Yes, it's a Minidisc machine and it's not even a multitrack, just a stereo recorder. Why on earth could you possibly want one in the studio? DAVE SHAPTON explains...

How's this for a deal: a 20-bit digital-to-analogue converter, with co-axial and optical inputs, for less than £250. Oh, and by the way, it includes a sample-rate converter so that all that stuff you mastered at 48kHz can be reduced to 44.1kHz. Even better, it comes from Sony, a company that knows a bit about digital audio. And what if I told you that the price includes a high-spec Minidisc recorder/player? You'd probably do what I did. I bought one, and am still wondering how you can possibly get so much hi-tech magic for so little.

pros & cons SONY MDS JE520 pros Remarkably cheap random access digital recorder. Digital I/O. Built-in sample rate converter. cons Daft and pointless SCMS. summary At this price, you can't afford not to buy one.

I'm a recent convert to Minidisc. I've worked with digital audio for a very long time and I've always tried to avoid any sort of audio compression, figuring that the closest you could get to the original sound was to leave it alone after it has been digitised. Now I've got a different viewpoint for several reasons -- not the least of which is that Minidisc is now so good that I really can't tell the difference between the original and a compressed Minidisc recording. Another reason is that Minidisc is now getting stupidly cheap. So cheap, in fact, that I wouldn't be surprised if Sony and the other manufacturers of Minidisc equipment are making very little money indeed on the sale of their products, for the sake of building market share for the format.

I got hooked on Minidisc when I saw a little Sony recording Minidisc Walkman in an airport Duty Free shop. I don't normally go in for this sort of impulse buy, but I was looking for a better way to record interviews and this seemed ideal. Incredibly, you can get nearly two and a half hours on to a Minidisc if you use Mono mode. This use alone would justify the expense of £160, not to mention the fact that with a decent stereo microphone I could make location recordings to a very high standard. The Walkman (an MZ R35) was even better than I had hoped, with great converters and the ability to record digitally from anything with an optical digital output. The only real drawback I could find was that the line out was a miniature stereo jack. This, however, is hardly a justified criticism of something you are supposed to listen to while you are jogging. And speaking of jogging, there is a 20-second buffer which means that you can shake the thing like mad for what seems like an eternity, and it won't even glitch.

But there is something intrinsically naff about using any kind of Walkman device as a music source with a full size hi-fi, or in a studio. I can't help feeling that such a tiny thing is not going to stand up to heavy, or even moderate use, for very long. Mine has worked perfectly so far, but with the price of full-size players being so low, I felt compelled to buy one of these as well.

The Sony MDS JE520 is the same size as almost every other bit of hi-fi gear that doesn't describe itself as Midi or Mini. It is black as well, so it will match practically every other piece of high-tech equipment you have, and certainly wouldn't look out of place in a project studio. It has a large fluorescent display, at least half of which is devoted to displaying disk and track names. The big remote control has a full alphanumeric (but not QWERTY) keyboard to speed up the process of titling (until you've tried it, you might not realize how useful it is to be able to see information like "Recorded June 1997 at Big Dave's. Good guitar solo. Listen for the string breaking at the start of the third verse").

Using a Minidisc device is just like using a CD player, until you realize that you can record as well. The MDS JE520 caters for this in several ways. Firstly, there are conventional analogue inputs. You can also record digitally via the co-axial or optical inputs, and the sample rate converter automatically changes the sample rate to 44.1kHz from either 48 or 32kHz. When recording digitally, it is not normally necessary to set any levels, because the digital data stream contains its own absolute level information in the digits themselves. Surprisingly, though, the MDS JE520 allows you to vary levels digitally, which may at times be useful if an original recording was a bit low throughout. But it's not a panacea for bad levels, because any gain applied during the transfer to Minidisc will also bring up the noise floor, with the result that the recording will sound the same as the original, but louder.

