Another month, another MIDI-controllable digital delay line for our beleaguered reviewing team to get to grips with. The SDE2500 is Roland's latest. Is it their greatest?

Whatever the Chinese may tell you, 1985 is the year of the MIDI controlled effects unit. Already we've had two wonderful digital reverb systems from Roland and Yamaha (see last month's E&MM for reviews of these), plus Korg's cunning SDD2000 sampling delay, all of which have had MIDI fitted to the back of them in the interests of giving people some means of selecting effects memories remotely from a MIDI musical instrument.

There are to be a lot more of these rackable MIDI wonders before the year is out, too. Take this new offering from Roland. It allows you to create and store up to 64 delay effects, which you can address either by using the panel controls or by implementing MIDI patch change information in the range 0 to 127. As you'd expect, there's a modulation section onboard for the generation of all the standard delay-related effects. And the combination of a 17kHz bandwidth and some rather sophisticated high-resolution converter electronics means the SDE2500 should be capable of satisfying most professional requirements.

Curiously though, the delay time at full bandwidth is a modest 350mS, and increases to a maximum of 750mS in the 'Time X 2' mode, where the bandwidth is reduced to 8KHz. In real life, however, this restriction on delay time isn't as serious as it might first appear, as most delay effects, including straight echo, can be set up using delay times of 350mS or less. If you want to be more adventurous than that, look elsewhere.

A glance at the photograph shows all the normal delay line controls located to the left of the 2500's front panel. The first of these is the obligatory and very necessary bypass button which is a nice, big, easy-to-use affair with a neat little status LED located just above it. Again, the input level control works just as you'd expect, and usefully, your endeavours in this department are monitored by a six-section LED meter — so you've no excuse for giving the Roland more than it can handle at its input.

The Modulation controls, Rate and Depth, hold no surprises - the same is true of Feedback and Delay Level, except that these actually exist as separate knobs rather than as increment/decrement buttons or as a single assignable controller. In this age of computer-based hardware, it's refreshing to see that the 2500's designers have gone out of their way to adapt their machine to the user, and not vice versa.

With the exception of the input level pot (which should only need setting up once each session), all the Roland's controls are linked to the programming electronics, so all their settings can be stored and recalled as patch information - the fact that the level of delay relative to the direct signal level can also be stored is particularly welcome.

Bang in the middle of the front panel is a type of rocker switch labelled 'Memory No', and this does work in an increment/decrement fashion to step through patches or memories. Push down both sides of this button and the rate at which the memories step through increases greatly, the direction of stepping being dependent on which side you press first. This button also doubles as the MIDI Omni Mode on/off switch, by the way.

Further to the right is the display window, which houses five seven-segment numeric LED displays. Under normal circumstances, the first two display the patch number whilst the last three indicate the current delay time in milliseconds. But in true Roland style, the display is dual-function and can also serve to indicate Omni on/off status and MIDI channel number. Two additional LEDs indicate delay on/off status and the LFO modulation rate, the latter by flashing at the oscillator frequency.

The right-hand side of the panel takes the form of a keypad containing nine buttons, and the first of these is another of those ingenious rocker switches, which this time allows the delay time to be altered up and down. The remaining buttons are arranged in two rows, the top row for programming and MIDI functions and the bottom row for modifying effect parameters. The latter comprise Time x 2, Delay Phase, Filter and Hold, and each one has a built-in status LED. As we've seen, Time X 2 doubles the maximum delay time to 750mS, while as you might expect, Delay Phase gives you the choice of feeding back signal in normal or inverted phase. This option only has any significant effect at very short delay times, and really comes into its own when you want to change the character of flanged sounds; the difference is clear, as they say.

Filter comes next, and there's more to this than meets the eye. What it gives you is the option of having the high-frequency content of any fed back signals progressively reduced. If you set up a straight delay with feedback, bringing the filter into play produces echoes which become softer in tone as they die away. That might not sound too exciting, but some people reckon it to be a useful and realistic replica of the characteristics inherent in tape-loop echo units. And we've all met some musician somewhere who's preferred the sound of tape echoes to any other. And the feature is certainly useful for treating vocals, where it can make repeat echoes less obtrusive, and consequently more natural-sounding, than simple full-bandwidth repeats.

Hold is the familiar feature that allows anything captured in the machine's memory to be looped around constantly, giving an infinite repeat effect. This particular Roland has no triggering facilities, though, so this function is of rather limited use. Actually, I rather expected to find some form of triggered sampling system on a unit of this price and sophistication. I guess Roland's marketing people would say that if you want the degree of programmability the SDE2500 offers, you'll already have a cheaper delay line to take care of such mundane tasks as sampling. Personally, I think they should have stuck a triggering facility on there anyway.

"Performance - The 2500's designers have gone out of their way to adapt their machine to the user, and not vice versa."

