Stereo Effects Pedal

Published April 2024

Although, at heart, this is ‘just’ a stereo reverb pedal, it’s capable of some very unusual sonic treatments...

The world is awash with reverb pedals, but if you want to go beyond the boundaries of conventional reverb and head out into sound‑design territory, I’m pretty sure that the MercuryX from Meris will tick all your boxes and then some. Meris tell us that the MercuryX is built upon their Mercury7 (reviewed by Bob Thomas in SOS August 2018) but that it includes both some additional algorithms and some very imaginative processing and routing options. While all the studio classic reverbs are here and modelled to a very high standard, it’s the more creative reverb algorithms and processing combinations that have really had me struggling to confine my bank card to my wallet! And since the operating levels can be switched to accommodate guitars and synths or line‑level sources, it could therefore appeal to guitarists, keyboardists and mix engineers alike.

In addition to the choice of eight reverb algorithms (more on those later), there’s a stereo pre‑delay of up to 2.54 seconds with the option to add feedback. Each channel of the pre‑delay can be set independently to different note values if required. Why such a long pre‑delay? The delay lines can be modulated, HF damped, filtered and configured for cross‑feedback, with routing that allows any of the processing elements to be inserted into the pre‑delay’s feedback loop as well as before or after the pre‑delay. This routing flexibility enables the core Reverb Structures, Types and Processing Elements to be combined in numerous ways to create uniquely creative effects, and is key to the creation of some of the less obvious reverb treatments. Meris have also created what they call a Deep Modifier Section that enables control signals such as LFOs or envelopes to be routed to specific processing parameters, rather like a synth’s modulation matrix. There’s a Stereo Freeze function and a Hold Modifier Switch for ringing the changes during performance. Unusually for a reverb pedal, you also get a tuner.

Hardware

Physically, the MercuryX is a fairly large pedal, with four footswitches, six generously spaced control knobs, and a colour display in the centre of its front panel that provides both graphical and text information. The inputs and outputs, located on the rear panel, are dual quarter‑inch jacks, and make possible any permutation of mono or stereo in and out. While the pedal’s effects are digital, a great deal of attention has been paid to the sound quality of the analogue stages, which include an Analog Devices JFET input stage and an analogue mix bus. On the digital side of things, this pedal has 24‑bit A‑D/D‑A conversion, and the 32‑bit floating‑point DSP runs on an ARM processor. Power requirements are 9V, centre negative at 300mA or more; there is no included PSU, but most people using this class of pedal will probably have a good pedalboard power supply.

The hardware can store 99 presets, all of which can be edited, and there’s a software control/librarian app on the way too (it wasn’t available at the time of writing, but I expect it to be out by the time you read this). The presets are saved within the pedal as 33 banks of three presets each, and all are directly accessible using the footswitches, which are used in pairs for changing banks and then for selecting the required preset within a bank. There’s also a very handy favourites preset bank, to give you fast access to three ‘go‑to’ presets.

In addition to the audio I/O, there’s MIDI In and Out on standard five‑pin DIN sockets, plus a USB port for firmware updates. The USB port will also support connection to a Mac or Windows machine running the planned Meris prEDITOR, as Meris’s desktop editor/librarian package will be known. This was still in beta testing as I wrote this review, but Meris expected it to be available in the first quarter of 2024. MIDI Continuous Controller parameter control is supported, in addition to patch selection and MIDI Preset Send and Receive. MIDI Clock is recognised and is used when sync’ing relevant effect parameters to note values. There’s also an Exp jack socket that allows a connected expression pedal to adjust up to six parameters at the same time.

The MercuryX supports both MIDI and expression pedal control, while the USB port will also cater for a Mac/Windows editor/librarian app.

Orientation

Despite the obvious complexity of what is going on under the hood, the user interface is very streamlined, with dedicated controls for Decay, Pre‑delay, Mod, and Mix, plus three additional rotary encoder known as C1, C2 and C3, which are described as the main navigation controllers. By default, the Preset page is shown when the pedal is powered up. This is the Graphic View, in which the circle on screen shows both the preset’s name and its number. Two favourite parameters for the current preset are adjusted using the two controller knobs below the display, and once it’s been changed, the preset can be resaved using the ‘save as’ function. Graphic View focuses on one block and/or parameter at a time, but the alternative Text View allows six parameters to be adjusted at the same time, using six of the knobs. Switching between Graphic View and Text View is done in the Global settings.

The pedal slopes up gently from front to back.Pressing the Preset/Pages controller gets you into editor mode, for which the screen shows several circles with names of sections that can be edited. The desired section can be selected using the leftmost encoder, while the lower right controller can be used to adjust values and the Preset/Pages controller cycles thought the available processing blocks. The Preset/Pages controller can also access a different edit level showing global and system settings and information. While this is very neatly thought out, I’m looking forward to the editing software becoming available, as I suspect that could make patch creation a lot easier, especially given the manifold possible routing options.

