Tiny TV Celebrates The Forgotten Tech Of CRTs

February 11, 2022 by Dan Maloney 35 Comments

For those of us who grew up before the Internet, the center of pretty much every house was the TV. It was the shrine before which we all worshipped, gathering together at the appointed times to receive the shared wisdom of mass entertainment. In retrospect, it really wasn’t that much. But it’s what we had.

Content aside, one thing all these glowing boxes had in common was that which did the glowing — the cathode ray tube (CRT). Celebrating the marvel of engineering that the CRT represents is the idea behind [Matt Evan]’s tiny desktop TV. The design centers around a 1.5″ CRT that once served as a viewfinder on a 1980s-vintage Sony camcorder. [Matt] salvaged the tube and the two PCB assemblies that drive it, mounting everything in a custom-built acrylic case, the better to show off the bulky but beautiful tube.

The viewfinder originally used a mirror to make the optical path more compact; this forced [Matt] to adapt the circuit to un-reverse the image for direct viewing. Rather than receiving analog signals off the air as we did in the old days — and we liked it that way! — the mini monitor gets its video from a Raspberry Pi, which is set to play clips of TV shows from [Matt]’s youth. Rendered in glorious black and white and nearly needing a magnifying glass to see, it almost recaptures the very earliest days of television broadcasting, when TVs all had screens that looked more like oscilloscope CRTs.

This project is a nice homage to a dying technology, and [Matt] says it has spurred more than one conversation from people you grew up knowing only LCD displays. That’s not to say CRTs are totally dead — if you want to build your own old-school TV, there’s a kit for that.

A bird-shaped yellow PCB with legs wound out of wire, perched on its creator's arm. The bird has a lot of through-hole components on it, as well as an assortment of different-colored LEDs.

Printed Circuit Bird Family Calls For Us To Consider Analog

January 23, 2022 by Arya Voronova 16 Comments

On our favourite low-attention-span content site, [Kelly Heaton] has recently started sharing a series of “Printed Circuit Birds”. These are PCBs shaped like birds, looking like birds and chirping like birds – and they are fully analog! The sound is produced by a network of oscillators feeding into each other, and, once tuned, is hardly distinguishable from the bird songs you might hear outside your window. Care and love was put into making this bird life-like – it perches on Kelly’s arm with legs woven out of single-strand wire and talons made out of THT resistors, in the exact same way you would expect a regular bird to sit on your arm – that is, if you ever get lucky enough. It’s not just one bird – there’s a family of circuit animals, including a goose, a crow and even a cricket.

Why did these animals came to life – metaphorically, but also, literally? There must be more to a non-ordinary project like this, and we asked Kelly about it. These birds are part of her project to explore models of consciousness in ways that we typically don’t employ. Our habit is to approach complex problems in digital domains, but we tend to miss out on elegance and simplicity that analog circuits are capable of. After all, even our conventional understanding of a neural network is a matrix of analog coefficients that we then tune, a primitive imitation of how we assume human brains to work – and it’s this “analog” approach that has lately moved us ever so closer to reproducing “intelligence” in a computer.

Kelly’s work takes a concept that would have many of us get the digital toolkit, and makes it wonderfully life-like using a small bouquet of simple parts. It’s a challenge to our beliefs and approaches, compelling in its grace, urging us to consider and respect analog circuits more when it comes to modelling consciousness and behaviours. If it’s this simple to model sounds and behaviour of a biological organism, a task that’d have us writing DSP and math code to replicate on a microcontroller – what else are we missing from our models?

Kelly has more PCBs to arrive soon in preparation for her NYC exhibit in February, and will surely be posting updates on her Twitter page! We’ve covered her work before, and if you haven’t seen it yet, her Supercon 2019 talk on Electronic Naturalism would be a great place to start! Such projects tend to inspire fellow hackers to build other non-conventional projects, and this chirping pendant follows closely in Kelly’s footsteps! The direction of this venture reminds us a lot of BEAM robotics, which we’ve recently reminisced upon as something that’s impacted generations of hackers to look at electronics we create through an entirely different lens.

