As the demand for sampling digital delay lines becomes more widespread, many machines are compromising sample length for sound quality, or vice versa. We test a British machine, the Bel BD240, that does neither.

The trouble with reviewing effects units is that you can easily become carried away (and some of us should, I know) with the sounds they help to produce. A simple echo unit can keep me amused for hours; let me loose on a digital delay-cum-sampler and you've lost me for days.

Some while ago, Bel introduced just such a range consisting of three models: the BD80, BD240 and BD320. The figures refer to the maximum delay/sampling time available in tenths of a second, and are shown on the LED display at switch-on. Just in case you forget, the display stays there for a full minute (30 seconds on the BD80) while random data from memory is dumped, so make sure the unit is switched on before you start your hour in the studio. The standard units have far less memory, but you can add to this in three stages with the help of plugin boards. Some links must be removed during the process, but they don't constitute anything the average musician/E&MM reader couldn't handle.

It was the BD240 with a full 23,830ms (that's nearly 24 seconds to you) delay which found its way into my grubby hands. It's nicely designed, being two 19"-rack units high and finished in matt grey. The extra height over the fashionable 1U design has more than aesthetic value, as it means there's plenty of room in which to select functions and alter values - no ergonomic fiddliness here. Unlike the current digital-access, increment/decrement brigade, the Bel has lots of buttons to push and knobs to twiddle, so I might as well get down to describing them and their functions.

The delay or sampling time is indicated in the LED window and set by pressing four buttons. Two of the buttons are for counting up and two for counting down, with fast and slow versions for each. In everyday use, I found the display didn't respond very quickly or accurately to the buttons: it was sometimes necessary to jab at them to reach the exact time required. In fact, I even managed to get the BD240 to oscillate between 2999 and 3000ms. A veritable niggle, especially when you're experimenting with effects and altering the times constantly.

With such a wide delay range, there are few common studio effects the Bel can't produce. No hints are given - either on the unit or in the manual - as to which delay ranges produce said effects, but the chances are a prospective purchaser would know these things already.

The Input and Output controls have to be tweaked carefully to produce the best results, but then the manufacturer who comes up with self-adjusting level controls will do very well, thank you. The Bel's Input socket is balanced, but you can unbalance it quite easily.

A Delay Phase button changes the phase of the delay signal, and a Feedback Phase button changes the phase of the feedback signal. Two Oscillator controls-governing speed and depth - sweep the delayed signal up and down, while an LED gives a visual indication of the speed.

Using these three controls, some pretty impressive chorus, flanging and ADT effects can be produced. A Filter button attenuates the high frequencies when the feedback signal re-circulates for a more natural echo. Add a Dry/Delay Mix control and another for Feedback level and you have a neat, comprehensive delay machine which, thanks in part to those modulation and phasing options, is a good bit more versatile than much of its immediate competition.

A switch labelled 'Delay X2' doubles the delay time but halves the bandwidth. On the BD240, this gives you almost 48 seconds' worth of delay at 9kHz: almost long enough for half a song, and certainly long enough to sample a jingle. If only you could save these samples...

Onto the sampler proper. There are no simple Record, Hold or Playback buttons on the BD240, omissions which betray the machine's DDL origins. Sync, Start/Stop and Hold buttons take their place, and these must be used together in cunning - and not terribly obvious - combination in order to produce sampled sounds.

To record a sample, you proceed as follows. Ensure the Loop Reset switch is in Normal position, press the Sync button, set your required sampling time, turn down the Feedback switch, press the Bypass switch to bypass the delay circuitry, wait until the LED decimal point is steady, press the Start/Stop button and then press the Hold button. To play back, press the Bypass button again to re-enable the delay circuitry, and press the Start/Stop button to play the sample. If the Sync button is released, the sound loops. When the Loop Reset Switch is in the Normal position, the sample plays through to its end, ignoring any attempts to re-trigger it; in the Reset position, each re-trigger causes the sample to play from the beginning.

All in all, the above process does seem like a bit of a palaver, especially when so many samplers are becoming more straightforward to use. I'm sure the whole sampling procedure could have been made simpler, but that said, the process is far simpler than it reads.

A more irritating gripe is the lack of an audio trigger to get the sampling ball rolling. In other words, you have to press the Start/Stop button fractionally before the beginning of the sample you want to take - which means that if you want to record the attack portion of a sound properly, you need pretty nifty fingers. In practice, this means it can take an age to capture a perfect sample, so a serious omission there, I'm afraid.

Once you've got a sample inside the Bel, however, you can do a number of things with it. You can make it loop by releasing the Sync button, but there is invariably a glitch at the start of the sample. This may be acceptable on long samples, but it precludes the possibility of generating a long note from a short sample, for instance, and won't be appreciated by users for whom ultimate fidelity is paramount.

