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Lexicon LXP1 Multi-Effects Processor

and MRC MIDI Remote Control

The 'Lexicon sound" for a less than Lexicon price? Matt Isaacson checks out a state-of-the-art reverb unit intended to help make Lexicon a household name.

From a company long associated with expensive, high-quality reverb units comes a cost-effective effects processor - and a remote control with a twist.

MENTION OF THE "Lexicon reverb sound" is sure to raise heart-rates among the recording fraternity. Talk about that sound and a £400 price tag and you could have a couple of cardiac arrests on your hands. But the LXP1 offers 16 preset reverb patterns, 128 user memories accessible with a suitable MIDI controller, a couple of adjustable parameters and mix controls for a tidy £399. Add an optional remote programmer/controller and you have some idea of the significance of this unit.

Panel Stuff

THE SIGNAL LEVELS going into and out of the LXP1 are controlled by the Input, Output and Mix knobs. The first two do exactly what you'd expect. Mix lets you adjust the relative amounts of unaltered input signal and processor output signal appearing at the output jacks. A green LED above the Input knob lights when adequate input level is present, while a red LED nearby lights when the processor is close to overload. Left and right jacks are provided for both input and output. Effects are generated in stereo from any source - stereo source material is not actually processed in stereo, but if the source signal is being "passed through" the LXP1 (as in onstage use), stereo inputs are kept separate when mixed to the outputs. A 16-position rotary switch selects from an assortment of preset reverb and effects programs, and a Defeat jack allows connection of a footswitch for remotely cutting effects in and out.

Next to the program select knob are two more 16-position knobs labelled Decay and Delay. These provide editing control (16 settings each) over two key parameters in each of the available programs. With reverb programs these are as indicated by the labels - reverberation decay time (range varies depending upon the program) and pre-reverb delay (up to roughly 0.25 seconds in all cases). In other programs, the nearest appropriate parameter is adjusted. For example, with delay programs, the decay control adjusts the amount of feedback around the delay line, while the delay control adjusts the delay time. In normal operation, these edits are temporary. If another program is selected, the new program comes in with its default settings for the adjustable parameters and the edit is lost.

MIDI Control

WITH A MIDI keyboard (or other source of program change messages) connected to the LXP1's MIDI In, edited LXP1 programs can be stored in any of 128 internal program memories. Having edited a program, you hold down a button labelled MIDI and send the LXP1 a MIDI program change with the desired program number. An LED next to the MIDI button blinks rapidly for a couple of seconds to acknowledge the action, and you release the button. Incidentally, in the process you've also told the LXP1 which MIDI channel to listen to (it's always in Poly mode). From now on, when this program number is received (and you're not holding down the MIDI button), the program will be recalled in its edited form. Of course, since the front panel is very simple, no readout is provided to indicate the currently selected program number, nor is there any form of memory protect. In fact, since the edit knobs in effect are the readout, the MIDI LED normally blinks slowly if one or both of the adjustable settings in the current program does not match the position of the knob used to adjust it.

If they stopped there, the programmability and MIDI features of the LXP1 would be enough to make it interesting, but both go a good deal further. Lexicon have also included Dynamic MIDI (their registered trademark), a feature first introduced on the PCM70.

As implemented on the LXP1, this allows you to patch virtually any MIDI controller to one of the current program's adjustable parameters so that it can be remotely controlled in real time. This is done by holding down the MIDI button, sending a controller message (say, by moving the mod wheel slightly), and then moving the knob associated with the desired control to establish the software connection between the two. This knob is then moved to a position which sets the scaling (control range) of the incoming MIDI messages - full-scale positive or negative control and a dozen values in between are available. Finally, the MIDI button is released, freezing these settings, and the parameter knob is adjusted in the normal fashion to set the base value of the parameter, from which MIDI control will cause deviation. This procedure can be repeated for the other adjustable parameter as well, allowing dynamic control over each one using separate controllers or a single controller patched to both. If the program storage procedure is now executed, all of the controller-patch info is saved with the program and is available for instant recall. Now you can control reverb decay time, say, with your synth's mod wheel while playing. Another option is varying the length of a delay line under MIDI control. Care must be used in this case - in contrast to typical dedicated DDLs which operate by varying the speed of the through signal in a fixed-size memory block, the LXP1 does this by keeping the speed constant and altering the amount of memory used instead (or moving the taps on the delay line if you prefer). This causes audible glitches if sound is passing through while the control is adjusted.