Continue reading “Printed Circuit Bird Family Calls For Us To Consider Analog” →

Giving Vintage Synths New Life In A Potentiometer Cleaning Showdown

January 19, 2022 by Maya Posch 24 Comments

As anyone who has ever owned a piece of older equipment that has a potentiometer in it can attest to, these mechanical components do need their regular cleaning ritual. Whether it’s volume knobs on a receiver or faders on a mixer, over time they get crackly, scratchy and generally imprecise due to the oxidation and gunk that tends to gather inside them.

This is your potentiometer caked with gunk.

In this blast from the past, [Keith Murray] shows a few ways in which fader-style potentiometers can be cleaned, and how well each cleaning method works by testing the smoothness of the transition over time with an oscilloscope. It’s enlightening to see just how terrible the performance of a grimed-up fader is, and how little a blast of compressed air helped. Contact cleaner works much better, but it’s essential to get all of the loosened bits of gunk out of the fader regardless.

In the end, a soak in isopropyl alcohol (IPA), as well as a full disassembly followed by manual cleaning were the only ones to get the fader performance back to that of a new one. Using contact cleaner followed by blasting the fader out with compressed air seems to be an acceptable trade-off to avoid disassembly, however.

What is your preferred way to clean potentiometers to keep that vintage (audio) gear in peak condition? Let us know in the comments below.

Thanks, [Grant Freese], for the tip!

The Eerie Sounds Of Ioalieia: An ESP32/Valve/Analog Hybrid Circuit Sculpture

January 15, 2022 by Dave Rowntree 18 Comments

We’ve not had a circuit sculpture piece for a while, so here’s “ioalieia” a lovely hybrid digital-analog sound sculpture by [Eirik Brandal] to dig into.

The host of the show is the ESP32 module, which generates audio frequency square waves, which are fed into a MCP4251 digital potentiometer. From there, it is fed into a AS3320 Voltage controlled filter (VCF), from Latvia-based ALFA (which is new to us, despite them being manufacturing electronics for sixty years!) This is an interesting device that has a four independently configurable filter elements with voltage controlled inputs for frequency control and resonance. The output from the VCF is then fed into a 6n2p (Soviet equivalent to the 12ax7) twin-triode vacuum tube, which is specifically aimed at audio applications.

The suitably distorted filtered square waves then pass into a Princeton Tech Corp PT2399 echo processor chip, which being digitally constructed, uses the expected ADC/RAM/DAC signal chain to implement an audio echo effect. As with the VCF, the echo depth can be modulated via the digipot, under the ESP32’s command. For a bit of added bling, the vacuum tube output feeds back into the ESP32, to be consumed by the internal ADC and turned into a light show via some PWM controlled LEDs. Lovely.

The final audio output from the echo chip is then fed into a speaker via a pair of LM380 amplifiers giving a power of about 5 W. It sounds pretty good if you ask us, and software configurable via Wi-Fi, giving this sculpture plenty of tweakabilty.

Of course circuit sculpture come in all shapes and sizes, and it wouldn’t do to not mention at least one sculpture clock project, and while we’re on it, here’s last year’s Remoticon circuit sculpture workshop.

Continue reading “The Eerie Sounds Of Ioalieia: An ESP32/Valve/Analog Hybrid Circuit Sculpture” →

PsyLink An Open Source Neural Interface For Non-Invasive EMG

January 7, 2022 by Dave Rowntree 30 Comments

We don’t see many EMG (electromyography) projects, despite how cool the applications can be. This may be because of technical difficulties with seeing the tiny muscular electrical signals amongst the noise, it could be the difficulty of interpreting any signal you do find. Regardless, [hut] has been striving forwards with a stream of prototypes, culminating in the aptly named ‘Prototype 8’

The current prototype uses a main power board hosting an Arduino Nano 33 BLE Sense, as well as a boost converter to pump up the AAA battery to provide 5 volts for the Arduino and a selection of connected EMG amplifier units. The EMG sensor is based around the INA128 instrumentation amplifier, in a pretty straightforward configuration. The EMG samples along with data from the IMU on the Nano 33 BLE Sense, are passed along to a connected PC via Bluetooth, running the PsyLink software stack. This is based on Python, using the BLE-GATT library for BT comms, PynPut handing the PC input devices (to emit keyboard and mouse events) and tensorflow for the machine learning side of things. The idea is to use machine learning from the EMG data to associate with a specific user interface event (such as a keypress) and with a little training, be able to play games on the PC with just hand/arm gestures. IMU data are used to augment this, but in this demo, that’s not totally clear.

