The D1500 has the distinction of being the world's first MIDI (Musical instrument Digital Interface) compatible delay system, allowing any of its 16 memory banks to be remotely selected from a MIDI keyboard.

This new offering from Yamaha follows the cosmetic lines of the R1000 digital reverb (reviewed HSR January 84) but there the similarity ends.

Boasting a truly professional specification, the D1500 provides a maximum delay time of 1023ms with a bandwidth of 18kHz and furthermore, it can store up to 16 delay programs which may be remotely selected via a MIDI keyboard or other suitable MIDI compatible device.

Additionally, the D1500 has full modulation facilities with a choice of two modulation waveforms and a feedback invert feature lends extra flexibility to short delay flanging effects.

Before investigating the capabilities of the unit, a few words about its construction are in order.

Construction

Housed in the familiar 1U format rack-mountable case, the D1500 is finished in black satin enamel with gold legend, the now obligatory block diagram being printed on the top cover.

There are only two rotary controls on the front panel, the input and output level controls, all the other parameters are accessed by means of small soft-touch pushbuttons.

In order to optimise the input level, a seven segment illuminated display is mounted to the left of the input level control and a brightly lit five digit LED display simultaneously shows the delay time and program number.

In edit mode, the time display is used to indicate parameter values which may then be incremented or decremented by means of the adjacent buttons.

To the right of the display are a further 14 pushbuttons relating to data entry and parameter values and finally comes the bank select footswitch socket, by means of which the delay program number may be remotely incremented without recourse to MIDI.

Rear Panel

This unit has a particularly busy rear panel, there being no less than eleven connectors not counting the mains lead.

Both input and output connectors are on balanced XLR sockets as well as balanced jacks and both MIDI In and MIDI Thru are implemented using the usual five pin DIN sockets. There is no MIDI Out as the D1500 does not have anything to say to anyone.

To ensure successful matching with a wide range of audio equipment, both the input and output levels are switchable for -20dB or +4dB levels.

In anticipation of the clientele who are likely to use the D1500 in a variety of countries, a safely recessed switch sets the transformer tappings to accept 240V or 110V, the two most common international mains voltages.

Three jacks are provided for further footswitches, one to cancel the delay effect, one to disable the modulation, and one to activate the hold function.

If you're dissatisfied with the choice of sine or square wave modulators built in to the machine, you can insert the waveform of your choice into the CV In socket which requires a voltage in the range of 0 to 10V to operate correctly.

It transpires that in the hold mode, this is the only way to vary the pitch of the stored sound as the front panel controls have no effect on pitch in this mode. A suitable input could be provided by the multiwaveform low frequency modulation oscillator, described in Electronics and Music Maker, June 1984.

Operation

Having briefly introduced you to the controls, let's see what you have to press in order to elicit a useful response.

Well, firstly the manual tells us that pressing the on switch will cause the unit to come on and that the display will light up.

I did - it did, and the first thing you notice is that the first digit of the display is green, the others are red.

On powering up, the output is muted for three seconds to shield your sensitive ears from the sound of several kilobytes of random data being flushed out of the memory. The unit is now ready for use.

Initially, the display shows the program number and the delay time, the default condition being program bank A and this may be used without further ado. In order to make the system handle 16 programs using a single digit of display, the banks are numbered in hexadecimal and for those of you who hide under tables at the sound 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. The numbers 0 to 15 give you, of course, a total of 16 combinations.

To change programs, you can use the increment/decrement buttons, the foot-switch (which only increments) or MIDI (but more of that later).

In order to modify the parameters of a given program, the required parameter is selected using one of the function buttons and then its value is incremented or decremented by means of the data entry buttons.

If one of these buttons is held down continuously, the parameter value changes continuously until the button is released. Once all the parameter values are correct, the modified patch may be written over the original one simply by pressing the Store and Bank buttons.

Just in case you don't want to lose your original program, Yamaha have thoughtfully provided a copy key so that your precious patch can be copied into a spare memory bank before surgery.

One feature not found on many other digital delay units is a variable low pass filter which resides in the feedback loop and enables regenerated repeats to become progressively less harsh as they are recirculated. The cut-off frequency of the filter can be stored as a parameter value and the discrete frequencies available are 2.5, 4, 6, 8,10, 20kHz at a slope of 6dB per octave.

The feedback may be set between the values of 0 and 99, the maximum value being the most feedback that can be applied without the sound actually increasing in level and at this setting, the repeats take over 30 seconds to die away.

MIDI

The MIDI channel key is used to set up a MIDI channel between 1 and 16 corresponding to the channel of the controlling device. To set this up, you simply press the MIDI CH key, use the increment/decrement switches to get the right number, and then press MIDI CH again. No MIDI data can be received whilst the MIDI CH select mode is engaged.

Having selected your channel, it is still necessary to instruct the D1500 how to interpret the incoming MIDI commands and that is where the MIDI Program Change key comes in. When this key is pressed, the current program bank number and MIDI program number are displayed.

Using the Data increment/decrement keys, the desired MIDI programme number is entered, then the Bank Select keys are used to select the bank that will be selected by that MIDI Program number. Pressing the MIDI Program key again stores this data and disengages the MIDI program change function.

The most obvious use of the MIDI function is to select delay programs from the voice selection buttons on a MIDI keyboard and indeed, we used a Yamaha DX9 in this way for the tests, but a MIDI/computer interface could also be used.

So much for the operation, there's not much point in going into greater detail as Yamaha do provide a perfectly adequate manual complete with a selection of useful patches to get you started.

Effects

Now that we can drive it, what does the D1500 sound like?

Well, as you'd expect from the technical spec, the sound is bright, clean and free from undue quantisation noise but there is a slight discernible difference between the direct and delayed sounds, the highs don't seem quite so clear in the delayed version.

Many digital delays fall down on the flanging effects but not so the D1500, the flange was deep and exciting as it should be. The feedback invert mode invokes a subtle but useful change in colouration at short delay times and shimmering chorus effects are easy to produce using lower levels of feedback.

The subjective sound quality should satisfy both the live performer and the discerning studio engineer and the only delay effect not possible on the D1500 was 'realistic' reverb - but this is the case with all digital delays.

Conclusions

This is a very desirable piece of equipment for both studio and live use and our reservations about it are few indeed. One such quibble is that without MIDI, much of the flexibility is lost as there is no way to select specific program banks instantly without some form of MIDI compatible device. This is particularly relevant to the studio engineer who wants to change patches during a mix. It can be achieved by using the footswitch or the increment decrement buttons, but this means arranging the memories in a particular order for each mixing session, not an enviable task.

It doesn't take much in the way of cost or technology to add a one-shot triggered sampling system such as in the Boss DE-200 and this is another valuable feature not incorporated in the design. Also the inability to alter the pitch of the stored sound in the hold mode limits creativity a bit unless you have an external modulation source or control voltage, but none of these gripes detract from the fact that the D1500 is a fine piece of equipment and sensibly priced at that.

The MIDI facility makes the D1500 a very flexible delay system for live use and in the studio, it'll create virtually any delay effect you need.

The D1500 retails for £639 inc VAT.

Further details are obtainable from Yamaha, (Contact Details).