NOTE: This article is from SOUND ON SOUND, VOL. 12 ISSUE 5, MARCH 1997.

(c) 1997 Sound On Sound Limited. All rights reserved.



When one from the Japanese development team for the new Sony MDMX4 MiniDisc multitracker flew into the UK recently, along with a member of the product planning department, it was an ideal opportunity to find out more about Sony's plans for the home studio-based musician. MARTIN WALKER listened in...


The Sound Of MiniDisc


MDMX4 Design


Future Plans

Sony's MDMX4 4-track MiniDisc multitracker (reviewed in last moth's SOS) is a departure for the electronics company. Although widely known and respected for their expertise at the high end of the professional and broadcast audio market, as well as for their vast range of hi-fi, TV and video products, Sony have only rarely dabbled in other areas of music technology. The DPS series of high-quality effects (the DPSD7 digital delay, R7 reverb, and M7 sonic modulator) appeared way back in 1991, and were quality specialist units that each concentrated on doing one thing extremely well, rather than attempting to better the multi-effects units other manufacturers were producing. After this, things went a bit quiet until the HRMP5 and GP5 heralded the arrival of more affordable units for the home studio and guitarist in 1994. Apart from these, and the DPSV77 effects unit of last year (which combined the best of the DPS series in one rackmounting processor - see review in SOS September '96), Sony have not really launched products that are fairly and squarely aimed at the home musician - until now.

When SOS learnt that Sony Japan's Hideki Nakano (from the Audio Product Planning Department) and Motonori Nakamura (from the new Pro-sumer Audio section, of which more later) were flying to Britain as part of a whistle-stop tour of Sony's European offices, a meeting was arranged at the London offices of Sony's new UK distributors HHB to discuss the company's forthcoming plans and look at a few aspects of the MDMX4's design in detail. Brian Kane of Sony UK and Mr Nori Nakaruma (no relation), the Marketing Manager of Audio Systems at Sony Broadcast & Professional Europe, were also present.


The MDMX4 allows up to 37 minutes of recording with four tracks, and uses Sony's proven MiniDisc technology, in which 74 minutes of stereo audio may be compressed onto a removable disc smaller than a floppy capable of holding 140MB of data,. Whilst MD Audio (the original MiniDisc intended for consumer use) continues to be sold in Japanese hi-fi systems, the format has yet to take hold in the UK. The more recent MD Data MiniDisc format used in the MDMX4 holds the same amount of data, but is more suited to computer applications.

When MiniDisc was first released several years ago, ATRAC, the data compression system used today by both MiniDisc formats (see the 'Sony Jargonbuster' box), imparted a characteristic metallic sound and fizzy noise to recordings, and many people still believe the format to be dogged by this problem. In fact, continual development and refinement have resulted in four versions of the ATRAC system so far, which currently stands at version 3.5. It is this latest version that is used in the MDMX4, and most professionals I have spoken to have admitted that although they can still hear a marginal difference in sound between first generation DAT and MiniDisc recordings, they cannot reliably tell which is which. With this in mind, I began by asking Mr. Nakano and Mr. Nakamura how the early MiniDisc sound had been improved. Throughout the interview, Hideki Nakano acted as translator for Motonori Nakamura, so their responses are not creditted to them individually.

"The format itself is exactly the same as the early MiniDisc, so there is complete compatibility between early and current versions of ATRAC, but the sound quality is different; the current version is much better than the earliest version. We have developed better algorithms with regard to compression, especially on the encoding side, and also semiconductor devices themselves have improved. For both reasons, MiniDisc is now better than its earlier versions."

As the encoding side has changed significantly, does this mean that recordings made on newer machines will actually sound better, even when played back on the early MiniDisc recorders?

"Right. Of course, there are some differences on the decoding side, but there have been more improvements made on the encoding side."

Since it has a 20-bit dynamic range, do you regard the sound quality of the latest ATRAC version as equal to or better than DAT recordings?

"[Laughs] As DAT is 16-bit linear recording and ATRAC uses compression, in theory the sound quality of the DAT recording will be better than the ATRAC. However, we at Sony believe that the difference is minimal, and have every confidence in the sound quality of the MiniDisc. Basically, the quality is only different between DAT and MiniDisc because their data capacities are completely different. But development is still on-going, so we feel that further improvements may still be made in the future."

As the MDMX4 encourages multitrack recording, many people are concerned about generation loss when bouncing and mixing tracks and putting them through the ATRAC compression several times. Do you see the ultimate ATRAC chip being able to withstand multiple bouncing without adding audible artefacts?

