1. PREAMPLIFIER - MIC/LINE GAIN, LINE/INSTR.
The MIC/LINE GAIN control determines the level of preamplification for microphone and line or instrument signals. In standard mode you control microphone preamplification. Engage the LINE/INSTR. switch to control line or instrument signals.
The preamplification values for microphone signals cover a range from +8 dB up to + 63 dB. If the optional microphone input transformer is installed, the scaled values are to be increased by ca. +14 dB.
The preamplification values for line and instrument signals cover a range from -12 dB to +22 dB.
2. COMPRESSOR / LIMITER
The COMPRESSION control sets the intensity of compression. Turning the control clockwise increases compression. The working area spans between 0 dB (fully left) and -32 dB (fully right).
The compressor applies the so-called “soft-knee” characteristic, which means it starts processing earlier than with hard-knee curve. Hard-knee compressors can sometimes gain more loudness, but they process abruptly and the danger to ruin a recording with compression artifacts is much higher. On the other hand the soft-knee compressor always helps very well to keep levels under control and ensures highest recording safety – and if there is a desire to gain further loudness, the signal can still be processed after recording.
At maximal compression it operates with a ratio of 1:3 between input and output signal – very effective dynamic processing are achievable with unobtrusive sound characteristics.
The LIMIT switch turns the compressor into a limiter. The COMPRESSION control now serves the purpose of controlling the threshold. The Limiter applies a “soft” characteristic and does not function as a peak limiter . In other words there is no guarantee that all peaks are limited. It is therefore advisable when driving a subsequent unit that a headroom of 2 to 4 dB remains. Peak limiters have a system-based disadvantage in producing audible distortions considerably sooner, so with regard to both sound quality and recording safety, we think the soft limiter mode is the better choice for a recording channel strip.
MAKE UP GAIN
With the MAKE UP GAIN control you can restore the overall level reduction caused by compression or limiting. With assistance of the GAIN REDUCTION display setting the MAKE UP GAIN control is made easy: If the maximal reduction value caused by the loudest tone amounts to -9 dB, for instance, the MAKE UP GAIN control should be set to values around +9 dB. If the compressor/limiter is now switched off the achieved gain in loudness will be audible.
This control serves to determine the intensity of S-sound reduction. Because processing is undertaken from comparison with the level of the entire frequency spectrum the processing is more intensive with extreme S-sound levels than with those of lower levels. This processing method achieves a consistent level of the remaining sibilants in the output signal.
In contrast to common de-essers based upon compressor techniques the SPL De-Esser makes use of the phase cancellation principle. It employs filters that process only the reducible “S-frequencies” but do not interfere with the remainder of the spectrum. The S-frequencies are detected automatically, the phase is inverted and mixed with the original signal. This method of operation has distinct advantages because it is unobtrusive and helps retain the original tonal quality. Compressor-typical side effects such as lisping or nasal tones do not occur. Finally its operation is as simple as pulling on the hand brake.
The center frequency of the half-parametric bass filter is set with the LMF control (low/mid frequencies). The adjustable frequency range lies between 30 Hz and 700 Hz so that this filter covers a range of about 4.5 octaves, allowing it to be used from the deepest bass to the lower mid range. This together with the MHF filter ensures that the entire frequency spectrum is covered.
The LMF-/+ control determines the boost or cut of the LMF filter; the maximum values lie between +/- 14 dB. The LMF filter also operates to the proportional-Q-principle.
The LMF filter can be applied in many ways. Examples are; to accentuate the fundamental sound of a voice, to cut “boom” frequencies and for placement of bass emphasized instruments during recording or subsequently when mixing etc.
The center frequency of the semi-parametric mid/high frequency filter is set with the MHF control. The frequency range can be set between 680 Hz and 15 kHz so that this filter covers a range of 4.5 octaves and can be equally employed in the lower mid as well as the high range. This together with the LMF filter ensures that the entire frequency spectrum is covered.
This control determines the boost, or cut of the MHF filter; the maximum values lie between +/- 12 dB. The MHF filter utilizes the proportional-Q-principle too. The filter construction permits the complete scope, from selective removal of accentuated frequencies through to character giving accentuations of an instrument, to be effectively and quickly covered.
The high frequency filter in the equalizer module is described as the AIR BAND. A coil-capacitor-filter with so called bell characteristics and a center frequency of 17.5 kHz comes into operation here. At this frequency the maximum possible accentuation is +10 dB, the maximum possible damping is -10 dB.
The soft and natural tonal property, characteristic of the coil-capacitor filter, lends itself extremely well to provide clarity and ... well, air, to vocals in the upper frequency range, thereby improving their presence. On the other hand harsh sounds can be lent a more pleasant sound characteristic through damping.