Digitech GNX4

Photo: Mike Cameron

Is it an amp modeller? Is it a multitracker? Is it an audio/MIDI interface? We stomp the facts out of Digitech's new box...

Unless you have just returned from an extended period in a sensory-deprivation unit, it will have been impossible to miss the rise and rise of the guitar amp modeller, whether hardware or software based. Indeed, there are probably a whole generation of recording guitarists who have never even felt the urge to stick a microphone in front of a real guitar amplifier/speaker-cabinet combination. In terms of hardware amp-modelling units, two formats dominate: desktop/rack units such as the PodXT or Behringer V-Amp, aimed predominately at studio use, and pedalboard units such as the new PodXT Live or the Vox Tonelab SE, which are equally at home either live or in the studio.

Digitech, in one form or another, are a well-established player in this market. With products such as the rack-based 2120 Artist, the J-Station (under the Johnson brand name), the relatively budget RP-series of floor units, and the Genesis desktop amp modellers (the Genesis 3 was reviewed by Paul White back in SOS October 2001), they have a good pedigree. The GeNetX amp-modelling technology used in the Genesis series has continued to develop and has now found its way into the GNX floor units. Latest in this line, and at the top of the pile in terms of features and price, is the GNX4. However, the GNX4 is more than just a studio amp modeller. While its floorboard format means it is a live-performance unit, the GNX4 also includes a drum machine, an eight-track audio recorder, a mic preamp with phantom power, and a USB-based audio/MIDI interface with software supplied for both PC and Mac. Apparently, there wasn't room for a kitchen sink, but it is pretty clear why Digitech have given the GNX4 the 'guitar workstation' title.

What's Under The Floorboard?

As you can probably tell from the photographs, the hardware layout consists of three elements. The first of these is made up of the seven large-format (well, large enough if you don't wear size-12 boots!) footswitches and the expression pedal. These controls provide access to key features during live performance — although they also serve a useful function in the studio, as they can be configured to provide hands-free control for a number of functions. The second operational area, filling the remainder of the top surface, contains the controls for the eight-track recorder (on the left); the amp, cabinet, and effects modelling (centre); and the drum machine (on the right). Sensibly, these are all well out of the way of all but the clumsiest stamp in the dark. The third hardware element is the equally well-stuffed rear panel that contains all the input and output connectivity. Aside from the usual guitar input and quarter-inch line and headphone outputs, perhaps the most notable features here are a pair of balanced XLR outputs, a USB connection, a slot for inserting a Compact Flash card and, most surprisingly, a balanced XLR mic input supplied with phantom power.

Photo: Mike Cameron

However, the package doesn't stop there. Included in the box is the X-Edit patch editor utility (for both PC and Mac), sequencing software (Cakewalk's Pro Tracks Plus for PC or BIAS Deck SE for Mac), Lexicon's Pantheon reverb plug-in (again, for both PC and Mac platforms), and some decent printed documentation. A USB cable and the wall-wart external power supply are also included. Perhaps the only notable omission is a Type-1 Compact Flash memory card — users are left to provide their own for use with the built-in eight-track recorder. Installation of the drivers, X-Edit and Pro Tracks Plus all proceeded as described in the documentation using my PC test system, and 15 minutes from opening the box I was ready to experiment with any of the considerable array of the GNX4's functions.

Model Performance

Despite the truckload of features, the core job of the GNX4 is, of course, to provide convincing guitar-amp and cabinet modelling. While the quality of the modelling and the processing power available have moved on, the basic functions of the GNX4 modelling are not that dissimilar to those of the Genesis 3 reviewed by Paul back in October 2001. For example, the GNX4 includes the same Warp option, where it is possible to blend between two different amp/cabinet model combinations to produce new tones.

As with most of the up-market amp modellers, the GNX4 provides models of a large number of effects. These include various classic distortions, wah, compression, pitch-shifting, noise gate, chorus/modulation effects, delay, reverb, and a selection of more synth-like processes such as Auto Ya, Ya Ya, and Synth Talk. In addition, pickup modelling allows a single-coil guitar to emulate a humbucker and vice versa.

Side-by-side comparisons with my own PodXT suggested little to pick between the two units in terms of the range of amp and cabinet models or the quality of the modelling, and I'd be more than happy to use either unit in a recording context. The quality of the effects is also excellent and, if anything, the range of effects on offer with the GNX4 is somewhat wider than that supplied by default with the PodXT. While guitar tones are always a matter of personal taste, on the whole the presets are very usable and do a good job of demonstrating the capabilities of the GNX4. All the sonic bases are covered, from sparkling cleans (such as the Twinverb preset) through to murderous metal (try Rectify) and the usual line-up of tones in the style of well-known guitarists are present (Carlos, Angus, and Eddie VH for example). I also found a number of the more effects-based presets served to get the creative juices flowing (such as Stutter, Trembo, and Divebomb).

The bundled X-Edit software editing utility provides easy access to the GNX4's modelling and effects parameters.

Of course, for any floor unit like this, a minor irritation can be accessing the various hardware controls when something other than switching presets or turning effects on/off is required. Fortunately, the GNX4 is supplied with the very competent X-Edit software. While this does not provide access to all the functions of the unit (for example, the audio routing or the eight-track recorder), for patch editing it is very comprehensive. Editing is performed through three main screens. The GeNetX screen provides access to the two channels of amp/cabinet modelling and the Warp function — the two models can be blended via the X-Y controller at the centre of the window. The Effects screen does pretty much what is says on the tin, while Expression Assign allows the footpedal and the two LFOs to be routed in various ways. While patch editing using the GNX4 control surface is straightforward enough, for those with a suitable computer X-Edit is even better and will certainly reduce the potential for backache!

