build a little Class A amplifier out of two more 12AU7s and an output transformer to drive a speaker for a truly 1960's experience, haha. Oh, and thanks for the shout out man! Keep up the excellent videos, looking forward to more! Ninja edit: I was looking at the schematic again and I don't know how I missed that the second grid on the 6BE6 tube is actually tied to ground! That's even more interesting - there's so much going on with each individual tube, it's super fascinating! I may have to build just that oscillator portion of it up someday to fully understand what's going on. My wild guess (at 2330 at night) is that the second grid is held at ground, but the potential of the cathode actually changes, meaning the relationship between the second grid (which is ground) and the cathode is oscillating, allowing electrons to flow to the plate or not. Though I could be completely wrong! What an awesome circuit!
Thanks man! I put the 2 OA2 regulators in series to ground right after the 2nd power supply resistor, this made sure the regulators were not directly connected to B+ and before all the supply rails. Yeah, I was just feeding it through a low quality amp. Although, I brought it over to my friends house and hooked it up to his fender amp and delay pedal. It really sounded cool then! I did build a class A tube amp a while back with a 12AX7 and a 6V6, but it is currently not working. You are welcome for the shout out, I really like your channel and I hope you were able to gain a few more subscribers. That is an interesting thought about how the first oscillator works, you should try that out. do you think that it could also be just acting like another supressor grid? This circuit is very cool!
@@TannerTech Thanks for the update on the 0A2s! And the 6V6 is a righteous amplifier tube. They’re pretty popular among the hi-fi crowd, but our Magnavox Concert Grand uses a how lineup of them and they sound phenomenal. Alright, I finally decided to clear off one of my breadboards and give this 6BE6 circuit a shot! First and foremost, the Hartley oscillator, like the Colpitts oscillator, is such a simple but insane little circuit, it’s hard to wrap your head around from an theoretical point of view. The inductor/capacitor oscillation part of it kind of makes sense, but where it gets wild is that the potential of the cathode is always changing, which means electron flow is being controlled not just by the grid, but also by the cathode. And, when using a 6BE6, electron flow is controlled by two separate control grids as well as the changing cathode potential. It all mixes in an absolutely wild way! So, I grabbed a spare 6BE6 and rebuilt this circuit, only I had to make a few small changes since I’m running at just 24V. First, R2 is 10k, C1 and C2 are 1nF each, and L1 is 2mH made up of two 1mH inductors with the cathode in the middle. I played around with a few different resistors for R1, the resistor that connects the two control grids and man, things got weird. Here’s the oscillator on the scope with the probes on the output and the cathode, and a 33k resistor for R1: i.postimg.cc/jq4g9SM3/6BE6-33k.jpg First things first, the scale is 5V per division for both. 0V for the cathode is in the center of the screen, and 0V for the output is at the bottom of the screen. So, the output is oscillating from about 20V to 24V, and the cathode is oscillating from about -10V to +10V. The cathode is a hot mess and a half, and the entire thing feels like its on the edge of chaos, haha. It oscillates stably though, which is a testament to how awesome and forgiving the Hartley oscillator design is. I just randomly picked some values and am running at miniscule voltages and it (kinda) works. Things get really interesting once you change the value of R1 though. Here’s the oscillator with the probes on the output and the cathode, and a 3.3k resistor for R1: i.postimg.cc/kXM1dPZJ/6-BE6-3-3k.jpg Whatttt?! Yeah, the output has done something wild now. Alright, the basics, 0V for each is unchanged, so the output is oscillating from about 20V to 24V like before, but the cathode has really smoothed out and is now oscillating from about -2V to +4V. What’s absolutely blowing my noodle though is that the output oscillation doubled. Here’s the oscillator with the probes on the grid and the cathode and a 3.3k resistor for R1: i.postimg.cc/QMWskTky/6-BE6-Grid.jpg The cathode follows the grid almost exactly, so there’s some voodoo wizard magic going on here. My theory is that the cathode and grid are oscillating together, not because one is following the other, but from the LC tank circuit. However, the when the cathode bottoms out, the grid falls a little lower, making it negative relative to the cathode and stopping electron flow. This causes the output to go high. Then the grid and cathode come up together and the difference between the two drops, which brings the output low. Then we see the same thing again at the top - the cathode tops out just slightly above the grid, taking the grid negative in relation to the cathode again, stopping electron flow and bringing the output high once more. So, my theory, which is based on absolutely no research and mostly just guessing around at midnight (I gotta work on stuff earlier in the day…), is that by using the 6BE6 and a bit more voltage to stabilize things out, it doubles the frequency of the Hartley oscillator. With the 6AU6 Hartley oscillators I’ve built, they do not get that double bubble look on the output. But why does this specifically happen with the 6BE6? I have no clue, haha. The second control grid is at 0V so perhaps it acts as a control for keeping the two peaks and valleys somewhat equal? I truly don’t know, and I’ll have to do a whole lot more reading. But why would they want to set it up like this as opposed to just building the oscillator out of a regular pentode or triode? Perhaps it all comes down to the size of the inductor? If they were using a transformer that was on the order of 10s of mH, perhaps they couldn’t quite get a fast enough oscillation frequency. Again another stab in the dark, haha. At any rate, an absolutely fascinating use of the 6BE6 and there is some definite magic going on here!
