In keeping with Roland's MIDI/Modular path into the future, they have come out with their first MIDI Digital Delay — the SDE-2500, which has no less than 64 MIDI-controllable memories.

The idea behind a MIDI Digital Delay is that it should be a signal processor which works in tandem with a programmable synthesiser, giving effects such as chorus, flanging and ADT to the synth programs themselves. This is the first MIDI controllable Digital Delay to have the full complement of 64 memories (as many polysynths have 64 patches) and therefore is of particular interest to the MIDI synthesists among you.

The SDE-2500 is very similar in appearance to Roland's other two programmable DDLs — the SDE-1000 and the mighty SDE-3000. Its housing is a standard 1U 19" rackmounting unit, attractively styled with flashing coloured LEDs, two alphanumeric displays and all connections hidden away on its rear panel.

On either side of the facia are two large push buttons; one for power on/off and another for signal Bypass. To the right of the bypass switch is a six stage ladder meter and its respective input level attenuator, and the Input/Output level matching can be switched between the standard professional level of +4dB and the instrument level of -20dB from a button on the rear panel.

All the controls for sound processing are programmable, including the delayed signal's output level control. There are four of these programmable knobs on the front panel — Feedback, Delay, Out, and Modulation Rate and Depth.

Alongside the display is a switch whose primary function is to increase/decrease the program number. By depressing its top half, the program number increases, and by hitting its bottom half, the program number decreases. This switch's secondary function is for MIDI On/Off/Omni switching.

The display is divided into two sections. The left hand, two digit display shows the memory number, and the right hand three digit display indicates the current delay time in milliseconds.

To the right of the display are two LED indicators. One of these flashes at the rate of the Low Frequency Oscillator, and the other is a delay On/Off indicator. Further to the right are two rows of four push-buttons. On the top row are buttons for writing patch settings into memory locations, copying from one memory to another, and two buttons for MIDI communications labelled MIDI Program and MIDI Channel. The latter simply changes the MIDI channel, and the other button, MIDI Program, is very useful as it enables you to select any particular memory location in the SDE-2500 from any one of the synths patches. Therefore you can, for example, switch to voice number 12 on your synth, and automatically select memory number 57 on the Digital Delay. On the bottom row of this cluster of buttons are a x2 mode (which multiplies the delay time by two, whilst halving the delayed signal's bandwidth), a button for inverting the phasing of the delayed signal, a filter button (cutting off the very top end of the echoed signal), and a hold button.

IN USE

Whilst having an enormous amount of memory for storing patches, the SDE-2500 has a much reduced memory capacity for the delayed signal itself. At full bandwidth, it will only provide 375mS of delay, and 750mS of delay at an 8kHz bandwidth. Whilst this is more than enough delay time for the most common effects such as chorus, flanging and ADT, this is not over-generous when it comes to having long repeat echoes. In theory, however, I would guess that most people only occasionally find themselves using delay times of over a half a second under normal conditions, although I still would prefer to have the choice of a longer delay time.

The sound quality of the delayed signal itself is of a very high standard on the shorter delay times. The spec, sheet quotes a dynamic range of over 96dB, which I can well believe. It is clean (84dB S/N) and punchy, even when the input is driven well into the red.

On the rear panel are the connections for MIDI In/Out, Audio Signal In, Delay Out and Mixed Output, It also has half a dozen sockets for various remote switching/control — Delay and Hold On/Off, Preset Shift Up and Down jack sockets, External CV Input jack for control over the modulation rate, and a useful jack socket marked 'Playmate'. When a footswitch is connected to this socket, it will let you set a delay time of any length by pressing the footswitch twice in the particular timing (within the 750mS limit), which is a useful way to sync into tempos.

CONCLUSION

With Roland's SDE-2500 it is possible to link many effects to the actual programs in a MIDI master synth. If you are synthesising a very rich, orchestral string sound, you might set the SDE-2500 to a medium repeat with a little pitch modulation therefore add ing a lot of depth to a synth's patch. A bass synth sound too, will often be augmented with some tasteful flanging, and now all these permutations are possible with the SDE-2500 MIDI'd up to a synth.

Although for £600 there are quite a few DDLs with longer delay times than the SDE-2500, it does offer alternative and very useful functions to the synthesist, and while this unit would not be too uncomfortable in a recording studio, the persons to whom I would imagine it selling most is to the pro/semi-pro musicians with a Juno 106 or DX7. In this context it will thicken up and add extra depth to a synth's sounds as well as adding special effects very easily in a live situation. However, I can hardly wait for the arrival of Roland's new MIDI Digital Reverb.

Price: £600