Lexicon MPX1

Paul White explores the far reaches of space with the first of a new generation of effects processors from Lexicon.

Last month, we previewed Lexicon's new MPX1 digital effects unit. Now we've managed to get hold of one for a little longer — and this time it's equipped with the latest software. Judging by the introduction in the manual, this is just the first of a new series of Lexicon mid‑price effects units. In the case of the MPX1, the underlying philosophy seems to be to provide access to multi‑effect algorithms while not compromising on reverb quality. By contrast, some multi‑effects units divide their processor power up in such a way that the more effects you have, the less power can be dedicated to reverb.

Lexicon get around this by using one of their LEXI Chip 2s to handle the reverb, and a separate DSP to handle the remaining multi‑effects. In this respect, the architecture is not dissimilar to that of the PCM80, which also uses a LEXI Chip 2 plus a DSP chip, but the MPX1's processor can create more simultaneous effects than the PCM80 is able to. However, the PCM80 uses both the LEXI Chip 2 and the DSP to build its reverb algorithms, so this would suggest that the MPX1 reverbs are slightly less complex than those in the PCM80. In fairness, one shouldn't compare the PCM80 with the MPX1, as they are designed for quite different tasks — but people are bound to ask!

In theory, the MPX1 can handle up to four effects at one time as well as stereo reverb — the first preset manages five, but one of these is only volume. More often than not, you're restricted to reverb plus two or three additional effects, depending on which algorithms are chosen. The basic effects types are listed as Pitch, Chorus, EQ, Mod, Delay and Reverb, though as you might imagine, these are further sub‑divided and, in fact, provide 56 different effect algorithms in all.

To clarify the MPX1's market position, the new unit comes beneath the PCM80 but well above the LXP15. The PCM80's sophisticated multi‑tap delay architecture allows it to produce resonant chord programs as well as complex stereo delays, and it also has more complex editing options. What's more, the PCM80's card slot enables the user to load in new algorithms, not just new presets. On a subjective level, the reverb section of the MPX1 sounds roughly comparable to that of the PCM80, though some of the algorithms differ in structure and type and they don't have such sophisticated delay elements around them. However, the MPX1 has Ambience algorithms, which the PCM80 does not have. Before the MPX1, you had to buy a PCM90 or one of the high‑end units to get the Ambience effect, and while the algorithm has been scaled down to make it run on a single LEXI Chip 2, it still sounds extremely good.

Lexicon are aware that in‑depth programming of the PCM series is quite heavy going, so they've given the MPX1 a new and ostensibly simpler operating system, including a comprehensive database sorting option. Here effects can be sorted by name, number, source type or effect type.

To my ears, the quality of the reverb is the equivalent of that in the PCM80.

To make the MPX1 as flexible as possible, the effect blocks may be connected in any order (up to the maximum the processor can support), with numerous series/parallel routing options. Each block can be edited independently, and many effects have tempo‑related functions that can be modified by means of a real‑time tap function. The comprehensive internal modulation matrix has been brought over from the PCM series, allowing various effect parameters to be modulated via on‑board LFOs, input envelopes, pedals, MIDI data, arpeggiators, random function generators, and so on. While you don't have to get involved with this if you don't want to, it does allow the ambitious sound designer plenty of scope for creating unusual effects that respond to the dynamics of the signal being treated. What's more, the arpeggiator may be triggered by a single MIDI note to produce an arpeggiated MIDI output for driving other MIDI sound modules.

Some of you may remember the Lexicon Vortex, a delay/modulation box with some interesting morphing capabilities. The morphing process involves the real‑time modification of the parameters of one effect so that it gradually changes into a second effect. Often, some extremely unusual iterations are to be heard along the way. While the Vortex was a budget box and had several weaknesses which Lexicon readily acknowledge, the morphing concept was a good one, and has been included in some of the MPX1's preset effects. If morphing is available from within a patch, the A or B LED adjacent to the A/B button will light to show that it can be used. When you program your own effects, any parameters can be patched to morph between two sets of values.

Taken in isolation, most of the effects are very familiar, but the ability to route them in various configurations, and to modulate, or even morph, them in unusual ways means that some of the effects sound far more complex than you'd expect from looking at their component parts. Another surprising inclusion is a sweepable analogue filter emulation, which may be controlled by input envelopes, ADSRs, LFOs, MIDI note triggers, and so on, in true analogue synth fashion.

