From the makers of the Emulator, the successful digital sampling and polyphonic playback keyboard, comes the Drumulator, a relatively inexpensive digital drum machine. Comparisons with the LinnDrum and Oberheim DMX are inevitable, and although the Drumulator does not offer one hundred per cent of the features of these machines, it is much cheaper, simpler to use, and offers all the basic facilities of either.

Sounds

The Drumulator has twelve sounds, these are Clave, Bass Drum, Cowbell, Snare, Claps, Rimshot, Open Hi-Hat, Closed Hi-Hat, Low Tom, High Tom, Mid Tom and Ride. These are available on six buttons with a seventh button to select between the conventional drums and the more exotic percussion sounds. Each sound has been sampled individually, as distinct from the method on the LinnDrum, for instance, which uses the same sample played at different clock rates to produce the three tom-tom pitches. It will be possible to install different sound chips, but this won't be particularly easy for the average musician.

Any of the sounds can be assigned to the four Play push-buttons at the bottom of the control panel, simply by selecting the sound, the play button desired, and pushing Enter. After four sounds have been programmed in, another four can be selected; Accent can also be selected and programmed in. The level of Accent is set with the left-hand slider, which also acts as an incrementor for the Tempo and for the individual volumes of the drums.

Dynamics

One unique feature which the Drumulator offers is the ability to program dynamics. A second 'accented' version of any voice can be assigned to one of the play buttons and its level set from 0-15 on the slider. This allows about 30dB of dynamic range to be set. Levels can be programmed differently between Segments and between songs.

Metronome

Before programming can take place, the Metronome has to be activated. Once this is done, the sound buttons take on alternative functions to provide 8, 8/3, 16, 16/3, 32 or 32/3 measure lengths. A simpler quarter note click is also available, and strokes tapped in using the different sounds are corrected to the closest beat. This is not dissimilar to the LinnDrum programming method, and like the Linn there is a facility for 'humanising' the patterns once programmed. This takes the form of a Swing control, which has six selectable degrees of possible offset from the 'correct' beat. These 'swing factors'are 50%, 54%, 58%, 63%, 67%, and 71%, and when used sparingly on occasional bars the Swing facility can help to create "a series of segments which are more psycho-acoustically interesting than merely repeating the same pattern over and over" — in other words, more realistic.

Segments

The Drumulator can store 36 rhythm patterns, or segments, in 6 banks of 6. The drum sound Selector buttons double as segment selectors, with the segment being played displayed numerically in the right-hand LED display. The time signature and tempo of a segment can be programmed, and segments can be erased or edited beat by beat. It's also possible to append new pieces to a programmed segment and to define or re-define its length numerically or in real time; the upper right controls for Insert/Erase, Delete/Record, Enter, Step/Sequence Length and Step Back/Measure length between them control these functions.

The Drumulator has several information symbols such as SEGF (Segment Full) and FULL (total memory full) which indicate any possible problems during programming. An attempt to play an empty segment results in a beep, which is equally useful for locating empty segments in order to copy information. Use of the Copy control makes it possible to select a segment and transfer it to any other memory (the previous content of the memory being erased), with a beep confirming successful copying. An Append mode allows several copies to be made in series; this is a useful function, since no one segment can be longer than a quarter of the total memory, and so it's necessary to be able to chain segments as described below.

Songs

As on the LinnDrum, DMX and Korg KPR-77, the Song facility allows segments to be arranged in complex patterns to accompany an entire piece, including (unlike the LinnDrum) an end point. A song can be repeated, or can lead into another song with a different programmed drum mix and set of accents. A song can have up to 99 steps, with the left-hand LED display showing the number of the step being played and the right-hand display showing what occurs during that step — a segment number, repeat, tempo change and so on. To save memory space, repeat commands are used if a segment is to be repeated within a song. A total of eight songs can be programmed, and song programming is, if anything, simpler than segment programming, in that it only uses the upper 8 edit function buttons. It's possible to insert or delete individual segments within a song, provided no 'illegal' commands are given — such as attempting to have one repeat inside another.

