The science of digital sound sampling has been with us for several years now, but the affordable version never looked like it was going to arrive in the music shops — until now. Paul White reports.

Electro Harmonix have always had a reputation for building inexpensive effects units that deliver a strong sound, and now, after the arrival of designer David Cockerell (formerly of EMS) they have produced these simple to use sampling devices at a price that should be within reach of most musicians who take their work seriously.

Theory

Both these devices utilise digital storage, not to be confused with digital tape recorders: there is no tape and no moving parts.

The sound to be sampled is converted from its analogue form into a series of numbers, which are then stored in a random access memory (or RAM) in much the same way as in a home computer. Some time later it is replayed via a converter that restores the original analogue form.

Sampling theory dictates that the waveform must be sampled at a rate which is at least twice that of the highest frequency to be stored, and because of the limitations imposed by filter circuitry, a practical figure is nearer two-and-a-half times.

This means in effect that more memory is required to store a given length of sound at a large bandwidth than at a smaller one, and these parameters have to be juggled carefully by manufacturers in order to produce the right balance of delay time, sound quality and cost.

Both Replay devices have had to compromise on bandwidth in order to obtain relatively long storage times, but even so, the subjective results are fairly bright and not too noisy.

The Instant Replay

This is the cheaper of the two units and, like its more sophisticated relative, is built into the characteristic Electro Harmonix stainless steel box that will be familiar to owners of old Clone and Electric Mistress pedals.

Both pedals were reviewed at Syco Systems with members of staff in attendance, meaning that we couldn't pull them to bits as is our general practice and can't therefore comment on the units' internal construction, but I would imagine that the PCB is suspended from the controls in the usual EH manner: not particularly elegant but generally satisfactory.

The Instant Replay is designed mainly for the user who wishes to store percussive sounds, and these may be retriggered by means of the touch-sensitive drum pad supplied or by an external trigger pulse from a drum machine or synth. As the trigger input has a variable level control, the unit can be made to trigger from analogue signals (such as the voice output of a drum machine), enabling a variety of triggering sources to be employed.

Recording is very simple. A recording level LED is provided which should just glow at the loudest part of the sample, and once this has been achieved, pressing the Record button erases any previous samples. When the required sound is presented to the input, the LED flashes and the unit starts to record, thus ensuring that the sample starts in sync with the trigger pulse during replay.

The stored sound may be set to single-shot mode or repeat, in which the sample will cycle continuously: the one-shot mode is obviously the more useful for percussive sounds. A two-octave tuning range for the sampled sound is available by means of the pitch control, giving a maximum sample time of two seconds, and an external frequency input is fitted so that a keyboard producing a pure tone may be used to exercise a degree of pitch control over the stored sound.

The Super Replay

Working on a similar principle to the Instant Replay, this upmarket version offers a maximum storage time of four seconds, the frequency being controllable by any monosynth having a one-volt-per-octave control voltage output and a suitable positive gate output.

The pitch of the stored sound may be fine-tuned by means of the pitch slider, while a Superimpose button allows a new sound to be recorded on top of the original, though perhaps not surprisingly, the sound quality deteriorates slightly every time this is done. Two or three layers may be recorded without problems, however, and a metronome beat sounds during recording to assist in the judging of sample length.

A Blend control allows the replayed signal to be mixed with the incoming audio signal, and a Decay Time control causes the sample amplitude to decay at a pre-determined rate when the key of the controlling synth is released. This facility is very useful and can be used to modify the envelope of the stored sound, enabling some quite novel sonic effects to be created.

Conclusions

Both units worked as they should do with no problems and, although their sound quality is undoubtedly a compromise, it is still more than adequate for live use or semi-pro recording.

The Instant Replay is really limited to use with percussive sounds, but it does this job very well. The Super Replay, on the other hand, is the more interesting unit as it opens up the possibility of keyboard-controlled sampling, albeit over only a two-octave range.

My own impression is that these devices are rather expensive considering the sound quality and facilities on offer, and their less-than-impressive appearance does nothing to dispel this feeling. However, if these are the sort of facilities you're after, there isn't much choice at this end of the market - yet!

The Instant Replay retails at £299 including VAT and triggering pad, while the Super Replay costs £499. Further information is available from the UK distributors, Syco Systems, of (Contact Details)