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Smart Research C2

Compressor By Paul White
Published March 1998

Smart Research C2

Paul White finds he has a crush on the Smart Research C2 compressor — but at what cost?

Smart Research are a small British company who, in a very low‑key way, have been making inroads into the high‑end signal processing market. The company is headed by engineer Alan Smart, who has been in the pro audio industry for 16 years, starting his career as an assistant engineer at Waves studios in London, before becoming an electronics engineer at Digital Audio Systems. Since then he's been involved in a number of prestigious projects, including work for Peter Gabriel, both on tour and in the studio.

The new C2 compressor is distinctive in appearance and is priced in the esoteric league, but at first glance the controls look pretty standard — until you spot the button marked 'Crush', that is! In fact, the original concept for the C2 has been around since 1984, when Alan used the prototype on his own recording sessions at Blue Wave Studios in Barbados, where he was chief engineer.

The current C2 incorporates a number of improvements, and is a 2‑channel, 1U‑high rackmount compressor that can be used in stereo link mode to treat finished mixes, or used as two independent compressors. 'Crush' mode, which I'll come onto later, can only be selected globally, so either both channels have it or both don't.

Inputs and outputs are on XLRs only, with a further pair of XLRs fitted to provide side‑chain access. The side chains may be left permanently connected, as they can be selected via buttons on the front panel.


As soon as you power up the C2, the front‑panel buttons flash in a brief test sequence, which suggests some kind of digital switching rather than the more normal analogue switches that sit directly in the signal path. All six buttons have a short travel and illuminate when active, providing bypass for each channel, side‑chain access for each channel, stereo linking, and Crush mode.

Though the compressor timing controls seem fairly standard, they are in fact switched rather than being continually variable, and there's no soft/hard switching or auto attack/release mode. Judging from the graphs supplied, the compressor seems to have a progressive 'knee' which is very soft at low ratios and becomes harder at higher ratio settings. Threshold is continually variable from ‑20dB to 20dB, while Ratio is adjustable in six steps, from 1.5:1 right up to hard limiting. The Attack time has seven steps, ranging from simply very fast (which is around one third of a millisecond) to 30ms, and Release time is set in six steps, from 100ms to 2.4s. These controls are followed by a variable make‑up gain control, offering up to 20dB of additional gain. Metering is via moving coil, non‑backlit meters and these always show gain reduction — there's no additional metering or meter‑switching to show the output level.

Compress Or Crush?

Before a compressor can sound good while compressing, it has to be able to sound good while doing nothing, so the designers have gone to great lengths to make the basic signal path as clean as possible. The circuit frequency response extends from 20Hz to 100kHz, within half a dB, while adding no more than 0.005% distortion (at 1kHz). The output can drive at up to +28dB into a 600Ω load, and if there is a power failure or power supply failure during use, a failsafe relay connects the input directly to the output. Even the side‑chain inputs are balanced.

Because a differential pair of very high‑quality VCAs has been used (see 'Inside The Box' box for technical details), the designers have at their disposal a low‑noise, distortion‑cancelling block, and for most applications this is exactly what is required. However, compression can be as much an effect as it is a process, which is where the Crush control comes in. Crush brings in an FET gain‑control stage that works in conjunction with the VCA to produce harder compression and progressive distortion at high signal levels, ostensibly to recreate the sound of classic compressors. However, Crush also brightens up the sound in a subtle but noticeable way, by adding a filter with a gently rising response. The effect is a little like the so‑called 'air' or 'gloss' controls on some high‑end equalisers, and it is quite independent of the amount of compression added. As far as I can ascertain, this filtering effect is not dynamic — it's a straightforward (but very nice sounding) fixed EQ.

The Ears Have It

I checked this compressor out with live vocal mics, live acoustic guitar mics and pre‑recorded sections of drums, submixes and final mixes, all of which confirmed that it is indeed a very well designed and incredibly quiet compressor. With Crush mode off, modest levels of compression provide near‑transparent gain control with no loss of top‑end detail, while hard compression invokes a little musically benign pumping at faster release times. The degree of pumping is just enough to add character and energy to a sound when you need it, but it certainly isn't excessive.

Switching in Crush mode makes an immediate difference, both in tonality and in the way the compressor behaves. The amount of gain reduction on signal peaks seems to increase by three or four dBs ( at least according to the meters) and the sound takes on what can only be described as a punch or smack. Kick drums really come alive on the Crush setting, as do bass sounds, and if you really pile on the compression hard in this mode, the feed‑forward compressor circuit makes cymbals splash and pump just like the old '60s recordings where the cymbals seem to swell in level after they are hit. If you need compression with attitude, look no further than Crush — although, being critical for a moment, I do feel that on a compressor of this price the EQ boost should have been made variable. As it is, if you select Crush you get the EQ boost thrown in, and, nice as it is, it's a hint too much for some sounds, especially if they're quite bright already. I think an auto attack/release mode would have been useful for some applications too, especially mixes that include radical changes in their dynamics.

These minor criticisms aside, the C2 is a technically superb compressor that adds negligible noise, and no distortion, unless you really want it to. It has enough flexibility to be useful on most types of solo and mixed material, it can provide polite gain reduction, or it can exude attitude — it's all up to the user — and because the controls are so simple, setting up is very easy.


Despite its esoteric price tag, the C2 is different enough from the competition to carve its own niche. The general signal quality is exemplary, and it's great for creative compression effects as well as routine gain‑levelling. I have to admit that I'm surprised by some of the omissions, especially the lack of output metering, but there's no denying that this unit sounds good and is easy to use. The Crush mode is tight and hard hitting, but, as mentioned earlier, I feel the associated EQ effects should have been made switchable or variable.

In short, the C2 seems as happy dealing with a full stereo mix as it does a solo vocal or drum track, and because it has such a technically transparent signal path, it should be warmly received in mastering circles, as well as for general studio recording and mixing. If you're in search of something a little special, I recommend you give the C2 a try.

Inside The Box

Technically the C2 is quite sophisticated, with elaborate high slew‑rate, low‑distortion input and output stages designed to avoid the noise that occurs with more common designs. The input stage may be used balanced or unbalanced with no gain‑change penalty, and the output stages incorporate discrete devices to provide the capability to run into low impedances or long lines. Rear‑panel 3‑way switches select balanced or unbalanced operation for the output stages, as well as giving the option of ground lift.

Gain control is handled by a differential pair of the latest THATs VCAs, though in Crush mode a further stage of FET gain reduction joins the party. A symmetrical signal path is used throughout, to reduce distortion, and apparently there are no electrolytic capacitors at all in the audio chain.


  • Clean, quiet signal path.
  • Choice of polite or aggressive compression.
  • Simple to set up.
  • Crush setting produces some great drum sounds.


  • Very expensive.
  • Crush setting EQ can't be varied or bypassed.
  • No output level metering.


An esoteric and impeccably specified compressor that's just different enough to attract a lot of interest. It's a shame that few project studio owners will be able to afford to consider it.