Guilty Pleasures: The Most Unique Music Player You’ve Never Heard Of

29 September 2023 | 10:30 am | Mitch Fresta

This music-listening device far outstrips modern digital products, and yet, you've likely never heard of it.

Sony SRF-39

Sony SRF-39 (Source: Supplied)

In the early ‘90s, Sony introduced one of the most unique portable radios ever designed. But unfortunately, you won’t find this retro-styled product at your local audio store. In order to get your hands on this device, you’ll need to go to prison.

At any given moment, more than 12 million people are living behind bars. For some, these stints are as little as a few days, but for an unlucky group of individuals, time on the inside can be a lifelong sentence. With as little as one hour per day outside of their cells, the remaining hours of the day can feel almost eternal. While some turn to literature, meditation or exercise, an extensive number of inmates have always turned to one universal form of solitary enjoyment; listening to music.

And for over two decades, inmates around the world have relied on one unique piece of musical equipment to pass the time: the blandly named Sony SRF-39.

Initially designed in 1992, the SRF-39 was unlike anything else on the market. Not purely because it was created by Sony specifically for inmates - and never officially reached the commercial market - but for its unique design. Unlike normal Walkmans, which were coated in everything from sleek, phantom blacks right through to vibrant canary yellows, the SRF-39 was completely clear. A totally see-through outer shell gave users (and, more importantly, onlookers) a behind-the-scenes look at the basic yet powerful circuitry hidden within.

Fastened beneath the thick casing was a murky brown circuit board covered in neon blue capacitors, a lime green headphone jack and a series of tricky grey components. At the top, tucked below a white Sony logo, sat room for a single AA battery, an on/off switch, a thin tuning knob and nothing more.

Dissimilar to commercially available devices, the SRF-39 had no place for a cassette tape or any third-party device. All for one good reason: safety. It was believed that the fewer removable parts inmates had access to, the less chance that items such as the harsh plastic outer casing of a cassette tape could be fashioned into prison weapons. Moreover, the design was democratic. No prisoner had access to anything more or less than any other prisoner, just the AM/FM radio waves that they were presented with. Music couldn’t be stolen from other inmates or used as prison currency, and tension could be largely avoided.

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Prison wardens and guards also liked the design. The clear housing and intricate design made it nearly impossible to hide or carry unwanted items like razor blades, needles, or contraband like drugs. And at a price of $40 per unit - a vast majority of a weekly spending limit - it was unlikely that any inmate would risk damaging their biggest connection to the outside world for a largely ineffective weapon. While playing cards, exercising, writing, and reading were still viable options for inmates to pass the time, no other item gave them access to real-time news, fresh conversation topics and music from the outside world.

While various other models and brands appeared in the prison market over the decades, the humble SRF-39 was always hailed as the gold standard of jail-house music devices, not just for the prison-approved design, reliable nature or affordability, but for its raw power.

These small yet mighty bits of industrial design packed a punch, with users across the west coast of the United States reportedly picking up AM signals from as far abroad as Japan and Korea. Thanks in part to an ingenious bit of design that utilised an industrial-grade microchip alongside a single integrated circuit receiver, the SRF-39 could give inmates access to audio beneath the heavy concrete walls that fortified the prison with surprising ease. The straightforward, no-frills design also meant less energy was wasted, and a single battery could offer up to more than 40 hours of continuous listening time.

In 2016, The SWLing Post - a community of shortwave radio and amateur radio enthusiasts sharing shortwave radio reviews and news - ran a marathon battery test on the SRF-39. Using just one standard alkaline battery, the device could continuously run for 163 hours and 54 minutes, far outstripping modern digital products that hit prison shelves in subsequent years.

In the outside world, the dreaded ‘20% low battery’ warning on an iPhone can mean as little as getting to a charger within the coming hours. But the importance of battery life in prison cannot be underestimated; music devices are relied on for more than just the act of actually listening to music, and when batteries cost money, and money doesn’t come quickly or easily, the lifespan of a product that allows you to mentally escape is crucial.

A study conducted in 2007 at San Vittore prison in Milan found that “in a place where privacy is constantly denied, radio becomes a vital tool for building and maintaining one’s private self”. Further studies have shown that inmates who engage in meaningful activities that keep their minds occupied while incarcerated, such as listening to music, have fewer violent incidents and better mental health and recidivism outcomes once their term of incarceration is complete.

The simple act of listening to music while locked behind bars can be beneficial on numerous levels, from drowning out noise and relaxation to drawing a connection to the outside world and sparking important, emotional memories.

In recent years, programs such as Australia’s 'Songbirds' initiative and ‘Music For The Future’ have spawned around the globe, giving prisoners direct access to music and instruments within the jail, and many prisons have begun selling alternative digital MP3 players at their facilities. However, the Sony analog radio is far from dead, and the humble art of listening to music on a portable radio behind bars remains strong, thanks in part to an unwritten code among inmates.

For many locked on the inside, it’s considered bad luck - and poor manners - for fellow inmates to take practical, working, non-sentimental possessions into the outside world once their time in the slammer is up. This cultural tradition has helped the SRF-39 remain behind bars, even if their owners haven’t, and has kept a vast majority of these prized items off sites like eBay and Craigslist.

So, while this unspoken pact is the reason that coming across a working model in the outside world is becoming harder and harder for avid collectors, the scarcity is a sign that somewhere, in some strange part of the world, someone in a less than ideal situation can pop in their headphones, drown out the noise and use music to escape the position they’ve found themselves in. Even if just until the battery runs dry.