Top producer / engineer, George Shilling, also takes time out to review interesting audio equipmentGeorge Shilling reviews:

Mutronics Mutator



It is not uncommon these days for record producers to have ProTools systems with software plug-ins to digitally emulate analogue effects. There are also many studio units with digital gates, digital compressors and even digital EQ, all trying to treat signals with approximations of analogue effects. However, there are still some of us who appreciate the real thing – Fairchild limiters, Pultec EQs, Valley People Kepex gates: equipment from a bygone era that is still the preferred choice of many, because it does the job so well, and sounds so good.


So it is with great pleasure that I tell you that the Mutator retains those ancient units' tradition as a characterful yet no-nonsense, no-frills, piece of outboard. It uses tried and trusted technology, indeed technology that was at its most popular in the 1970s. There is nothing digital about this unit. And yet, it is something quite new and original for the recording engineer..


mutronics mutator



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The Mutator is effectively the filter section of an analogue synth stuck inside a 2U-high,19-inch rackmount box. To a synth player, the filtering is the source of major fun, and to the recording engineer a similar filter opens up possibilities rarely exploited in a professional unit.


The chunky black front panel features big black knobs for all variable controls, and cheap 'n' cheerful metal toggle switches. The unit runs in stereo and so has separate controls for each channel. There are three main sections, the first of which contains the envelope follower with selection of internal or external envelope source, gate or envelope operation and knobs for SENSITIVITY (threshold in gate mode), ATTACK and RELEASE. The second section hosts the LFO with knobs to control RATE, WAVEFORM and DEPTH, and switches for LINK and LINK INVERT, and also VCA, VCF or both. Finally there is the filter itself giving control over positive or negative envelope sweep, cut-off frequency and resonance. Each channel also has a BYPASS switch and a VCA IN-out switch.


At the back there are cheap plastic jack sockets for input, output, external envelope input, and CV input for each channel. These are all unbalanced mono jacks, and some might have preferred to see balanced connections for better interfacing with professional equipment. Here there are MIDI In and Thru connections and a notched rotary MIDI channel selector – I prefer all my controls on the front. In fact, the MIDI implementation appears to be something of an afterthought, but it is an option that most will nevertheless find useful..


There is certainly none of your tc or Lexicon sophistication here, but then who needs it? This box was built to do a job, not to bolster the looks of glossy magazines (I suspect a kind of inverted snobbery at work here). Possibly the only concession to modern studio equipment design is to make the legending front and back so small as to be unreadable in all but the most brightly lit studios, which may be acceptable in certain circles, but surely not to those with their sights on the Mutator – we're trying to create a vibe here. Making the knobs different colours (they are all black) would be a start. But you'll appreciate that these are minor quibbles when I tell you what Mutation is.


FIRST, I tried some envelope following. If you've ever used a Boss Touch-Wah pedal you'll know where I'm coming from – level-dependent wah-wah. Mutator helped me round out, and give a bouncy transient, to each note of a rather nasal synth bass part. The sound was transformed dramatically, the Mutator giving a superb warmth and character to the part. On keyboard lines I was able to add a resonant analogue twang to each note, although setting the sensitivity was difficult on some parts with varying volume levels. (This could be helped by adding compression to the signal before it reached the Mutator, or if using MIDI setting the note velocities all the same).


I should explain that the sensitivity- threshold setting is made easy with a variable brightness LED or each channel. There are no rows of multicoloured lights here, but then they're really not necessary. The variable attack and release settings give a wide variety of effects. When modulating a stereo source, you can parallel the input of channel one to the EXT input of channel two to enable tracking of the two channels. However, there is no way, other than by using an external CV or MIDI, to synchronise the frequencies of the filters of each channel. With the resonance turned right up the filter goes into self-modulation where the cut-off frequency produces an audible note or tone.

The envelope section's ATTACK and RELEASE controls allow you to vary the speed of the filter sweeps from a subtle swoosh to an intense wah-wah. I obtained some great effects with long sounds such as pads, by sending a rhythmic pattern to the Mutator's Ext input as a key. I keyed a voice pad with a hi-hat part to create a wonderful, bubbly, pulsating, new part. Sending drums through the main inputs gave some great effects, especially those Ultravox-style, filter-swept, explosive whooshes – now that's a sound that hasn't been used for a while.