Nice job! I really want to build a theremin one day. Be careful with that arcing at 5:09, though. That's not a good sign. Maybe you should have a different filament winding for the rectifier to reduce the cathode to filament voltage. I'm not sure if that causes this, but it's worth investigating.
Thanks! I noticed that as well. It only happened for the first 5 minutes of the regulator tubes running. The neon inside had not started glowing yet and it was arcing. After a bit, the tubes started glowing and I haven't had the problem since. That might be a good idea to have a different filiment winding. If the problem ever returns I will try that.
Wow Tanner that was a good one indeed. A transistorized version of this would be interesting. Instead of the hexode tube you could use a dual gate FET or maybe better a balanced mixer. Glad you're back :).
That would be cool, I am planning on making a transistorized version in the future sometime. Most dual gate fets are new-old-stock, it might be worthwhile to buy one to experiment with. Glad to be back!
@@TannerTech Best would be to use a quadrature balanced mixer or analog multiplier that are still available. They are more precise than dual gate FETs.
@@TannerTech They have a FEW in the outlet. I was there yesterday and I went to see what ones they had. Im pretty daft when it comes to vacuum tubes tho so cant give any details :( Edit: They had that giant triode there when you went there a few years back no? Did you buy it?
I think you did an excellent job building, explaining and showing the issues one might encounter with this Theremin. I have been asked to build a similar unit and I would like to know if you have a schematic with component values that I could get. I already have everything needed except the three small inductors. Would you have a Mouser part number or whoever where I might get these components? You might like my TH-cam channel also. ElPaso TubeAmps. Thanks...
Nice T-shirt Branding. Amazing theremin. On another note, do you have any use for used lithium batteries? In the future there will be a glut of them. Already I have a dozen waiting for toxic pick up day.
What kind of lithium batteries? A lot of times, the old lithium laptop batteries have 8 or 9 cells in them, and typically only 1 cell is bad. I have used the remaining good cells to power some of my projects, like a handheld soldering iron. amzn.to/2WwFI56 These battery charger boards are awesome, especially if the batteries are 3.6 volts.
@@TannerTech Good to know. I've 2 dabblers that might take them if I gift the recharger as well. I've drained batteries from 1 scooter, 2 digital cameras, 1 Debot vacuum, and 12+ coin cells from Christmas ornaments.
Hey tanner i really love your channel and I try to watch every video you make So keep those videos coming(: Oh and by the way I really like your haircut :)
Fantasic explanation of the circuit! I wanted to build this theramin for a long time. I live in europe and here the voltage is 240 do you think getting a suitable transformer will be good enough or should i change other things in the circuit?
@@TannerTech Thanks again for the detailed video and comments. Can you please explain where did you use the oa2 regulator tubes in the circuit? i can't see it in the schematic.
Fantastic and fascinating. It's amazing how someone can build such a beautiful operational piece of equipment from a 50 year old map. I'd love to learn the craft of electrical engineering. Hard to know where to start. Im reading The Art of Electronics but it's still pretty dense. Do tube amp for guitar next! Haha.
