Manual

206 PRO X User Manual
Soft clip level
When compression is used creatively with slower attack times, it is possible to generate very large peak signals that can eat up headroom. When soft clip is activated
the compressor output (post-make up gain) is fed through a nal fast acting soft clipper circuit. This adds progressive gain reduction to any signals that exceed a
threshold set by the clip level control. When set sparingly, this can recover 3dB to 6dB of headroom without introducing any undesirable audio artefacts. (In the
past, limiters have been employed for this function but their time constants are invariably intrusive on the programme.) The high-speed nature of the soft clipping
introduces no time related artefacts. This is because it only acts during the transient peaks, when it produces predominantly third harmonic distortion, which is very
musical in nature.
Presence
Presence boosts the upper mid-range frequencies to give added depth to the sounds of voices and instruments with similar tonal ranges.
Compressor envelope modes
The ve envelope modes, or signatures, are the key to the sonic character of the PRO X compressors, and they allow adjustment far beyond the normal capabilities of
simple attack and release settings. They largely fall into two application types:
1. Compressors that are good at capturing and controlling dynamic transients: corrective mode and vintage mode.
2. Compressors that emphasise dynamic transients and provide creative control of levels within a mix: adaptive, creative and shimmer modes.
The Vintage and Adaptive compressors tend to morph a little between these two categories depending on threshold control settings. This makes them easy to use
intuitively with minimal ne-tuning of the envelope control settings.
Further renement and enhancement of the envelope modes is provided by the threeposition KNEE switch. It is best to understand the operation of this function in
more depth before looking at the detail of the compressor signature switching.
Knee
The soft knee curves behave in a traditional way to blend the compression ratio around the threshold setting (as described above), but more importantly they also
have a signicant eect on the attack envelope shapes. The soft knee typically slows down attack speed on signals in the knee area, which is desirable for natural
sounding compression because it compliments the reduced ratio eect of the soft knee. This produces very gentle compression in the knee region.
The KNEE switch has three settings: hard (4 dB); medium (12 dB); and soft (40 dB). In hard setting the compressor still retains some soft knee characteristics. This is
because the implementation of an extremely hard knee produces undesirable sounding distortion on low frequency programme material.
Corrective mode (exponential peak - fast)
This is a peak sensing compressor (like many older designs) with exponential attack and release. It produces aggressive compression that gives good fast control/
limiting of dynamic material. It can be used to add colour to low frequency signals, thus making it ideal for controlling extremely dynamic instruments like the bass
guitar. The compressor tends to sound best with fast attack time settings that capture transients and with release adjusted to taste to either emphasise or minimise
distortion and pumping eects.
Adaptive mode (exponential RMS - accurate)
This is a root-mean-square (RMS) sensing compressor with exponential attack and release. The RMS averaging process interacts with the attack and release to produce
a very adaptive envelope character. This allows faster attacks on large (over-threshold) signal changes and produces slower attacks on small signal changes, regardless
of attack time setting. The attack control is still active, allowing some user intervention although the adaptive nature makes envelope control setting fairly non-
critical. The compressor is therefore very fast and simple to set up on most programme material. It is also sonically accurate and works well for both compression and
limiting of vocals and many other sources. The most natural sounding compression is normally achieved with soft knee settings.
Creative mode (linear peak - slow)
This is a peak sensing compressor with linear (dB rate) attack and second order release. The compressor is very transparent, providing some dynamic control but
without unduly aecting the intentional dynamic content of the source material. The linear attack provides a constant rate of attack, such that large changes in
programme signal level take longer to become compressed than smaller changes. Adding soft knee noticeably delays these attacks, which can be particularly useful
on drums where compression can be applied to emphasise transients giving more punch while retaining a good deal of artistic dynamic from the drummer.
The compressor normally sounds best with slower attack time settings, when it can be used on dicult instruments, such as the acoustic guitar, with relatively fast
release to keep equal perceived loudness within a mix without producing excessive utter or distortion.
Vintage mode (adaptive peak - bright)
This is a peak sensing compressor with a partially adaptive nature. It produces extremely subtle attack and release curves during the onset of compression that are
largely independent of the envelope control settings. However, as it is driven harder, that is, signals are further over-threshold, the attack and release times become
more aggressive and gradually return to manual control so that the operator can optimise the capture (or otherwise) of larger transients etc. The peak sensing
algorithm intentionally increases harmonic overtones during compression, which adds a valve-like brightness and sparkle to the programme, producing extremely
natural and lively sounding compression of acoustic instruments.
Shimmer mode (overshoot peak - slow) - output only
This is a peak sensing compressor with an exponential release and unusual second order attack character that tends to overshoot. If used sparingly, the compressor
sounds very soft and natural, and can provide additional control of material that already has a fairly low dynamic content. It can sound very transparent on vocals
where it retains a good degree of life in the performance. If used at higher ratios with slow attack and fast release times, the compressor can produce a very soft,
bouncy sound character.