Of course, you can twiddle the knobs in real time as you record a part, adding your own wah-wah as you go. I would love to have had one of these when I was recording the Soup Dragons 'I'm Free': all that guitar wah on the record is no wah- wah pedal, it's me twiddling the EQ. I remember the record company ringing up after hearing the rough mix, saying they wanted to hear 'more of the "wackawacka" sound – it's a hit sound!'. It was, sure enough, and if you are after that hit sound, then this is the box for you.


For yet more dramatic effect, you can switch the envelope filter key to Gate mode. Instead of the envelope smoothly following the key signal, the sensitivity becomes a threshold control. When the threshold level is reached the gate opens or closes the filter by the amount set with the envelope + - knob, at the speed set by the ATTACK control. As the signal drops below the threshold, the filter returns to its original setting at a speed determined by the release knob. The circuit includes a switchable VCA, so the choice is yours whether to have level affected as well as or instead of the filter. This gives you possibilities of all sorts of juicy pulsating sounds, which might bear little relation to the clean signal you fed in originally – but are great for dance remixes and the like. You can also use the unit as a straightforward stereo noise gate, of course, and it works well in this mode with fast attack times opening the VCA without any audible click.


With the appropriate patching you can use the filter of one channel to process the Ext key input of the other, for those difficult gating situations where you need to hone in on a particular frequency. THE LFO SECTION is useful for autopanning and tremolo effects. Autopan is achieved by linking the two channels in Inverted mode. This means that as the filter and-or VCA opens up on one side, it closes on the other. There are four LFO sweep waveforms – sine, square, and saw-tooth ramped up and down – giving a wide range of effects. The LFO has a toggle switch to select whether it controls VCF, VCA, or both. This can lead to some unusual tremolo effects, or wonderfully swooshy autopanning if you use the filter appropriately. Unfortunately, there is no way of controlling the speed of the LFO externally, although MIDI Note On and Note Off commands retrigger the LFO when the unit is in Envelope (not Gate) mode.


MIDI clock might have offered one way of controlling LFO speed, but it would need additional hardware for selecting note length values which would clutter the straightforward design and push up the price.


As already noted, the MIDI implementation is something of an afterthought, but very useful nevertheless. The selector knob on the back gives you two adjacent MIDI channels – one corresponding to each audio channel.


When Gate (as opposed to Envelope) mode is selected a MIDI Note On command will open the gate, and the MIDI note value of the note played controls the cut-off frequency of the filter. Resonance and VCA volume are available via MIDI controllers: Resonance on MIDI Controller 1 (the modulation wheel on most synths) and VCA volume on MIDI Controller 7 which is, logically enough, MIDI main volume. The front panel controls remain operative even when parameters are under MIDI control, so some hands-on control is still possible.


The external CV (Control Voltage) inputs allow a standard 1V-per-octave control to adjust filter cut-off frequency from your vintage synth, or more likely via MIDI through a MIDI-CV converter. The manual frankly admits that it would generally be easier to sequence a part with varying velocity, and send the audio to the external input for this kind of operation. The choice is there if you are an analogue synth enthusiast, or if you have one of the new generation of synths, such as the Novation Bass Station, which features a CV output.


An engineer who has never used an analogue synth, or who is familiar with more subtle desk EQ will be pleasurably surprised by the intensity of effect available here. You can twiddle with the Mutator to get subtle movement, thickening or resonance, but it is easy to get carried away and make everything squidgy – which is probably what most engineers want. I suspect the main purchasers of this unit (undoubtedly the dance- orientated remixer, producer and musician) will love the exceptionally high knob-twiddle factor.


The manual is a slim but helpful and friendly booklet, with an engagingly humorous foreword by the enthusiastic designer – himself a recording engineer. Thankfully, there are none of those patronising connection diagrams with mixing desks and amplifiers so beloved of some manufacturers. Nor do you get one of those unfathomable MIDI implementation charts, just straightforward descriptions of features, and a few example settings to get you going.


In terms of signal quality, the Mutator is quiet and clean, despite the use of unbalanced connectors. Its straightforward conception reveals its designer as a professional user and obvious enthusiast. I loved it – ts something different and useful, and already has a long list of professional endorsees. However, the rather steep asking price and lack of glamour might deter some of the bedroom ADAT brigade.


(Footnote: This is, so far, the only device that I have ever reviewed that I have liked so much that I actually ended up spending money on one!)


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