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Korg A5 Multi-FX/Guitar

Performance Signal Processor

Korg's A5 series of effects is aimed to offer a variety of effects to a variety of musicians. Simon Trask test drives them and discovers guitar distortion works for drum machines.

Korg's new budget multi-effects processor chains five effects together in a floor-standing unit optimised for live use.

WHERE MOST EFFECTS units fit neatly into a 19" rack and don't take kindly to being stomped on, Korg's new budget multi-effects processor has been designed for floor-level use and positively invites you to put the boot in. And where most effects units include MIDI sockets and allow their patches to be selected remotely from a sequencer or from the front panel of a MIDI instrument, the A5 forgoes MIDI communication and puts effects patch selection not at your fingertips but at the soles of your feet. Whether it's a unit to be looked down on, however, is a matter of perspective - so let's consider the different angles.


THE A5 IS a multi-effects unit providing five digital effects organised in a single effect chain - the Multi-FX version is so called because it's intended to be used as a multi-purpose effects unit, whereas the Guitar version has been optimised for a specific instrument. Well, that's the intention, but if technology was only ever used in the way the manufacturers intended it to be used, we'd all be poorer for it (and that includes the manufacturers, too - sampler manufacturers, for instance, have benefited greatly in sales terms from their instruments being used to lift breaks off records, surely an application which they never envisaged). And so it is that the A5 Guitar unit's inclusion of distortion and overdrive effects needn't preclude it from being used with synths, samplers and drum machines.

In fact, the only differences between the two versions, aside from the cosmetic one of colour-coding to enable ready identification (red stripe for Guitar, blue for Multi-FX), are that the Multi-FX version has an exciter effect while the Guitar version has distortion and overdrive and the two versions have different sets of ROM preset effects patches reflecting their different applications. I say "only" differences, but of course these aren't minor in practice.


THE FIRST, FOURTH and fifth effects in the A5's effect chain are compressor, chorus/flanger and reverb/delay respectively. The other effect common to both versions, three-band EQ, is placed in the position that best suits its application in each case - on the Multi-FX version second (before the exciter), and on the Guitar version third (after the distortion/overdrive).

Of the six footswitches which run across the lower half of the A5's front panel, the rightmost is dedicated to switching the unit between effect select and effect edit modes, while the two pinpoint LEDs located above it indicate which of the two modes is active. Depending on which mode is selected, the remaining five footswitches allow you to call up one of five effects patches or turn individual effects within the currently-selected patch on or off. Pinpoint LEDs located above these footswitches allow you to tell at a glance which effects patch is selected or which effects are enabled and which disabled within the selected patch. The A5 switches from one effects patch to another smoothly and all but instantaneously.

Like footswitches 1-5, the six-position slider located in the upper half of the A5's front panel has one function in patch select mode and another in patch edit mode - respectively, selecting a patch Bank and selecting an effect or Utility mode within the current patch for editing. The A5 has a total of 30 effects patches stored in six Banks; five of these (Bank one) are user-programmable, while the remaining 25 are preset in ROM. The ROM presets on each A5 version offer a well-implemented range of effects suited to each unit's intended uses.

In patch select mode, the A5's two-digit LED display indicates which Bank is currently selected and whether or not the active patch is within that Bank (a dot lights up in the lower right-hand corner of the display if it is).

Effect and Utility parameters together with their value ranges are listed in a matrix format next to the six-position slider. Once you've selected which effect you want to edit, turning one of the knobs located at the base of the matrix columns both selects and edits the relevant parameter. The knobs aren't of the infinite rotary type, so turning one selects the value determined by its absolute position. This value is displayed in the two-digit LED, while the dot mentioned earlier lights up whenever the stored value for the selected parameter is displayed (a feature born of necessity, but one which manufacturers might usefully consider adopting more widely). Korg have got maximum mileage out of this little dot, also using it in patch edit mode to indicate whether or not the on/off states of the five effects correspond to the stored on/off states for the current patch.

The only other features of the A5's front panel are an input level knob with associated peak-indicator pinpoint LED, an output level knob, a Write button and an (effects) Bypass button. Any of the unit's 30 effects patches, edited or not, can be Written into the five user-programmable patch locations in an operation which can take a mere two seconds.

