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Zoom ZFX Control Package

Guitar Amp Simulation Software, Interface & Controller By Sam Inglis
Published September 2008

Zoom ZFX Control Package

Zoom's first computer product is a guitar amp modelling system that offers an impressive list of features at a bargain price.

Zoom will be familiar to most SOS readers as a long–established manufacturer of rackmounting studio processors and, especially, guitar effects. They have built an impressive reputation as a company who always offer a lot of product for not much money, and their first foray into the world of audio software is no exception. It combines a Windows–only software amp simulator, called ZFX, with a choice of two hardware units. The desktop S2t interface costs a mere £169 including VAT, while the more fully featured S5.1t floorboard retails at £229.

That price begins to look all the more impressive when you consider exactly what the S5.1t offers. Not only do you get a pretty well–specified foot controller, with five switches and a rocker pedal, but its capabilities as a USB audio interface are pretty unique. If you choose to play your guitar through it, you can blend between two signal paths, one based around solid–state preamplification, the other involving a real vacuum tube. And that's not all: there are also two mic preamps with phantom power, plus analogue direct monitoring circuitry allowing you to hear your performance with no latency. (The S2t offers all of this apart from the footswitches and pedal.)

The software component of the package is likewise crammed with features. ZFX can run either as a stand–alone program or a VST plug–in, and offers a bewildering variety of emulations of classic guitar and bass amps, effects and processors. In terms of features, then, the ZFX Control Package appears to be a serious rival to the likes of Native Instruments' Guitar Rig Kontrol Edition, yet its RRP is the same as that of the Guitar Rig software alone — tempting indeed.

Getting Going

Although the documentation isn't as clear as it might be, installing and setting up the interface and the ZFX program is fairly straightforward. Both ZFX and the hardware interfaces are compatible with Windows XP and Vista. The hardware takes its power from the USB connection — there is no option for a separate power supply — and it acts as a copy–protection dongle for ZFX, which can't be run without the interface connected. Unlike the USB2 Rig Kontrol, the C5.1t is a USB 1.1 device, and as a consequence, it can only record and play back 16–bit audio, at either 44.1 or 48 kHz.

The C5.1t's construction is reassuringly solid, with thick rubber end–cheeks and a stiff metal case that doesn't flex under pressure. Five footswitches are arranged in an 'M' formation, and each has a red LED that indicates its status. These are reliable and easy to trigger, though they lack the satisfying 'clunk' that expensive switches have. The rocker pedal feels smooth, but has a fairly limited angle of travel, and I found its response rather abrupt at the bottom of the range; when patched as a volume pedal, it was difficult to get a smooth fade from silence. It does have an associated switch, of the sort you'd expect to find on a conventional wah pedal, but on the review unit it was extremely difficult to apply enough force to operate it.

Although the C5.1t is only a  two–in, two–out interface, it has enough sockets to connect guitars, line inputs and mics simultaneously. Although the C5.1t is only a two–in, two–out interface, it has enough sockets to connect guitars, line inputs and mics simultaneously. The selection of inputs and outputs is healthy: a single high–impedance guitar input is joined by two combi jack/XLR sockets for mics, a second pair of jacks for line inputs, and a stereo 'aux' input on a mini–jack. The C5.1t is only a two–in/two–out device, so you can't bring all of these into your PC on separate channels (a three–position switch selects whether you're recording guitar, mics or line sources), but it's nice to have everything separated out like this. A pair of full–sized jack outputs is joined by a headphone amp with associated level control. There's no display, nor any metering, but I think that's forgivable given the price.

Direct monitoring works in a way that will be familiar to users of the original Digidesign M Box: a single level control adjusts the amount of raw input signal that is fed directly to the output, and a switch allows this to be collapsed to mono (so that if you're recording vocals you can hear them centrally panned rather than hard left or right).

I confess to being a little sceptical about the "Tube Accelerator" element of the design, which uses a 12AX7 valve to warm up your guitar input prior to further shaping in software. Given that the whole interface is running off USB power, one suspects that the golden glow which emerges from the front–panel grille is not emanating from the valve itself, and since there's no way to attenuate the tube gain prior to the A–D converter, you can't drive it into obvious distortion without clipping the input to the computer. The tube path does sound subtly different from the solid–state one, but not in a way that I particularly liked — it feels a bit tight and closed–off at the bottom end — and I could have done without it. The solid–state alternative is decent enough, though, with an open sound and plenty of gain.

Under Windows XP, there are very few driver options. Instead of a buffer size setting, you get a single 'Latency' slider calibrated in milliseconds, but the relation between this setting and the actual latency is obscure. The default 6ms setting was way too high for comfortable real–time input monitoring, so I lowered it to 3ms. This gave a reported Input and Output Latency of 4.5 and 10.5 milliseconds respectively, and was fairly comfortable to play, but produced occasional clicks and pops on my machine. For mission–critical recordings, I'd be tempted to raise the latency and use Direct Monitoring.ZFX Plug–in is a  modular application that allows complex chains of effects to be set up using the patch cords at the bottom.ZFX Plug–in is a modular application that allows complex chains of effects to be set up using the patch cords at the bottom.


