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Lexicon PCM70

Paul White gets to grips with the first digital reverb to be fully touch-sensitive over MIDI, and finds it throws a whole load of additional effects into the bargain.

Lexicon's new PCM70 is much more than a good digital reverb: it has a number of unique delay features, and allows you to control its effects dynamically from a MIDI keyboard.

First, a word of explanation. The Lexicon PCM70 isn't really a digital reverb at all. For once, the name on the panel tells no lies, and 'Digital Effects Processor' sums up the machine's function nicely. It can produce a wide range of reverb effects (including gated and infinite varieties), but it's also capable of performing a good many other musical functions, such as flanging, chorus, echo, multi-delay and resonant chord programs (see later), all in stereo.

The newest Lexicon comes with around 40 preset reverb and delay effects, and room to store around 50 more of your own edited versions — the exact number varies slightly depending on the current software version.

It's a MIDI-compatible unit, so you can change its programs remotely from a MIDI synth or sequencer. More than that, the PCM70 recognises MIDI note number, velocity and pitchbend information, so you can vary its effect parameters directly from the controlling keyboard. For instance, you can alter the reverb decay time according to the note played, or change the feedback of a delay patch from your synth's bend wheel.

For a box that does so much though, the PCM70 has relatively few controls. A multi-purpose display unit lies at the centre of operations, and to the right of this is a rotary controller that turns indefinitely, known as the Soft Controller. At various points in the manual's text, Lexicon shorten this to Soft Knob, but for reasons that should be obvious to most of you, I'll continue to refer to it by the former name. Whatever you call it, though, the control can be used to alter just about anything that's alterable on the PCM70, in conjunction with the two rows of switches to its right.

There's a pair of increment/decrement buttons and a set of pushbutton switches numbered 0 to 9, and these are used to access presets, user programs and parameters.

Further to the right is a cluster of four switches that determine which mode the machine is in. PRG selects the preset programs, REG calls up the user programs, LOAD lets you load up any selected effect ready for use, and BYP (for bypass) sends the signal to the output in much the same state it was in as it entered the machine, muting the effected part completely.

You call up Parameter mode when you want to create new effects, a process that involves loading a preset sound and then editing it, rather than starting from scratch with a 'non-effect'. The variable parameters depend on the patch called up, but for reverb, you can select from plate or room simulations and alter pre-delay, reverb time, high and low frequency damping, dry/FX balance and level. Additionally, you can alter the attack time of the initial reflections, reverb density, and even add chorus and gating to the reverb treatments.

There's a good deal more besides — depending on which preset you start out with — but if I mentioned them all, you'd probably get bored halfway through. Instead, I'll describe some of the effects in each category (and row number) and comment on any outstanding features.

Row 0 contains the Chorus, Flange and Delay effects, and these include some extremely effective multi-tapped delay treatments. Preset patches include Spin Echo, Swarble and Psycho Echoes, names that all seem quite appropriate once you've heard the relevant effect. In this row, it's possible to alter the delay time of each of six taps, all of which have individually adjustable delay time, feedback and pan position. Maximum delay time is 432mS.

Row 1 contains what are referred to as Multi-band Delay programs. Again, these have six available taps which have independent level, delay, pan and HF/LF filtering, but the first two voices or taps have further control over feedback, while a master diffusion control affects all the taps. Maximum delay time in this instance is higher, at 936mS.

Row 2 brings us onto the mysterious Resonant Chord programs mentioned at the start. Everyone knows what flanging, phasing and echo effects are, but resonant chords? Well, here's my attempt at an explanation.

You may be familiar with the effect achieved by setting up a delay unit to give a very short delay, and then applying feedback. On feeding a drum beat into the unit in question, the delay line resonates and produces a distinctive note, the pitch of which can be varied by changing the decay time. The Lexicon goes one better than this by offering six such delays. These can be tuned to the notes of a chord and then sequenced, so that an input creates an arpeggio as the different resonances are excited in sequence. Each of the six resonators has variable level, pitch, duration and high-frequency cutoff. In addition, there's a master resonance control which increases or decreases the resonance of all six sections simultaneously.

Along with several other effects available within the PCM70, the resonant chord programs contain the letters BPM — standing for beats per minute — in their names. This facility enables you to program the rate at which the effect occurs in beats per minute, so you can match the tempo of the effect to the piece of music you're working on — especially neat if your music is playing to the metronomic beat of a sequencer or drum machine.