The Hardware

In its styling, the MPX1 follows the usual Lexicon 1U format, and features the PCM‑series black and blue livery, but the control surface is quite different to the PCM series, and seems a little simpler. Both an alphanumeric display window and a large numeric indicator is fitted, and a quick glance around the back reveals both balanced XLR and balanced jack audio ins and outs (switchable ‑10/+4), S/PDIF digital I/O on gold‑plated phonos, a full complement of MIDI In, Out and Thru sockets, and two control jacks for a footpedal and a footswitch. Power is directly from the mains — no adaptors.

The front‑panel controls are limited to input and output level knobs, a data entry Value knob and two small groups of buttons, one set relating to the effect blocks and the other to access various editing options. Tap and A/B buttons provide a real‑time means of interacting with the effects — see 'Tap & A/B Buttons' box for details. The Value data knob does different jobs depending on whether you're in Program or Edit mode, and on whether or not the Value button has been pressed. When Value is pressed, the functions of the knob and the left/right arrow keys are reversed. While this means you can decide whether to use the knob or the buttons to work with (and there's no disputing that it's fast when you're working your way through long menus), I found it potentially confusing and frequently hit the wrong control, leaving me to figure out how to find my way back.

It's worth mentioning that Lexicon have worked hard to reduce the time it takes to change patches. They seem to have achieved this by getting the various effect blocks to load in order, and while the beta software took the best part of a second to change patches, the latest version seemed at least four times as fast.

Organisation

In all, there are 250 on‑board memory locations, configured as 200 presets and 50 user patches. Calling up a patch is a matter of using the value knob to scroll through the patches while in Program mode, then pressing Program to load the patch (though there is also a direct load mode available). Prior to loading, the Program button flashes, while after loading, the button remains steadily illuminated. Patch names and database sort category are shown in the LCD window, while the patch number is shown in the numeric window. If a patch is edited but not stored, an asterisk shows that the previous values have been changed. This window also shows the digital input status and the MIDI clock rate.

Unlike the PCM‑series processors, there's no provision for using a data card to expand the number of user patches or to import third‑party patches, though data can be saved and loaded via MIDI SysEx dump. To simplify editing, soft controls provide quick access to frequently‑adjusted parameters for each patch without having to enter edit mode.

The unit may be set for stereo input or for a mono feed to either of the two inputs, and the mono/stereo designation also carries over into the digital I/O. A degree of digital gain control is available for level matching. As mentioned earlier, the MPX1 has a very flexible routing system, and fundamental to this is the ability to create two parallel chains of effects which are mixed together later in the chain. Lexicon call these the upper and lower path. Each block has its own dry/effect mix parameter, and the connection between blocks can be handled by virtual patch cords (shown as short lines in the LCD window), for stereo, left only, right only, left out to both ins or right out to both ins. For example, I put together a rather nice ethereal patch using just delay, reverb and chorus, and on screen it appeared as follows:

D=p=R=e=C=m

where the effects in use are those in upper‑case, and the lines between show the routing.

Once in the Routing Map, the various available algorithm options can be stepped through for each effect block, and as illustrated in the previous example, inactive effects blocks are shown in lower‑case letters. User patches are created by editing any existing patch — you can tell which blocks are currently active in any patch, because the corresponding named effects buttons light up green. Effects within a patch can be turned on or off using these buttons, without having to enter edit mode. Pressing Program shows the effects used and the way in which they are connected. Inactive effects blocks can be turned on if there's enough DSP power left to handle them; if there isn't, a 'Won't Fit' message flashes up on the screen. If you attempt to edit an effect that's turned off, you get a warning message telling you it's not active.

So far then, effects blocks may be turned on or off, the order and routing of the blocks may be changed, and the effect algorithm type within each block may be selected from the menu of available options. Once you've settled on the effects types and routing, the individual effect parameters may be changed as required, as may the dry/effect balance of each block. Finally, you can set up modulators, such as LFOs, envelope followers or MIDI controllers, then use them to modulate destination parameters within the various effect blocks. Effect blocks can also be copied from one program to another.

