If you have ever had a go at building a tube-based project you will probably be familiar with the amount of metalwork required to provide support structures for the tubes themselves and the various heavy transformers and large electrolytic capacitors. Electronic construction sixty years ago was as much about building the chassis of a project as it was about building the project itself, and it was thus not uncommon to see creative re-use of a chassis salvaged from another piece of equipment.
This morning we stumbled upon a rather nice solution to some of the metalwork woes facing the tube constructor courtesy of [Bruce], who built his tube audio amplifier on a chassis made from a cake tin and with its transformers housed in decorative display tins.
The circuit itself is a straightforward single-ended design using an ECL82 triode-pentode on each stereo channel, and comes courtesy of [Nitin William]. The power supply is on-board, and uses a pair of silicon diodes rather than another tube as the rectifier.
It’s true that [Bruce] has not entirely escaped metalwork, he’s still had to create the holes for his tubes and various mountings for other components. But a lot of the hard work in making a tube chassis is taken care of with the cake tin design, and the result looks rather professional.
We have something of a personal interest in single-ended tube amplifiers here at Hackaday, as more than one of us have one in our constructional past, present, or immediate futures. They are a great way to dip your toe in the water of tube amplifier design, being fairly simple and easy to make without breaking the bank. We’ve certainly featured our share of tube projects here over the years, for example our “Groove tube” round-up, or our look at some alternative audio amplifiers.
There is a rich history surrounding the improvisation of electronic components. From cats-whisker foxhole radio detectors using razor blades through radio amateurs trying antique quartz lenses as crystal resonators and 1950s experimenters making their own point-contact transistors, whenever desirable components have been unavailable the ingenuity of hackers and makers has always sought to provide.
In an age when any component you might wish for is only a web browser and a courier package away, you might think there would be no need for such experiments. But it is in our curious nature to push the boundaries of what can be made without a factory at our disposal, so there are still plenty of ingenious home-made components under construction.
One such experiment came our way recently. It’s a few years old, but it’s a good one. [Nyle Steiner, K7NS] made a working triode without any form of vacuum, instead its medium is a flame. He’s demonstrated it as a rectifier, amplifier, and oscillator, and while it might not be the best triode ever it’s certainly one of the simplest.
In a traditional vacuum triode the current flows as electrons released from a hot cathode and are able to cross the space because there are no gas molecules for them to collide with. The flame triode has an abundance of gas, but the gasses within it and its immediate surroundings are also strongly ionized, and thus electrically conductive. Flame ionization detectors have exploited this phenomenon in scientific instruments for a very long time.
A roaring flame might not be the most practical thing to keep in your electronic equipment, but [Nyle]’s experiment is nonetheless an impressive one. He’s posted a video showing it in action, which you can see below the break.
Continue reading “Flame Triodes Don’t Need Any Vacuum”
It all began with a cheap Chinese rotary vane vacuum pump and a desire to learn the witchcraft of DIY vacuum tubes. It ended with a string of successes – a working vacuum chamber, light bulbs, glow tubes, diodes, and eventually this homebrew power triode and the audio amplifier built around it.
[Simplifier]’s workshop seems like a pretty cool place. It must have a bit of an early 20th-century vibe, like the shop that [John Fleming] used for his early work on vacuum tubes. Glass work, metal work, electronics – looks like [Simplifier] has a little bit of everything going on. True to his handle, once [Simplifier] had a cheap but effective vacuum rig he started with the easiest projects – incandescent and gas discharge lamps. Satisfied that he could make solid electrical and physical connections and evacuate the tubes, he moved on to diodes and eventually triodes. The quality of the tubes is pretty impressive – stray gasses are removed with a bake-out oven and induction-heated titanium getters. And the performance is pretty solid, as the video below reveals.
Very impressive overall, and it’s not just the fact that he’s building tubes from scratch – we’ve seen that before. What shines here is that specialized equipment is not needed to make working and reliable tubes – just a MAPP torch, simple hand tools, and a low-end vacuum rig. Anybody could – and probably should – give this a try.
Continue reading “Home Brew Vacuum Tubes Are Easier Than You Think”
The triode is one of the simplest kinds of vacuum tubes. Inside its evacuated glass envelope, the triode really is just a few bits of wire and metal. Triodes are able to amplify signals simply by heating a cathode, and modulating the flow of electrons to the anode with a control grid. Triodes, and their semiconductor cousin the transistor, are the basis of everything we do with electricity.
Because triodes are so fantastically simple, they’re the parts most commonly crafted by the homebrew tube artisans of today. You don’t need a glass blowing lathe to make the most basic vacuum tube, though: [Marcel] built one from the light bulb used in a car’s tail light.
The light bulb in your car’s tail light has two filaments inside: one for the normal tail light, and a second one that comes on when you brake. By burning out the dimmer filament, [Marcel] created the simplest vacuum tube device possible. In his first experiment, he turned this broken light bulb into a diode by using the disconnected filament as the anode, and the burning filament as the cathode. [Marcel] attached a 1M resistor and measured 30mV across it. It was a diode, with 30μA flowing.
The triode is just a diode with a grid, but [Marcel] couldn’t open up the light bulb to install a piece of metal. Instead, he wrapped the bulb in aluminum foil. After many attempts, [Marcel] eventually got some amplification out of his light bulb triode.
The performance is terrible – this light bulb triode actually has an “amplification” of -108dB, making it a complete waste of energy and time. It does demonstrate the concept though, even though the grid isn’t between the anode and cathode, and this light bulb is probably filled with argon. It does work in the most perverse sense of the word, and makes for a very interesting build.
Born well into the transistor era of the late 80s, [Fernando] missed out on all the fun you can have with high voltage and vacuum tubes. He wanted to experience this very cool tech, but since you won’t find a tube checker down at the five and dime anymore, where exactly do you get a vacuum tube to play around with? [Fernando]’s solution was to rip apart the vacuum fluorescent display from an old radio (Google Translate) and use that as a triode.
Inside every VFD is a filament, grid, and cathode – three simple elements also found in the triodes of just about every tube amp ever made. By applying a small voltage to the filament, a larger voltage to the cathode, and sending an audio signal to the grid, this triode amplifies the electrical signal coming from a stereo or guitar.
[Fernando] built his circuit on a breadboard, and with a little tweaking managed to get a fairly respectable amount of gain from parts salvaged from a radio. While using VFDs as amplifiers is nothing new – we’ve seen it a few times before, tube builds are always great to see, and bodged up electronics even more so.
[Claude Paillard] is truly talented. He makes triodes by hand. This is a long and arduous process that has many steps, each of which could be messed up pretty easily. [Claude] makes it look easy though.
You might recognize this from way back in 2009 when we covered it on hackaday.com
[thanks for the tip David]
[Claude Paillard] makes his own triodes (google translated) for short wave radios. The site doesn’t have a lot of details itself, but links to entire books on the history of radio tubes and manufacturing of them. [Claude] takes us through the entire process of building a triode in a 17 minute long video. Even if you aren’t into them, this is fascinating. From the looks of it, several of us might only be a pump or two short of being able to cobble one together.