Having got that disappointment out of my system, I crept up behind the SDE2500 to see what else I could or could not find. First there was MIDI, catered for by In and Thru DIN sockets. Then there was a switch for operating level, to match +4dBm or -20dBm systems, and delay only and mixed outputs, the inclusion of which is now more or less common practice.

Having remote jacks for Delay on/off and Hold is also par for the course, but the socket labelled Playmate looked more interesting. Hardly able to contain myself, I connected my footswitch and waited for the scantily-clad bunny girl to appear... alas, Mr Roland is a man of honourable intentions, and the reality is less smutty than my imagination could ever cope with. The Playmate function is really a rather clever timing device that lets you set your delay time via the footswitch; the new delay time is the same as the time that elapses between two consecutive depressions of the pedal. This means you can tap your foot on the pedal in time with your music and automatically set a new delay time that fits the tempo of the piece. Of course, the maximum delay time can't exceed the maximum capability of the unit (750mS), but this mode of operation should be mighty useful in a live situation, or if you're short of time in a studio and don't want to spend too long twiddling front panel controls.

Two further sockets allow for the connection of footswitches which you can use to increase or decrease the program number if you're not already using MIDI to handle this task. Should you opt for this method, it's probably wise to program your effects in the order you intend to use them in, to avoid any unnecessary complications.

Also in evidence is a CV input jack, but don't get too excited about this. It's designed to let you control pitch modulation using something like an external LFO, rather than as a means for controlling the pitch of a sampled sound from a CV keyboard. Inserting a plug into this socket disconnects the internal modulation oscillator, and shortly after doing this, you realise just how useful this external modulation business can be.

I started this thing off by talking about MIDI, so I might as well give you a few more details about how the new Roland implements the omnipresent digital communications link. The SDE2500 can be set to operate in MIDI Omni mode, or to respond to any discreet MIDI channel in the range 1-16. When one of the 64 memories is allocated to a MIDI program number in the range 0-127, this information is stored as part of what Roland call a number table. Four such number tables can be stored and recalled, and when the unit is powered up, the last number table used is the one that comes into operation. This is made possible by the battery backed-up memory system, which is responsible for preserving all other program information when the machine is switched off. The battery is intended to last for at least five years, by which time MIDI will be the subject of retrospective E&MM features and the session keyboard player's equivalent of old wives' tales.

Unlike Mrs White and her ailing Vauxhall Chevette, you shouldn't have any trouble learning to drive your SDE2500 and building up a productive working relationship with it. This is mainly due to the wonderfully clear and comprehensive manual, something that's worth mentioning at a time when many Oriental manuals, even some Roland ones, are less than complete and of little more help than the original Japanese manuscript.

For those not entirely au fait with exactly what you need to do to set up different effects, the manual contains a complete section on sample settings, all of which are clearly illustrated with front panel drawings showing appropriate control positions.

As the essential controls are real knobs rather than bits of software activated by pairs of unresponsive buttons, setting up a sound is really very straightforward, especially if you've used any kind of DDL before. What's more, a simple ritual involving the programming buttons locks your desired sound into the memory location of your choice. Existing memories can be edited but, if you want to have your cake and eat it, you can first copy the patch into a spare memory location and so keep the original intact.

Personally, I've lost count of the number of delay lines I've used in the course of writing a magazine review such as this one, so I know from experience that it's all too easy to get blasé about the sort of effects these things can introduce. But with the possible exception of the Filter parameter, the SDE2500 does nothing really new. What it does instead is to produce all the standard DDL effects to a very high standard, with exceptional clarity and a marked lack of background noise which is an obvious advantage in any studio environment.

"Operation - You can tap your foot on the pedal in time with the music — and automatically set a new delay time."

With the unit set to Time X 2, the reduced bandwidth isn't nearly as detrimental to the sound quality as you might imagine, and though there's an obvious difference in high-frequency response, this isn't going to be too serious for most applications.

One thing to bear in mind is that the delayed sound is muted for up to 400mS whenever you change the program or alter the delay time, so don't expect to be able to program a composition that needs one delay effect to switch instantly to another with utter smoothness. To keep matters in perspective, this problem is inherent in the design principles of DDLs, and is in no way confined to the SDE2500.

In the SDE2500, Roland have produced a straightforward, high-quality delay unit equipped for MIDI control. It has no real faults, but it does have a few omissions. There's currently a huge demand for DDLs which also offer a sampling facility that can be controlled from a keyboard, but it's a demand the SDE2500 is going to miss out on. And regardless of whether or not longer delay times are actually necessary, maximum delay time is a strong selling point out there in the marketplace, and for a unit of this price, I'd really like to have seen at least a one-second delay at full bandwidth.

Then again, the SDE2500 is an attractive performer, with exemplary credentials in the areas of noise, distortion and dynamic range.

And you wonder why writers have trouble coming to concrete conclusions about review equipment...