For most people, MiniDisc is just one of countless media formats that became obsolete when music went online. Not so for MiniDisc enthusiasts, many of whom still use a MiniDisc deck at home and a MiniDisc Walkman on the go. Unfortunately, high-end headphones these days often come with Bluetooth connectivity only, necessitating the use of clunky signal converters that ruin the tidy compactness of those portable players. [Daniel Rojas] cleverly solved this problem by directly adding Bluetooth functionality to a Sony MZ-R500 MiniDisc Walkman.
MiniDisc Walkmen are famously compact devices, so adding a full circuit board to one wasn’t easy. [Daniel] managed to squeeze the PCB from a Schosche wireless audio transmitter inside the front of the Walkman, next to the control buttons. He connected the audio signal to the transmitter’s input and rewired the little-used “End Search” button to become the “Pair” button. Sadly, the recording head and some associated hardware had to be removed in order to make space for the new component, turning the Walkman into a playback-only device.
The project’s GitHub page contains a detailed walk-through of the modification process that should enable anyone to reproduce the end result. [Daniel] didn’t arrive at the optimal solution in one go however, and he describes the three major revisions of his project in separate sections. In the first iteration for example, the Bluetooth module caused interference on the audio signal, which [Daniel] solved by adding isolation transformers in version two. He also includes a page full of technical information he collected during his project, which will come in handy if you ever want to perform other modifications on your MiniDisc Walkman.
Between the era of the CD and the eventual rise and domination of streaming music platforms, there was a limbo period of random MP3 players mixed in with the ubiquitous (and now officially discontinued) iPod. In certain areas, though, the digital music player of choice was the MiniDisc, a miniature re-writable CD player with some extra digital features. Among them was the ability to transfer music to the discs over USB, but they did not feature the ability to transfer the songs back to a computer. At least until now, thanks to this impressive hack from [asivery].
Although it sounds straightforward, this trick has a lot of moving parts that needed to come together just right. The MiniDisc player uses a proprietary encoding format called ATRAC, so a codec is needed for that. The MiniDisc player stores data from the disc in a 40-second buffer when playing, so the code reads the data directly from DRAM in 40-second chunks, moves the read head, repeats the process as needed, then stitches the 40-second parts back together. It can work on any Sony NetMD portable, if you are lucky enough to still have one around.
The project is a tremendous asset to the MiniDisc community, especially since the only way to recover data from a MiniDisc player prior to this was to use a specific version known as the RH-1. As [asivery] reports, used RH-1 players are going for incredibly high prices partially because of this feature. Since this new method demonstrates that it’s possible to do with other devices, perhaps its reign in the MiniDisc world will come to a close. For those still outside the loop on this esoteric piece of technology, take a look at this MiniDisc teardown.
There was an odd era at the start of the 1990s when CDs had taken the lead from vinyl in pre-recorded music, but for consumer recordable formats the analogue cassette was still king. A variety of digital formats came to market to address this, of which Sony’s MiniDisc was the only one to gain significant traction outside the studio. These floppy-disk-like cartridges held a magneto-optical medium , and were the last word in cool until being swept away around the end of the decade by MP3 players. Hackaday alum [Nava Whitford] has disassembled a MiniDisc optical head to document how the physical part of the system worked.
The first surprise is that the MiniDisc was in fact a two-in-one system. The recordable discs were magneto-optical and wrote data by heating the disc with a laser under a magnetic field, while the pre-recorded discs used etched pits and lands in a similar way to the CD. Remembering the technical buzz around the system back in the day, either we audio enthusiasts glossed over this detail, or more likely, Sony’s PR did so to emphasize the all-new aspect of the system.
The teardown goes in depth into how while like a CD player there is a photodiode array involved, the extra components are a diffraction grating and a Wollaston prism, an optical component which splits polarized light into two beams. The photodiode array is more complex than that of a CD player, it’s speculated that this is to detect the different polarized beams as well as for the task of maintaining alignment with the track.
All in all this is a rare chance to look at something we know, but which few of us will probably have dismantled due to its relative scarcity compared to CD mechanisms. Definitely worth a look. Meanwhile if this era is of interest, take a look at a Hack Chat we did a while back looking at the MiniDisc’s would-be competitor.