Adventures in MiniDisc & Sony MDS-JE770 Repair

I missed the MiniDisc format. I was born in the mid 90s not long after the format emerged in 1992. CD was the dominant format and cassettes were still somewhat relevant though they would only last another ten years or so before largely disappearing from the market. Cassettes were still the preferred home recording media for most owing to their low cost, durability and the sheer number of players capable of recording to a cassette.

The magneto-optical MiniDisc offered better quality audio than a cassette, though few record labels embraced the format, the discs and machines were costly and the sound quality didn’t match that of the CD due to the 292 kbit/s ATRAC (adaptive Transform Acoustic Coding) compression algorithm. ATRAC is a psychoacoustic lossy data reduction system, meaning that it omits some of the musical content claimed by Sony to be inaudible. ATRAC was designed so that the same amount of audio a CD can carry (encoded at 1411kbit/s) could fit onto a smaller disc.

The introduction of the CD burner in 1996 allowed anyone to produce CDs at home and (when the cost came down) was eventually responsible for the demise of the inferior MiniDisc format, though the format enjoyed a few years of limited success and is still enjoyed by collectors and enthusiasts today. Later revisions to the ATRAC system, the introduction of 80 minute and later 1GB Hi-MD data discs improved the format, though it was effectively killed by Sony in 2011 and the company shipped the final players in 2013.

I’ve always been fascinated by the format having never heard a MiniDisc in person. The cost of the players and discs somewhat quashed my enthusiasm until I happened across a player in need of repair and bagged it for the agreeable sum of nothing. A mint condition Sony MDS-JE770 was the player in question, a £200 budget player in its day but one capable of demonstrating many of the format’s features.


As found the player refused to eject though it happily played the disc trapped within its mechanism. A tiny belt inside which drives the eject mechanism had stretched, resulting in a lack of torque. The mechanism is surprisingly simple to service, though it’s important to make sure the mechanism is correctly aligned during reassembly.


A fresh belt saw the player back in business and it was time to find some discs. Some more shots of the mechanism:

Motors and Cogs

The first brand new separates I ever owned were part of Sony’s 370 series. Though a little newer than this player the design is identical with an angled display set into a profiled plastic front and tiny push button controls arrayed on either side. The JE770 includes a PS/2 keyboard port on its front panel which can be used with any PC keyboard for character entry. Characters can also be entered via the units front panel using the encoder knob, also used for navigating menus and tracks. Transport controls feature as does a standby control and a quarter inch headphone jack with volume control. The back includes analogue RCA and digital optical / coaxial inputs, analogue RCA and digital optical outputs, sync jacks for control of other Sony components and a fixed power cable.


The discs themselves are similar in form to a 3.5” floppy disc, though they’re smaller (68 x 72 mm), thicker (5 mm) and heavier. A sliding shutter protects the media inside, which is opened automatically by a mechanism on insertion into the player. The disc uses a magneto-optical system to record data. A laser heats the disc to its curie point to make the material on the disc susceptible to a magnetic field, and a magnetic recording head on the opposite side of the disc alters the polarity of the heated area, recording the data onto the disc. The laser alone reads the disc on playback, and Sony claim that a recordable MiniDisc can be reused up to one million times. 74, 80 and 60 Minute discs were available though the latter was phased out in the early years of the format and are rarely seen.

Write Head
Write Head

A table of contents is written to each disc containing the start positions for each track as well as meta information (title, artist etc). Tracks don’t need to be stored sequentially and can be moved, split, combined or deleted. On playback, data is read into a memory buffer storing at least 6 seconds of audio. This acts as an anti-shock system allowing the laser to reposition itself if the player is bumped in operation and allows for uninterrupted playback of discs with data fragmentation. It also allows the spindle motor to spin down for longer periods resulting in better battery life in portable players.