When adjusting Decay, Pre‑delay, Mod or Mix, the so‑called Tactile Pop‑Up view is shown for a few seconds, and reveals the precise values as four bar columns. This can be helpful, though for those who find this sort of dynamic interface behaviour a distraction, it can be disabled or made persistent in the global settings. Favourite parameters can also be assigned to C1 or C2 in the Edit Page.

When it comes to setting up Modifiers, each of which can be assigned to a specific parameter, the user can set how quickly changes occur, the range over which they occur and also the magnitude of the changes. The LFO A, LFO B, sample & hold and Sequencer all have speed parameters. The Envelope Modifier has Attack and Decay Time adjustments. Note‑division sync of modifiers is also possible, and when this is set it overrides the modifier’s speed parameter. The Hold Modifier is an envelope generator that can be triggered using the rightmost footswitch, and may be set to latching or momentary operation. Alternatively, this switch may be used to set tap tempo rates.

Reverb Algorithms

The MercuryX includes Ultraplate and Cathedra algorithms derived from the Mercury7 which, designer Angelo Mazzocco tells us, were inspired by the moody Vangelis soundtrack to the film Blade Runner. The 78 Room, Plate and Hall algorithms are informed by classic studio hardware, while Spring, Prism and Gravity are new for MercuryX.

Ultraplate is a plate emulation, and the user gets control over all key parameters plus modulation. Cathedra is an ethereal algorithm, with a slow buildup. Spring recreates the classic spring reverbs found in some guitar amps, while 78 Room emulates the ambience of a real space. 78 Plate has a rapid build‑up and a dense decay, and 78 Hall emulates a large hall with a medium build‑up of reflections. Prism synthesizes geometric rooms based on settings for size, distance and reflectivity, and includes a configurable modulation section that’s independent for the two channels. Gravity? Well, it’s a distinctive sound, but I’ll have to go with the handbook description for this one: “The Gravity Structure works by accelerating individual windows of your signal and stretching them across the horizon.” Poetic, or what? Its modulation section includes pitch manipulation.

Most of the special reverbs offered by MercuryX are created by using processing in and around the pre‑delays, before the sound hits the actual reverb algorithm, but there’s plenty of flexibility and you can deploy these processors pretty much anywhere in the signal path, including after the reverb blocks. As the pre‑delays can be pretty large, this allows for the creation of some long reverbs that change character in interesting and sometimes unexpected ways as they develop. There are lots of options, including a generous dynamics section that includes compression, swell (slow attack), a limiter, diffusion with adjustable density and Freeze, which sustains the reverb tail indefinitely. There’s preamp modelling to emulate various types of analogue circuitry, as well as resonant filters and pitch‑shifting in both a smooth polyphonic shift mode and a lo‑fi mode. There are numerous modulation effects on offer too, such as chorus, vibrato, vowel filtering, tremolo and something called Hazy, which adds some lo‑fi pitch wobble.

While the MercuryX nails the classic studio reverb sounds perfectly, other premium pedals can manage that too, so for me it’s the special‑effect reverbs that really set this pedal apart.

Special Effects?

Even in mono, this pedal sounds superb, but heard in stereo it is even more impressive! While the MercuryX nails the classic studio reverb sounds perfectly, other premium pedals can manage that too, so for me it’s the special‑effect reverbs that really set this pedal apart. In fact, I can honestly say that I’ve never heard special reverb effects as inspiring as these from any other pedal, regardless of cost.

The kind of thing you can expect is a reverb that starts off fairly normally but then fades in a sub‑octave reverb a second or two later and then, after another second or two, evolves into an upper‑octave shimmer reverb. Or maybe the reverb tail has a lo‑fi wobble to it, or even plays a pitched sequence. Then there’s the Hold/Modifier button, which can be used to freeze reverb tails or to bring about other changes during performance, such as introducing pitching effects. Bring an expression pedal into play, and the MercuryX become an extension of your instrument, offering lots of performance options.

For me, it’s the way the different reverb flavours and treatments morph into each other in such a natural‑sounding way that makes the special‑effect reverbs so pleasing. The deep MIDI control is also to be applauded, and once the editor software becomes available I’m sure that will make patch creation a lot more intuitive. But even if you are not into deep editing, the presets cover a lot of ground already — you may well be able to get the effect you desire just by tweaking the presets, rather than building patches from scratch.

In short, there can be no doubt that the MercuryX is a remarkable device, and one that lends itself perfectly to sound design, cinematic soundtrack creation and of course ambient music styles.