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Sony MDMX4

Digital Multitracker By Hugh Robjohns
Published February 1997

Sony's new MDMX4 digital multitracker heralds the beginning of a conscious attempt to woo the home recording market, and uses the company's own MiniDisc technology to put a digital spin on that home studio mainstay, the compact 4‑track recorder. Hugh Robjohns checks it out.

The Sony MDMX4 is the third in the current trio of MiniDisc‑based 4‑track recorders to come on to the market in the past year, the others being the Yamaha MD4 (reviewed SOS September '96) and the Tascam 564 (previewed SOS August '96 and reviewed December '96). Although all the machines are clearly designed to do the same job and to appeal to the same sector of the home recording market, each has slightly different facilities.

Sony are relatively new to the world of home‑recording systems, and are therefore some way behind both Yamaha and Tascam in terms of practical experience of this market place. However, MiniDisc technology is Sony's own invention, after all, and they have manufactured audio mixers for a great many years, so there is nothing in the MDMX4 which is entirely new to the company.

First Impressions

The MDMX4 is split roughly down the middle, with the 10‑input mixer section on the left, monitoring in the centre and the MiniDisc transport on the right hand side. It is intended to work with MD‑Data discs, although straight audio MiniDiscs may be used if some of the functionality of the system is sacrificed (ie. you only get two tracks instead of four, and limited MIDI facilities). Audio is recorded onto the disk as a series of Songs, and you can have up to 255 of these per disc — provided the total record time doesn't exceed 37 minutes for 4‑track audio, or 74 minutes for stereo‑only material, as this is all that will fit on a MD‑Data disc.

The mixer has two balanced inputs with XLR/jack sockets, capable of handling microphone levels (there's no phantom power), two more unbalanced channels and one stereo channel. Fixed three‑band equalisation is available on the first four strips, and there are two auxiliary outputs available from the single send level control on each channel. There are also two pairs of effects returns, which may be used in mono or stereo. All input connections are accessible from the top of the mixer panel.

The rear panel of the MDMX4 carries two pairs of phono sockets, providing a stereo monitor output (from the monitoring buss) and the main stereo output from the mixer. There are no digital audio inputs or outputs at all, but the horizontal section at the back of the mixer carries direct outputs from the four MiniDisc replay tracks, allowing mixdowns through an external desk, or direct transfers to another multitrack medium. Needless to say, there is a full set of MIDI connectors on the rear of the machine, together with a couple of footswitch sockets on the front which may be programmed to perform a variety of functions. Also on the front is a single, standard‑sized headphone connector. The mains lead is captive on the rear panel, and the power switch is next to it on the back of the machine.

The Mixer

The mixer section of the MDMX4 is pretty much par for the course in terms of its facilities. It has four full‑facility inputs, two more arranged as a stereo pair, and two stereo effects returns, making a total of 10 individual input channels. The first two inputs have combi‑XLR sockets which accept quarter‑inch jacks in their centres. These are wired to accept balanced sources, whereas the other inputs (all on quarter‑inch jacks) are for unbalanced signals.

There is no mic/line switching, merely a level knob which provides a 40dB gain range. Immediately below the gain trims on the first four channels, push buttons select the mixer input from either the mic/line input socket or the appropriate MiniDisc channel for mixdowns and track bounces. Next down on the channel strips are the three knobs for the equaliser section. The mixer has fixed EQ curves, with only the Boost or Cut control available to the user. The top and bottom section are standard shelving filters (with turnovers at 50Hz and 15kHz) with up to 15dB of boost or cut, while the mid section is a bell (peaking) response with a 12dB range, and is centred at 2.5kHz. Unfortunately, EQ bypass buttons have not been provided, so you can't easily compare the EQ'd signal with the original.

Below the equaliser section, a single knob is provided for the two auxiliary sends, with a centre detent which represents the zero point for the auxiliary controls. Turning the knob to the left increases the send level to Aux 1, whilst turning it to the right sends to Aux 2. Although I have not seen this kind of economy on send controls before, it actually works very well, and the compromise of only being able to send to one auxiliary buss at a time is reasonable in the circumstances.

...the MD format is so far ahead of any cassette multitracker in terms of original recording quality, low noise, and dynamic range... that it is not really fair to make a comparison.

