Test Drive: The Lexicon MPX500 24-Bit Dual Channel Processor


Once you have selected and loaded a preset, you’ll need to set a few parameters before you can get started. These include input mode (mono or stereo) and source (analog or digital), which are selected within the system pages. The mix between wet and dry signals depends on whether you’re using the unit in line or in an effects loop. The MPX500 has two options, selectable in the system pages, which let you choose to have the wet/dry mix saved with the patch or be determined globally for all patches.

The manual suggests that you first set the Input Trim using the front panel knob, and gives you a step-by-step guide to doing so. The Input Trim knob is just that, in other words it will trim the input but cannot turn it off. According to the manual, the Input Trim knob turned fully counterclockwise should be optimum for +4dBu balanced gear, while turning the knob fully clockwise should be right for ­10dBV unbalanced gear. In practice, using the line out of a CD player and the Aux send of my console, I verified this. At no time was I easily able to cause input clipping, and the MPX500 seemed to handle whatever material I threw at it.

Likewise, within the system pages is an option to set the output level of the unit to anywhere between 0dB and ­12dB, to yield the best level downstream.

As mentioned, the MPX500 features true stereo operation, and the signal path allows a number of routing options, from stereo-in/stereo-out to dual mono-in/stereo-out, or dual mono-in/dual mono-out. It’s also possible to select from a number of dual effects connected either in series or in parallel, and in the case of series connection, to vary the amount of the first effect feeding the second. Normally, the Effects Level parameter accessed via the third Edit knob in parameter page one sets the balance of the two effects in a dual effect program, but in serial configurations, it varies the balance of effect one/dry signal that feeds effect two.

The MPX500’s ability to operate in true stereo mode also means you can use it as if it was two separate effects devices. So if you’re short on effects, you can connect one aux send to the left input and another to the right, then use one of the dual effect modes to provide two independently adjustable effects that are either mono-in, mono-out or mono-in, stereo-out with both stereo outputs mixed together. The choices here generally break down into reverb plus something else or delay plus something else.


With the unit up and running, the first thing to check out has to be the reverbs. The reverb presets are organized into banks of ten each by the basic reverb category. These include Plate, Gate, Hall, Chamber, Ambience, and Room. You select each reverb patch sequentially by turning the stepped Program knob. Pushing the Program knob in activates a shortcut that immediately takes you to the next reverb category, for example from patch 12 (called Drum Gate) directly to patch 20 (the first of the Hall programs).

However, one annoyance that cropped up as I auditioned patches was the sloppiness of the Program knob. As I indicated earlier, it is a stepped knob, but there is enough slop in it that the program numbers can jump back and forth within a single step. This is especially true when turning the knob slowly, and it was not uncommon to feel the knob click and simultaneously see the program advance, then retreat to the previous patch.

That said, there are two points that immediately impressed me as I listened. First, there is a clever implementation of the Tap feature, with a number of reverbs having tap-able predelays, making it easy to tweak them in real time. You can also use audio input to set the tempo of a tap-able function by holding down the Tap button. The MPX500 will then detect the tempo of the audio and set the BPM rate accordingly.

Second, the choice of names given to the presets is excellent. This may sound like a small thing, but on some units you have to page through a lot of strangely- named presets or ones that sound nothing like their names. The MPX500 offers clearly-named reverb presets that sound very realistic. For example, Marble Foyer makes great use of the “ambience” algorithm with a “liveness” factor assigned to knob number one.

That brings up another fine point on the MXP500. The leftmost of the four knobs is designated as the “Adjust” knob. This control lets you make quick adjustments to the most critical parameters of the sound. In many cases, the Adjust knob controls several effect parameters simultaneously to provide simple control of a complex editing process. So in many of the Chamber and Room programs, the Adjust knob does indeed control the “liveness” of the space by changing decay, EQ, and early reflections all at the same time.


So how do they sound? The reverbs are impressive, especially at this price point. They are of a uniformly high quality, and they benefit from the 24-bit converters. Most importantly, the reverbs have that true Lexicon character which helps keep a sound in focus while adding space.

In A/B listening tests with other reverbs I have available, the MPX500 stands up well. It is nearly as lush as a PCM-70, although I definitely heard grittiness in the PCM-70 that didn’t exist in the MPX500, no doubt due to the superiority of the converters. When stacked against a TC Electronics M2000, the MPX500 was surprisingly competitive, which is all the more surprising considering that the M2000 costs nearly three times as much! When A/B’ed against the built-in reverbs in my Yamaha 02R, it was literally no contest. The MPX500 stomped on the Yamaha reverbs hard. That was no surprise, given that effects have never been a strong suit for Yamaha.

The non-reverb effects in the MXP500 are also good. The delay offers a choice of tape-like high cut or straight delays, and the rotary speaker emulates the speed-change rate of the real thing. The stereo chorus uses up to six delay taps to provide a really smooth, rich chorus, while flanging passes through the zero delay point, just as tape flanging does. However, these algorithms do play better parts in the dual effect presets.

The Tap facility makes sense and is well done on the tremolo and some of the rotary presets for setting speed. The Adjust knob also plays some useful roles in the rotary programs. And the delay presets make good use of the Tap feature, offering a variety of mono and panning delays, with a maximum mono delay time of 5.5 seconds.

The only obvious weak spot is the pitch shifting patches, which generate some serious artifacts at anything over a few semitones of shift. This would seem to be a fact of life for many moderately priced products that feature pitch shifting. If you want really good pitch shifting, be prepared to spend some big bucks on software or hardware. Has anybody seen my Eventide?

The dual effect programs combine either a delay or reverb algorithm with a flange, pitch or chorus one. This means that you can’t run two reverbs or delays simultaneously, but the MPX500 dual programs are perfectly usable and well programmed nevertheless. And because the screen displays the source algorithm, you can easily see which building blocks were used to construct the patch.


My complaints with this unit are minor. Although there are 240 factory programs in the MXP500, there are only 30 user slots for edited programs. That seems inadequate, especially in a processor that makes it relatively easy to tweak the factory settings. I want more slots in which to store my tweaks. I also didn’t like the sloppiness of the Program knob, and I despised the fact that the contrast control is on the back of the unit.

But there’s no question that this is a Lexicon. It looks, feels, and sounds like a Lexicon. (You know, I think it kinda smells like a Lexicon, too.) Considering that it’s selling on the street at under 500 bucks, it’s straightforward to tweak and program, and it sounds great, the MPX500 seems to provide good value for money spent. Did I mention that it sounds like a Lexicon?

The MPX500 Dual Channel Processor has a suggested retail price of $599.00. For more information in the US, contact Lexicon Inc. at 781-280-0300. For more information worldwide, visit www.lexicon.com.

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