Drumming Up Support

The built-in drum machine contains more than 100 internal patterns, covering styles from rock, funk, and jazz through to Latin, hip-hop, and dance. Fortunately, there are also eight different drum kits suitable for use with these various musical styles. The combination of patterns and drum sounds gives the feel of a respectable GM-style drum machine — although solid enough for practice purposes or assembling a song demo, something more sophisticated might be required for the final master.

While patterns cannot be chained, there is a facility to use the footswitches to select patterns and to set the tempo while in Recorder mode. However, the drum machine will play back MIDI files, either stored on a Compact Flash card or received via MIDI from a sequencer. Interestingly, the drum machine also includes a function to play back an MP3 stored on Compact Flash. This would certainly be useful for practice or for a solo performer during a live performance. MP3 playback cannot be used simultaneously with the drum-machine functions.

Compact Flash Multitracker

The built-in eight-track audio recorder is fairly simple in operation, but can record either one or two tracks simultaneously at 16-bit/44.1kHz resolution, provided that the user acquires their own Compact Flash card. A suitable 256MB card can be purchased for under £30 and would provide about 48 track minutes — just about enough for a couple of three-minute eight-track hits! Either a drum pattern or MP3 files can be triggered to playback with a particular song, and these can also be recorded as audio to a mono track or stereo pair. Recording to a particular track or track pair simply requires you to arm the tracks using the appropriate track buttons and to press the Record button. Punching in and out is provided, and can be done 'hand-free' via the footswitches. However, subsequent audio editing is somewhat limited, aside from the ability to digitally bounce tracks.

Usefully, it is possible to monitor the signal being recorded with effects applied while recording 'dry'. This also forms part of the re-amping function, where a guitar part is monitored through all the amp modelling and effects processing, but is actually recorded with this processing bypassed. This recording can then be replayed through the amp/effects modelling and the final guitar sound adjusted to taste. Given that the GNX4 is a 'guitar workstation', the inclusion of the mic preamp might seem like a bit of a gimmick. However, in tests recording vocals and acoustic guitar with a mid-priced condenser microphone, it actually produced very respectable results. While I would not perhaps choose to use it over a dedicated channel strip or audio interface with phantom power, it certainly does make the built-in eight-track capable of surprisingly good demos.

One further useful feature is the Compact Flash Storage mode. With this mode engaged, the Recorder is disabled, but if the USB connection is present then the Compact Flash card becomes visible as a removable storage device and files can then be transferred to and from the host computer. This would obviously be useful for data backup, for moving MP3 and MIDI files to the GNX4; or for moving audio form the GNX4 for further editing/mixing within a more powerful software editing environment.

Photo: Mike Cameron

USB Audio & MIDI Interface

As mentioned earlier, the GNX4 acts as a USB-based four-in/two-out audio interface to either a PC or Mac, and is capable of 16-bit or 24-bit operation at 44.1kHz. MIDI In and Out sockets are also provided. I tested the PC version via Pro Tracks Plus. Audio routing within the GNX4 allows the user to specify which of the inputs (guitar/mic/line-in) get passed to the PC via USB — either with or without effects. Audio from the drum machine can also be passed to the PC via USB. Pro Tracks Plus is a functional enough sequencer, supporting up to 63 audio tracks as well as MIDI tracks. It is, however, limited to Direct X-format effect or instrument plug-ins plus Rewire support. That said, someone new to computer-based recording is unlikely to see the lack of VST support as too much of a problem. The supplied Lexicon Pantheon reverb plug-in also does a very good job.

I was able to get down to 10ms latency via the supplied WMD drivers, and this gave a suitably responsive performance for the Tassman SE DXi synth supplied with the sequencer. Latency while recording audio via the GNX4 is not a major issue, as direct input monitoring can be toggled on and off within Pro Tracks Plus. Usefully, the GNX4 footswitches can also be configured to provide hands-free control of some of Pro Tracks Plus 's recording functions — great for the solo musician who often finds they do not have enough hands to operate both the guitar and their recording software.

Cakewalk's Pro Tracks Plus integrates well with the USB-based MIDI and audio I/O on the GNX4 hardware. In the foreground of the screen above you can see the included Lexicon Pantheon reverb plug-in.

With 24-bit A-D/D-A conversion and quoted signal-to-noise ratios of greater than 106dBA on all inputs and outputs, the combination of the GNX4 and Pro Tracks Plus is undoubtedly capable of producing very decent multitrack recordings. Perhaps the only downside of this aspect of the package is that, at present, no ASIO drivers are supplied — nor is there any clear indication on Digitech's web site about plans for this. ASIO drivers would certainly make the GNX4 more appealing to those already using a PC for recording based around an alternative sequencer.

All-round Performer

Having experimented with Digitech's flagship amp modeller, I can say two things without hesitation: that the GNX4 is an excellent amp-modelling device capable of results on a par with the best of the rest; and that, given the sheer number of features packed in, it represents excellent value for money in the UK.

However, there may be a question of how many users would need all the features on offer? If all that is required is a studio/live amp modeller, Line 6's PodXT Live or the Vox Tonelab SE are probably the most obvious competition, and would undercut the GNX4 in price, although Digitech's own GNX3 might be the more direct competition on that front. That said, for guitarists making their first foray into the hi-tech world of amp modelling and digital recording, the GNX4 is an extremely good option, with all bases covered. Despite being a relatively new unit, I've already seen the GNX4 advertised for considerably less than the recommended retail price listed here — if it does fit your particular requirements, then such pricing turns a bargain into an absolute steal.