It's worth mentioning that not only the "usual" MIDI controllers, but note number and note velocity can be used as Dynamic MIDI control sources. Also, in many cases, MIDI control offers greater resolution and sometimes a wider control range than is available from the front panel. And of course, MIDI messages used to control the LXP1 can be recorded into a sequencer which can be used to automate effects changes - possibly the most important use of this capability.

Factory Programs

THE BASIC PROGRAMS which can be dialled up on the LXP1 fall into two main groups: reverb and effects. Within the reverb category are Halls (Dark and Bright), Plates (as per Halls), and Rooms (two each of Small, Medium and Large). I won't try to tell you what each of them sounds like, except to say that they're appropriately named, very clean and smooth, as would be expected from a Lexicon unit (Lexicon claim that the digital portion of the LXP1 has much in common with that of their PCM70).

In the effects category are Inverse (reverse) and Gated reverb plus two each of Chorus and Delay programs. The first two will hold no surprises for anyone who's heard these effects before, but the latter four are more complex than their names might imply. Chorus 1 is a stereo flange program with separate delays for left and right channels. The delays are swept together and are slightly offset from one another to enhance the stereo effect. With control over feedback and delay time, this provides sounds ranging from subtle chorusing to heavy flanging. Chorus 2 is actually a set of 12 resonators tuned to chromatic intervals (with alternating intervals panned left and right) and adjusted to near-oscillation. The resonators are set ringing by musical tones of related frequencies, in much the same way as the strings of a piano vibrate sympathetically in response to ambient sounds. Control is provided over resonance and fine-tuning of all the resonators as a group.

Delay 1 at first sounds like a conventional single delay, but the delay output is in fact a six-voice random chorus (three stereo pairs) with main delay adjusted in tandem and feedback around one of the chorus voice pairs. Finally, Delay 2 is a four-tap delay in which successive taps are panned to alternate sides. In this program the delay control simultaneously adjusts the delay between adjacent taps to keep them evenly spaced.


HALF OF THE LXP1 manual is devoted to a detailed description of its MIDI System Exclusive implementation.

It reveals that all of the programs in the LXP1 actually have more than two adjustable parameters - some have as many as nine, none have fewer than seven. For example, the Reverb algorithm parameters include Decay Time, Pre-Delay Time, Pre-Delay Feedback, Size, Diffusion, Bass Multiply, High-Frequency Cutoff, and Effects Level, of which only the first two are adjustable by any means other than SysEx messages. In fact, all of the preset Room and Hall programs are variations on one algorithm created by using different settings of the remaining parameters. Thus, the edit knobs and Dynamic MIDI control discussed above only scratch the surface of the LXP1's programmability, while the 16 presets represent a small subset of the huge number of programs possible. What's needed is a convenient way to access these hidden programming features - which brings us to the MRC MIDI Remote Controller.


THE MRC IS a software-configured multi-purpose MIDI control panel. Its sole raison d'etre is to control other pieces of MIDI equipment, with the emphasis on equipment of the Lexicon kind. Amongst its other functions, it serves as a "full" front panel for the LXP1, providing easy access to its SysEx programming options. It can also be used as a high-level editor for Yamaha DX/TX six-operator FM synthesisers.

Physically, it's about the same size as the LXP1 and housed in a smart-looking black moulded-plastic case suited to table-top use. Its most prominent feature is a 2X24-character backlit LCD. Directly below this are four undedicated switches, and below these are four slide pots, also unmarked. The functions of these switches and sliders are determined by the current operating mode of the MRC. There are also an assortment of dedicated switches used to select operating modes or enter numerical information. On the back panel are two MIDI Ins, two MIDI Outs, and two ¼" jacks which allow the connection of external controls such as volume pedals.

How It Talks

FOR BETTER OR for worse, the MRC's MIDI Ins and Outs are in two separate sets - messages arriving at input 1 can be echoed only to output 1, and likewise for the other pair. While this means that a single master keyboard cannot directly drive slave synths on both outputs, it isn't really a typical application for the MRC. On the other hand, if you want to independently control two LXP1s from the same MRC, this isolation of the outputs makes the setup very simple.