The disc stuck in the player on receipt was a self-recorded disc containing a jazz concert live from Ronnie Scotts jazz club, broadcast live on BBC Radio 3 and a couple of other radio program extracts. I used the player to record a few tracks of my own choosing from both its analogue and digital inputs. As I have no point of reference for how a MiniDisc ‘should’ sound, it would be unfair for me to offer any kind of judgement on the player itself. Suffice it to say that I found the sound to be decent – better than decent in fact. I found it similar to the sound of a modern 320KBPS MP3 rip of a CD track – it’s close to the CD, but side-by-side the difference is audible. Where the MiniDisc outshines the CD is of course in its flexibility and editing functionality which is largely consistent but will differ slightly from player to player.

I had every intention of starting a small MiniDisc collection, but ultimately it’s not going to happen. The MiniDisc technology was cutting edge on its introduction and something that few if any home computers could replicate. These days however the MiniDisc is easily outshines by the most basic digital players. While it’s a nice format, it’s not difficult to see why it has faded into obsolescence.

MiniDiscs themselves are expensive too. They fluctuate wildly, £20 can buy you a job lot of 20 or so discs, or a single Sony branded disc depending on the day and the disc quality. Used discs are a plenty and are often sold in job lots, but they’re far more expensive than a pack of CDs or even a brand new pack of blank metal cassettes. I could produce 250 CDs for the cost of a small number of MiniDiscs with better quality and compatibility with a far wider range of devices. The players themselves range in price to anywhere from £20 or so for a basic model to half a grand for a high-end player from the format’s heyday. While I’ve enjoyed my glimpse of the MD format, this is one best left to the collectors and enthusiasts.

By Ashley

I founded Audio Appraisal a few years ago and continue to regularly update it with fresh content. An avid vinyl collector and coffee addict, I can often be found at a workbench tinkering with a faulty electronic device, tweaking a turntable to extract the last bit of detail from those tiny grooves in the plastic stuff, or relaxing in front of the hi-fi with a good album. A musician, occasional producer and sound engineer, other hobbies include software programming, web development, long walks and occasional DIY. Follow @ashleycox2


  1. I understand your pleasure trip into an historic music recording format. It obviously concluded as it should – living in the music and technology of your time. In the same way, an appraisal of vinyl and FM radio by those not having lived during their heyday will usually end the same. It is a fact – one cannot ‘believe’ in a simulation unless it is ‘real’. Reality is related to best-technology then known and ‘in custom’. e.g. When remote tribes are introduced to electronic recording-playback systems it is not unusual for a lack of recognition/comprehension of sounds heard just a little while before! Animals can however still be deceived by good simulations – but this is different from human choice in selecting a method: few manufacturers expect hi-end vinyl systems to replace hi-end digital players even though the former may be acoustically identical. So in my view MD was just as good as DAPs in its time but this matters little now to those coming after. Concerning ear tickling, any system doing this is probably sub-optimally arranged, e.g. non-premium earphones. Also, ATRAC Type-R should exceed ChromeDioxide tapes on linearity in dynamic range alone (15kHz,-20dB) as it was designed as a direct replacement technology – it’s just that few tribal ears had become accustomed to the new ‘sound accuracy’ and masking technology. (c.f. Some find 64kbps DAB+ perfectly acceptable after a while.) Just some thoughts for (mental) food – enjoy your music!

    1. P.S. It should be noted too – transcoding dynamic range relationships between media can cause discomfort I believe; most older master recordings are optimised on or for tape, vinyl or radio modulation. Modern recording linearity may differ in order to suit modern reproducers.

    2. Very well said John. This is quite an old article now and I must confess the MD player was sold shortly after. I haven’t since done anything with the format.

  2. I used Mini-Disc for a while, back in the early noughties. I had a portable Walkman-style player (can’t remember the brand, though I don’t think it was a Sony) and a Sony Something Something 930 or 940 with the Type-R ATRAC encoding system. I found that headphone listening on the portable was only bearable for short bursts. The only way I can describe it is like a tickling sensation in the ears. Even the Creative Zen Micro MP3 players I experimented with before crossing over to the dark side that is Apple were far more bearable. The best encoding I used for portable audio is Apple Lossless or AIFF files, as played by an iPod Classic. The sound card in iPads and iPhones is sonically inferior to the Classic’s – even if the latter wasn’t so LOUD sounding. The music industry lost something special when it jettisoned the compact cassette, I think.

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