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Alesis Micro Effects

David Hughes tries out three new low-cost companions to the Alesis Microverb - the Micro Enhancer, Micro Gate, and Micro Limiter. Are they the Accessit range of the Eighties?

The Alesis name will be familiar to most readers as the originators of those digital wonders, the MIDIverb and MIDIfex signal processors. Recently, the company has attracted a great deal of attention with respect to their HR16 drum machine and MMT8 MIDI sequencer (reviewed SOS January 1988).

However, the subject of this review is the recent additions to their range of studio quality effects units, the aptly named 'Micro' series. The first product in the Micro series was the 16-bit Microverb which, like its larger forebears, produces real studio quality digital reverb at a truly affordable price. The latest additions to the series are three effects boxes: a noise gate, a psychoacoustic enhancer, and a compressor/limiter.

Each of these comes in a sturdy, 1U high by 147mm x 157mm metal box with stereo inputs and outputs on the rear. Furthermore, each box comes with its own 9 volt power supply and an excellent manual. The units all have the same basic appearance, three rotary potentiometers and an effects bypass switch. (This similarity can be a little confusing if you're trying to read the front panel settings from the other side of the studio.) Also, since each box is powered from its own external transformer, if you're using all three devices as I was for the purpose of this review, then you've got to have another three mains sockets to plug them into, which is quite tiresome if your studio already has a serious wiring problem. Hopefully, Alesis will do the right thing and provide a single adaptor with a number of outputs to power multiple units.


The first box to come under scrutiny was the noise gate. A 'noise gate' is basically a means of electronically 'masking out' the general background noise that tends to be generated by all types of electronic equipment. Every musician eventually learns about the problems caused by noisy leads and devices such as chorus pedals, etc. If you're like me and have a neighbour whose idea of a quiet Sunday afternoon is to spend two hours sanding the front door with the Black and Decker he got for Christmas, then a noise gate is essential if you're to cover up all of the minor annoyances such as 'spikes' on the mains supply that tend to make your recordings sound like an advert for a well-known breakfast cereal.

The 'noise gate' is a simple technique that mutes the output stage of the audio path when the signal drops below a predetermined level so, although the 'snaps', 'crackles' and 'pops' are still there, the noise gate mutes them during the quiet passages of your music and, consequently, they are not as obvious. If this sounds like a rather savage technique to apply to an acoustic chain that you've probably spent hours attempting to perfect, then you're perfectly right. That's why most good noise gates have a built-in envelope generator/shaper which modifies the response of the gate so that the sound isn't chopped about unless you want it to be.

To evaluate the Alesis Micro Gate properly, in terms of how effective it is in a real situation, I compared it with a very similar device - the Boss RCL-10. This has a compressor/limiter and a noise gate combined in one unit and so provided an excellent reference point for the review.

The Alesis gate proved very simple to become acquainted with. The Threshold pot sets the transition point of the gate from open to closed; the Delay control allows you to set the time taken for the gate to close after the signal has fallen below the threshold level; and the Rate control sets the rate of closure of the gate. This method of controlling the noise gate worked very well. The state of the gate is determined from three LEDs on the front panel: a single red LED indicates that the gate is closed; a green LED indicates that the gate is open; and the yellow LED lights to indicate that the input signal has fallen below the threshold level and that the gate will close as soon as the time period set by the Delay control has elapsed.

To compare the Alesis gate with the Boss equivalent, I used an old string synthesizer which I custom built in my University days. As with all early attempts at polyphony, my string synthesizer was based on simple electronic organ technology and involved an enormous number of connections in a wiring 'loom'. Each of the connections involves an audio signal which tends to pick up the audio signals from other adjacent connections and the resultant background noise/hum is known as 'beehiving'. This machine was the ideal test-bed for the noise gate. Beehiving is always present, it's just that it tends to stand out more when the instrument is supposed to be silent, ie. not actually being played.

Both the Boss and Alesis devices proved to be extremely useful in this application and the string synth was, in fact, almost usable again. However, where the Alesis unit really shone was in the fact that it is a stereo unit and this meant that I could treat both left and right outputs of the instrument from the same box and maintain channel separation. Sadly, the Boss gate is strictly monaural. However, I still could not give the Alesis unit top marks because of the effect bypass switch on the front panel, which generates a considerable 'thump' when the switch is used. I would have thought that silent, electronic switching would be essential on an effects unit which purports to be 'studio quality'. By comparison, the Boss gate was completely silent when switching. First impressions: not at all bad, quite useful, and good value for money.