I actually have built a few guitar amps before to sell to my friends! It is a really fun experience. I'd say the best place to start is to find some old electronic devices, open them up, and research how the components inside work. Or just study about how different circuits work. I love this website: www.allaboutcircuits.com/
I did it sir, and so can you! I'm not Laura btw I feel obliged to tell you. It's my girlfriend's account. Anyway I started poking around on the internet back about 2004 learning all I could about tubes, tube circuits, different amps, anything I could find. I don't even know if TH-cam was thing back then, I was getting all my info from forums. Nowadays you can find some awesome TH-cam channels that will show you all you need to know to build amplifiers. Check out Uncle Doug for one, he is a wealth of old tube technology information. Start with something simple say....a Fender champ. You'll be surprised at just how simple a champ circuit is and how great it sounds when you're done. Good luck on the journey man.
How comes the volume gets louder when bringing the hand closer to the volume antenna? Usually Theremins are constructed the other way around, bringing the hand closer mutes the Theremin. Is the original circuit designed this way or was it your idea to flip the behaviour?
This was the original circuit where the volume control is flipped. I could probably reverse it by making the volume control oscillator output control the cathode instead of the grid bias though.
In all things tube, isn't it that the shorter the wire you can get away with, the better? They act like antennas Having said that, does the sound change if you are statically charged? Or say, try sticking a battery on yourself🤔
Hi Tanner! This is an EPIC project (like all the others). I wish I was as good as you at electronics. All my circuits seem to fail in some way. I'm a HAM too! I'm an extra, what class are you? I'm not going to share my callsign for privacy reasons. Also, how would you recommend I learn electronics/circuit design? I'm pretty young, so I don't really know where to start out. Thanks! I would love a response if you have time.
I am WD6EDZ yet the internet seems to have made that obsolete. Young Tanner is and will be a great one. “The world is a university and everyone in it is a teacher. Make sure when you wake up in the morning, you go to school.” - T. D. Jakes
Thanks NotYou! I am currently a general class. When I first took the ham test, I had only studied for tech class, but just took the additional 2 since it was free. I missed extra class by one question! I know what it feels like for all your circuits to fail. That is what it feels like for me half the time. It makes the moments where the circuit works all the better! I suggest taking apart some electronic devices and just researching the components inside and how they interact. Wikipedia is actually a pretty great source for research, because you can just keep clicking links and hopping to different topics. This website is also really good. www.allaboutcircuits.com/ Let me know if you have any questions!
@@TannerTech Thanks for replying! Over the summer, I was bored, so I decided to get a licence. I just planned to get a technician one, but after a few days, I was passing practice tests easily, so I decided to study for the general one too. Then I thought that I might as well study for the extra class too. All the tests were free. I wanted my dad to study and get a technician license with me too, but he didn't and failed the test. I think people make the tests seem a lot harder than they really are. Taking the extra test is definitely the hardest of the three though, but taking it gains you the least.The education section in allaboutcircuits is really helpful. Thanks for recommending it! By the way, so you play chess or go or something? You just seem like the type of person who might. Sadly, I can't take apart many electronic devices, as my mom would go ballistic. Right now, I'm working on making a hidden transmitter for radio foxhunting. One major problem that I have is that I can't tell I what part of my circuit isn't working, as I don't have enough money for a oscilloscope or fancy multimeter. Pretty much, if I build a circuit and it doesn't work (which is every time), I either have to rebuild it or give up. Then, if I rebuild it, I don't know if one of the components was broken or not because I can't test them, so I have to guess. Do you think I need an oscilloscope or component tester or something? Thanks again.
Канал громкости работает неправильно. Традиционно должно быть так: максимальная громкость звучания когда рука далеко от антенны. Она уменьшается когда рука приближается к антенне и звук выключается совсем если рука находится очень близко к антенне или касается её.
Could you connect the output through say a signal generator, that way you could theramin any frequency The antennas have no resistor, so there is a path to high voltage, maybe one could be added, or, paint the pipes to prevent accidental shock
That would be interesting, technically I could use the volume control antenna to control any audio signal. Both antennas have a straight DC path to ground through the oscillator coil, so it is perfectly safe to touch them, as long as the circuit is properly grounded.
Hey Mom, I found Dads old 200 watt Marshall. Let’s check it out with 8 fresh 6L6’s on the Theremin! Kitchen windows blow outward. Mom stuck to the ceiling like Velcro.
@@TannerTech So cool that you adopted a "closer for louder" topology! That is much more logical than the classical design, but shunned by many traditionalists.
I had to buy the tubes and sockets, that was about 80 dollars. The wood was another 20 dollars(Lots of scrap wood left). Luckily, MIT funded me for this project, so it was basically free. I am also grateful that y'all watch my videos, that generates a bit of income that lets me afford supplies.
