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Win Korg's New MIDI Modules

The second part of our competition requires you to read our review of the Korg EX800/RK100 system, and then answer questions about their respective specifications.

Win Korg's new £1000 MIDI keyboard system in E&MM's exclusive two-part competition

This month's second and final competition instalment takes the emphasis off what you can do with your eyes (viz last month's spot-the-difference illustrations) and on to how carefully you can read and absorb information.

Below you'll find our review of the Korg EX800 MIDI expander and RK100 remote keyboard. All you need do in order to fulfil this part of the competition is read the review carefully and then answer the questions listed on the entry form: basically, it's a high-tech comprehension exercise, though if you read the text with even a modicum of attention to detail, you shouldn't have too many problems filling out the form with confidence!

So, eyes down, here comes the copy...

The EX800

This is an eight-voice polyphonic synthesiser expander module that communicates with the outside world via MIDI. Deceptively small, the EX contains all the functions of the self-contained Korg Poly 800, the only real difference being the lack of a keyboard.


Measuring a very modest 404 x 222.5 x 64.5mm, the EX800 boasts virtually the same front panel controls as the Poly 800, though the layout itself is somewhat dissimilar.

The top half of the panel is taken up by the Parameter Index, a look-up table detailing parameter codes and their respective ranges. Each of the expander's variable parameters is given a code through which it can be addressed by the user, and the Index lists this as well as the range over which the parameter can be adjusted. For example, the level of DCO 1 is addressed via code 17, while its value may be set at any integer between zero and 31, giving a resolution of 32 steps.

Below the Parameter Index is the control section, and the most noticeable features of this are the three display windows, behind which are pairs of numeric seven-segment LED displays. These yield information relating to program, parameter and value respectively.

The volume control incorporates the on/off switch, and next along the panel is the tuning control, which enables the EX800 to be fine-tuned to other instruments or synthesisers with which it may be interfaced.

Next is the sequencer which comprises only speed, step and start/stop controls and which, in conjunction with the keyboard, is capable of storing 256 notes polyphonically: these can be programmed in step or real time.

An eight-button numeric keypad is used for programming in conjunction with the 'bank hold' and parameter increment/decrement switches, and this is used to enter patch numbers, parameter codes and parameter values.

Turning our attention to the rear panel reveals a pair of five-pin DIN sockets for use as MIDI In and Out, followed by a jack socket labelled 'program step up'; when a footswitch is connected to this socket, the voice programs may be stepped through one at a time, though only upwards. Mini jacks are provided which allow the connection of a cassette recorder and, using this facility, voice programs or sequences may be stored to or loaded from tape for future use. The internal memory is non-volatile so that the integrity of the voice and sequencer programs is preserved when the expander is powered down. Both sequencer and program write functions have enable/disable switches, and the main output is in stereo to make full use of the built-in stereo chorus effect.

Finally, a DC input socket connects to the mains unit provided; there is no facility for battery operation (unlike the Poly 800) which is fair enough, as the current required by the circuitry would make this a fairly expensive way to operate the expander.


Sounds are built up from waveforms provided by eight digitally-controlled oscillators, and these can be configured to operate as eight-voice or four-voice polyphonic generators, in which case each voice uses two oscillators. In the interests of economy, only one voltage-controlled filter is provided, and this has its own envelope generator, as have the two oscillator sections, DCO 1 and DCO 2. All three envelope generators have the usual ADSR parameters but additionally, two new functions of 'break point' and 'slope' are provided. These functions allow the decay to be interrupted at a user-defined break point, and either a new decay rate or a second attack rate introduced, respectively. New percussive effects can be created in this manner and, by setting different envelopes for DCO 1 and DCO 2, the voice can be made to change dramatically, so long as a key is held down long enough to allow the second envelope to take effect.

Each oscillator has four octaves or footages, each of which is available with ramp or square waveforms, and these may be used simultaneously in any desired proportion. This is particularly useful for simulating organ sounds: a convincing Hammond voice can be programmed very easily, for example.

Any sounds created may be stored in any of 64 memory locations, configured as eight banks of eight sounds.

The modulation section is fairly conventional and includes delay vibrato, which may be fed to the DCOs or the VCF as required. Noise may be added to the DCOs for voice generation, while the stereo chorus is preset, only on and off controls being accessible to the user.