Finally, at the bottom of the channel strip, two push buttons and a pan pot provide the means of routing channels to recorder tracks. It is not clear from the panel markings, but the post‑fader channel output is always available to the main stereo mix buss, the push buttons merely adding the track destinations to the channel output. The faders have an optimum working position indicated, and the handbook stresses the importance of setting the input gain correctly to optimise this position (minimising noise and avoiding distortion).

Channels 5/6 are configured for a stereo source, and so have only one set of shared controls. There is no input gain control on these channels, only the top and bottom shelving sections are available in the EQ section, and there are no auxiliary sends. The pan pot becomes a balance control, there is a single stereo fader, and the normal track routing is retained. This section is clearly intended for stereo keyboards or maybe pre‑recorded backing tracks, although I found the absence of an auxiliary send facility rather frustrating.

Adjacent to channels 5/6 is the master stereo output, with main fader at the bottom. Above the main fader is the monitoring section, which has four sources, selected on push buttons labelled Cue, Stereo, bus 1‑2 and bus 3‑4. The Stereo button picks up the main stereo mix buss, whilst the bus 1‑2 and 3‑4 buttons monitor the track routing busses. The Cue button selects the output of a separate monitoring mixer, where independent level control knobs are provided for each of the four MiniDisc replay tracks. A Volume knob controls the monitoring level available to both the phono connectors on the rear panel and the headphone socket on the front edge.

At the top of both the master strip and that of channels 5/6 are facilities for the two stereo effects returns. Each section has a level knob and a set of buss assign buttons for recording the effects (both returns permanently feed into the main stereo mix buss). Immediately below the effects returns, on the 5/6 channel strip, two knobs control the master send level for the two auxiliary outputs. In general, the mixer is well laid‑out, the function of each control is clear, and everything performs as expected.

Display & Transport

The MiniDisc transport has a pleasantly neat and simple collection of controls, with an excellent display screen. The disc drive is mounted on the right‑hand edge of the machine, with an Eject button above the display, so the MDMX4 will have to be installed in such a position that the right‑hand side is not obstructed, to allow discs to be loaded and removed.

The transport section is dominated by the display panel, which incorporates six bargraph meters (for tracks 1‑4 plus main stereo output), a large numeric time display (minutes, seconds, and frames, or bars, beats, and clocks), various function indicators, and an alphanumeric section for edit and system instructions.

The meters are a little small and of limited resolution, with 3dB steps around the peak levels (the top bar is red and indicates clipping), increasing to 6, 8 and finally 10dB steps down to ‑40dBFS. In practice, however, setting appropriate recording levels was not a problem, provided a generous headroom was allowed (I tended to peak things at around ‑10dBFS). Very brief transients illuminating the clip lights were often found to be OK on replay.

Immediately below the 4‑track meters, bright red record tallies show which tracks are recording. These are activated by pressing one or more of the four arming keys just below the display. On the right‑hand side of the transport section, a vertical block of eight buttons provides facilities to configure the machine, and performs various editing functions on the disc. These include facilities for selecting the time display modes, accessing the editing modes, adjusting the transport speed (pitch), setting the system parameters, rehearsing editing functions, and punching in and out; and there's also a very useful Undo button which erases a previous edit or punch‑in action, retrieving the original data.

On the left‑hand side of the transport section, eight more buttons in a horizontal block provide locator facilities and in/out marks for the editing functions, and below, six more buttons provide the transport control functions. The Play and Stop buttons are both large and easily identifiable (the Play button has a small green LED to indicate its status), and there are a couple of smaller buttons above the Stop button to locate to the start of each track on the disc. A useful control above the Play button, labelled Top, locates the start of the current track, or finds blank space to record a new track. The Record button is circular to separate it visually from the others, and it lights up red when active.

Finally, a large jog dial in the bottom right‑hand corner completes the control facilities. This wheel is a dual‑concentric affair, with a continuously‑rotating inner section and a spring‑returned outer section. It is used to search through songs (providing brief and infrequent snatches of audio rather than a continuous fast replay), select items and set parameters in the various control menus, and adjust the locators and marker time values.

In Use

The MDMX4 is initially very intuitive to use. The mixer is easy to set up, and even a complete novice can be recording tracks within a couple of minutes, without having to read through the manual first. Having said that, the 65‑page manual is crucial to mastering the many complex track editing functions and the MIDI facilities, and has some very important information hidden away amongst its pages.

