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Bel BD80S Stereo Delay/Sampler

As sampling keyboards rapidly reach saturation coverage, is a sampling delay unit which offers 6.5 seconds stereo sampling still a useful tool? David Mellor assesses Bel's new unit in comparison with a more expensive alternative.

What do you think of when you hear the words 'sampling delay'? Alright - after you've thought of that, what do you think of? To me, 'sampling delay' means AMS. Their DMX 15-80S unit is the grand-daddy of all such devices - and it began life as a mere delay unit, with no sampling or pitch changing facilities whatsoever.

The days when delays and echoes were produced by analogue tape recorders are thankfully long gone. Trying to time echoes with the rhythm of the track, using the varispeed control, was a tedious process at best. How much easier it is to set a delay time in milliseconds on a nice bright LED display. The first digital delays had very short memories: they could often only produce a delay of 200 to 300 milliseconds, which is not enough for all the variety of musical purposes one might have in mind. As delay units matured and achieved values of a second or more, people began to assume a look of smug satisfaction - you never need a delay of more than a second!

However, there is always one bright spark who just has to have more. In this case, so the story goes, a film post-production sound engineer had the idea that if the delay could hold sound inside, waiting to be triggered instead of continuously spewing it out, and the length of this sound could be four or five seconds, then it would make dialogue replacement so much easier. Whether this is true, and I expect there are dozens of people who could claim to be AMS's inspiration, I'm sure no-one knew what was going to happen next.

'Put a weird device in a studio and someone will find a use for it' could be the manufacturer's motto. When AMS units with long delay times and sampling capability found their way into control rooms up and down the country, they first found employment replacing drum sounds. You could store a good snare sound in the AMS, then trigger it from the not-so-good one that was already recorded on the track. From that comes the idea that if you have nine or ten seconds sampling time, then you can store a whole line of vocals and play it on to the multitrack master whenever necessary. This technique makes it easy to get four good choruses in a song, without the slog of recording them all separately.

So far, so good. But the AMS is not a cheap gadget. For the price of a new AMS, you could have a decent set of wheels out there on your driveway. Admittedly, AMS have continued to increase the capability of their unit - all but the earliest models are upgradable - but there was a need for something which had much of its capabilities but not all of its cost.

To the rescue, among other companies, came Bel. Their latest offering, the BD80S, is a fraction of the price of an AMS. It doesn't offer real-time pitch changing, but it does offer stereo sampling of up to 6.5 seconds, and mono sampling up to 13 seconds, not to mention MIDI compatibility. Let's examine the unit in more detail.


The BD80S has five beautiful rotary controls which actually have real analogue signal going through the potentiometers behind them. Or at least it feels so much like it that I have been fooled completely. They run as follows: Input, Mix, Feedback, Output, Modulation Speed, Modulation Depth. To put it simply, setting these controls is so direct that you'll have a sound minutes before the guy with the SPX90 has found the right program!

On the right of the unit is the digital section, which is not so straightforward in its operation, apart from the up/down nudge buttons used for setting the delay time. Never mind, the AMS isn't straightforward either and the buttons on its keypad are not marked according to their function - you just have to know what they do.

When you switch on the BD80S - with a loud clunk - it is ready for stereo delay, just set the required delay time. The Feedback control will set the number of repeat echoes, and the Modulation controls will give you a nice chorus effect. Mix, obviously, sets the balance between the clean signal and processed signal. Pressing the Mono switch shunts all the available memory over to the right channel. Strangely enough, the clean signal is still delivered in stereo to the output, although the delayed signal is right channel-only going to the right output. I would rather have had the two channels monoed together and the delayed signal coming out of both outputs - or at least had the option. It's not a matter of urgent importance, however.

Short delays, between 2ms and 20ms, are used to give flanging effects, rather than echo. There are two buttons that can alter the sound produced, these are the Phase Change buttons for the delayed signal and for the feedback signal. Inverting either of these alters the way in which different frequencies cancel each other out, and distinctly different effects can be produced. They are impossible to describe, except that the range goes from the most subtle to the most vicious flanging effects you could possibly desire.