Sound wise it is shit... technology wise it is great ... that you can pluck sounds from the air is impressive but not musically impressive... I always wanted to get round to doing something with valves as they glow and things, never gave myself the time .... so well done.
Just wanted to say that I teach an undergraduate electrical engineering class about electromagnetism, and I showed this video in class. The students loved it.
Glad to hear, that is awesome! What college do you teach at?
Plot twist: The theremin doesn't work, Tanner is just making the sounds with his mouth. That's why his mouth stays open.
You caught me!
Good sense of humor Tanner, but I know better
Thats not unusual for a thereminist to do, its called harmonizing. Tanner is demonstrating the voice range of his Theremin.
I just finished building my tube theremin. I looked up the article in EI 1961 and I remember seeing it back in the day. I chose to build mine in an LMB aluminum chassis box about 12 by 8 by 2 inches high. I used the dual OA2 regulators and added better filtering than shown in the article. I built it stage by stage and tested each circuit as It was assembled. The hardest circuit to get working was the 6AN8 resonant amplifier. My antennas form are still up in the air, but i chose a simple vertical 14 inch whip and a half loop for audio level. It works pretty good. Now I am going to attempt the sold state version.
Thank you so much! @1:37 I am weeping. Yes I am old and sentimental. Now forwarding this to my friends. You sir are one of my mentors. Your enjoyment is contagious!
"It is 12 30 and this theremin has become an AM radio"
haha that was funny. 2 projects in 1 video?
I do like the antenna insulators you used.
Knowledge regarding how and why components interact is as or more important as the enjoyment of creating. Much appreciated!
No fucking way I have NEVER seen a home made one before thats like one of the coolest things ive seen built on youtube. You're fucking awesome dude.
Wonderful job. Figuring out the circuits and sourcing the parts.
I discovered this channel yesterday, searching what components are worth desoldering and came across with this channel. Intro hooked me in, personality is fine AF, and i genuinely think this channel should be more popular because there's real passion here.
Thanks! I am glad you are enjoying it!
The impressive part isn't that you built it, it's that you managed to play something on it!
What a great project you took on! and amazing results. Thanks for sharing your notes with us.
Super impressive video - your scientific knowledge is so inspiring.
Really nice presentation of a great project. I particularly enjoyed the explanation at the end and the trouble-shooting tips. Thanks for posting.
No problem! It was a fun project to make
Awesome, man! Love it. That's a project I'd love to tackle too.
Wish they had a kit. Lol
A company called PAIA makes a kit called theremax out if Oklahoma. I recommend it highly as I used that kit for my stydenrs in high school to build. You can buy the entire kit or buy it in sections as you can afford to. They even have a knock down cabinet you can build and finish off.
Thats interesting! Capacitive coupling can allow for some amazing stuff!
Tanner, that's an amazing accomplishment - building a Theremin. They are difficult to bring into alignment and difficult to play well. The addition of the regulating tubes helps greatly to stabilize the device. Personally I might have built it into a metal chassis instead of wood, but it appears to be working well as is.
Thanks! I wanted to make a metal chassis, but did not have any of the parts to do so. Wood is a bit easier to work with.
Very cool man, this video was put together perfectly.
Your fascination with analog is like an old soul reincarnated. Your theremin volume response direction is reverse of what is considered the standard today. Volume control your way does make the most sense but skill developed backward will prevent you from playing most other theremin models. Another great video in your fine collection.
Thanks Chris!
V5 really needs a separate filament supply, as you are relying on the cathode heater insulation, which at red heat is likely to leak slightly, which can result in a heater cathode short circuit. Normally the transformer has a separate 6VAC winding, that is well insulated, to provide this supply, so the rectifier cathode can float at the HT rail, so that it will not short out and blow the tubes from a massive heater current spike.
Cool! Love it! Excellent work!
Wow what an amazing video! It's so hard to find a video of a real Theremin build! Is there a big difference in sound quality etc if it's built using semiconductors instead? Cheers!
Awesome! This is the coolest theremin ever. Can't wait until you experiment with making your own synthesizer.
Thanks, Tanner. That's a really interesting tube circuit. The volume oscillator interference affecting output bias was obviously the result of a creative mind in the analog paradigm of the time. Tubes are inefficient, distorted, and suffer a plethora of other weaknesses, but they're awesome anyway .
