Crane Song Ltd. STC-8 Discrete Class A Stereo Compressor-Peak Limiter

Review by George Shilling

This is a sophisticated US-built stereo compressor, designed with attention to detail in both function and form. The unit's designer David Hill has taken a very scientific approach: the manual is littered with charts and diagrams. But this approach is firmly based on sonic performance. The circuitry is all Discrete Class A, with the benefits of second harmonic distortion components, which are more musical than the odd-order harmonics you tend to get with Integrated Circuit Op-Amps. One disadvantage is of course a higher price, another is that a significantly greater amount of heat is generated. Indeed, the rear of the STC-8 feels warmer than many valve units. There are external and internal heatsinks, the latter holding hot discrete transistors. With its meshed top panel, extra rack space must be allowed for adequate ventilation above the 2Us that the STC-8 occupies.

This is an extremely well constructed unit with sturdy internal bracing. Connectors are XLR of course, but there is also a DB-15 connector for sidechain connections and switching, so you will need to get a special lead and switch for this. The metal front panel has a smart arrangement of attractive bluey-green knobs, smart black toggle switches and excellent LED-segment metering. If it sounds as good as it looks, this should be some compressor. And it certainly is. The Crane Song is surely one of the smoothest compressors I have used. You can make it distort using very short times and winding up the Shape control, but it never sounds unpleasant. Although there is a conventional Threshold knob, the Shape knob takes the place of Ratio. Being a soft-knee design, this unit's ratio varies depending on input level (and release times). Shape controls the steepness of the compression curve. This is akin to a ratio control but is a much more intuitive way of controlling the 'depth' of compression. The ratio typically reaches only 5:1 with 18dB of gain reduction, and the STC-8 seems to work happily and cleanly with such large amounts of gain reduction. The Output Gain knobs have a sensible 14dB range of make-up gain. They also have a pleasant stepped action.

A virtually bullet-proof peak limiter is included. One can set this up for overload prevention, say when recording to a digital format, and it sounds remarkably clean and reacts very quickly, reaching a ratio of over 10:1.

A 16-way mode knob gives different combinations of available compressor modes. Unnecessarily complicated and poorly legended, I found it difficult to visualise what each setting meant at first, so new users would probably need to spend some time familiarising themselves with this. The Program Dependent Release (PDR) mode prevents unwanted background noise surging up in the gaps, whilst retaining faster release times within normal program level variations. Alternatively, fixed release times can be selected. The Dynamic Attack Modification (A-MOD) mode enables peak limiting to dynamically modify the compressor attack time, so that slow attack times can be combined with peak limiting. In this case, any signal triggering the peak limiter shortens the compressor attack. These two ‘on/off’ mode choices are offered in all permutations, adding up to the four main regions of the knob. Each of these sections is then sub-divided into four settings: three Attack/Release presets thus: A (for vocals), B (for bass or 'punch') and C (for program), and a Variable setting allowing you to manually set Attack and Release with the knobs. The three presets are achievable in V mode by setting the Attack and Release knobs to the values quoted in the manual. The duplication of these settings seems unnecessary and spoils the otherwise excellent layout. Separate four-way switches would have made preset and mode selection much more straightforward. Due to their variable nature, the Attack and Release knobs are simply calibrated from 0 to 10. Their ranges depend on, and interact with the Shape setting, mode selected, program material and gain change, giving much more usable ranges than those often encountered.

The intriguingly labelled Hara/Ki switch sounds intimidating, but is explained in the manual as a remarkable function to convert induced 3rd harmonic distortion into more sonically desirable 2nd harmonics in the Ki position. It certainly seemed add a very pleasant, subtle glow to some signals when using powerful and fast compressor settings, but much of the time it is almost or completely inaudible. The switch affects both channels simultaneously, and in the Hara position the signal is left 'transparent'.

This is not going to be your first choice compressor if you want to hear some pumping and grit. Subtly audible gain reduction is what the Crane Song does best, and it does this exceptionally, despite huge indicated gain reductions on the meters, (which can, incidentally, also display Output level or Peak reduction). The Crane Song is capable of very fast, almost ‘invisible’ gain control, as well as smooth slow compression, which can also be remarkably transparent. That is not to say it sounds bland. I enjoyed it particularly across a whole mix, and it was excellent with acoustic instruments such as piano and guitar. Although thoroughly modern, the STC-8 has a proper ‘Old School’ sound. Recommended.