MIDI keyboards and drum machines have already become commonplace, but now Yamaha have taken uniformity a step further by introducing the first DDL equipped with the new interface.

I suppose the obvious question must be: why put MIDI on a digital delay? Unlike synthesisers, rhythm machines, personal keyboards and music computers, the average DDL doesn't have a great deal to say to the outside world via MIDI or indeed any other kind of interface. Yet by equipping the D1500 with MIDI In and Thru sockets, Yamaha have given keyboard players the facility to control the unit's programmable memories from a MIDI synth. Hence, if you assign both synthesiser voice and DDL patch the same memory number, you get a tone colour accompanied by a delay effect tailor-made for it, all at the touch of a button.

In addition to providing all the standard delay effects up to a maximum delay time of 1023mS, the Yamaha boasts a professional specification and is capable of storing up to 16 programs, all selectable remotely via MIDI. In the normal run of things, I suspect that most users will use the patch change buttons on a keyboard to select these programs, but it's not inconceivable that a MIDI-compatible computer or drum machine could be used to perform the same task.

Construction

Housed in the now almost-obligatory, 1U-high 19" rack mounting case, the D1500 is smartly finished in black satin enamel with gold legending. Another compulsory fitting on Oriental DDLs these days is a block diagram printed on the unit's top cover, so the Yamaha has to have one of those, too.

The front panel sports only two rotary controls (for input and output level), all other parameters being accessed by means of small soft-touch pushbuttons. A seven-segment illuminated display is mounted to the left of the input level control to assist the user in optimising said level, while a five-digit alphanumeric LED display shows delay time and program number simultaneously.

When the D1500 is in Edit mode, this latter display indicates parameter values which can then be incremented or decremented by means of the appropriate pushbuttons: there are 14 of these, located to the right of the display window.

The Yamaha's rear panel is uncommonly busy, there being no fewer than 11 connectors in permanent residence. Both input and output connectors are on balanced XLRs as well as jacks, while MIDI In and Thru are implemented via standard five-pin DIN sockets. To ensure successful matching with a wide range of audio equipment, both input and output levels are switchable between -20dB and +4dB levels, while the unit can be set to operate from either 110V or 240V. Three jack sockets are provided for further footswitches (one can be connected to a similar socket on the front panel for remote stepping through of bank numbers), and these can be used to disable modulation, activate the Hold function, and cancel the effect altogether.

Should the sine and square wave modulation options not be sufficient for your purposes, you can insert the waveform of your choice into the D1500's CV In socket, which requires a voltage of between 0 and 10V to operate correctly. It transpires that the Yamaha's front panel controls do not function when the machine is in Hold mode, so the only way of varying the pitch of the stored sound if Hold has been selected is to apply some sort of waveform to the CV In: our own Multi-waveform LFO project (published in E&MM June) should fit the bill nicely.

Operation

On powering up, the D1500's output is muted for three seconds to shield sensitive ears from the potential aural armageddon of the sound of several kilobytes of random rubbish being flushed out of the unit's memory. The unit is then ready for use, and initially the display shows program number and delay time, the default condition being program bank A.

In order to get a single-digit display to handle 16 programmable memories, Yamaha have numbered the banks in hexadecimal. For those of you who hide under tables at the first mention of computer jargon, don't panic: all it means is that you count from 0 to 9 in the normal way and then from A to F, F being 15.

Creating a program is really pretty straightforward.

The required parameter is selected using one of the D1500's function buttons and its value subsequently raised or lowered using the data entry controls. Once all the parameter values are to your liking, the modified patch may be written over the original simply by pressing the Store and Bank selectors. And just in case you don't want to lose your original program, Yamaha have thoughtfully provided a Copy key that enables your precious patch to be transferred to a spare memory bank before receiving surgery. Needless to say, full battery back-up is provided so that patches and their memory locations are stored even when the D1500 is powered down.

Unlike the majority of its competitors, the 1500 incorporates a variable low pass filter. This resides in the feedback loop and enables repeats to become progressively less harsh as they're recirculated, giving an impression of distance. The filter's cutoff frequency can be stored as a parameter value, and the discrete frequencies available are 2.5, 4, 6, 8, 10, and 20kHz at a slope of 6dB per octave. Feedback may be set between values of 0 and 99, the latter being the most feedback that can be applied without the sound actually increasing in level: at this setting, the repeats take over 30 seconds to die away.

In order for the D1500 to communicate amicably with its controlling MIDI instrument, both devices must be set to the same MIDI Channel number, and on the delay, this is selected by - wait for it - the MIDI Channel key. Once you've selected your channel, however, it's still necessary to instruct the Yamaha how you want it to interpret incoming MIDI data, and this is where the Yamaha Program Change key comes into play. When this is pressed, the current program bank number and MIDI program number are displayed, and by using the data increment/decrement keys, matching specific memory banks to MIDI program numbers is a simple (if somewhat laborious) task. Pressing the MIDI Program key again stores this data and disengages the MIDI Program Change function.

Effects

Manufacturer's spec for the delayed signal passing through the D1500 includes a frequency response of 20Hz-18kHz and a THD figure of 0.08%, but curiously no indication of noise performance is given. This would seem to indicate that Yamaha are a little ashamed of the D1500's performance in this area, but judging by my experience with the unit, they've no reason to be. The delay sounds are clean, bright and free from any undue quantisation noise, though there is a slight discernible difference between the direct and delayed signal.

Many DDLs fall down in the area of flanging, but not so the D1500: properly set up, its flanging is as deep and exciting as the best of them. Meanwhile, the unit's Feedback Invert mode invokes a subtle but useful change in colour at short delay times, while shimmering chorus effects are easy to produce using lower levels of feedback.

Conclusions

This is a highly desirable piece of equipment for both the studio user and the gigging musician, though it's the latter that'll probably benefit most from the Yamaha's MIDI control options. My only reservation concerning the 1500's programmability is the fact that you actually need some sort of MIDI controller to select programs without incrementing or decrementing them one by one. It could be more than a mite awkward, mixing a multitrack recording with a DX7 on your lap just so that you can access the D1500's programs instantly...

The only other thing the 1500 lacks is some sort of triggerable sampling system. This facility costs very little provided that it's included at the design stage, and if Boss can include it in their budget DE200, why can't Yamaha do the same for the D1500?

In all other respects, though, Yamaha's MIDI delay is a finely designed and engineered piece of hardware that even the wealthiest electronic musician would be proud to include amongst a rack of signal processing gear.

Still, all good things must come to an end and, sadly, it's now time to give it back.

RRP of the D1500 is £693 including VAT, and further information can be had from Yamaha Kemble, (Contact Details).