There is only so much you can say about a digital delay unit, as long as it works, but the sampling function of the BD80S is much more interesting. Mono sampling is useful as far as it goes, but very often your source material is in stereo and just cries out to be sampled in that way. It sounds like an obvious thing to want to do, but stereo sampling is still in its infancy at the moment.


Data format: 14-bit
Sampling rate: 40kHz
Minimum delay: 2 milliseconds
Maximum delay (stereo): 6.5 seconds
Maximum delay (mono): 13 seconds

Rotary controls: Input Level, Mix, Feedback, Output, Modulation Speed, Modulation Depth
Note: For stereo sampling, all controls work simultaneously on both channels. It is not possible to set delay times individually for each channel.

Inputs: XLR electronically balanced (pin 3 hot)
Outputs: XLR electronically balanced (pin 3 hot)
External trigger: mono jack

To point out the benefits a machine such as this could have over a sampling keyboard, it is useful to go back to the AMS DMX 15-80S. This unit gets it right. The advantage of a sampler with a limited range of facilities - compared to the keyboard type - is that it can be made very easy to use. To take a sample with the AMS, you just listen to the input signal and when you hear a bit you like, throw the 'Lock' switch. The AMS continuously fills up its memory, and when you have heard what you want and have thrown the switch, then that memory stays fixed. The sample is taken. Editing the sample is more complex, but the initial 'capture' stage is very easy.

Unfortunately, Bel have not made things as simple as that on the BD80S. You have to decide that you want to take a sample, initialise the unit, then you play in the sample. This may seem like a very subtle difference but take my word for it, when you have used an AMS, you don't want to go back. Bel provide luxuries such as audio trigger and MIDI trigger for sample recording. The AMS doesn't need them.

There are two methods of taking samples on the BD80S, the 'Quick Record' method or the 'Preset Record' method. As may be guessed, the second way of recording offers the greater number of facilities. For instance, it is possible to set up the start and end point of the sample before you have taken it. This might sound a bit like buttering your bread before you put it in the toaster, but it means that you can have several different samples in memory at the same time. It's one of those facilities someone is bound to find a use for.

Similar to this are the 'Quick Playback' and 'Preset Playback' techniques. In the recording case and the playback case, 'Quick' basically means that you have to use the Manual Trigger button on the unit; 'Preset' means that you have the option of audio triggering or MIDI trigger.


Before moving on to playback techniques, I must examine sample looping. Bel have found the answer to the problem that seems to baffle keyboard sampler manufacturers. It never seemed to be a problem to make a loop on the AMS unit, so I was surprised that it was so difficult when I took delivery of my Akai S900. In fact, it wasn't just difficult, it took so long that I decided to think of it as impossible and not waste time on it. Akai's version 2.0 software with crossfade looping solved that problem, but by taking the proverbial sledgehammer to crack the equally proverbial nut. The secret to getting a good loop is - perhaps I could sell it for a small fortune, but here I am giving it away! - to edit the loop as it is playing. Now isn't that obvious? You wouldn't think so. All that stuff about zero-crossing points and such like is rubbish. You don't need to find zero-crossing points or points of equal slope or anything like that, you just have to be able to hear what you are doing and it will happen automatically. On the Bel, you can loop sine waves just like that - without crossfading.

As well as editing the loop while it is playing, Bel provide two other helpful features. The first is that you don't have to listen to the whole loop in order to edit either the beginning or the end. This is otherwise tedious when you have a loop of perhaps eight or nine seconds. The Bel unit gives you a 300ms 'window' to play with, which is just what you need. The other feature is coarse and fine editing. Coarse works in 1 ms increments. Fine works in steps of 33 microseconds which, to put it in perspective, is one thirtieth of a wavelength at one 1 kHz. There is ample resolution to find the perfect glitchless loop. There is coarse and fine pitch editing available too, anything from 1/50th of a semitone to one full octave up or down.