Tubes? Like being human with flaws, that is why they sound naturally beautiful particularly in theremin design.
Thanks for that very fine work, the investigations and explanations! Looking on the FFT signals there are side bands beside each of the overtones. That could be due to hum modulation.
what are the differences in Theremins you can buy (build)?
amount of different sounds?
clarity of sound?
volume?
...
I know some can switch from linear to non-linear. (is that possible to diy?)
That’s awesome dude. How much did it cost you to acquire all the electrical parts? I imagine some or all of the tubes are no longer being made?
Wow. That crystal is the actual heart of the instrument, IMO. That's what's making the actual sound & being amplified?
Not quite, but the crystal is essential in making the volume control work! The beat frequency of 2 HF oscillators is what is being amplified.
Absolutely awesome video Tanner!
Theremin's are wild, wild instruments, and the circuit is super interesting. You did an awesome job man, such a clean build!
Out of curiosity, where did you slot your two 0A2 regulator tubes into the circuit, since they aren't included on the original schematic.
Also, the 6BE6 oscillators are really interesting. The first 6BE6 looks to have the second control grid tied to the first grid through resistor R1. If I'm not mistaken, this effectively turns the 6BE6 into a fancy pentode (since the two grid potentials are essentially moving up and down at the same rate). I wonder if they did that to use the first 6BE6 as an amplifier for input into the second 6BE6, where the actual signal mixing occurs. That also raises the question of whether that could be shrunk down into a single 6BE6?
The 12AU7 is a really interesting setup as well. They're both set up as cathode followers, which means there shouldn't be hardly any amplification of the signal coming out. It looked like you were feeding the audio jack into an amplified speaker? It'd be fun to build a little Class A amplifier out of two more 12AU7s and an output transformer to drive a speaker for a truly 1960's experience, haha.
Oh, and thanks for the shout out man! Keep up the excellent videos, looking forward to more!
Ninja edit: I was looking at the schematic again and I don't know how I missed that the second grid on the 6BE6 tube is actually tied to ground! That's even more interesting - there's so much going on with each individual tube, it's super fascinating! I may have to build just that oscillator portion of it up someday to fully understand what's going on. My wild guess (at 2330 at night) is that the second grid is held at ground, but the potential of the cathode actually changes, meaning the relationship between the second grid (which is ground) and the cathode is oscillating, allowing electrons to flow to the plate or not. Though I could be completely wrong! What an awesome circuit!
Thanks man! I put the 2 OA2 regulators in series to ground right after the 2nd power supply resistor, this made sure the regulators were not directly connected to B+ and before all the supply rails. Yeah, I was just feeding it through a low quality amp. Although, I brought it over to my friends house and hooked it up to his fender amp and delay pedal. It really sounded cool then! I did build a class A tube amp a while back with a 12AX7 and a 6V6, but it is currently not working.
You are welcome for the shout out, I really like your channel and I hope you were able to gain a few more subscribers.
That is an interesting thought about how the first oscillator works, you should try that out. do you think that it could also be just acting like another supressor grid? This circuit is very cool!
@@TannerTech Thanks for the update on the 0A2s! And the 6V6 is a righteous amplifier tube. They’re pretty popular among the hi-fi crowd, but our Magnavox Concert Grand uses a how lineup of them and they sound phenomenal.
Alright, I finally decided to clear off one of my breadboards and give this 6BE6 circuit a shot!
First and foremost, the Hartley oscillator, like the Colpitts oscillator, is such a simple but insane little circuit, it’s hard to wrap your head around from an theoretical point of view. The inductor/capacitor oscillation part of it kind of makes sense, but where it gets wild is that the potential of the cathode is always changing, which means electron flow is being controlled not just by the grid, but also by the cathode. And, when using a 6BE6, electron flow is controlled by two separate control grids as well as the changing cathode potential. It all mixes in an absolutely wild way!
So, I grabbed a spare 6BE6 and rebuilt this circuit, only I had to make a few small changes since I’m running at just 24V. First, R2 is 10k, C1 and C2 are 1nF each, and L1 is 2mH made up of two 1mH inductors with the cathode in the middle. I played around with a few different resistors for R1, the resistor that connects the two control grids and man, things got weird.
