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This Japanese audio company seem hell-bent on making a name for themselves as producers of high quality products and this rack-mount electronic keyboard mixer incorporating a four channel MIDI Thru box certainly fulfils that aim. Ian Gilby reports.

Ian Gilby reports on this rack-mounting Japanese mixer, purpose-designed to attend to the needs of the modern musician.

The widespread acceptance and use of synthesizers in most fields of popular music has already had a knock-on effect in other associated areas of the music industry. With their ability to generate extremely fast transients and wideband sounds that contain vast quantities of pure harmonic energy, synthesizers make tremendous demands of both the amplification and speaker systems used to bring them to life. If you've ever stuck the output from your synth into your domestic hi-fi you'll understand what I mean!

Most speaker designs simply aren't up to doing the job. So a logical move you might well think would be to purpose-design loudspeakers that could cope admirably with the output from such demanding electronic musical instruments as synthesizers and drum machines. Well the Japanese company, TOA Electronics, did exactly that in the shape of their excellent 380-SE three-way speaker system launched earlier this year.

For an audio company, TOA haven't had the highest of public profiles in this country to date, their prime markets being the USA and Europe where their expertise in stage equipment/PA systems is widely recognised. Like Dynacord in Germany and Korg over here, they have come up with good products in the past but have been desperately lacking in the marketing department. At one of Japan's audiofair's last year for example, TOA showed a prototype rack-mount 8-track cassette recorder/mixer. Interesting? Certainly - but have we seen anything of it over here yet? No.

TOA, having at last recognised the UK as a 'serious' market, have already set about rectifying the aforementioned marketing situation with a vengeance and the British Music Fair will see the release of many new TOA products all aimed directly at the modern musician interested in recording and performing his music. One of those products is their D-4 Electronic Music Mixer (with MIDI) reviewed here.


Appearances can be deceptive and it would be foolhardy of anybody to quickly glance at the D-4 and dismiss it simply as a rack-mountable submixer for keyboards. It isn't, or rather it isn't just that, for TOA have graciously packed sufficient features into this 2U high, 19" box to make their four input stereo mixer versatile enough to play many roles. So let's run through what it offers.

First off, let me say that this unit is very well constructed both internally and externally. All the mixer controls are, as you'd expect, mounted on the dark grey enamelled front panel with over forty input/output connectors in total to be found on the (uncluttered) rear.

The front panel layout breaks down conveniently into two halves, the leftside being given over to the four input channel's controls and the right side to the master/output controls and power switch. Personally, I found there was too little visual discrimination made on the front panel between these two sections, similarly with the various channel controls - differently coloured knob caps on adjacent controls would help discrimination considerably here...

Each input channel features five knobs plus an inch-wide grey plastic identification tab on which you can scribble the connected instrument's name. Now I hate to kickoff the review on a down-note but it isn't exactly easy to find something that writes on this plastic surface. Being grey, even a black erasable felt pen doesn't show up too clearly - you really must use a white or yellow chinagraph pencil or resort to stick-on labels (a bit tacky though!). Why not change them to coated white plastic like on conventional mixers and make life easier?

Below this we have the channel Trim control for optimising the level of the input preamp stage, and there's a helpful red 'clip' LED above it to indicate the onset of channel distortion. As the word 'Trim' implies, this control attenuates the input which is set at the pro-equipment operating level of +4dB when fully anticlockwise and reduces to -30dB fully clockwise. This is sufficient range to allow the D-4 to accept any unbalanced sound source - synths, guitars, even some high impedance mics - and both phono and quarter-inch jack input sockets are fitted to cater for a variety of devices. If the jack input is being used, then the phono is automatically switched out of circuit. Having both connector types available increases flexibility and benefits the user by removing the need to make up jack-to-phono leads, as is often necessary on budget multitrack recorders.

Having just mentioned microphones, it's worth noting that TOA have also provided an electronically balanced XLR-type mic input on input channel 4 only, in addition to the jack/phono inputs. They have also built in a 48 volt switchable phantom power supply so that a high quality condenser mic may be used if desired. A welcome feature.

Continuing with the channel controls, TOA have also given the D-4 a simple but effective (bass/treble) two-band shelving EQ system. The inner of this dual-concentric EQ knob governs the +/-15dB boost or cut of the High frequency band whilst the outer ring offers the same for Low. Centre detents on both indicate the 'flat' response.

Although the channel EQ is perfectly adequate for overall equalisation of an input signal, its limitations may be overcome if more drastic tonal modification is required, by breaking the input signal path and inserting an external graphic equaliser unit connected via the rear panel Accessory In and Out phonos. As these useful 'insert' points are available on all four input channels and main outputs, you could easily connect a compressor, delay or reverb unit to independently treat each one - it needn't be a graphic equaliser.

A second dual-concentric knob determines the overall input channel level (inner control) sent to the main stereo left/right outputs and mono Sum output, and also sets the position of the channel signal in the stereo image (outer Pan control). Again, the Pan pot has a centre detent, this time indicating a centralised stereo position.

