For [ke4mcl], this whole cassette craze of late is not a new discovery so much as it is a personal nostalgia machine. Since [ke4mcl] sees a lot of basic questions go unanswered, they made an incredible beginner’s guide to all things cassette deck. This concise wealth of information covers everything from terminology to operation, basic maintenance like repairing the belt and lubricating the motor, and appropriate cleaning methods for the various parts. Yep, we’re pretty sure this covers everything but the pencil winding technique, which you probably already knew about.
You don’t need a lot of tools and supplies to maintain a cassette deck or twelve (apparently they’re addictive) — mostly just head cleaning fluid, isopropyl, window cleaner, and a bunch of cotton swabs. And given this guide, you’ll enter the enclosure confidently, armed with knowledge about everything from the belts to the capstan to the head. This is valuable information, the kind of stuff your older brother wouldn’t take the time to explain to you in the 80s. But maybe he didn’t know reverse bias from the holes in the top of the tape.
Don’t care for the quality of audio cassettes? Tapes are good for lots of stuff, like data storage and decoration.
In the early 1980s cassette tapes were the standard storage medium for home computer users; readers of a certain age will remember fiddling with audio jacks, tape counters and signal levels, then waiting for several minutes while a program (hopefully) loaded correctly. While most people happily upgraded to much more reliable floppy disks, [Zack Nelson] decided to go back in time and add a suitably classic storage medium to a retrocomputing project, in the form of a cassette interface. The cassette player he had available was a Pearlcorder L400, which uses the smaller microcassette instead of the familiar audio tapes used in your Walkman or boombox.
[Zack] designed the entire thing from the ground up: first he decided to use differential Manchester encoding, which provides immunity against common disturbances like speed variations (which cause wow and flutter). The data is encoded in the frequency range from 1 kHz to 2 kHz, which suits the bandwidth of the cassette player. Next, he designed the interface between the computer and the tape recorder; built from an op-amp and a comparator with a handful of discrete components, it filters the incoming signal and clips it to provide a clean digital signal to be read out directly by the computer.
The system is demonstrated by hooking it up to an Arduino Nano, which reads out the data stream at about 3000 baud. The noise it makes should bring back memories to anyone brought up with the “PRESS PLAY ON TAPE” message; if it inspires you to make your own, we’re happy to report that full schematics and source code are available. [Zack] is not the first one to make his own cassette interface; we’ve seen a somewhat more complicated analog design before, as well as one based on an FPGA.
It has been a long time since we stored software and computer data on audiotape. But it used to be the de facto standard for hobby computers and [Noel] has a great video about the Amstrad’s system (embedded below) which was pretty typical and how the process could be sped up since today, you have perfect audio reproduction, especially compared to consumer-grade audiotape.
The cassette tapes suffered from several problems. The tape had an inherently low bandwidth, there was quite a bit of noise present from the analog circuitry and heads, and the transport speed wasn’t necessarily constant. However, you can easily digitally synthesize relatively noise-free sound at high fidelity and rock-solid frequency. So basically a microcontroller, like an Arduino, can look like an extremely high-quality tape drive.
My DEF CON Safe Mode badge just arrived in the mail this afternoon. The Vegas-based conference which normally hosts around 30,000 attendees every year has moved online in response to the global pandemic, and the virtual event spins up August 6-9. Known for creative badges, North America’s most well-known infosec con has a tick-tock cycle that alternates electronic and non-electronic badges from year to year. During this off-year, the badge is an obscure deprecated media: the audio cassette.
This choice harkens back to the DEF CON 23 badge which was an vinyl record — I have the same problem I did back in 2015… I lack access to playback this archaic medium. Luckily [Grifter] pointed everyone to a dump of the audio contents over at Internet Archive, although knowing how competitive the badge hacking for DEF CON is, I’m skeptical about the reliability of these files. Your best bet is to pull the dust cover off your ’88 Camry and let your own cassette roll in the tape deck. I also wonder if there are different versions of the tape.
But enough speculation, let’s look at what physically comes with the DEF CON 28 badge.
A lot of projects we feature use video in some form or other, but that video is invariably digital, it exists as a stream of numbers in a computer memory or storage, and is often compressed. For some of us who grew up working with composite video there is a slight regret that we rarely get up-close and personal with an analogue stream, so [Kris Slyka]’s project putting video on a conventional audio cassette is a rare opportunity.
Readers with long memories may recall the Fisher-Price PixelVision toy from the late 1980s which recorded black-and-white video on a conventional cassette running at many times normal speed. This system does not take that tack, instead it decreases resolution and frame rate to a point at which it can be recorded at conventional cassette speeds. The result is not particularly high quality, but with luminance on one side of a stereo recording and chrominance on the other it does work.
The video below the break is a run through the system, with an explanation of how video signals work. Meanwhile the code for both encoder and decoder are available through the magic of GitHub. If you’re interested further, take a look at our examination of a video waveform.
After freeing the tape mechanism from the original enclosure and extraneous electronics like the AM/FM tuner, [Igor] got to work designing a retro styled enclosure for the hardware which would show off the complex electromechanical bits which would traditionally be hidden. With the addition of a clever 3D printed holder, he was even able to add microswitches under the original player’s buttons so he could detect the player’s current state without having to modify the electronics. This lets the finished player change the color of the RGB LEDs based on what it’s currently doing.
[Igor] came up with a very clever way of integrating light-up icons into the case by placing bright LEDs behind specially crafted thin sections of the print. It looked awesome in his tests, but after the considerable sanding, priming, and painting it took to turn the 3D printed parts into a production-quality enclosure, the LEDs are no longer visible on the final product. Even though they didn’t work in this particular case, we think it’s a brilliant technique worthy of stealing further research.
The detail that [Igor] but into this build is phenomenal. Seeing all the individual components he had to design and print to make the final product come together is really nothing short of inspirational. Projects like these are where 3D printing really shines, as trying to replicate this build with traditional manufacturing techniques would be an absolute nightmare.
You should probably hope you haven’t seen [Techmoan’s] cassette recorder before. That’s because it is a Neal interview recorder that was mainly used by police to tape interrogations. This one was apparently used by the Royal Navy and was sold for parts. Turns out, the repair was simple, but the teardown and the analysis of the machine — you can see it in the video below — is pretty interesting if you’ve never seen one of these before.
The unit looks like a heavy-duty piece of industrial electronics from the 1980s. Unlike a commercial tape deck, this one is made to do one thing: record. You can’t even rewind a tape in it. Also unlike a consumer recorder, the Neal has a few special features aimed at making sure you didn’t miss some important confession on tape. First, it beeps if there’s no microphone plugged in. When [Techmoan] showed the recording head, we noticed it looked like it was split in half. Towards the end of the video, we found out why. In addition, the unit records two tracks: one audio track and another with a voice reading the elapsed time every 10 seconds — pretty high tech for its day.