Here’s the oscillator on the scope with the probes on the output and the cathode, and a 33k resistor for R1: i.postimg.cc/jq4g9SM3/6BE6-33k.jpg
First things first, the scale is 5V per division for both. 0V for the cathode is in the center of the screen, and 0V for the output is at the bottom of the screen. So, the output is oscillating from about 20V to 24V, and the cathode is oscillating from about -10V to +10V.
The cathode is a hot mess and a half, and the entire thing feels like its on the edge of chaos, haha. It oscillates stably though, which is a testament to how awesome and forgiving the Hartley oscillator design is. I just randomly picked some values and am running at miniscule voltages and it (kinda) works. Things get really interesting once you change the value of R1 though.
Here’s the oscillator with the probes on the output and the cathode, and a 3.3k resistor for R1: i.postimg.cc/kXM1dPZJ/6-BE6-3-3k.jpg
Whatttt?! Yeah, the output has done something wild now. Alright, the basics, 0V for each is unchanged, so the output is oscillating from about 20V to 24V like before, but the cathode has really smoothed out and is now oscillating from about -2V to +4V. What’s absolutely blowing my noodle though is that the output oscillation doubled.
Here’s the oscillator with the probes on the grid and the cathode and a 3.3k resistor for R1: i.postimg.cc/QMWskTky/6-BE6-Grid.jpg
The cathode follows the grid almost exactly, so there’s some voodoo wizard magic going on here. My theory is that the cathode and grid are oscillating together, not because one is following the other, but from the LC tank circuit. However, the when the cathode bottoms out, the grid falls a little lower, making it negative relative to the cathode and stopping electron flow. This causes the output to go high. Then the grid and cathode come up together and the difference between the two drops, which brings the output low. Then we see the same thing again at the top - the cathode tops out just slightly above the grid, taking the grid negative in relation to the cathode again, stopping electron flow and bringing the output high once more.
So, my theory, which is based on absolutely no research and mostly just guessing around at midnight (I gotta work on stuff earlier in the day…), is that by using the 6BE6 and a bit more voltage to stabilize things out, it doubles the frequency of the Hartley oscillator. With the 6AU6 Hartley oscillators I’ve built, they do not get that double bubble look on the output. But why does this specifically happen with the 6BE6? I have no clue, haha. The second control grid is at 0V so perhaps it acts as a control for keeping the two peaks and valleys somewhat equal? I truly don’t know, and I’ll have to do a whole lot more reading.
But why would they want to set it up like this as opposed to just building the oscillator out of a regular pentode or triode? Perhaps it all comes down to the size of the inductor? If they were using a transformer that was on the order of 10s of mH, perhaps they couldn’t quite get a fast enough oscillation frequency. Again another stab in the dark, haha.
At any rate, an absolutely fascinating use of the 6BE6 and there is some definite magic going on here!
Great stuff. I'm inspired to make one myself
Awesome! Good luck! Let me know if you get yours working.
The intro made me subscribe
Nice job! I really want to build a theremin one day. Be careful with that arcing at 5:09, though. That's not a good sign. Maybe you should have a different filament winding for the rectifier to reduce the cathode to filament voltage. I'm not sure if that causes this, but it's worth investigating.
Thanks! I noticed that as well. It only happened for the first 5 minutes of the regulator tubes running. The neon inside had not started glowing yet and it was arcing. After a bit, the tubes started glowing and I haven't had the problem since. That might be a good idea to have a different filiment winding. If the problem ever returns I will try that.
Fascinating and inspiring. You rock!
Thanks!!!
Wow Tanner that was a good one indeed. A transistorized version of this would be interesting. Instead of the hexode tube you could use a dual gate FET or maybe better a balanced mixer. Glad you're back :).
That would be cool, I am planning on making a transistorized version in the future sometime. Most dual gate fets are new-old-stock, it might be worthwhile to buy one to experiment with. Glad to be back!
@@TannerTech Best would be to use a quadrature balanced mixer or analog multiplier that are still available. They are more precise than dual gate FETs.
Very well done!
Very cool. I'm wondering where you get your vacuum tubes and how much the whole thing cost?
Theres an electronics store in riverside that sells them for cheap. Coincidentally, I actually live near there as well.
Wait, the electronic warehouse sells tubes now? Also, I got these tubes from tubesandmore.com
@@TannerTech They have a FEW in the outlet. I was there yesterday and I went to see what ones they had. Im pretty daft when it comes to vacuum tubes tho so cant give any details :(
Edit: They had that giant triode there when you went there a few years back no? Did you buy it?