"This was of great concern to us at the development stage, since this type of machine is normally used by customers for bouncing or dubbing from track to track. Each time we go through the ATRAC compression system, the sound will deteriorate slightly compared to the original. With the latest version of ATRAC, there is of course a slight generation loss, but it is a great improvement on the original ATRAC compression system."

As I understand it, ATRAC takes the input signal in blocks of 512 samples before compression, but does not grab the same 512 sample chunks when decoding. If the same 512 sample chunks were expanded, such that identical data was reconstituted before any remixing, there would be no further decompression loss during bouncing. Is this something that would be feasible on ATRAC in the future?

"It is impossible to tell at the moment whether this sort of loss will ever be zero, but certainly sound loss in the future will be minimal, and the system will continue to be developed and improved. To achieve what you are suggesting, we would have to develop some kind of digital mixer with an ATRAC basis. Currently it is impossible to do this - but of course in the future, technology will be improved. Without using some sort of ATRAC-based digital mixing, though, the ATRAC compression must be used at each stage."


ATRAC (Adaptive Transform Acoustic Coding)

The compression method used to achieve a 5:1 reduction in audio signals so that they can fit on a MiniDisc.


The original format MiniDisc used in hi-fi systems.


An updated format currently used for 4-track and computer storage.

MO (Magneto-Optical)

Recording takes place using a laser to firstly heat up a spot on a disc, and then a magnetic head which writes data. Once the spot has cooled down, the magnetic data is 'cast' on the disc.

TOC (Table Of Contents)

The area on an MiniDisc used to store song and disc names and tempo maps. This can be edited without altering sound data to play back sound chunks in any order.


Can you tell us what the main differences are between the new MD Data format and the original MD Audio MiniDisc?

"With regard to the MiniDisc and compression of the audio format, there are two main areas of data - the programme area and the TOC area. On the MD Audio version, the programme area is made on 2 channels, each with 74 minutes of ATRAC audio sound. The disc name, song title and so on are recording in the TOC area. On the 4-channel MD Data format MiniDisc, we record 4-channel ATRAC-compressed data in the programme area, up to 37 minutes per channel. The big difference is in the TOC - of course we record the disc name and song title as before, but also tempo information to synchronise to sequencers. There is no difference at all in data quality or data transfer rate, and physically the formats are the same."

Does this mean that you can use MD Audio discs in the MDMX4 and lose only that tempo information?

"You can use MD Audio discs with this machine and record up to two channels, but it is impossible to record four."

What are Sony's future plans for the MiniDisc Audio format generally, now that you are moving into a different area? Are you going to continue to develop products that solely use the MD Audio discs?

"As you may know, in Japan, 2-channel MD Audio is already successfull and established. Pre-recorded discs are available, but the major use is for customers to buy blank discs to record CDs to listen to on an MiniDisc Walkman or car stereo. On the hardware side, 3 million recorders were sold in total by all MiniDisc manufacturers worldwide in 1996 - but 70% of these sales were in the Japanese domestic market."

With a maximum recording time of 74 minutes for stereo recordings, and 37 minutes for 4-track, can we expect other MiniDisc formats to appear in the future with greater storage capacity?

"We have just announced a 650MB version of the MD Data disc - the same physical size, but the data capacity is 4.6 times compared to that of current MiniDisc. I don't know the product schedule, but the format will be finalised and available this spring. Using this brand-new MD Data format, recording time will increase drastically, but you will need to use a new recorder to take advantage of the higher density format. Sony is a licenser of MiniDisc - we developed the MiniDisc format, and we have now expanded it significantly."

The majority of people using compact cassette recorders still use the cheapest tapes available. Now that MiniDisc media costs are approaching thoses of DAT, how low do you envisage them going, and do you see them eventually falling to current compact cassette levels?

"To have such a cheap media price, cassettes have been used for something like 20 or 30 years; with MiniDisc we have only just passed five years. I think it's down to economics of scale as well - once you've got an installed user base, that's when you actually start seeing the cost come down. In Japan, the MiniDisc market has expanded drastically, and in the future, that of European countries and the US market will expand rapidly. At that time, of course the MiniDisc hardware market will be huge, and the disc price will fall."

Do Sony still feel that the compact cassette is nearing the end of its working life?

"In the market, there will always be some kind of cassette tape recorder, but in Japanese stores, packaged stereo systems do not include cassette recorders anymore, just a CD player, a MiniDisc player, a tuner, an amplifier and speakers. We still produce stand-alone cassette-based components, but customers like MiniDisc much more than cassette systems. In the future - of course this is just a guess - almost all the cassette-based systems will be changed to MiniDisc. The prices of MiniDisc and cassette are different now, but in the future, when hardware prices have changed, and media prices become the same, at that time MiniDisc will take over. We can compare it with the changeover between LP and CD. Japan's trend was very fast, and after three or four years, the export market also changed from LP to CD. Nowadays, the young generation prefer the quicker access provided by CD and MiniDisc. There are always customers who like to play old records, so cassette will probably not disappear completely, but there is a big trend, and we believe it will probably also follow outside Japan."