The A5's rear panel contains the power on/off button and a DC 9V power input jack (the unit comes supplied with an AC adaptor), a mono audio jack input, L/Mono and R audio jack outputs, a stereo headphones mini-jack output and a volume pedal jack input (intended for use with a Korg KVP001 footpedal, and allowing footpedal control of the overall signal level - one use being to produce effect "swells'). Signal level to the headphones is governed by the A5's main output level control, the volume footpedal, and the master output level Utility parameter (which is programmable per patch - or preprogrammed by Korg in the case of the ROM patches, most of which are set at or near the maximum of 15). If you like your headphone signal loud, you won't be disappointed by the A5 - it comes through loud and clear even when the main input/output levels are set quite low (depending on the strength of the input signal to the unit, obviously).


PROCESSING OF INPUT signals is via 16-bit A/D conversion with 64 times oversampling and a 44.1kHz sampling frequency, with 16-bit D/A conversion taking the effected signal back out into the analogue world again. Background hiss in the output signal can be dealt with by utilising the unit's built-in digital noise-reduction, for which a threshold level (0-15) can be set per RAM patch to determine the extent of the reduction.

"What I had in mind was using distortion or overdrive on drum and percussion sounds as a means of 'roughing up' the sound of a rhythm track."

The first effect in the chain, compression, is used to reduce the dynamic range of the input signal. The A5's compressor has three parameters, governing the degree of compression, the compressor's response time, and the output level of the effected sound. For a compressor to do its job properly, it needs to be in-line with the signal to be compressed. In the A5's case this means either plugging an instrument directly into it or else using it on the insert point of a desk channel. However, if you want to use the A5 within an aux send/return loop on a mixer - which is quite reasonable given the other effects in its effects chain - you should think of the compressor more as a creative effect than a utilitarian signal processor. In other words, by changing the compressor settings you can change the character of the effected signal which appears at the audio outputs - and in fact the A5's compressor can make quite a difference.

The A5's three-band EQ allows you to cut and boost bass (100Hz), mid (one of eight programmable frequencies ranging from 200Hz - 5kHz) and treble (3kHz) frequencies. The amount of cut or boost is set on a numeric scale (+7) which tells you nothing about the actual value (dBs) being employed. However, you only need a pair of ears to tell you that cut and boost at maximum settings can be quite severe. This plus the swept mid-frequency's wide range makes the A5's EQ very flexible. There's also a Trim parameter which allows you to set the amount of gain for the input signal (0-15).

As mentioned earlier, on the Guitar version the three-band EQ is preceded by distortion and overdrive, well-described in the manual as high-gain fuzz-type and mild saturation-type effects respectively. You can select one or the other effect, set the amount of distortion or gain (0-15) depending on the effect, set the tone (0-15) and set the output level of the effected sound. Once again, this is no half-hearted effect - you can get some pretty extreme results out of it.

I mentioned earlier that distortion and overdrive needn't be limited to guitarists. Obviously, keyboard players deal with a wide range of sounds nowadays, and distortion is becoming an increasingly common effect on today's synths. However, the A5 Guitar could be a useful, and relatively inexpensive, addition to a sampler, an older synth, or a more recent synth which has dry outputs in addition to its effected outs. What I particularly had in mind, though, was using distortion or overdrive on drum and percussion sounds (collectively or selectively) as a means of "roughing up" the sound of a rhythm track. This is very much a play-it-by-ear scenario, as the same parameter settings can produce very different results on different patterns and different drum and percussion sounds, whereas of course passing a guitar straight into a distortion/overdrive processor gives a stable sound input. Overdrive is often the better suited of the two effects, but distortion can work well, too. The scope of these effects makes them satisfactorily versatile in this percussive context, but nonetheless the best results are achieved by using distortion/overdrive in combination with the other effects, which allow you to "fine-tune" the distortion or overdrive effect.

This sort of "rough treatment" of rhythm tracks may not appeal to everyone, but if drums and percussion play an important role in your music and you're not into playing things straight all the time, I'd recommend you give it a go.

There is one consideration to bear in mind, however: as most of the effects patches are preset, and obviously the Guitar unit's are not preset to take account of drum machines, you may find yourself focussing on the five RAM patch memories. There again, if the idea of live effects edits sounds interesting to you, that may not matter (see Angle Four).

The Multi-FX unit's alternative to distortion/overdrive, an exciter, is also good at making rhythm parts stand out, though in this instance through giving added clarity, definition and presence to the input signal. You can set the centre frequency and the depth of effect (-2/+12); again, rather than being expressed in terms which mean something (Hz and kHz), the frequency is set on a scale of 1-16.

The chorus/flanger effect allows you to select a mode (flanger 1 or 2, chorus 1 or 2, or slapback-created using different delay times), the speed of modulation, the depth of modulation, the feedback amount, and the mix level (the balance between the direct and effected sound); values for the last four range from 0-15. The character of these effects is more hard metallic than soft warm, and like most of the other effects on the A5 you can push them to extremes.