I think you did an excellent job building, explaining and showing the issues one might encounter with this Theremin. I have been asked to build a similar unit and I would like to know if you have a schematic with component values that I could get. I already have everything needed except the three small inductors. Would you have a Mouser part number or whoever where I might get these components? You might like my TH-cam channel also. ElPaso TubeAmps. Thanks...
This thing makes sound like a living creature
Nice T-shirt Branding. Amazing theremin. On another note, do you have any use for used lithium batteries? In the future there will be a glut of them. Already I have a dozen waiting for toxic pick up day.
What kind of lithium batteries? A lot of times, the old lithium laptop batteries have 8 or 9 cells in them, and typically only 1 cell is bad. I have used the remaining good cells to power some of my projects, like a handheld soldering iron.
amzn.to/2WwFI56
These battery charger boards are awesome, especially if the batteries are 3.6 volts.
@@TannerTech Good to know. I've 2 dabblers that might take them if I gift the recharger as well. I've drained batteries from 1 scooter, 2 digital cameras, 1 Debot vacuum, and 12+ coin cells from Christmas ornaments.
VERY K👀L device Nice Work on this build 👍👍💙
super cool thank you
Pretty damn good playing for not having a quantizer!
Thanks! The theremin is pretty fun to play. It helps that I already play the piano. It might be a cool project to build a quantizer sometime.
Hey tanner i really love your channel and I try to watch every video you make
So keep those videos coming(:
Oh and by the way I really like your haircut :)
Fantasic explanation of the circuit! I wanted to build this theramin for a long time.
I live in europe and here the voltage is 240 do you think getting a suitable transformer will be good enough or should i change other things in the circuit?
Thanks! A suitable transformer should be the only change you will need. Try looking for some broken vacuum tube gear to salvage a transformer from
@@TannerTech Thanks again for the detailed video and comments. Can you please explain where did you use the oa2 regulator tubes in the circuit? i can't see it in the schematic.
Fantastic and fascinating. It's amazing how someone can build such a beautiful operational piece of equipment from a 50 year old map. I'd love to learn the craft of electrical engineering. Hard to know where to start. Im reading The Art of Electronics but it's still pretty dense. Do tube amp for guitar next! Haha.
I actually have built a few guitar amps before to sell to my friends! It is a really fun experience. I'd say the best place to start is to find some old electronic devices, open them up, and research how the components inside work. Or just study about how different circuits work. I love this website: www.allaboutcircuits.com/
I did it sir, and so can you! I'm not Laura btw I feel obliged to tell you. It's my girlfriend's account. Anyway I started poking around on the internet back about 2004 learning all I could about tubes, tube circuits, different amps, anything I could find. I don't even know if TH-cam was thing back then, I was getting all my info from forums. Nowadays you can find some awesome TH-cam channels that will show you all you need to know to build amplifiers. Check out Uncle Doug for one, he is a wealth of old tube technology information. Start with something simple say....a Fender champ. You'll be surprised at just how simple a champ circuit is and how great it sounds when you're done. Good luck on the journey man.
@@TannerTech Fine job sir! Always wanted to build one of these myself. Nice playing as well!
How comes the volume gets louder when bringing the hand closer to the volume antenna? Usually Theremins are constructed the other way around, bringing the hand closer mutes the Theremin. Is the original circuit designed this way or was it your idea to flip the behaviour?
This was the original circuit where the volume control is flipped. I could probably reverse it by making the volume control oscillator output control the cathode instead of the grid bias though.
Beatles, Niceeeeee. Really awesome project.
Nice effort! Keep up the good work
Thanks!
This is awesome.
Cool
5:12 better sound ever
In all things tube, isn't it that the shorter the wire you can get away with, the better? They act like antennas
Having said that, does the sound change if you are statically charged? Or say, try sticking a battery on yourself🤔
Hi Tanner! This is an EPIC project (like all the others). I wish I was as good as you at electronics. All my circuits seem to fail in some way. I'm a HAM too! I'm an extra, what class are you? I'm not going to share my callsign for privacy reasons. Also, how would you recommend I learn electronics/circuit design? I'm pretty young, so I don't really know where to start out. Thanks! I would love a response if you have time.
