Retro Teardown: Inside An 8-Track Stereo Player

If you are a connoisseur of analogue audio, it’s probable you might have a turntable and a stack of records at home somewhere. If you are of a certain age you may even have a cassette deck, though you’re more likely to have abandoned that format some time in the 1990s. If you are old enough to have been around in the 1960s or 1970s though, you may have owned another analogue audio format. One of several that you might have found in a well-equipped home of that period was the 8-track stereo cartridge, a self-contained tape cassette format that fit four stereo tracks onto a single quarter-inch tape loop as eight parallel tracks, four each of left and right. A triumph of marketing, really, it should more accurately have been called 4-track stereo.

An 8-track stereo cartridge. Government & Heritage Library, State Library of NC (CC BY 2.0).
An 8-track stereo cartridge. Government & Heritage Library, State Library of NC (CC BY 2.0).

8-track cartridges were developed from earlier tape cartridge formats, largely to satisfy the demands of the automotive industry for interchangeable in-car entertainment. Thus if you owned an 8-track player it was most likely to have been found in your car, but it was not uncommon to find them also incorporated into home hi-fi systems. Thus we come to our subject today. Our retrotechtacular series usually highlights a video showing a bygone technology, but today we’re going to get a little more hands-on.

Some time in the early 1990s, I acquired an 8-track player, a BSR McDonald unit manufactured in the UK and dating from the early 1970s. BSR were much more well-known for their turntables, so this is something of an oddity. Where I found it has disappeared into the mists of time, but it was probably at a radio rally or junk sale. I certainly didn’t buy it because I wanted it to play 8-track tapes, instead I wanted a talking point for my hi-fi, something quirky to set it apart from everyone else’s. So every incarnation of listening enjoyment chez List for the last quarter century has had an 8-track player nestling within it, even if it has never played a tape while in my ownership. Thus we have a unique opportunity for this retro teardown.

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Scratchy Brings Digital Clarity To The Vinyl World

If you walk the halls of audiophilia, you may be aware that there has been a huge amount of work put in to software designed to clean up older audio recordings without compromising the quality of the recording itself. Sometimes the results can be amazing, such as when a stereo image is created from parallel mono recordings made before stereo was even a glint in the eye of a 1930s EMI engineer.

Bob Widlar on analogue versus digital. Original: EDN
[Bob Widlar] on analogue versus digital. Original: EDN.
But what if you are at home, without the benefit of a state-of-the-art studio or high-end digital signal processing? How can you then have pop and crackle free sound from your hi-fi when you put on a piece of vinyl? [Paul Wallace] may just have the answer, he’s made a smartphone app called Scratchy which listens to the output of a turntable, identifies the track being played, and plays the appropriate MP3 file for a digital experience from vinyl. It uses the algorithm published by Shazam to recognize tunes. The software also has a learn mode during which it can be taught about new records in the collection. The app itself is written using the Xamarin framework and has its source code in his GitHup repository, so it’s possible it could be produced for other platforms as well as Android.

Now vinyl purists will be speechless with horror at this wanton desecration of their format while audiophiles will be fuming at the smeary-in-the-midrange MP3s, but we can see its appeal if your vinyl is on the grubby side. It’s fair to say though that the stereo here won’t be sporting it, you’ll tear our analogue signal path from our cold dead hands. Take a look for yourselves, he’s put up a video showing it in operation.

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Introducing The Hackaday Passive Aligned Ferrite Active Quantum Crystal Nanoparticle Reference Sticker

As you know, here at Hackaday we take our audio equipment very seriously indeed. We’ve seen it all over the years and have a pretty jaded view of a lot of the audiophile products that come past our door, but once in a while along comes something that’s a bit special. That’s why today we’d like to introduce you to a new product, The Hackaday Passive Aligned Ferrite Active Quantum Crystal Nanoparticle Reference Sticker.

Here’s the problem: we’re surrounded by electrical noise. You can’t see it, you can’t touch it, and you can’t hear it, but your audio equipment can, and when that happens it will degrade your listening experience without your realising it. You might have shelled out your life savings on a top-end Hinari amp, Marc Vincent surround sound processor, Friedland carillon wire cables and a set of Saisho floor-standing speakers, but if you haven’t dealt with your system’s magnetic compatibility they’re never quite going to reach their potential and you’ll always be left wondering why your broader soundstage just doesn’t zing. You need an HPAFAQCNRS.

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Count Your Zombies! A Left4Dead 2 Stat Tracker

Sure, you’re getting further and further into the game and finishing missions, but the true progress for a zombie shooter is how many zombies you’ve killed, right? [Evan Juras] agreed, so he set off to build a hardware stat tracker for Left4Dead 2!

Left4Dead 2 tracks a bunch of stats and at the end of each level, those stats are updated on your Steam page. [Evan] used a Python script running on a Raspberry Pi to connect to the internet and grab four different stats from your Steam profile. Those stats are displayed on an RGB 16×2 display. To house the project, a case for it was designed and [Evan] had it 3D printed. There are two buttons on the case: one to update the stats and another to cycle through them. If no buttons are pressed then the display cycles through the stats every minute and updates the stats every 24 hours.