All hardware and software can be found on the project codeberg page, which did make us double-take as to why GnuRadio was being used, but thinking about it, it’s really good for signal processing and visualization. What a good idea!

Obviously there are many other use cases for such a EMG controlled input device, but who doesn’t want to play Mario Kart, you know, for science?

Checkout the demo video (embedded below) and you can see for yourself, just be aware that this is streaming from peertube, so the video might be a little choppy depending on your local peers. Finally, if Mastodon is your cup of tea, here’s the link for that. Earlier projects have attempted to dip into EMG before, like this Bioamp board from Upside Down Labs. Also we dug out an earlier tutorial on the subject by our own [Bil Herd.]

Continue reading “PsyLink An Open Source Neural Interface For Non-Invasive EMG” →

Know Audio: Mixtapes, Tape Loops, And Razor Blades

December 20, 2021 by Jenny List 16 Comments

In our no-nonsense journey through the world of audio technology we’ve so far have looked at digital audio and the vinyl disk recording. What’s missing? Magnetic tape, the once-ubiquitous recording medium that first revolutionised the broadcast and recording industries in the mid-20th-century, and went on to be a mainstay of home audio before spawning the entire field of personal audio. Unless you’re an enthusiast or collector, it’s likely you won’t have a tape deck in your audio setup here in 2021 and you’ll probably be loading your 8-bit games from SD card rather than cassette, but surprisingly there are still plenty of audio cassettes released as novelties or ephemeral collectables.

The Device That Made The Sound Of The Latter Half Of The 20th Century

"Like a travelling razor blade", a Blattnerphone steel-strip tape recorder at the BBC in 1937. Douglas Hallam, Jr., Public domain. — “Like a travelling razor blade”, a Blattnerphone steel-strip tape recorder at the BBC in 1937. Douglas Hallam, Jr., Public domain.

The first magnetic recordings were made directly on metal wires, but metal fatigues as it bends. By coating a flexible plastic tape in ferrous particles, the same simple technique of laying down an audio signal as variations in the magnetic field could be made smaller, lighter, and more robust. But the key to the format’s runaway success is the technical advancements that differentiate those 1950s machines from their wire recorder ancestors.

Whether it is a humble cassette recorder or a top-end studio multitrack, all tape recorders are very similar. There are two reels that hold the tape: the playback reel that houses the recording, and the take-up reel that stores the tape as it plays in the machine. The take-up reel is lightly driven to run faster than the tape speed, and the playback reel has a slight braking force to keep the tape under tension at all times. Continue reading “Know Audio: Mixtapes, Tape Loops, And Razor Blades” →

Know Audio: Get Into The Groove

November 18, 2021 by Jenny List 62 Comments

The legendary Technics SL1200 direct-drive turntable, as used by countless DJs. Dydric [CC BY-SA 2.5)], via Wikimedia Commons. — The legendary Technics SL1200 direct-drive turntable, as used by countless DJs. Photo by Dydric CC-BY-SA 2.5

For me, the vinyl record player is the spiritual home of my audio listening experience, probably because I’m of the last generation to grow up when vinyl was king. The 12″ album, with its full-size sleeve and copious sleeve notes, used to be an integral part of musical enjoyment that hasn’t been adequately replicated in the age of streaming.

And like anyone who became an adult while CD players were still expensive luxury items, I started my journey into Hi-Fi with a turntable set-up that sounded pretty good. Since a new generation have in recent years rediscovered vinyl, it’s once again something that should be part of any review of audio technology.

I would have started this piece with a full run-down of the constituent parts of a good turntable, but since that’s a piece that I wrote back in 2017, it’s time to investigate some of the audiophile claims about vinyl recordings. It’s fair to say that this is an area where a lot of complete rubbish is spouted by people who should know better, and that’s something I find immensely entertaining to poke fun at. Buckle up. Continue reading “Know Audio: Get Into The Groove” →