Replaying a sample is a simple matter of pressing the Manual Trigger button, or you can plug a MIDI keyboard into a socket at the back and have control of pitch over a two octave range. The thing not to forget is that this is not a sampling keyboard - or the rack-mounted equivalent - so there is no polyphony. Strictly one note at a time. There is the option, however, to have the sample play all the way to its end, no matter how long the key-press, or have it so that key-off means sample-off. The MIDI channel can, of course, be selected, and there is the option of Omni mode if desired.

Rather than MIDI control, I think it is the audio trigger facility of the BD80S which will get the most use. After all, the whole point is to make things simple, and what could be simpler than firing off a sample from the sound of a drum machine, or a real drum already recorded on tape. Thankfully, the response time is fast enough to deceive the ear, and you will not get that 'behind the beat' effect which is always a possibility with devices such as this.

The source for the audio trigger can be either the normal stereo inputs or a separate trigger input on the back panel. The trigger input is a simple break-jack which is activated when you plug into it. This is not a loop-through however, so a patch bay socket could not be normalled to achieve the same effect at a greater level of convenience. Decide which option you want before you mount it in the rack.


What level does your studio operate at? —10dBu or 0dBu? If you use a narrow gauge multitrack, chances are that your signals are peaking at around 0dBu at the absolute maximum. To get the red LED on the Bel to illuminate, you'll have to give it +4dBu, which is pushing things a little. You see, this unit is geared up to professional levels, and in a fully pro studio should cause few problems. If you are working at the lower 'home' level, then you probably will not be getting the full signal-to-noise performance out of the BD80S simply because you can't drive it hard enough - even with the Input control fully up. This is a pity. Many is the time you will want to plug a synth straight into the delay unit. If this is the case then you will be lucky to light up the -6dB LED, which means wasting a good 10dB of performance.

More bothersome is the audio triggering. You will also need to use a high level to get samples to fire. This is a pity because it is limiting the ease of use and versatility of the equipment. You can use it in your -10dBu studio, you'll just find it a little more difficult. Perhaps Bel can be persuaded to fit a 10dB gain switch on the rear panel or advise on a modification to make the unit more sensitive? It shouldn't be too difficult, and it would be helpful to everyone, including the pros who can simply turn the input level down a little. Thank you Bel, by the way, for the Output level control. It's very welcome and often missed off by other manufacturers.



- Although not of broadcast quality, the subjective audio quality is perfectly adequate for all conventional studio delay/sampling applications.

- The analogue controls have adequate ranges of operation apart from the Input Level control, which does not provide sufficient sensitivity for all uses, and the Feedback control, which will not allow 'build-up' of echoes. This could be achieved by other means.

- Audio triggering and MIDI triggering are reliable, and fast enough for replacement of drum sounds.

So, let me put in a nutshell what you can and can't do with the Bel BD80S:

You can take stereo samples of up to 6.5 seconds, or a mono sample up to 13 seconds. Left and right channels can be sampled separately, but all subsequent editing and triggering operations operate on both channels at the same time. Recording and playback can be triggered manually, or by incoming audio or MIDI. Editing is straightforward and quick. Samples can be played at different pitches either by manual editing or via MIDI.

Although I have spent some time comparing this unit with the AMS near-equivalent, I haven't yet considered the price differential. For the cost of a moderately specified AMS DMX 15-80S, you could buy several BD80S's and an SPX90 to handle the real-time pitch shifting. This puts it in the kind of perspective that just has to make you stop and think. Whether you would go the Bel route or perhaps put your money into a sampling keyboard plus a less well-specified delay unit is another matter. It's making this kind of decision that makes studio life interesting.

In all respects, the Bel BD80S is a thoroughly competent machine and deserves consideration - even if you have a sampling keyboard or rack equivalent already.

Price £977.50 inc VAT.

Contact Studio Equipment Distribution, (Contact Details).

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Digital Audio Workstations

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Russ DX7 AI Editor

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Apr 1988

Gear in this article:

Studio FX > Bel > BD80S

Gear Tags:

Digital FX

Review by David Mellor

Previous article in this issue:

> Digital Audio Workstations

Next article in this issue:

> Russ DX7 AI Editor

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