MIDI

The MIDI implementation is characteristically thorough, and includes up to three MIDI patch maps. All the unit's effect parameters may be accessed via MIDI, and of course patches may be called up via MIDI too. The mod wheels on a synth may be used to control continuously variable effect parameters, such as filter frequency, and in true US fashion, Lexicon have registered the term Dynamic MIDI to describe this function.

As well as receiving MIDI data, the MPX1 can also transmit MIDI data in response to movement of the control knob or a footpedal connected to the rear‑panel jack. MIDI is also transmitted when the arpeggiator is used. When an MPX1 controller is assigned to a MIDI controller, the MPX1 will also respond to incoming controller messages of the same type, exactly as though its own controls were being used. For example, if the Value knob is set to send MIDI sustain messages, the MPX1 will interpret incoming sustain messages as though the Value knob itself were being turned — providing that a patch including that destination parameter is loaded. A MIDI Learn mode is also provided which recognises the MIDI source automatically when you're setting up such things as MIDI controllers.

Bank Select provides access to all 250 on‑board effects, as two banks of 100 presets and one bank of 50 user patches. A full SysEx mode is provided for the benefit of those people wanting to write editing software for the MPX1, and the unit also recognises Reset all Controllers, which has the effect of resetting patched parameters to their stored default values.

The tempo source can be set to MIDI (MIDI Clock) in the System menu, and it is also possible to sync LFOs to MIDI by setting their tempo source to MIDI. You can even use MIDI clock as a dynamic controller, where the tempo range 41‑350bpm corresponds to controller values 0‑127. Dynamic MIDI patch sources are: MIDI controllers 1 to 119, Pitch Bend, After Touch (Poly and channel combined), Note On Velocity, Last Note, Low Note, High Note, Tempo, Clock, Clock Commands (MIDI Start, Stop and Continue), Gate Switch, Trigger, L (Legato) Gate and Touch Switch (derived from aftertouch).

SysEx data dumps can handle either the current patch or multiple patches, as well as maps, chains and setups.

The Effects

The effects repertoire covers all the usual chorus, flanging, phasing, delay and reverb treatments, as well as pitch shifting and EQ up to four bands. Less obvious inclusions are crossover and frequency‑splitter modules, sweepable resonant filters, wah wah, overdrive — and, by using the arpeggiator source, synth‑style arpeggiation. The overdrive isn't intended for serious guitar applications, but more for 'flavouring' sounds like organ patches, or for adding an aggressive edge. The chorus section also has some less obvious variants, such as the Aerosol stereo chorus/flanger and the Orbits modulated delay/panner, taken from the Lexicon Vortex. Rotary speaker effects are also included.

Unlike the multitap delays of the PCM80, the MPX1 is limited to just two taps, but there are still plenty of usable options, including ducking delay and an infinite looper. Unusually, a test‑tone oscillator is provided, which can be set to any chromatic musical tone. This is employed in one or two of the sound effect patches.

In common with other Lexicon high end units, the reverb tails are exceptionally smooth and natural, the sense of real space is uncannily convincing, and no matter how thick you lay it on, the original sound never seems to get swamped.

The reverbs are classic Lexicon, and all include pre‑delay — so you don't have to rob your delay module. In common with other Lexicon high end units, the reverb tails are exceptionally smooth and natural, the sense of real space is uncannily convincing, and no matter how thick you lay it on, the original sound never seems to get swamped. The basic types are Chamber, Hall, Plate, Gate and Ambience — reverse reverb is available within the gate algorithm. To my ears, the quality of the reverb is the equivalent of that in the PCM80, and having the wonderful Ambience algorithm is a real bonus. In fact, the only effect that disappoints in any way is, predictably, the pitch shifter. Unless restricted to mild detuning effects, the inevitable modulation creates an artificial, slightly out‑of‑tune effect, and though the unit performs rather better than most budget unit in this respect, the side‑effects are still intrusive enough to put me off using it for anything other than special effects. Various shift modes are available to optimise the performance to the type of signal being processed. The range of ‑4800 cents to +1900 cents at least means that you have plenty of scope for weird special effects, if weirdness is your thing!

