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Alesis Nano Compressor

Stereo Compressor/Limiter By Paul White
Published March 1997

Paul White plugs in the smallest compressor he has ever encountered, and finds that there's nothing small about the sound.

Though it's little larger than a DI box, the new NanoCompressor has a wealth of features, some of which you don't get even on many full‑size units — a side‑chain insert point, a choice of soft‑ or hard‑knee operation and even a choice of peak or RMS side‑chain sensing. Attack and release times are fully controllable using rotary controls, ratio is variable from 1:1 right up to hard limiting, and threshold is also fully variable. In RMS mode, you get the benefit of program‑dependent attack and release times too. On top of that there's separate gain reduction and metering, switchable input/output level metering and an output level control. Though I don't know too much about the circuitry used here, I'd guess that, at least in part, it's a spin‑off from the full‑rack 3630.

So how is all this possible in a box so small? The external PSU helps, but that hardly accounts for all the space‑saving — the real trick is that the NanoCompressor is a dedicated stereo unit, so each control actually relates to both channels. This feature combined with truly tiny, flat buttons, results in one of the most compact yet uncluttered front panels I've ever come across. The audio connections are on unbalanced jacks on the rear panel with a TRS jack handling the side‑chain insert point. Some people think that unbalanced gear is rather unprofessional, but when it comes to gates and compressors unbalanced connections can be a real bonus, as the vast majority of project studio desks have unbalanced insert points. Connecting balanced equipment often results in a significant gain loss, and the noise incurred by restoring this gain far overshadows any benefits that balancing might have to offer.

... you hear the sound gaining attack, density and punch — which, after general gain control, is why most people want a compressor in the first place.

Most of the controls will be familiar to anyone who has used a basic compressor before, but having a choice of hard‑ or soft‑knee operation on such a low‑cost unit is, to my knowledge, unprecedented. Switching from hard‑ to soft‑knee operation in some compressors can cause a significant change in output level, but Alesis have obviously arranged things so that the threshold is linked to the Soft/Hard switch, in order to allow the user to flip between both modes without experiencing a noticeable change in level, even though the amount of gain reduction being applied will change.

Having side‑chain access means that an equaliser can be patched into the side‑chain for de‑essing (simply boost the frequency at which the problems are occurring and the compressor will respond more to those frequencies), or you can patch in a control signal for ducking the level of one signal by another.

In Use

Because this is a dedicated stereo compressor, it can be used for processing either stereo signals or a single mono signal, but it can't be used as two independent mono channels. The control range is actually quite wide — Ratio is continuously variable from 1 to infinity, Attack can be varied from 0.1 to 200 milliseconds, and Release goes all the way from 50 milliseconds to 3 seconds. As in most compressors, the faster the attack, the less chance transients have of overshooting, but this can also lead to a dulling of the sound, so in situations where a brief overshoot is acceptable it's more normal to increase the attack time to a few milliseconds.

Knowing that this unit is likely to be bought by people inexperienced in using compressors, Alesis have wisely arranged things so that if all the knobs are set to their 12 o'clock positions, the resulting settings will give good results on most material. However, a little experimentation pays dividends.

Budget compressors often disappoint because they tend to rob the sound of clarity and definition, but the NanoCompressor is an exception. It isn't totally 'invisible', but instead you hear the sound gaining attack, density and punch — which, after general gain control, is why most people want a compressor in the first place. Drum sounds become harder and more solid, while rhythm guitars seem to swell to fill the spaces between strums with warm, even sustain. Vocals can either be compressed gently just to keep their level in check, or you can treat them more harshly to get that dense, mildly pumping 'rock vocal' sound. Even bass‑guitar recordings are improved. It's invariably necessary to set the attack time so as to allow the leading edge of the sound to pass through without being clobbered, but this is normal practice, and in RMS mode seems to happen automatically.


I'd rather expected not to like the NanoCompressor, because I'm a pathological hater of anything that isn't full rack size, and I feel that having a dedicated stereo unit is rather restrictive on those occasions when you want to compress two independent mono sources at the same time. These observations aside, however, I was more than a little impressed by both the flexibility and the sound quality of this tiny unit. Not only can it be used on a variety of different programme material, both single sounds and mixes, but it also manages to add an appreciable amount of punch without wrecking transient sounds. At increased levels of gain reduction, the NanoCompressor asserts its authority without fuss or tantrums, and though the side effects of compression do start to show up at medium and high levels of gain reduction, they are in the main benign and musically interesting.

Given the extremely low price of this unit, it would be churlish for me to complain too much about either its size or its dedicated stereo nature, as these are the very factors that have enabled Alesis to build such a good performer for such a low price. The package may be nano but the sound is most definitely mega, and though it's been some months coming it's been well worth the wait.

Compression And Detection

  • COMPRESSION KNEES: During hard‑knee compression, no gain reduction occurs until the signal level reaches the threshold, and then gain reduction occurs abruptly at whatever ratio is set up on the Ratio control. Soft‑knee compression, on the other hand, usually involves gain reduction coming in at a low ratio — around 5dB — before the signal level reaches the threshold, and by the time the threshold is reached, the ratio has increased to that set by the user. This progressive approach to compression usually results in more benign gain control, with fewer side effects than hard compression.

(For a comprehensive explanation of compression and limiting, see our April '96 issue.)

  • DETECTION PEAKS: While most people know the difference between soft‑ and hard‑knee compression, the difference between peak and RMS detection is less well known. Peak detection, as its name suggests, causes the compressor to respond to peaks in the input signal — even very short peaks. RMS, on the other hand, responds more to the average signal level (short peaks tend to be ignored), and in this mode the attack and release controls are overridden and the time constants controlled by a program‑dependent circuit. As a rule, peak detection is more suitable for use with transient sounds such as drums or aggressively played bass, whereas RMS detection would be used with voice, rhythm guitar and so on.


  • Flexible, but easy to use.
  • Good sound quality.
  • Inexpensive.


  • Non‑standard packaging requires adaptor for rack mounting (holds three units).
  • Dedicated stereo format precludes 2‑channel mono operation.


At the price, this is a supremely proficient little compressor with a tight, punchy sound.