The software component of the package is known to your computer as 'ZFX Plug–in', although it runs as a stand–alone program as well as in VST form. If you're used to other amp simulations, most aspects of its operation will be familiar, and in some respects its modular approach is similar in philosophy to Guitar Rig. Aside from the row of controls and meters along the top, there are four main areas. At the right–hand side of the screen, you see your currently selected amplifier, and below it, a graphical representation of a speaker cabinet, with a mic that can be moved around. The left half of the window can display either the preset browser, a guitar tuner, the means for assigning C5.1t controls to software parameters, or a 'catalogue' of amps, effects, processors and so on.

Running along the bottom, meanwhile, is a strip of virtual flooring on which your effects pedals sit. This can be scrolled left and right for full access to long effects chains, while if you want to see the controls on individual pedals, you'll need to zoom in. If you're creating a setup of any complexity, you will spend a lot of time scrolling and zooming, and in this respect, it's not as user–friendly as something like Guitar Rig, where most of the parameters are readily visible in one place.

The way the foot controller relates to what you see on screen can be confusing, because there's no obvious way to see which footswitch is assigned to which control(s) on screen, and in the factory sounds, the order of the pedals on screen doesn't always correspond to the order on the pedalboard. What's more, where the footswitches are assigned to turn on–screen effects on or off, they work the other way around from the pedals, so the switch's LEDs light up when the associated pedal is off.

All of the C5.1t's controls can be assigned to multiple ZFX parameters.All of the C5.1t's controls can be assigned to multiple ZFX parameters.The Control panel is where you assign parameters to the C5.1t's switches and pedal. Two separate menus allow you to assign the switches to parameters within the preset, and to global parameters and preset/bank stepping. The top two switches default to stepping forward and back through the current bank of presets, but you can disable this behaviour globally, allowing them to be reassigned to effects pedals or whatever. Up to five control destinations within a preset are available for each physical control, and the switches can be assigned to continuous as well as on/off parameters — so you can, for instance, switch between two different delay times. This is flexible and works pretty well, although the small graphics can get fiddly. A possible improvement for future versions would be to make it possible to assign pedals and switches simply by right–clicking on the parameter in question, rather than having to visit the Control panel every time. I would also dearly love to be able to turn off the 'Patch has been edited. Are you sure?' message that appears almost every time you use the mouse to select a new preset.

A curious option at the top of the screen is 'Pickup Selector', which can be set to Single or Humbucker, or switched off altogether. Annoyingly, this setting is stored on a patch–by–patch basis; for me, it would make more sense to have it switched globally, as you're likely to change preset much more often than you change guitar. After a while, I ended up ignoring it most of the time, as I wasn't convinced that matching the Pickup Selector to the guitar necessarily improved the sound.

Choices, Choices

ZFX modules are accessed through an on–screen 'catalogue'. ZFX modules are accessed through an on–screen 'catalogue'. All ZFX's pedals, amps and other devices are found among themed pages in an on–screen 'catalogue'. They can be researched in more detail by turning to the appropriate page, and added to your setup by dragging them to the appropriate place. When you do so, ZFX automatically adds on–screen patch cables where it thinks you'll want them; if it gets it wrong, you can correct it by clicking and dragging, although this can get a bit awkward at times. The linear way the devices are arranged on screen works best for straightforward effects chains into (and out of) the amp, but you can easily go beyond these to create fairly complex modular setups. Thanks to the Splitter, Mixer and Isolator modules, it's possible to send the signal to multiple amps and cabs, as you can in Guitar Rig. However, there's no equivalent to Guitar Rig's more experimental Modulators; nor is it possible to patch anything between amp and cabinet, should you wish to. (Since none of the amp models include reverb, this means that you can only patch spring reverb either before the amp or after the cab.)

ZFX presets are arranged in banks of 128, and there are 27 factory banks, each containing a handful of presets and a lot of empty space. Some of the factory sounds are modelled on well–known artists' signature tones, while others show off the capabilities of ZFX's various amps and effects. They do a fair job of displaying the range of sounds that's available, although personally I found it a bit annoying that all the factory presets incorporate a rather aggressive noise gate.

The catalogue as a whole contains far too many devices to describe in detail here: suffice it to say that whatever your musical genre of choice, you haven't been neglected. The 12 guitar amps and five bass amps emulated here are mostly familiar from other programs, while the effects on offer run the full gamut, from the obvious phasers, flangers, tremolo, delay and reverb to more outre devices such as an intelligent harmoniser, ring modulator, step pitch–shifter and reverse delay.

Bass players will find plenty for them in the ZFX catalogue.Bass players will find plenty for them in the ZFX catalogue.The amp and speaker emulations are, of course, the most important, and there are both high and low points to be found, even among ostensibly similar amps. I really liked the '1959' Marshall emulation, which spits out a gloriously dirty distortion; yet although the Hiwatt model is also nice when cranked up, its clean sound is disappointingly generic, with none of that characteristic glassy, compressed treble you'd hope for. Similarly, Zoom's take on the Matchless DC30 is a very playable and flexible amp, but their Vox AC30 emulation lacks the complexity and richness of the real thing, and adds an unmusical 'clah' sound on note attacks. In general, as is often the case with software amp simulations, I felt that ZFX did a pretty good job with ultra–clean Jazz Chorus–type sounds, and also with crunchy distorted tones, but was weaker on those warm, edge–of–break–up sounds beloved of country players.