Technically, the effects are superbly clean, with a frequency response of 20Hz‑20kHz (+/‑1dB) and a 95dB signal‑to‑noise ratio. The delay from analogue input to analogue output due to digital conversion is 1.82 milliseconds at a sampling frequency of 44.1kHz.

Using The MPX1

Though the MPX1 is arguably simpler than most serious Lexicon units, it still shows the same attention to detail; for example, the explanation of the Bypass switch takes up one and a half pages in the manual, to cover how the bypass is operated and whether it should act as a true bypass, an input mute, or an 'all mute'. Similarly, you can select auto or manual program load, change the database criteria by which patches are identified and set how the internal oscillators and envelopes should behave. The digital I/O has a built‑in error log, there' s a soft‑knee analogue limiter that can be patched into the input to help prevent overload (something I've been harping on about for years!), there are master mix and tempo functions that can override the values set in each patch, there's a MIDI implementation as long as your arm, and there's even a section for calibrating the response of an external control pedal. What's more, the manual actually tells you what sort of switches and pedal may be used, complete with diagrams and potentiometer values — more manufacturers should be this thorough.

When it comes to basic operation, the manual is commendably approachable, combining clear instructions with useful block and menu diagrams. Even so, there were times when I got lost, usually because I turned the knob instead of pressing a cursor button, or vice versa, and quite often there seemed to be no easy way back to where I wanted to be without going back to Edit and starting over. No doubt this comes with practice, and when you look at the various menus laid out in the manual, they're really quite straightforward.

Programming new effects is reasonably painless, unless you get heavily involved in patching modulation sources to parameters, in which case you might do well to write a few notes on what you hope to achieve before you dive in. The physical act of assigning sources and destinations isn't a problem, but you do have to consider the effect of the modulation, as it can both add and subtract from the default parameter value, depending on the nature of the source. However, it's worth persevering, because the modulation capabilities of the Lexicon range are the key to some of the most dramatic and dynamic effects on the planet.

Summary

The truth is that there are just too many hidden aspects tucked away inside this unit to mention in a relatively short review. To fully explore a machine like this would take months, so it's not a unit you'll grow out of, but it can also be used at a fairly simple level straight out of the box — you don't have to tackle a steep learning curve before you can get any results.

The 'Soft Value' feature is an excellent way to explore the presets, because you can access the key three or four parameters of each effects block just by hitting Value and then stepping through the options. Similarly, you can press Mix when in Program mode and do a similar thing with the dry/effect mix balance of each effect block. When you want to go further, enter Edit mode and the individual effects block buttons get you into a useful copy mode where you can copy an effects block from any of the other patches for use in your current patch. It's all there — editing at any level from a passing schmooze to a close encounter — and several stages in between.

The effects themselves are quite lovely, especially the reverbs. Around a dozen parameters per reverb block are available for editing, including Shape and Spread, but excluding Spin and Wander. If these are the same algorithms used in the PCM range, I assume these parameters are preset. Ambience is a particularly effective treatment, as it allows a sound to be given real presence and depth without making it muddy or obscuring the detail of the sound.

Also worthy of mention are the supremely clean chorus effects, some of the best flanging algorithms since the Electric Mistress (but without the noise‑to‑signal ratio!) and the surprisingly analogue‑sounding swept resonant filter. The factory patches cover a useful range of effects, most of which are musically valid, and it's very easy to fine‑tune these to your own needs without getting to deep into edit mode.

Weaknesses are few, but aside from the inevitable pitch shifter, it's also less than obvious how many effects you can get going at once until the 'No room at the inn' message comes up, so it's best to pick an existing program that uses the blocks you want before editing. On balance, though, this is a very polished unit, with impeccable sound quality, totally uncompromised reverbs and some multi‑effects that stand head and shoulders above the more obvious delay/chorus/reverb things we hear so much of. The price is little over half that of a PCM80, and though the PCM80 is a more flexible and professional tool aimed at a quite different market, in the MPX1, Lexicon seem to have succeeded in building a stunningly good multi‑effects box that pulls far more tricks out of the hat than any of the similarly‑priced competition. For both the audio professional and the serious enthusiast who aspire to 'grown up' Lexicon quality but without the price tag, the MPX1 really delivers.