Either multiple or single triggering may be selected, and the whole unit may be set to respond to any MIDI Channel between 01 and 16. The sequencer clock may be selected to run at the rate set up on the EX800 or to respond to a MIDI clock, but no sequencer trigger input is provided for use with conventional trigger pulses, which is a shame.


Given the limitations imposed by a single VCF, the EX800 is surprisingly versatile and, consistent with most recent Korg synths, has a fat filter sound as well as the capacity to generate more abrasive voices when required.

One system present on the Poly 800 but missing from the EX800 is the chord memory feature and, while this in itself is no great loss, it was the only way to force all the oscillators into unison, and this is a facility which will be missed on the EX800 as there is no unison mode as such.

As there are no performance controls on the expander, the 'bend' function is implemented via MIDI, and this was found to be compatible with most other MIDI products, including hardware by Roland and Yamaha, but check with your own synth before you buy if this function is one of your prime requirements.


This is a flexible synth capable of providing a wide range of both powerful and delicate sounds. The single filter is a limitation, but it does keep the cost down, and its omission is not as serious as it may at first appear.

To my mind, the real naughties are the lack of a conventional trigger input for syncing the sequencer to a conventional drum machine and the lack of a unison button.

I would imagine that the EX800 would appeal particularly to owners of MIDI pianos or Yamaha DX synths, as its fat textural sounds would make an ideal complement to their existing voice capabilities and the purchase price makes it a very realistic addition to the semi-pro keyboard player's armoury.

Altogether, this is one of the neatest and most impressive synth add-ons that we have yet had the pleasure(?) to test.

The RK100

This is the ideal companion for the EX800, and allows the keyboard player the freedom of the guitarist whilst giving him the means to control any MIDI-equipped synth.

Built on a wooden chassis, the 100 features a three-and-a-half octave keyboard (C-to-E), and a bank of performance controls fitted within convenient reach of the player's left hand. Onboard controls allow the keyboard to be switched to select programs zero to 63, and an LED display shows the current 'bank and program' status for a maximum of 64 patches.

Available in black, white, red or natural wood finish, the RK100 weighs only 4.4 kg and balances in much the same way as a guitar. All except the natural wood models are coated with a tough, thick lacquer which visually resembles perspex.

Modulation Controls

The pitch-bend and vibrato wheels are ergonomically placed on the neck of the instrument and are spring-loaded, unlike the volume wheel which sensibly stays exactly where you set it. A switch is provided so that the modulation wheel may be routed to pitch or filter modulation, its speed and maximum depth being determined by the capabilities of the receiving synthesiser.

Step buttons are also provided so that the program number may be incremented or decremented, and a three-way switch allows the pitch to be transposed up or down by one octave during performance. Additionally, the shift and number buttons can be used to specify a voice patch number directly.

The portable nature of the RK100 means that mains power would be impractical, so the unit normally runs from six AA-type cells which can be either standard or rechargeable.

The only connection is the MIDI Out cable, which has a locking plug to prevent embarrassing disconnections during performances, though it is possible to run the RK100 from an external 9V DC source if on-stage gyrations are kept to a minimum!


As with all high-technology instruments, a good handbook is a must and fortunately this offering from Korg lists all the MIDI information required to understand what is going on when you plug the ubiquitous DIN plug into a remote synth.

The RK100 incorporates active sensing, ie. five times every second, the synth asks the RK100, "Are you still there?", and the RK100 answers "Yes!" This is the digital equivalent of the scene in Cool Hand Luke where Paul Newman has to shake the bush to prove that he isn't running away when he's out of sight! If anyone accidentally disconnects the cable, the synth will get no reply and will then go into a mode of ongoing silent sulkiness until someone talks to it. Joking aside, this is a preferable alternative to having your last note sustained after the plug falls out...


The RK100 is well thought out in terms of both ergonomics and facilities, and the MIDI department behaves well, with no unpleasant surprises. It's probably most at home driving the EX800, as other synths (such as those with more than 64 patches) could present some problems, as could early MIDI synths with suspect software.

Providing that you like the playing position and feel at home with its modulation controls, the RK100 is pretty much user-transparent: its keyboard has a conventional feel and the instrument isn't too heavy to play for long periods of time.

If you want to stand up and be counted, try one out - but don't trip over the footlights!

Previous Article in this issue

On Stage

Next article in this issue

The SynthMix

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Sep 1984


Previous article in this issue:

> On Stage

Next article in this issue:

> The SynthMix

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