The video below shows a summary of the build process and describes the hardware and software used. [Evan] has plans for tracking stats from other games through Steam and his python code is available on Github. Python is becoming the go-to tool for interacting with video game bots and now, stats — see this list of Pokemon Go bots. Also, check out this feature about running MicroPython on an ESP8266 if you wanted to build something similar to this without the Raspberry Pi.

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Record Players Explained for the Streaming Generation

How do you consume your music, these days? Aside from on the radio, that is. Do you play MP3 or other files on your phone and computer, or perhaps do you stream from an online service? If you’re really at the cutting edge though you’ll do none of those things, because you’ll be playing it on vinyl.

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
A few years ago reporting on a resurgence of sales of vinyl records was something you would never have expected to see, but consumer tastes are unpredictable. Our red-trousered and extravagantly bearded hipster friends have rediscovered the glories of the format, and as a result it’s popping up everywhere. For those of us who are old enough to have genuinely been into the format before it was cool again, the sight of Sergeant Pepper and Led Zeppelin II on 12″ at outrageous prices on a stand at the local supermarket is a source of amusement. It’s good to see your first love back in vogue again, but is it really the £20($25) per album kind of good?

With the turntable having disappeared as an integral part of the typical hi-fi setup the new vinyl enthusiast is faced with a poor choice of equipment. Often the best available without spending serious money at an audiophile store is a USB device with the cheapest possible manufacture, from which the playback will be mediocre at best. We’ve lost the body of collective knowledge about what makes a good turntable to almost thirty years of CDs and MP3s, so perhaps it’s time for a quick primer.

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Cheap LCD TV gets cheaper fix

Most hacks need some fair bit of skill and knowledge if you want to come out successful at the other end. Others, you just plunge in blindly with a “heck, it’s already broken so I can’t make it any worse” attitude. Throwing caution to the wind, you dive in, rip things up, and see if you can manage to catch the bull by the horns.

[Jim]’s cheap LCD TV, barely a few years old, died. It was purchased from the store whose blue polo-shirted cashiers can drive you nuts with their incessant questions. [Jim] just rolled up his sleeves and rather haphazardly managed to fix his TV while adding an extra feature along the way.

His initial check confirmed that the LCD panel worked. Using a flashlight, he could see that the panel was displaying video which meant it was the backlight that wasn’t working. Opening up the TV, he located the LED driver board whose output turned out to be zero volts. [Jim] happened to have a lot of WS2812B strips lying around, along with their power supplies and RGB color controllers. The obvious solution was to ditch the existing LEDs and power supply and use the WS2812B strips.

Surprisingly, the original backlight consisted of just 21 LEDs arranged in three rows. He ripped those out, put in the WS2812B strips, and taped the jumble of wires out of sight. After putting it back together, [Jim] was happy to see it worked, although the new strips were not as bright as the old ones, causing some uneven light bands. He solved this by adding a few more strips of LEDs. It took him a couple of hours to fix his TV, but by the end of it, he had a TV whose backlight could be adjusted to any color using the external color controllers — although we’re not too sure what good that would be.

Adding Stereo VU Meters To A Turntable

A pleasing development for those with an interest in audio equipment from decades past has been the recent resurgence in popularity of vinyl records. Whether you cleave to the view that they possess better sound quality or you simply like the experience of a 12″ disk with full-size cover art and sleeve notes, you can now indulge yourself with good old-fashioned LPs being back on the shelves.

[Michael Duerinckx] is a fan of older trance records, and has an Ion Pure LP turntable which is fortunately for him not such an exclusive piece of audio equipment that it can’t be readily hacked. The hack he’s applied to it is a relatively simple one but nonetheless rather attractive, he’s added a set of LED VU meters in a ring round the edge of the platter.

Behind the LEDs is the trusty LM3915, an integrated circuit which will no doubt be familiar to any reader whose earlier life was spent among 1970s and 1980s audio gear. Internally it’s a stack of comparators and a resistor ladder, and it simply turns on the required number of outputs to match the level on its input. He’s put a pair of them on a little PCB with an associated PSU regulator, and mounted the LEDs in a row of holes drilled in the MDF base board of the turntable following the edge of the platter. Power and audio come from the turntable’s circuit board, which contains a preamplifier and the USB audio circuitry. A traditional turntable with a low-level output would not be able to drive an LM3915 directly.

This is a relatively straightforward project and the turntable itself isn’t necessarily the most accomplished on the market, but it’s very neatly executed and looks rather pretty.

Turntable projects are not as common as you’d expect here at Hackaday, but we’ve had a few. There was this concrete example for instance, and a very pretty one using layered plywood.

Courtesy of SoMakeIt, Southampton Makerspace.