I am WD6EDZ yet the internet seems to have made that obsolete. Young Tanner is and will be a great one. “The world is a university and everyone in it is a teacher. Make sure when you wake
up in the morning, you go to school.” - T. D. Jakes
Thanks NotYou! I am currently a general class. When I first took the ham test, I had only studied for tech class, but just took the additional 2 since it was free. I missed extra class by one question! I know what it feels like for all your circuits to fail. That is what it feels like for me half the time. It makes the moments where the circuit works all the better! I suggest taking apart some electronic devices and just researching the components inside and how they interact. Wikipedia is actually a pretty great source for research, because you can just keep clicking links and hopping to different topics. This website is also really good. www.allaboutcircuits.com/ Let me know if you have any questions!
@@TannerTech Thanks for replying! Over the summer, I was bored, so I decided to get a licence. I just planned to get a technician one, but after a few days, I was passing practice tests easily, so I decided to study for the general one too. Then I thought that I might as well study for the extra class too. All the tests were free. I wanted my dad to study and get a technician license with me too, but he didn't and failed the test. I think people make the tests seem a lot harder than they really are. Taking the extra test is definitely the hardest of the three though, but taking it gains you the least.The education section in allaboutcircuits is really helpful. Thanks for recommending it! By the way, so you play chess or go or something? You just seem like the type of person who might. Sadly, I can't take apart many electronic devices, as my mom would go ballistic. Right now, I'm working on making a hidden transmitter for radio foxhunting. One major problem that I have is that I can't tell I what part of my circuit isn't working, as I don't have enough money for a oscilloscope or fancy multimeter. Pretty much, if I build a circuit and it doesn't work (which is every time), I either have to rebuild it or give up. Then, if I rebuild it, I don't know if one of the components was broken or not because I can't test them, so I have to guess. Do you think I need an oscilloscope or component tester or something? Thanks again.
Канал громкости работает неправильно. Традиционно должно быть так: максимальная громкость звучания когда рука далеко от антенны. Она уменьшается когда рука приближается к антенне и звук выключается совсем если рука находится очень близко к антенне или касается её.
Should the volume part be circular, gives more surface area you can... Nearly - come in contact with
Probably, but the copper pipe I bought was too wide to bend
Could you connect the output through say a signal generator, that way you could theramin any frequency
The antennas have no resistor, so there is a path to high voltage, maybe one could be added, or, paint the pipes to prevent accidental shock
That would be interesting, technically I could use the volume control antenna to control any audio signal.
Both antennas have a straight DC path to ground through the oscillator coil, so it is perfectly safe to touch them, as long as the circuit is properly grounded.
Hey Mom, I found Dads old 200 watt Marshall. Let’s check it out with 8 fresh 6L6’s on the Theremin!
Kitchen windows blow outward.
Mom stuck to the ceiling like Velcro.
But how do the variable capacitors figure in?
They are placed between the antenna and ground. They are there so I can tune the volume oscillator and one half of the pitch oscillator.
Ah. So in addition to the tank capacitor. Cool.
Arthur Harrison
3 minutes ago
Another vacuum tube theremin design: www.theremin.us/126/126revised.html
Thanks! I may just build that theremin next
@@TannerTech So cool that you adopted a "closer for louder" topology! That is much more logical than the classical design, but shunned by many traditionalists.
Also, if you sell that merch, I will DEFINATLY buy it :)
Thanks! I will hopefully start selling merch again in the next few months.
ngl i literally dont understand a word of what ur saying here but. damn this is cool as hell
Hey man did you make this?
get video good job..!
Where is the speaker, or rather what acts as the speaker?
I have a cheap amplifier hooked up to it. I also tried it with my friend's fender amp and delay pedal and it sounded awesome!
i mean.... how much for one bro
How much did the whole device cost you?
I had to buy the tubes and sockets, that was about 80 dollars. The wood was another 20 dollars(Lots of scrap wood left). Luckily, MIT funded me for this project, so it was basically free. I am also grateful that y'all watch my videos, that generates a bit of income that lets me afford supplies.
Now I have a headache
Do u want to sell it?
Sound wise it is shit... technology wise it is great ... that you can pluck sounds from the air is impressive but not musically impressive... I always wanted to get round to doing something with valves as they glow and things, never gave myself the time .... so well done.
Too expensive to built a non programmable theremin ,i can't afford,so i build a midi theremin
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