Remember, though, that the resonant chord feature is only really usable on voices and instruments if the notes of the arpeggio don't clash with the key of your song. To this end, the selection of treatments contains major, minor, seventh and thirteenth chords to get you started, and the overall pitch can be controlled in semitone steps.

If you doubt the validity of this feature (as I did initially), bear in mind that with it, a single drum machine can be made to sound like an entire backing track in any key of your choice, and that the pitch of a chord or arpeggio can be varied via MIDI to produce different musical arrangements. It's a must for anyone involved in recording ambient or mood music — the more you play with the section, the more you discover.

Row 3 contains a selection of Concert Hall reverb programs of fairly low reverb density. All the reverb parameters can be changed to produce a wide range of user reverb effects, making this section an obvious source of building blocks from which to edit your own reverb patches.

The same can be said for Row 4, designated Rich Chamber. This sounds like Paul Ghetty's loo, but turns out to be a source of good general-purpose reverb treatments — useful if several instruments within a mix need to be processed at once, as many of the effects are clean and unobtrusive.

Row 5 presents a selection of Rich Plate programs, which are a fine basis for percussion treatments, as they're bright and have a high level of initial diffusion.

Incidentally, all the Lexicon's reverb programs offer around 20 user-variable parameters which the manual lists in the form of a set of tables, and gating may be applied to any reverb setting via the editing system.

Row 6 doesn't contain any new effects as such, but is used to store existing programs whose patch parameters are assigned to specific kinds of MIDI data. Patches exist for controls that feature on many popular synths, but there's no need to worry if you need something a little different, because you can edit the patch parameters to suit your own needs. For example, the Lexicon's Mix parameter is assigned to operate from the data entry control fitted to most synths, but you can change this if your synth doesn't use a data entry controller.

All these pre-programmed patches are detailed in the manual, and editing isn't too difficult once you know what you want to achieve.

Row 7 contains switching software that takes care of memory protection, autoloading and MIDI mode and channel assignment. The PCM70 transmits and receives on all 16 MIDI channels with Omni, Poly or Mono status, and note numbers between 0 and 127 are recognised, as are program changes over the same range.

Objectively, the Lexicon comes with a fairly high technical spec in terms of dynamic range, bandwidth and distortion, the figures being 80dB, 20Hz-15kHz and 0.05% respectively for the effected sound.

Subjectively, there's little to choose between the new generation of digital reverbs, though they all sound subtly different when compared directly. Digital reverb always sounds artificial in test conditions, but it's an artificiality that's become accepted as the norm, and there's no real harm in that. If a machine saves you having to take your drum machine into a Cappadocian cave and gives you a sound almost indistinguishable from what you'd have achieved had you done so, it makes sense to use it.

The PCM70's reverb programs are of high quality, and their range is amongst the most flexible available; the only obvious omission is a reverse reverb preset, and no way that I could find of simulating one.

The delay effects are of a similarly high standard, and the multi-delay treatments are particularly versatile. The only problem here — and this is something relevant to all machines that combine reverb with longer-delay effects — is simply that you can only use one effect at any one time. Thus, in a recording situation, you're forced to use chorus and flanging effects as you lay the tracks down if you want to use reverb during mixdown. An important practical consideration, that.

The Lexicon is surprisingly easy to use: you don't have to keep going back to the manual to find out what the controls do, as the operating system is utterly logical. However, there are so many parameters to edit that it's all too easy to feel obliged to alter every one of them. Further proof that the more options technology gives you, the more confused you're likely to become.

It's an expensive machine, this Lexicon, and I can only recommend it if you have a real need for its auxiliary effects and/or its unique facilities like the resonant chord feature and the beats-per-minute programmability. If you don't, you can get a good reverb-only device for about half the money.

Still, this is the first digital effects unit to offer dynamic MIDI control over reverb and delay parameters, and I suspect that for many keyboard players, this will prove an irresistible attraction.

Price RRP £2127 including VAT

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Talk Talk To Me

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Sequential Prophet VS Polysynth

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


Electronics & Music Maker - Mar 1986

Scanned by: Stewart Lawler

Gear in this article:

Studio FX > Lexicon > PCM70

Gear Tags:

Digital FX

Review by Paul White

Previous article in this issue:

> Talk Talk To Me

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