The input channel functions are completed by an Auxiliary Send and an Effects Send level control. Each one sets the amount of channel input signal sent to the Auxiliary and Effects mixing busses whose overall output levels are controlled by the right-hand master Aux Send and Effect Send rotaries. The channel Effects Send is a post-fader/post-EQ signal naturally; if it were pre-fader and connected to a reverb unit, say, then even if the channel level control was turned right down, the input signal would still reach the reverb and be heard since it would have been tapped off and sent to the reverb unit before (ie. pre) the level control (or fader).

The Auxiliary Send knob on the other hand is multi-functional: in the centre detent position it is completely off; turned left it sets the level of the pre-fader/post-EQ input sent to the Aux buss; turned right it sends the post-fader/post-EQ signal instead. Since the Auxiliary Send on any mixer is traditionally used as a cue or foldback output, this choice allows the D-4's Auxiliary to be employed as a second channel Effects Send instead, greatly enhancing its application as a four channel recording mixer.

TOA haven't stopped there mind you. Removing the D-4's casing gives access to the interior and to the small PCB-mounted slider switches which make it possible for you to select the previously mentioned Accessory insert point on each channel to be either pre- or post-fader and EQ. Likewise the Aux Send may be switched for pre- or post-EQ operation but only if it is being used as a monitor cue ie. its front panel control is turned anticlockwise (prefader).

This all adds up to a very comprehensive configuration choice which effectively allows you to tailor the D-4 to better suit your needs either for live performance or recording. A direct (phono) output per channel also makes it possible for a 4-track recording of your performance to be made whilst simultaneously using the D-4 in stereo to play a gig...


Along with the master Aux and Effects Send controls already described, the D-4 provides two independent sets of Return controls for both Aux and Effects Sends. These comprise a mono return to the Sum output, which is a mono mix of the inputs for foldback purposes, fed to jack and XLR-type connectors (both +4dB) on the rear; then there's a mono return to the stereo L/R outputs with a dual-concentric Pan and Level control so you can position the Effects and Aux Return signals in the stereo image. Additionally, a Pre/Post pushbutton selector lets you choose whether or not the mono Sum output (controlled by its own Level knob below) is affected by the setting of the master stereo output controls.

Finally, comprehensive headphone monitoring is also provided on the D-4 and the front panel output jack will accept headphones with an impedance above 8 ohms. The dual-concentric inner knob governs the headphone monitoring level whilst the four-position rotary selects the monitor source: either Effects, Auxiliary, or Sum signals (all in mono) or alternatively the main stereo programme output (in glorious stereo).


I couldn't end the review without mentioning the MIDI aspect of TOA's D-4 Mixer. As well as the above features, TOA have recognised the interconnection problems suffered by Thru-less MIDI keyboard owners and have seen fit to incorporate no less than four MIDI Thru sockets on their mixer's rear panel along with one MIDI In. This thoughtful act means you can use a single connected MIDI synthesizer, for instance, to control up to four other MIDI devices. And since the MIDI In signal is split and sent unmodified to each Thru output, it reduces the risk of MIDI time delays and data corruption.


The D-4 is most definitely a comprehensive and versatile mixer in many ways: it has plenty of useful insert points for patching in external effects and the multiplicity of input/output connectors and dual operating levels make it extremely flexible in use. Phantom powering, a balanced microphone input, and a very low background noise level open up even more possible recording applications for the D-4. Yet, to my mind, the very limited EQ and the low number of input channels take away some of the appeal when considering the D-4 in isolation. However, the knowledge that TOA have an identical 6 input Expander version of this unit (but without the master section), which derives its power direct from the D-4 and links busses to provide 10 input channels in total, makes the D-4 a more attractive package.

Having peeked inside the review unit in order to changeover several pre-/post-EQ channel switches, normal 'on the road' use should present no problems, for the D-4 is well-built and looks robust enough to cope.

When you consider that some MIDI Thru boxes alone cost well over the hundred pound mark, the D-4's retail price of £350 plus VAT seems good value for money. Sockets and plugs, ridiculously enough, are what add the most cost to equipment these days, yet TOA have certainly not skimped on that count.

Performance-wise the D-4 didn't put a foot wrong whilst being used to make a recording on a friend's Teac 3340 recorder. It was straightforward to use and quiet. Most of my criticisms of this unit concern the non-functional cosmetic layout and choice of colourings - the red numbers around the controls, for instance, are murder to read in a dimly lit studio never mind a darkened stage! So why not make them white?

But overall, TOA's D-4 MIDI Mixer proved a good workhorse product that should easily fulfill the demands placed on it by the modern gigging and recording multi-instrumentalist.

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Painter In Sound

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Just Can't Stop

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Aug 1986

Donated & scanned by: Mike Gorman

Gear in this article:

Mixer > TOA > D4 MIDI Mixer

Review by Ian Gilby

Previous article in this issue:

> Painter In Sound

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> Just Can't Stop

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