There's also a simple editing facility by which several samples can be played one after the other. This is done by recording each sample with a successively shorter sample time. The Bel's memory remembers information stored above the delay time, so reducing it does not automatically lose it, as long as you're pressing down either the Sync or the Hold buttons. A number of novel effects can be produced in this manner, but the dreaded glitches still appear between samples.

It would have been nice to be able to chop the sample up and take slices out of it. As it is, reducing the time after recording a sample removes time from the start. And you still can't get rid of the glitches.

On the credit side is an Overdub facility, which is great for building up thick sounds such as big choirs or rich strings. All you do to start this process is to mix some of the existing sample with the new one, by setting the Feedback control to around 2 or 3. By adjusting the Input and Feedback levels you can vary the mix, though if you make a mistake, it's back to square one.

"Specification: Halving the bandwidth gets you almost 48 seconds' worth of delay at 9kHz: almost long enough for half a song, and certainly long enough to sample a jingle."

The modulation oscillator can be used to affect the samples, as can the X2 button which, when used in conjunction with the Pitch control, can produce a pitch range of over two octaves up or down. So now you know how Barry Humphries does it.

To make the most of any sample, you need to be able to play it back at different pitches and the BD range, in common with other samplers, lets you plug in a keyboard to do this. In the case of the BD240, said keyboard has to be a 1V/octave model, and the (always monophonic) playback range is limited to around two octaves. Few of today's synthesisers offer a CV output, but my favourite music shop, Rock City, came to the rescue with a Roland SH101.

Try as I might, however, I couldn't get the SH101 to tempt the BD240 into responding to anything other than its very lowest octave, and even that did not produce a perfect scale. The moral seems to be to check that your 1V/octave source falls in the range the Bel responds to - take it along with you and try before you buy.

There's no MIDI connection on the BD240 and that, again, is a sad omission. Many potential users - be they primarily musicians or studio engineers - may have a 1V/Octave keyboard in the cupboard under the stairs, but many more will have part-exchanged them for something housing a MIDI socket. After all, MIDI connections are generally more reliable, pitch-wise, than their traditional analogue counterparts.

Other gadgets and gizmos as yet unmentioned include an external audio trigger socket, which triggers the sample whenever a suitable audio signal is applied. This is useful for connecting things like drum-machine triggers, and there's no doubt that good old-fashioned analogue technology does this job just as efficiently as the MIDI kind. Outputs include a Direct Out, a Delay Out and a Mix Out, each having a jack and an XLR socket - fine for patching into either a recording mixer or live PA.

With a bandwidth of 18kHz, sound quality should be high, and subjectively the BD240 lives up to the promise of its paper specification. In fact, I'd say it's one of the best-sounding DDLs available, and for that reason, obviously well-suited to studio use.

On the whole, sound quality is one of the Bel's strongest points. In addition, there's the extraordinarily long delay and sampling time, the ease of use in most areas except sampling, and the reputation of a company with long experience of producing sturdy, reliable machines for professional environments.

But the debit list is also a long one. The lack of MIDI may not bother some studio owners, but to keyboard-playing musicians and, to some extent, modern small recording studios, the missing five-pin DINs may prove critical.

On a similar tack, programmable memory locations are also a major and important omission. Their inclusion obviously requires a fair amount of chip memory and software-writing on the designers' part, but the benefits they provide - preset effects to act as a basis for user-programming, instant storage and recall of favourite patches - are too great to be forsaken at the altar of R&D costs. If the BD240 had memories - even just eight or 16 - and they were selectable via MIDI, it would be a whole lot more useful both live and in the studio. There's nothing in the way of external memory connection, either, so you can't dump the contents of the Bel's memory to an outside storage medium such as cassette or disk.

Curiously enough, it's precisely these sorts of modern facilities that will shortly be offered by Bel's new BDE series of upmarket digital effects processors. The BDE2400 and BDE3200 offer the same sampling times and bandwidth figures as the BD240 and BD320 respectively, but add an 89-patch programmable memory, MIDI control of pitch and pitchbend, and the option of a dual disk drive for external memory storage. Intriguingly, they promise comprehensive built-in sequencing sections, too.

As it stands, the BD240 is a fine starting point for sound-processing experimentation, and offers a sampling facility that doesn't sacrifice quality for length.

But it lacks the sort of controllability that other modern machines can offer in abundance, and if that's the area of performance that appeals most to you, Bel's BDE series shows more promise.

Thanks to Tom Cleugh and the boys at Rock City for their help with the loan of ancillary equipment for use in this review.