Recording individual tracks is a trivial process — you simply route the appropriate signals to the right tracks at sensible levels, arm the desired recording tracks, and press the play and record buttons. Lamps flash until the system is up to speed, and then away you go.

During testing, I found the mic inputs on the review sample to be disappointingly noisy at the higher gain settings necessary for typical moving‑coil microphones (I was using mainly Beyer M201s and AKG D202s, not untypical of the sort of mic this unit is likely to be partnered with). This problem was brought to the attention of UK distributors HHB, and after investigation, they were able to report the discovery of a faulty batch of units. We were assured that this fault would not be present on any unit sold in the UK. At lower gain settings for line‑level inputs, the first‑stage noise on my unit was more acceptable, so I used an outboard microphone preamp for all of my demo and test recordings, thereby feeding only line‑level signals into the MDMX4.

Overdubbing additional tracks is no harder than initial recording, once you have mastered the monitoring system to hear the replay of earlier recordings. The interesting bit comes when you have recorded four tracks, but wish to add more. Imagine a situation where you have stereo drums on tracks 1 & 2, bass on 3 and a guitar part on 4. You now need to reduce these to a stereo mix, leaving space to record new keyboard parts or vocals. The process on the MDMX4 is to perform the mixdown of all four tracks (using the input selector switches to route the replayed tracks through the mixer), replacing say, tracks 1 and 2 in the process. Tracks 3 and 4 can then be over‑recorded with the new additional tracks.

This works well enough, but as you erase the original recordings in this process, what do you do if the mix goes wrong halfway through, or you later decide to change something? Well, Sony recommend that before each stereo mixdown, you copy the entire song to a new part of the disc. This copy is an internal digital clone of course, so there is no degradation of the original tracks, although it takes time, and seems to be a real‑time copy (I was expecting it to make a copy faster than in real time). The copy acts as a backup if you have problems later, in which case you can try your stereo mixdown again, working from the copy (though you ought to make another backup before you do this, of course).

To put this whole process into context, I set out to record a demo as Song 1. Having recorded the stereo percussion and an organ part across four tracks, I copied the whole thing to Song 2. I then bounced the four parts of Song 1 down to a stereo track (1/2) and overdubbed tracks 3 and 4 with a couple of acoustic guitar parts. All four tracks were then copied to Song 3 and I bounced down the guitars and backing tracks in Song 1, leaving tracks 3 and 4 free once again — this time for the vocals.

This recording, copying, and bouncing procedure allows you to go back and change things at a later time should you need to, and provides the very important protection against losing your original material if a bounce goes wrong, but it is time‑consuming. In comparison, Tascam's 564 MiniDisc Portastudio (reviewed SOS December '96) offers a 'bounce‑forward' facility, where a combination of four tracks in the original song can be mixed down and re‑recorded as a new song on a different part of the disc. This allows you to retain the original tracks without having to make copies first. I know the bounce‑forward technique used in the Tascam requires a very fast disc drive, so that the system can replay from one part of the disc and record on another, but if Tascam can do it, why not the original inventor of the MD format?

...certainly represents a major step up for any cassette‑based home recording setup.

Punching in and out of recording is easy to do, either manually or by preset editing points. The machine can be set up to rehearse an automated drop‑in, and the pre‑ and post‑roll times can be set to suit the material or performer in one‑second increments up to 10 seconds. At the front of the machine, two footswitch jacks allow a variety of user‑configurable start/stop and punch in/out operations to be remotely activated.

As with other MiniDisc formats, obvious audible degradation occurs after about five generations of bouncing down, and in my case, the rather dynamic percussion track I used in the demo was not quite what it had been after only one generation (a slightly dull, 'fizzy' effect appeared on the hi‑hats). However, to put the quality in context, the MD format is so far ahead of any cassette multitracker in terms of original recording quality, low noise, dynamic range and the number of generations which can be tolerated, that it is not really fair to make a comparison. It may not be up to the best of professional digital multitrack formats, but it is not that far off, and certainly represents a major step up for any cassette‑based home recording setup.