Moving on to the MDMX4 itself, what sort of user do you see buying an MiniDisc 4-track recorder, and why should they choose MiniDisc rather than a hard disk recorder?

"The most important point is that it is removable media, which makes it possible to more easily exchange songs between friends. There are also other manufacturers making multitrack recorders based on the same format, such as Yamaha and Tascam, and these machines are completely compatible, so that any disc recorded on the MDMX4 will play back on any other MiniDisc 4-track. As to the type of customer, amateur musicians are the first priority - the ones currently using cassette-based 4- or 8-track systems. This machine gives them a digital multitrack recorder at a cheap price. Professionals can use the MDMX4 - it's fine - but after several dubbings the sound quality can be noisy."

What are your recommendations for maintaining maximum fidelity when bouncing down? What sort of intruments lose their freshness first of all?

"Normally, customers record drums and bass - the rhythm section - first, and then after that, add keyboards and guitar, and then finally add the vocals. We recommend this type of approach, and we checked and found that six or seven bounces are better than current cassette systems, but dubbing 14 or 15 times, for example, will give problems with sound quality. We have no specific recommendations for different instruments - you can use any normal type of recording method."

The MDMX4 allows you to make a digital clone of an existing song before performing any mixdown. Is this a real-time copy, as it appears, and if so, why?

"We need the exact song time to make a song copy, because we write the same data on the disc. To make a clone, the data doesn't go through the ATRAC compression system, but we have to go through the drive itself, so the time is very much dependent on the drive transfer rate. For the MiniDisc, this is 150kB/s, so we need real time to make clones."

SOS reviewers of the MiniDisc multitrackers have been concerned over possible corruption after recording with MiniDisc if the TOC is not manually updated. Why does this not take place automatically?

"For the MiniDisc format, TOC information is really important, because it controls all data on the disc. It is possible on this machine to have an Undo function, so that TOC information can go back to the previous version. When using functions such as Track Edit, Section Edit, and Song Edit, the audio data itself doesn't change, only the TOC. Every action during recording and editing requires TOC information to be updated on disc, and if the recorder wrote brand-new TOC information on the disc after every operation, the user would have to wait a few seconds after each edit, each new recording and so on. At some point, the machine has to write this information, but it is up to the user when they record the TOC information, for instance before they take a break. If the customer forgets, and tries to eject the disc, the machine will automatically write the TOC information. This saves having to wait for a TOC update every time an operation is performed."


I'd like to move on to the area of reliability - obviously something that people are concerned about when it's their own music. There have been difficulties with mechanical reliability with some consumer DAT machines. How does MiniDisc reliability compare with DAT?

"The MDMX4 uses a device which has also been used on MD Audio decks for a long time. This is mechanically very reliable, because we have long experience of this type of machine."

But there is error correction built into the system, so that it can recover from any data loss. One aspect of this is that with DAT, error correction circuitry is sometimes so good that recordings have seriously deteriorated before audible effects occur. Does this also apply to MiniDisc?

"Of course, the error correction system is not exactly the same as that of a DAT machine, but it is similar in a MiniDisc recorder. There are two major advantages compared to DAT: the first is that it is possible to retry for the signal, as the tape has not gone past, because we use a random access memory and compression system, whereas DAT is a linear recording. Also you don't have any physical contact like that between DAT tape and the heads, so there is no long-term wear involved. The possibility of errors is very small, and fortunately, we have several chances to re-read any that occur."

Many SOS readers have concerns over the differences between consumer and professional machines. In the past, some DAT recorders have been bought by recording studios, but they have purchased so-called 'consumer' machines, and they found it difficult to get any technical problems repaired under guarantee. Machines that are only used a few hours per week, but still classed as 'consumer', fall into a grey area, and dealers sometimes say that they cannot then support them, because they have not been used solely in the home. If a professional musician bought an MDMX4, what are the support implications?

"The main target for the MDMX4 is, as I mentioned previously, consumer musicians. Of course, some professional people would use this as a professional machine - the quality is good enough - but the main target is the consumer. We don't propose that the professional musician uses it for his job."

But a lot of professional organisations like HHB have in the past sold consumer products which have been bought by recording studios because they are considerably cheaper than 'professional' models. Products such as 4-track recorders can enter a grey area. Will they be supported if they are being used in recording studios?