The MRC also supports "interactive" System Exclusive editing modes in which the target device responds to parameter dump requests issued automatically by the MRC. This is mainly for the FM programming mode and allows the MRC to have full knowledge of the current settings in the synth, as opposed to knowing only the ones which it has lately sent to the synth. It can use this information both to modify its own behaviour during the editing process and to ensure that any setups which it stores in its own internal memory are complete and repeatable. This bi-directional communication requires that the MIDI Out of the synth be connected to the corresponding MRC MIDI In. Since this complicates the inclusion of a master keyboard into the system (an external merge box is needed), it's better suited to use with a DX keyboard than with a TX rack module.

MRC Operation

THE MRC PROVIDES ten "slots" which can be configured as various machines and can be rapidly recalled. At present there are four machine "types" defined inside the MRC: LXP1, PCM70, DXTX6 (FM synths), and GMIDI (generic MIDI). Each of the machine slots can take on one of these four personalities - having ten of them means you can control multiple identical devices by putting them on different MIDI channels and/or MRC Outs. The machine types themselves are not user-definable.

The basic property of each machine type is its use of the front panel resources as program editing controls. While operating any machine type, the LCD is divided into four fields, each of which is associated with one of the sliders. Each field shows parameter names on the top line and current values on the bottom. A Page button cycles through different groups of settings which are active on the sliders while visible - the MRC thus allows editing of 7-8 settings on the LXP1 (depending upon the processing algorithm in use), 12 on the PCM70, and 15 on DXTX6 machines.

It should be mentioned here that for the Lexicon machines, these settings correspond one-to-one with specific editable parameters in the target machines, while for DXTX6 machines, editing is done on a set of "virtual settings" such as Brightness and Waveshape. The MRC handles the dirty work of translating these edits into the much less intuitive FM language by means of what Lexicon calls "macros" - software constructs which give a single name to a control that affects a large number of FM parameters simultaneously. As implemented on the MRC, this technique does not give access to the full range of FM parameters or sound types, but instead aims at "middle ground" FM, encompassing many conventional musical instrument sounds.

The result of this compromise is to make FM programming more approachable. While no substitute for direct "low-level" FM programming, it's certainly a powerful tool when combined with the "direct approach".

Associated with each machine type is a bank of setups (32 for each type except GMIDI, which has ten), each of which can be given an eight-character name. For the LXP1, PCM70 and DXTX6 machine types, each setup holds a set of program parameters which can be transmitted at any time to the device in question as a SysEx program dump (this occurs automatically when a setup is selected). In addition to transmission of individual setups, the MRC can dump all of its setups to all defined machines in a single operation, providing an easy method of setting up an entire system at the beginning of a session. The parameter information stored in each setup includes the digital processor or FM algorithm setting, which the MRC also uses to decide which parameters should be made available for editing (in the case of reverbs) or how FM virtual settings should be translated into actual FM parameters.


THE GMIDI MACHINE type is a bit different from the others. Instead of addressing itself to the task of SysEx programming of a specific unit, it deals with performance control of any type of MIDI gear by means of standard messages - mainly channel messages such as switch and continuous controllers and program changes (although just about any message is available, including note events and sequencer Start, Stop and Song Select). Thus, GMIDI setups contain no program parameter information at all - instead they hold complete configuration information for all of the controls on the MRC, including the external pedal inputs and the four undedicated switches below the LCD.

Programming of GMIDI setups is a bit bewildering at first because of the large selection of MIDI "destinations" available for each of the ten control sources, plus fine-tuning options associated with each destination. Fortunately, programming in general is easy because of the way it is presented. Operating under a GMIDI setup is in some ways simpler than with other machine types, since all switches and sliders are active with their assigned functions at once - you deal with the LCD and the Page button only if you need to know the precise value of a particular control (usually you don't).


THE MRC IS the type of device which I would expect (or at least, hope) to see from other manufacturers before long. It offers a neat solution to the dilemma of in-depth programmability versus low-cost front panels. By making the front panel a separate device, there's no need to duplicate its hardware in each box which it controls, which lowers the cost of these boxes. It also centralises the management of program data. And not least, by throwing in some encoded equipment-specific intelligence, the programming process itself can be made more accessible and less tedious. Finally, in combination with the LXP1, you have an excellent-sounding, highly-programmable and very small digital effects system. It's worth a close look.

Prices LXP1 £399; MRC £324. Both prices include VAT

More from Stirling Audio, (Contact Details).

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


Music Technology - Dec 1988

Donated & scanned by: Mike Gorman


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Gear in this article:

Studio FX > Lexicon > LXP1

Remote Control > Lexicon > MRC

Gear Tags:

Digital FX

Review by Matt Isaacson

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