The Alesis Micro Limiter, to paraphrase the manual, is a true stereo input, stereo output compressor/limiter which can be used for automatic gain riding and special effects on both live and recorded instruments and vocals. This device, like the noise gate, is essential in any studio. The 'limiter' effectively puts a lid on the level of a signal. Even when the input signal is below that limit, it can be compressed so that for every four decibel rise in the input signal the output will only rise by, say, two decibels. (This is a compression ratio of 2:1.) The effect is most useful in, say, the recording of vocals when the vocalist isn't perhaps aware of how loud he or she may be.

Operation of the Micro Limiter proved to be a little disorientating at first, since its control pots don't immediately function in the manner I expected. The manual states that this is because the limiter was designed to be "more musically useful", which is a little difficult to comprehend.

The control functions are as follows: the Input control sets both the level of the incoming signal and the degree of limiting to be applied to the input signal. The LEDs on the front panel indicate this wonderfully. The Release Time control sets the time taken for the limiter to recover from an input signal so that the compression/expansion of the signal is smooth with no audible jerks. The Output control is provided so that you can easily match levels after the limiting process.

In use, the Alesis compressor/limiter worked very well. I liked the stereo option a lot, it simplified the treatments a great deal. However, the problem of silent switching reared its ugly head yet again. There was another audible 'thump' when the in/out effect bypass switch was used. Possibly Alesis think that it is more 'musically useful' to have the device permanently connected and to only use the bypass switch for setting-up purposes (?). Strange omission in a studio quality product. First impressions: excellent.


I reserved my judgement of the third addition to the Alesis Micro range until last. The Micro Enhancer proved to be a very, very curious device. To briefly explain, the process involved in psychoacoustic enhancement (not something used by Alfred Hitchcock to 'pep up' Anthony Perkins prior to the famous 'shower scene') is a very subtle technique described as a mixture of high frequency boosting, compression and harmonic generation designed to resynthesize the upper harmonics of sounds which are otherwise lost in the recording process.

I tested the Micro Enhancer on a number of sources: vocals, guitar (both acoustic and electric), synth, even a couple of old recordings which I made years ago on an old Decca cassette machine with no tone controls. I asked several other people for their opinions of the effect and we all agreed on one thing - there was very little perceptible difference between the input (direct) and output (treated) signals. Certainly, there was a change; not a great change but a very subtle one. And not a change that we could all agree on. There was an improvement in the degree of bass resolution and a general improvement in high frequency definition. But nothing really tangible that you could say 'Yes, there's definitely a psychoacoustic enhancer in there.' This made me stop and think very hard. Is my hearing at all impaired? Is the amplifier suspect? Are the speakers up to the job? Well, I don't believe that my hearing is at all impaired, other than the natural wear-and-tear one might expect for a 26 year-old pair of lug 'oles. My amplifier is getting on a bit but certainly seems more than capable of the job and so do the speakers. Even when monitored through a pair of Beyer Dynamic D550 headphones, there was very little in the way of difference between the input signal and the output signal. Very, very puzzling...


What can I say? If I had to choose between the Alesis Micro Gate, the Micro Limiter and the Boss RCL-10, then I would go for the Alesis products happy in the knowledge that it had been a good buy. This should not cast the RCL-10 in an unfavourable light. Both units proved to be extremely easy to use and their effect on the recording process more than justified the small sum spent on either unit. It's just that, to my ears, the Alesis units sounded cleaner and were stereo rather than mono. Also, the Alesis effects boxes are definitely of a sturdier construction than the RCL-10.

I do have some reservations, however. If you intend rack-mounting these devices (all three slot neatly together, side-by-side, to facilitate this) then you should consider using a patchbay of some sort so that you can simplify the connection process. Personally, the separate mains adaptor is a minor annoyance. At a time when I'm attempting to cut down on the number of leads that invariably get too muddled to sort out properly, having three extra leads dangling in the way is no joke. Finally, I can't understand why the bypass switching on these units is not silent. This is very sad on units of this quality. I hope Alesis rectify the problem before the devices get into bulk production.

To finish then, I would recommend both the Micro Gate and Micro Limiter to anyone with serious aspirations but with limited cash. They really are good quality and excellent value. However, if money is a problem, I would find it very hard to recommend the Micro Enhancer. It just doesn't do enough to justify the expense.

If you want another Alesis unit to fill the third location in your 19" rack, buy a Microverb instead.

Price £129 (inc VAT) each.

Contact Sound Technology pic, (Contact Details).

Previous Article in this issue

Delirious Xcitement

Next article in this issue

GenPatch ST MIDI Librarian

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Mar 1988

Review by David Hughes

Previous article in this issue:

> Delirious Xcitement

Next article in this issue:

> GenPatch ST MIDI Librarian

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