One of the real strengths of the MiniDisc format is its ability to act as a kind of musical scratchpad. You can very quickly bash out a few ideas and knock up a demo, just like an analogue cassette system. But the real advantage is that you can then try altering the complete structure of a song. Move the second verse, insert another chorus, try different endings — it is all possible by simply editing the table of contents (TOC) on the disc, so that the machine plays the recorded data in different orders. This is an excellent facility, and one which, to many people, would make a MiniDisc multitracker worth its purchase price alone! The operational aspects of this kind of editing on the MDMX4 are quite good, although I found trimming an edit point with the jog wheel to be a little fiddly, and achieved the best results by marking edit points 'on the fly' (ie. hitting the marker buttons as I heard the appropriate beat).

Editing is not limited to complete sections of songs across all tracks, either. You can very easily remove a section from a single track, or copy a section to another track. Parts can be also exchanged (so the bassline in one verse could be exchanged with that in another, for example). All you have to do is to mark the beginning and end of the source material (using dedicated In and Out Mark Locator buttons), and then store the new position with another dedicated button. A Rehearsal function allows the exact in and out points to be checked before performing the edit, and an Undo button cancels the edit, restoring the previous audio sequences. Once all the timing information is logged, the Edit mode is entered, and the appropriate source and destination tracks are identified. After dealing with the usual 'do you really want to do this?' type of message, the job is done!

The editing functions are extremely useful, but there are a couple of points which are not entirely obvious, and serve to catch out the unwary. Firstly, the nature of data storage on a MiniDisc is such that it is not possible to move or copy sections shorter than about four seconds (eight seconds in 2‑track mode). Secondly, it is not possible to punch in after a song has been edited (the whole edited song has to be copied to a new location first). Lastly, the point which caught me out on several occasions was that song editing can only be performed once the disc's table of contents (TOC) has been updated after any recording. This is easily done by simply pressing the Stop button twice, but it had me scratching my head for a while! The TOC is not automatically updated on the disc — the machine keeps its own version in memory, only updating the disc's TOC when the Stop button is pressed or the disc is ejected. Another consequence of this is that if the power is turned off while the disc is still in the machine, the TOC may not be fully up to date, and there is a very real risk that the entire disc's contents may be unretrievable! Although this problem affects all MiniDisc recorders, it's pretty scary...

Other TOC editing functions allow a song to be divided into two (or more) separate songs, or a number of songs to be combined into a single one. Songs can also be deleted, of course, or named to make finding them easier (which is especially useful with all that song copy business before overdubbing, as it helps you to keep track of what instruments are on each song). The entire disc can also be named, which could be useful if you want to identify particular selections of material.


As Sony's first foray into the world of home recording, this is a very creditable effort. Overall, the mixer section is a good compromise between functionality and cost, the transport section is easy to use, and the display is very clear. Finding your way around the machine is really pretty intuitive for the most part, although I had to resort to the handbook once or twice to fathom out the detail of some of the editing functions.

The need to copy songs to preserve tracks prior to bouncing down is tedious, and interrupts the flow of work — especially since the Song copying process seems to be a real‑time operation. Tascam's bounce‑forward system puts it ahead of both the Sony and the Yamaha MD4 in this respect. On the whole, however, I think the Sony MDMX4's good solid construction, attractive looks and comfortable user interface will make it a worthy contender in the MiniDisc multitracker race.


The MDMX4 has all the usual MIDI facilities you might expect. Synchronising a sequencer to the MDMX4 may be performed using either MIDI Time Code (MTC) or MIDI Clock. In the case of the latter, a tempo map must be created first (specifying the bar, time signature, and tempo), but this is very easy to do. Up to 50 tempo maps may be stored with each song, but not on standard audio MiniDiscs — MD‑Data discs must be used for this. The MDMX4 also accepts MIDI Machine Control instructions (MMC), so that the whole transport may be controlled from a suitably‑equipped sequencer system. All the MIDI aspects of the MDMX4 worked flawlessly in the time I had to play with it.


  • Very solidly built.
  • Looks attractive.
  • Clear displays.
  • Simple user interface.


  • No bounce‑forward facility.
  • Noisy microphone inputs.
  • No digital outputs.


A first for Sony in the home recording market, the MDMX4 is well‑built, functional and easy to use. Some users, however, may find it a bit tedious to have to make a safety copy of the song whenever you want to record more than four tracks. Nevertheless, the MiniDisc format seems particularly well‑suited to providing the next generation of home multitrack recorders, and it is good to see Sony widening the choice in this area.