Finally, there's reverb/delay. Here the limited number of parameters Korg have provided for the A5's effects is most disappointing. You can select one of seven effect types: hall, ensemble, room, plate and live stage reverbs, echoverb (a combination of delay and reverb) and delay. The reverb types present a reasonably flexible range of reverbs, but there's no getting around the disappointment that the only other parameter you can set is the balance of dry and reverbed sound; you can't even change the reverb time, let alone high-frequency damping or early reflections. The quality is reasonable, but don't expect any kind of finesse. There again, the A5 is not really intended for situations which require finesse.

"What really sets the A5 apart is the front-panel accessibility of its parameters, which makes programming easy and opens up the possibility of real-time effects edits."

There are three further parameters you can set for echoverb and delay: delay time (0-3 for the echoverb, 0-4 for the delay, in 100ms steps), delay fine time (0-9 in 10ms steps) and feedback amount (0-15), the latter, as usual, increasing the number of repeats. Note that we're not talking stereo delay here. Again, the flexibility is really not there (not there, not...).

A peak LED on the output level would have been a useful indicator to have, as the signal level can be boosted quite considerably as it moves through the effects chain.

Helpfully, each version of the A5 comes with a booklet which lists the parameter settings for its 25 ROM effects together with names which indicate the suggested use for each effect. A page at the back of the booklet provides two blank patch charts which you can photocopy and use to note down the settings of your own effects - necessary given the absence of MIDI, and not burdensome given the relatively small number of parameters and the ease of programming on the A5.


REAL-TIME EFFECTS EDITING is not a possibility which springs to mind when confronted with a typical rackmounted effects unit. However, when confronted with an A5 it's a possibility which readily springs to mind - in fact, before you know it you're doing it. For a start, you can switch individual effects in and out with the mere shake of a leg - simple, but it adds a whole new layer of flexibility to the A5's processing.

If you want to get into editing individual effect parameters then you really need to get the unit off the floor and up to hand level. The MT review model started out on the floor, but after a while I moved it to a board straddling the extensions on an X-stand, sitting comfortably next to a Yamaha RY30 drum machine, and there it stayed. The amount of resistance in the footswitches is enough to give you a feeling of substance when stabbing at them with your foot, but not so much as to make operating them with your hands feel uncomfortable or cumbersome.

With multiple knobs in place of centralised digital parameter access, you can edit more than one parameter at once (within an effect), though the close proximity of the knobs can make simultaneous editing of adjacent parameters awkward. Knob-twiddling isn't entirely crackle-free (as in digital distortion rather than dirty pot, as the A5 tries to make the necessary real-time adjustments), but it's minor and something you only really pick up on if you're listening to a clean sound in isolation. Hiccup-free Writing of effects settings into memory makes it feasible to store an edited patch "on the fly" during live edits, while if you switch to patch select mode you can twiddle the knobs without affecting the effect parameters - useful in the case of some parameters for setting the knob position "next to" the value you want to select. Also useful is being able to edit an effect while it's switched out of the effect chain, so that if you know what parameter settings you need you can quickly set them up and then switch the effect in - if you don't, well, life is full of surprises.

It's all so easy - not to mention addictive - once you get into it. The problem is that the more you get into live edits the more you lament the A5's omission of MIDI, which could have allowed all these edits to be sequenced.


THE A5 IS an uncomplicated yet reasonably versatile multi-effects processor at an accessible price. Compromises obviously have to be made on a budget unit, and clearly there's a significant reduction in flexibility compared to more expensive effects processors. There again, more expensive units have become so sophisticated these days that even a scaled-down version is still a powerful and versatile unit. Personally I liked the character of the effects processing, which I'd characterise as sharp, incisive and powerful. Of the two versions, the Multi-FX is the more generally useful through its incorporation of the exciter effect, but the Guitar version is well worth investigating if you're taken with some of the uses outlined earlier.

What really sets the A5 apart is the front-panel accessibility of its parameters, which makes programming easy and opens up the possibility of real-time effects edits - though if you want to automate effect changes and record live parameter edits using a MIDI sequencer, clearly the A5 isn't going to be of much use to you.

Prices A5 Multi-FX and Guitar, £235 each; KVP001 Volume Pedal, £45.98; all prices include VAT.

More from Korg (UK), (Contact Details).

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Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.


Music Technology - Oct 1991

Gear in this article:

Guitar FX > Korg > A5

Review by Simon Trask

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