Brian Kane, Sony UK: "Maybe I could answer some of the support issues from a UK perspective. The MDMX4 comes from what we term the Prosumer section, which is trying to address this grey area - they realise that some professionals will use these products. This is the reason why we've got someone like HHB involved as distributor. For example, if you look at the rackmounting Sony DTCA6 DAT machine, as supposed to one of the consumer products, we would give that machine a 'pro' type of support, whereas you're quite right in what you say about consumer products. We realise that this new product will cross both fields, and what we will endeavour to do is give it support that you would associate more with the 'pro' side. HHB will be the main people in the UK, and we got them on board because we appreciate their technical expertise, and we have total faith in their ability to support the machines."


During this interview, Sony mentioned a new format of MiniDisc which will start to appear in Spring 1997. Although the same physical size as the current MD Data format, it manges to cram in 4.6 times the amount of data. This is done using various methods - a reduction in the laser beam spot, laser strobe magnetic field modulation technology, and high-density magnetic film technology. Finally, the magic figure of 650MB can be stored on the new format, the same as on a CD. In addition, the transfer rate has been increased from 150kB/s (the same as single-speed CDs) to 580kB/s (4xCD speed). MiniDisc was always intended to be a convenient and robust medium that could make high-quality recordings. Once this new version appears, and sells in sufficient quantity to bring the price down, it could prove perfect for the musician on the move, with the advantages of random access, and none of the problems of DAT, such as susceptibility to magnetic fields and head and tape wear.


When DAT was first introduced, it was expected that a lot of DAT recorders would be used by consumers. In fact, they are very rarely used in the home, but are used an awful lot by professionals. MiniDisc was originally targeted primarily as a consumer audio format. Does the arrival of the MDMX4 indicate that this is no longer the case? Are you moving into a different area, or simply widening the existing one?

Hideki Nakano: "In these early days, we regard this primarily as a consumer machine, but a 4-channel version. Of course, we would like to expand the line-up of this category as well, both at the low end and high end."

Brian Kane: "There are basicly two areas in Japan - a consumer area for home AV, and the new section which has just been set up, called Pro-sumer audio. The MDMX4 is one of its first products. The consumer people continue to do what they are already doing, but a new group of people have been taken aside, and they are now dedicated to the MI market - guitar processors, powered speakers, and further developments in this area. It is a subset in some respects, but it is very focused on the musician."

Following this first Sony product in the project studio area, do Sony have plans for other associated products?

Hideki Nakano: "As you know, about five years ago, we introduced a range of signal processors - the DPS series - for the MI market. A little bit expensive, but designed for musicians. We also introduced the HR signal processors, a consumer product. Now we are introducing this new type of MiniDisc multitrack recorder, and we are continuing the signal processing business. Today, I'm afraid that I cannot talk about any exact product ideas, but in the future we would like to make many more MI products, following this type of multitrack recorder."

Is there anything that we might see in the next six months?

"One product is an active speaker. As you may know, we have already introduced the SMS1P active speakers, and we will introduce a larger version, the SMS2P, with a 16cm woofer and built-in amplifier, for the studio market. We will be showing this at the coming Frankfurt Musik Messe."

Professional multitrack arguably starts with 8-track machines. Do you have any plans to develop anything along these lines using any of the MiniDisc technology?

"We now have the larger capacity MiniDisc format, and also the ATRAC 2 compression system. Currently the ATRAC 1 compression system has 128kbits/s per channel, and ATRAC 2 will be half transfer rate, which means 64kbits/s per channel. With this technology, it is possible to do an 8-track version - not yet, but we would like to do it. We have a large technical resource, but which way is best to go we have not decided yet. We just have the intention to do it in the future."

With the possibility of using ATRAC to record at 20-bit resolution onto 16-bit media with a 5:1 data reduction, will we ever see this same technology finding its way into products without MiniDisc, such as Sony hard disk recording systems?

"We don't have any plans to do this with hard disk rather than the magneto-optical format. Of course, one good application is networking. Transferring data through networks will be a major application in the future, and for that you have to use some sort of compression system, for example RealAudio. We think ATRAC will be really good in these sort of applications. This is just an idea, and not studied as yet, but regarding ATRAC and hard disk and ATRAC magneto-optical, we don't have any plans right now."

Finally, would you like to tell us what direction Sony is going to take in the future?

Nori Nakamura, Sony Broadcast & Professional Europe: "As a whole, Sony have established their video and audio field of professional production in the last decade or so. Also, in the consumer field, we are successfull in the areas of hi-fi, TVs and videos. What Sony is now trying to do is to widen one part of our market - in musical instruments. We are very new to this field, but with the technology from the high-end and also the consumer field, we feel that we can produce a lot of exciting products in the MI market of the future. It will present a lot of new challenges, but in order for Sony as a whole to expand, we would like to participate. We hope the MI business will be very challenging for us for many years."

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