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AHB Inpulse One Drum Computer

While they're not exactly the first company that would spring to mind during a discussion on the production of digital drum-machines, Allen & Heath Brenell are nevertheless widely respected as designers and manufacturers of fine recording equipment, so it came as no surprise to me when I discovered that the Inpulse One - their first foray into the world of electronic percussion - was as well conceived and as well executed as their mixers. What was more in doubt however was the company's ability to keep pace with manufacturers of considerably greater research and design experience in what is becoming an increasingly competitive market sector...

First Things First

The Inpulse One comes complete with eight factory preset sounds built-in, these being controlled from the eight pads that take up most of the instrument's front panel. These are touch-sensitive over an approximately 30dB range. A further eight sounds also come supplied with the unit, these being stored in digital data on a standard audio cassette. It is hoped that this philosophy will be extended over the coming months, so that it will be possible for Inpulse owners to buy cassettes of different percussion samples from AHB, these coming from a growing library of voices.

It is not envisaged that the manufacturers themselves will provide optional live pads for the Inpulse, but since each pad has an external trigger input (with adjustable sensitivity) mounted on the rear panel, it should be possible for the user to control the voices from any of the multitude of electronic drum-kits that are becoming available should this be desired. Also on the rear panel is a 40-pin expansion connector, which provides an interface for the Apple II microcomputer and also acts as a connector for future related modules. This interface is also used as an access port by AHB during manufacture. There's also a metronome click output which acts as a guide for real-time playing, while a pulse output - with pulse-rate and resolution programmable from the Inpulse's keypad - can be used to sync the machine to sequencers, other drum-machines, and so on. Finally, SMPTE code inputs and outputs (with a level control for the latter) are provided on quarter-inch jack sockets, which should make working with the Inpulse in conjunction with multitrack tape in a studio environment a lot easier.

Front Panel

Working from left to right, the main control panel can be split into several control sections, and each one of these has a distinguishing letter. Section A contains, among other things, the output stage, which houses a pan control for the overall stereo output, and three pairs of increment/decrement buttons to adjust pitch, decay and level respectively: these operate on whichever pad was last triggered. The decay can be anything from 40ms to about 13 seconds, which is no mean feat.

Section B is to do with recording, programming, and loading data into the machine. There are two ways in which to programme the Inpulse. 'Record' puts the unit into real-time recording in time with the metronome click-track, while 'program' selects step-time recording. When this latter mode is selected, a flashing cursor appears on the Inpulse's LED display, and this is moved from side to side along the LED bar until it reaches the desired point, whereupon a simple tap of the required pad will insert one beat at that point. A second tap deletes the beat. The display also acts as a visual indication during real-time recording.

Further pushbuttons in the same control section select whether a song is to be played once or cycled over and over again. A song consists of any number of bars or patterns up to 199, while each pattern can be between 1 and 32 beats in length.

Section C contains the tempo adjusters and related controls. It's possible to store a particular tempo in memory, while the LED display can be programmed to show Beats Per Minute if you require a visual reminder. Section E is simply the 'stop/go' button which is pretty self-explanatory really, while Section F next to it houses the controls to select the click-track and open or closed hi-hat metronome. Both these sounds can be inserted into the stereo mix if required.

Section D is the display, which has been alluded to above and really represents the Inpulse's nerve-centre. In addition to the functions already described, the display can show the number of beats-per-bar and number of bars-per-song selected, as well as the time-signature (any can be used) and sundry other functions.

Feel And Scatter

Section G is the 'feel' panel. Irrespective of any dynamics that might be programmed into a particular pattern (it is possible to programme a rhythm with no dynamic feel at all, using the 'dyn' pushbutton on the extreme left of the unit) the user can programme accents of as much as 4dB higher or (unusually) lower than unaffected beats, while the 'shift' key enables you to move a beat forwards or backwards along the display by a programmable amount, so that occasionally a voice can be triggered slightly 'off-beat'. 'Scatter' is basically similar to another digital drum manufacturer's 'shuffle', and can be programmed in eighths or sixteenths; the effect can be repeated over one bar or over an entire song.

The remaining control sections contain the numeric keypad and further pushbuttons for control of programming functions. All in all, it must be said that the control layout on the AHB is an extremely logical one, particularly so when you consider the complexity of some of the facilities offered, and should be learned fairly quickly by most users.


Inpulse One is built into a flightcase as standard, partly because its designers had received several complaints from musicians who found other less well-protected devices didn't stand up too well to the rigours of live use. Both the two main component boards are shock-mounted, so all in all the unit should take a fair battering before there's any risk of failure due to maltreatment. Internally, the Inpulse makes use of two Z80 (surprise, surprise) microprocessors, and it is hoped that plans to incorporate a standard MIDI interface into the design should reach fruition soon, when machines not already so-equipped will be able to accommodate it as a retro-fit.

Sound Quality

Shortage of time and the fact that the Inpulse tested was in effect a pre-production sample precluded a thorough subjective assessment of its sonic capabilities, but on the basis of what I did manage to hear, I'd say the AHB could rank alongside the very best as regards sound quality. The bass and snare sounds in particular were virtually indistinguishable from the real thing (though whether or not the purpose of drum-machines should be to imitate real kits is another matter altogether, of course) and the pitch tuning and decay adjustment proved invaluable in creating sounds that were individual without resorting to costly and inconvenient outboard effects units. No other samples other than those for the basic eight-drum kit of bass, snare, hi-hat, two cymbals and three toms were available for evaluation at press-time, but I for one fully expect any future sounds that might become part of the AHB library to live up to the standard set by the voices tested.

It is hoped that additional sounds (which can be assigned to any one of the eight percussion pads) will be available at a very modest cost, and the fact that they are stored on compact cassette should mean there are very, very few Inpulse owners for whom the prospect of using such voices is not a viable one. Even more excitingly, AHB's engineers are currently working on an additional module (to connect to the Inpulse via the 40-way port) which will enable the user to sample his own percussion sounds, or indeed any sound at all of short enough duration. They do stress however that this development is still a little way off, and that, initially at least, the makers' sound library will be the most practical way of adding voices to the Inpulse's repertoire.


Although the world of electronic drums and machines has grown massively over the last two years or so, very few devices could honestly be said to have broken really new ground. Yet it is my belief that the Inpulse One will do precisely that. AHB quote a provisional RRP of just under £2000, which is expensive but not extortionate when you consider the amount of research that has gone (and is still going) into the model's design. The Inpulse would appear to be one of the few drum-machines currently in production whose development can truthfully be said to be open-ended, and in that respect it could almost be seen as the drum-machine equivalent of the Fairlight.

Even given the fact that the most exciting aspect of the design's overall concept is still some way from reaching completion, as it stands now the Inpulse is an excellent device of immense programming flexibility and design sophistication, all within a simple, robust shell. Few people will be able to ignore it with any safety.

Previous Article in this issue

Yamaha MR10 'Finger Pad' Drum Machine

Next article in this issue

Roland TR-909

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Mar 1984

Review by Dan Goldstein

Previous article in this issue:

> Yamaha MR10 'Finger Pad' Dru...

Next article in this issue:

> Roland TR-909

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