Outputs and Inputs

The Drumulator can be programmed to output trigger pulses for sequencers or arpeggiators on every eighth note, eighth note triplet, sixteenth note, sixteenth note triplet, thirty-second note, or thirty-second note triplet. These occur at the rear panel Met/Trig socket, and can take place throughout a song or only in certain segments, so that, for instance, a sequencer could accompany only part of a song without having to be faded in and out.

Other rear panel sockets are as follows. Run/Stop accepts a short-to-ground from a footswitch or synthesiser, while Repeat accepts a similar control in order to override an infinite repeat section which is part of a programme. This allows a solo passage to be of any desired length over a repeating drum backing, the programme continuing only when a footswitch is pressed.

Four Gate Inputs, A to D, accept plus 5 Volt TTL-compatible pulses to play or programme the Drumulator's sounds from external pads. Up to four sounds can be played manually over a programmed pattern which is already running.

Clock Input and Output jacks provide a sync-to-tape facility working on the 24 pulses per quarter note standard of the Roland TR-808, 606, 303, the Korg KPR-77, the PAIA Master Synchroniser and the Alpha Syntauri. The Drumulator can also divide down higher speed clocks, such as the LinnDrum's 48 pulses or the DMX's 96 pulses.

Cassette Dump

Song or segment data from the Drumulator can be saved on tape at any time if it is necessary to clear the memory for more workspace. Save, Check and Load functions are available, with Save to cassette taking about 30 seconds. Errors due to dropouts on the tape produce a bAd display, and programmes can be checked for integrity whether or not they match the contents of the Drumulator. In other words, if you suspect an old tape has been damaged, it's possible to check it regardless of what's in the memory at the time.

It is possible to load a single segment by holding down the Load button and pushing the segment button 1-6 as required. It's also possible to identify songs verbally on the cassette, but as this may possibly cause triggering of the interface it has to be done at a very low level, or listened to with the interface disconnected.

Mixing

The Drumulator doesn't have the onboard mixing and panning facilities of the LinnDrum in an attempt to save cost and reduce complexity. It does, however, have individual audio outputs for the sounds on the back panel. Apart from a composite Mix Out there are sockets for Bass Drum, Snare/Rim-shot, Open/Closed HiHat, Ride Cymbal, Claps, Clave/Cowbell, High/Mid Toms, and Low Tom. The individual outputs are affected by the programmed levels and accents, and this makes it possible to programme a pseudo-automated mixdown for the drum patterns of each song.

For more versatile mixing and for the addition of ambient effects, the individual outputs can be sent to a stereo mixer where reverb, delay, equalisation or effects can be used, in addition to stereo panning. It's also suggested that a chorus unit should be used on the handclap to provide a degree of randomisation.

Design and Construction

The basic objective which the Drumulator designer, Dave Rossum (interviewed in E&MM April '83), had was to develop a drum computer with sampled voices which would retail under £1,000. To do this he has minimised the panel controls and made the most of the single LED display and slider. As he put it - "minimise the hardware and maximise the software — we plan to make a lot of these which makes the software very cheap."

Unlike the Linn, which has a section of memory with its own counter circuitry for each voice, the Drumulator has four 16K ROMS which contain all the voices. To play the required voices the Z80 CPU reads the memory into one companding DAC and multiplexes the signals onto sample and holds. Each channel has its own filter which prevents the distortion associated with such a system.

This does mean that individual voices cannot be replaced, as can be done with the Linn.

The Z80 is made to work very hard in this system since not only does it handle the voice routing but it also controls the programming functions, LED display and switch scanning.

CMOS memory is used for program storage with battery protection, allowing data to be retained with the power off.

All of the components are mounted on the PCB, which was designed using a computer. The circuitry is on one side, with hardware, such as the switches, pots and LEDs on the other. This considerably reduces assembly costs and hence keeps the price down.

No photograph has been provided of the internal construction as E-mu were rather protective towards their new baby, at least until the impending patent has been secured.

Conclusions

Overall, the Drumulator is a very impressive package both in terms of sound quality and programmability. The samples were recorded and digitized at Ayre Studios in California and are certainly convincing.

Programming is a simple task, once the controls have been mastered, allowing a host of complex rhythms to be assembled quickly and easily.

Clever use of the circuitry, rather than cutting corners, has allowed E-mu to produce a professional product at a reasonable price.