There's a choice of four virtual mics to place on your virtual cabinet, and control over distance and position with respect to the centre of the speaker cone (but not over the angle of the mic) is provided. The audible consequences of moving the mic are pretty subtle, with a slight increase in brightness at the centre of the cone, and a pleasant but not overwhelming early reflections–type reverb creeping in as you move it away. Differences between the mics and cabs themselves are more obvious, and usefully extend the range of sounds available, though it's annoying that changing the mic or cabinet resets the mic position to the default.

Given Zoom's heritage as a manufacturer of effects, you'd expect their selection of virtual stompboxes to be a strength, and it is. They are not particularly user–friendly, since you need to zoom in quite a long way to adjust the controls, but the range of effects on offer is very broad. The only obvious gap I can think of is that there is no rotary speaker emulation, but other than that, all bases are covered very nicely. The modulation effects can generate everything from a subtle shimmer to a seasick lurch, the delays do pretty much what you'd hope, and there's plenty of fun to be had from the pitch–shifters and other weirdities.

The C5.1t driver panel is very simple.The C5.1t driver panel is very simple.

Summing Up

On paper, the ZFX/C5.1t bundle looks almost too good to be true. It's little more than half the price of its most obvious rival, NI's Guitar Rig Kontrol Edition, and is even more fully featured: the C5.1t's mic preamps might mean you don't need to buy a conventional audio interface as well. But it's probably worth pointing out that there are still reasons why some users will feel that Guitar Rig is worth the extra money. The most important of these is the relative slickness and maturity of the software involved. As of version 3, Guitar Rig is a very friendly and intuitive application to use, with a beautifully crafted user interface that always seems to place things exactly where you expect to find them. The same can't really be said of the current version of ZFX, which feels a little clumsy and unfinished by comparison.

At least on the review machine, CPU usage was also an issue. ZFX has its own built–in CPU meter, which tended to register rather alarming figures — typically between 30 and 50 percent. Windows Task Manager reported slightly lower numbers, and when I loaded the VST plug–in version, Cubase's CPU meter suggested a load closer to 10 percent. However, the plug–in version seemed very prone to spikes in CPU load, which led to glitching in all but the most basic projects, as well as making the plug–in GUI rather slow and unresponsive. Zoom say they are aware of the issue and hope to fix it within the next four or five months. Should you find ZFX hard to use on your computer, though, all is not lost, as the bundle actually includes a cut–down LE version of the Guitar Rig software too.

All in all, Zoom's entry into the computer recording arena is one that will have other manufacturers looking nervously over their shoulders. If the teething troubles with ZFX can be smoothed out soon, the bang–for–the–buck factor could make this package irresistible to guitarists!

Recording Your Controls

One of the nice touches about NI's Guitar Rig system is that control messages from the floorboard are embedded into the audio stream, so that they can be automatically recorded in your DAW without any messing about with MIDI and so forth. That doesn't seem to be the case with ZFX and the C5.1t controller. If you want to use the floorboard during recording, you'll need to set up a MIDI track to receive its input, route its output to the plug–in's MIDI input, and switch on the MIDI Control option within ZFX. This is straightforward enough to do, and does give you the option of editing the control data afterwards, but could get messy, and is not well documented. 

By far the most directly comparable product on the market is Native Instruments' Guitar Rig Kontrol Edition, and I've gone into some detail in the main text about the relative merits of the two systems. IK Multimedia now offer the StompIO floorboard/interface to partner their Amplitube modelling software, but the combined system is a lot larger and pricier. 

At the more affordable end of the spectrum, the Zoom S2t/ZFX bundle goes head to head against Line 6's Toneport UX1 and UX2 range. The latter offer Line 6's unique low–latency 'Tone Direct' system, but the amp models can't be used as plug–ins unless you upgrade to the full Gearbox Plug–in.


  • Excellent value for money.
  • C5.1t controller is solidly built, and includes mic preamps, line inputs and high–impedance inputs as well as foot controls.
  • ZFX models a huge range of guitar and bass amps, speakers and effects.


  • Compared with its more expensive rivals, ZFX software can be frustrating to use, and feels less polished and mature.
  • It's hard to run the C5.1t at a low latency with the current driver.
  • In the review system, ZFX seemed to cause CPU spikes and associated glitches.
  • On the review unit, the rocker pedal and associated switch were difficult to use.


Although there are areas where some rawness is apparent, there's no denying that Zoom's amp modelling package offers a remarkable amount of power, at a price that few of its competitors can match.


£229; ZFX Stack Package (with S2t interface) £169. Prices include VAT.

Exclusive Distribution +44 (0)1462 481148.

Test Spec

  • ZFX 'host version'; plug–in version
  • PC laptop with 2GHz Intel Pentium–M CPU and 2GB RAM, running Windows XP Service Pack 3.
  • Tested with Steinberg Cubase 4.1.