Tech Flashback: Sony MiniDisc

Just this month, it was announced that Sony will make its last MiniDisc system next month, so I thought this was a good time to reminisce about MD and what it really meant …

The MD was basically a small Magneto-Optical disc inside a plastic cartridge. A decedent of larger rewritable optical disc technology used in computers, shrunk down into something you could carry in your pocket. It relied on media with a coating which, when heated by a laser in the presence of a magnetic field, would alter the polarization of reflected light. This is different to how CD-RWs work – they depend on the amorphous/crystalline phase change depending on the laser heating rate. There were MD singles that were pre-recorded, and these used pressed discs similar to how CDs are made.

The cartridges featured a sliding door, which wasn’t very well sealed but still stopped the discs from being scratched. Dust could still enter, but that’s not too bad. There was areas for labelling and a write protect switch.

Introduced in 1992, they were marketed as a miniature CD – without much mention of the fact that ATRAC lossy compression was involved. The discs themselves were sold at 74 minute and then later 80 minute sizes. Initial MD recorders only recorded the amount of time as listed, and would be able to record music at realtime via optical (lossless) or analog (lossy) cables. As you can imagine, this isn’t any better than a cassette.

Sony MZ-R55

Many MD units were powered by a single AA battery or gumstick rechargeable battery. MD was very power efficient – being able to play for a long duration without battery changes, much better than the average discman. Even better was the ability to perform field recording – some units featuring mic inputs (with questionable preamps) and line/optical inputs. This contributed to its popularity amongst bootleg recording enthusiasts. Unfortunately, those rechargeable gumstick batteries tended to leak when overcharged and corrode the unit from the inside – the MZ-R55 above is one example of a pre-NetMD device.

The concept of compression and buffering was the secret to a long battery life and a very skip-free experience, which made things enjoyable compared to the discman. The much smaller physical size at the time was very beneficial.

It also introduced the idea of storing metadata with tracks – in the form of track names and artists on the disc itself, along with a disc title. There was also free-editing abilities that allowed you to cut songs, define tracks all from the MD unit itself. It was a bit tricky to use, but was much easier than mastering a CD and then trying to edit that – as this could be done after the recording as well (with certain limitations, to ensure the fragmentation of the MD would be kept in check). This also made it popular for radio jingles as it was quick to edit and randomly access.

The sound quality initially was somewhat lacking – not as good as CD, but not as bad as cassette. Some of the compression artifacts could be objectionable to some – especially when copied analog as it suffers severe generational loss.

Many units also featured an advanced corded remote control, featuring twist jog wheels and alphanumeric LCDs. Unfortunately, the units themselves weren’t cheap, which was one reason for their lack of popularity.

Later portable MD units introduced the concept of NetMD which allowed you to download recordings to discs via a computer at faster than realtime speeds. Convenience at last – except it wasn’t to be. Sony’s interests in the music scene really hampered their products because they put DRM ahead of the consumer’s interests with very stupid rules about checking files out, and not being able to check in recordings from the MD unit back to the computer. They also introduced a different set of non-backwards-compatible codecs – LP2 and LP4 which allowed doubling and quadrupling of the play-time of the discs, but with consequences to the audio quality.

After a lawsuit involving Dolby Laboratories in regards to a patent, they were forced to remove the original SP ATRAC codec – so it was not possible to make full quality transfers.

Finally, the last hurrah for MD came in the form of Hi-MD which introduced a new physical layer coding which allowed for increased capacities on regular MD discs (if reformatted to Hi-MD) but not being backwards compatible. Further ATRAC3plus rates became available, as well as lossless, and a new type of MD disc called the Hi-MD was introduced that stored 1Gb within the same form factor. This involves the use of a new MO technology termed Domain Wall Displacement Technology which allows for great capacity increases. Too bad MO technology had fallen out of favour with computers, otherwise this development would have seen use in other things aside from MD. Hi-MD also allowed for the use of MD recorders as data storage devices, being accessed as mass storage devices with a 2kB sector size.

Sony Hi-MD MZ-NH600

The MZ-NH600, above, is a Hi-MD device with all its benefits. At this stage, Sony was pretty much out of the running – so the restrictions on the Sonicstage software became a lot more lax. Finally – recordings made by the recorder can be downloaded back to the PC only from that recorder, and music files on the PC can be checked out to disc an unlimited amount of times, and in some cases, checked back in on the same recorder.

They never really got too popular in Australia – although reportedly they are quite popular in Japan. Nowadays, it makes no sense to continue with MD technology – even an elderly iPod Nano holds more music and the power source all in a space smaller than a single MD cartridge.

Size Comparison

MD discs were widely available and costed about $3 a disc. Many manufacturers made discs, however, one couldn’t easily discern the quality of the discs without special MD decks and access to their diagnostic modes. In general, things just worked.

So, I salute the humble MD goodbye with my very small and modest collection of colourful MD discs. I was late to the MD party, and most people who had never used MD really didn’t miss out on anything good … Some of the claims made by MD manufacturers are somewhat outrageous given the digital nature of MD – but I’ll refrain from saying too much more since audiophiles will do and say almost anything. But it’s clear that solid state recorders and music players have made the optical ones obsolete.

TDK MD-XG 74TDK MD Colour 74 GreenTDK MD Colour 74 YellowTDK MD Colour 74 BlueTDK MD Colour 74 PinkLaser MD 80Maxell MD 74Sony MD Colours 74 RedSony MD Colours 74 AquaSony MD Colours 74 OrangeSony MD Colours 80 BlueSony MD Colours 74 GreySony MD Colours 74 OrangeSony MD Colours 74 Purple

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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