COMPRESSION As you can tell from its eponymous title, Minidisc is very small. So it can't store as much data as a (merely) 'Compact' Disc. The only way to get the same amount of music on an MD as on a CD is to shrink the data until it does fit. It's actually very easy to make digital audio fit into a smaller space: you can halve the sample rate, reduce the number of bits to eight instead of 16, and you can make it mono instead of stereo. And it would sound terrible. Alternatively you can use some terrifyingly sophisticated algorithms to analyse the full-resolution audio, extract the parts of it that are important to our brains when we are 'perceiving' the audio, and, quite simply, not bother to record anything else. This is what the ATRAC Minidisc compression algorithm (Adaptive TRansform Acoustic Coding) does. Rather than simply reducing the resolution of the recorded material, and hence the quality, ATRAC looks for parts of the frequency spectrum that are hidden, or masked by other frequencies that may be louder or in a frequency band that is more sensitive to the ear (or, arguably, the brain). Essentially, it works on the principle that what you don't hear in the original you won't miss if it's not reproduced. Bear this in mind when considering the following: what happens if you make a copy of material that is already compressed? The numbers would suggest that if you throw away four fifths of the data and then re-compress, you will end up with audio at one twenty-fifth of its original quality. But if you actually try this you will be amazed at how little is actually lost (as long as you use the same kind of compression -- if you move between different compression types then you are in big trouble). What's going on here? Remember that ATRAC works by leaving out information that would not have been audible because of masking effects by other frequencies. ATRAC knows that it can only store a fifth of full-bandwidth audio information. But that's not as much of a problem as it might seem, because the other four-fifths of the information was discarded the first time the audio was compressed. So it isn't there to be compressed a second time. Therefore all the available bandwidth can be used to store the remaining frequencies, which hardly need to be compressed at all. Nevertheless, ATRAC, in common with most compression schemes, has to work harder with complex mixes than with individual voices or monophonic instruments. But I have to say that I have heard very few examples of music that really catch out the latest ATRAC algorithms.

There is also a digital fade facility that hints at the possibility of producing fully edited master recordings with no additional equipment (especially since the Minidisc format allows track re-ordering and even within-track edits).

ATRAC 4.5 The latest Sony Minidisc recorders use ATRAC 4.5 compression. A new compression chip (the CXD 2537R, if you want to impress people at cocktail parties) "offers superior fidelity by use of adaptive high-frequency control technology" according to a Sony press release. What this means is that the algorithm looks at the frequencies present and varies the encoding resolution, depending how important an individual range of frequencies seems to be in the overall context of the music. The result is an even better use of the available data bandwidth. This, together with a "24-bit coefficient for word length calculation" has improved the total dynamic distortion caused by ATRAC by around 8dB relative to previous incarnations of the chip. (For a detailed discussion of audio data reduction and compression, see Hugh Robjohns' piece in the August edition of SOS.)

Is is as good as DAT? Well, I couldn't reliably tell the difference between my Minidisc recorder and the CD original. At that point, I think you have to say that, subjectively, it is as good as DAT. Remember, though, that Minidisc is a compressed format and that as much as 80 percent of the original data is thrown away during the compression process (but see the box on this above). As such, you won't be able to make perfect copies of a Minidisc recording on to another Minidisc, even via a digital connector -- because inevitably some quality will be lost as the ATRAC compressed digital audio is uncompressed for transfer via the optical digital interface, and recompressed as it is recorded onto the destination Minidisc. You could actually make loss-free copies if there were a way of duplicating the data, as opposed to the audio that the data (imperfectly) represents. If this were possible, making perfect digital copies would be as simple as a file-copy operation on a desktop computer, because, essentially, that's what it would be. Sony already has the ideal way to do this: Firewire (also attractively known as IEEE 1394 and Sony's preferred appellation, 'iLink'). Firewire, as I shall continue to call it, is a scorchingly fast data connection that is quick enough for several channels of digital video, never mind digital audio. It's cheap and robust, and could no doubt be used to copy MDs several times faster than real time. Inevitably, though, I suppose the copyright lobby would object, which is why MDs are lumbered with the anti-musician, anti-common sense and generally completely daft Serial Copy Management System (SCMS), which prevents a digital copy being made from a recording that was itself recorded via a digital interface.

CONCLUSION

The MDS JE520 has no right to sound as good as it does, and still only cost around £230. But it does sound brilliant and, incredibly, certain hi-fi chains such as Richer Sounds are selling it for even less than £200, together with blank Minidiscs that cost less than £2. I may be wrong, but I don't think there's ever been a bargain quite like this one. Remember, this is not old stock being dumped -- it's the latest model from a range that is growing all the time.

Prices vary, but most Sony Centres sell the JE520 for £229.95 including VAT.     Sony UK (Consumer Division), The Heights, Brooklands, Weybridge, Surrey KT13 0XW, UK.     +44 (0)990 111999.     www.sony.co.uk

 

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