Building Better Tube Amps With Heathkit Parts

[Justin] had been trying to find a good tube amp for years, but all the best examples were either expensive or a complete basket case. Instead of buying a vintage stereo tube amp, he decided to build his own using the guts of a Heathkit AA-100, a popular tube amp from the 60s and 70s that doesn’t have a great reputation for sound quality.

This project was based on an earlier project from a decade ago that replicated the very popular Dynaco ST-70 tube amp from parts taken from the Heathkit AA-100. The schematic for this conversion was readily available on the usual tube head message boards, and a few PCBs were available for the input stage.

With the schematic in hand, the next thing for [Justin] to do was get a nice enclosure. High quality tube amps are valued as much for their appearance as they are for their sound quality, and after giving his father-in-law a few sketches, a cherry hardwood chassis stained in a beautiful golden brown appeared on [Justin]’s workbench.

The big iron for this new tube amp was taken directly from the old Heathkit, and a few hours in front of a mill netted [Justin] a chassis panel drilled out for the transformers and tube sockets. The rest of the project was a bit of assembly, point-to-point wiring, and wire management giving [Justin] a fantastic amplifier that will last for another fifty years until someone decides to reuse the transformers.

One Man’s Awesome Collection Of Projects Done Over A Lifetime

[Robert Glaser] kept all his projects, all of them, from the 1960s to now. What results is a collection so pure we feel an historian should stop by his house, if anything, to investigate the long-term effects of the knack.

He starts with an opaque projector he built in the third grade, which puts it at 1963. Next is an, “idiot box,” which looks suspiciously like “the Internet”, but is actually a few relaxation oscillators lighting up neon bulbs. After that, the condition really sets in, but luckily he’s gone as far as to catalog them all chronologically.

We especially enjoyed the computer projects. It starts with his experiences with punch cards in high school. He would hand-write his code and then give it to the punch card ladies who would punch them out. Once a week, a school-bus would take the class to the county’s computer, and they’d get to run their code. In university he got to experience the onset of UNIX, C, and even used an analog computer for actual work.

There’s so much to read, and it’s all good. There’s a section on Ham radio, and a very interesting section on the start-up and eventual demise of a telecom business. Thanks to reader, [Itay Ramot], for the tip!

Flame Triodes Don’t Need Any Vacuum

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.

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Faking a Hollow State Device

There’s been a resurgence of interest in vacuum tubes. Even if you do think audio sounds better through a tube, you have to admit the care and feeding of filaments and plate voltages isn’t trivial. [Ed Nisley] decided to sidestep all that and just build an objet d’art that looks like a tube.

A burned out halogen bulb stands in for the tube, and a ceramic base holds the bulb. It also conceals–what else–an Arduino. The Arduino drives a knock-off Neopixel LED hidden in a faux plate cap. The result is a glass envelope bathed in a cold blue and purple glow that changes under software control.

We’d really like to see this kind of tube inside some rebuilt piece of tube gear. Or maybe Korg should offer LED lighting options for their recent tube in a chip form factor. If you really want to be a top-tier tube hacker, you can always try your hand at repair.

Building Triodes With Blinker Fluid

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.

Nixie Tube Clock Isn’t Just a Clock

With everything that’s been happening in the news lately, [Jarek] decided it was finally time to finish up his latest project. The Internet of Things has been exploding with projects lately, and this clock that also alerts him of the weather is the latest addition. Plus it has the added bonus of using everybody’s favorite display: nixie tubes!

Of course, using high voltage for the nixies can be terror-inducing, but [Jarek] found a power supply on eBay that was able to power the tubes for not too much money. The controller is an HV5622 which can control up to 32 nixies while only using up three pins on a microcontroller which is pretty handy if you have a limited number of output pins.

The clock also has another device hidden behind all of the wires for the tubes: an ESP8266 to give it network connectivity. The clock connects to the Internet and searches for the nine-hour weather forecast. There are a few nixie lights behind the display which illuminate cutouts in the case to indicate a few different weather statuses. It’s a very polished project, and since it’s enclosed in a nice case it’s not likely to be mistaken for any movie props. Of course, other nixie projects don’t have the same comforting look.

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An Internet Speedometer With A Dekatron

[Sprite_tm], like most of us, is fascinated with the earlier ways of counting and controlling electrons. At a hacker convention, he found an old Dekatron tube hooked up to a simple spinner circuit. The prescription for this neon infatuation was to build something with a Dekatron, but making another spinner circuit would be a shame. Instead, he decided to do something useful and ended up building an Internet Speedometer with this vintage display tube.

Like all antique tubes, the Dekatron requires about 400V to glow. After a bit of Googling, [Sprite] found a project that drives a Dekatron with an AVR with the help of a boost converter. Borrowing the idea of controlling a boost converter with a microcontroller, [Sprite] built a circuit with the Internet’s favorite Internet of Things thing – the ESP8266 – that requires only a 12 volt wall wart and a handful of parts.

Controlling the rotating glow of a Dekatron is only half of the build; this device is an Internet speedometer, too. To read out his Internet speed, [Sprite] is using a managed switch that allows SNMP to read the number of incoming and outgoing octets on a network interface. By writing a simple SNMP client for the ESP8266, the device can read how clogged the Intertubes are, both incoming and outgoing.

With an acrylic case fresh out of the laser cutter and a remarkably good job at bending acrylic with a heat gun, [Sprite] has a tiny device that tells him how much Internet he’s currently using. He has a video of it running a speedtest, you can check that video out below.

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