DeCompressor, Expander and
This section of the Mastering Dynamics Processor can be used in several different ways.
- as Expander to suppress noise
- as DeCompressor for the repair of over compressed mixes
as special 'Pump Up' Compressor
The section has controls for Threshold, Attack, Release, Ratio and a GR-Limit control. Independent of the operation mode, the regulation is always downwards, which means that levels above threshold do not cause any regulation and the gain or gain reduction increases when the level below threshold drops down. In difference to compressor and limiter, the treshold is the upper limit for the regulation and not the lower limit. Above theshold the signal remains unchanged.
Attack and Release
The Attack and Release controls of the section are not different from the corresponding compressor controls; however, the different regulation characteristics has to be considered. The attack control determines the reaction delay of the regulation when the input level is increased, while the release control determines the reaction time when the level drops down. This can be a bit confusing; depending on the point of view, attack and release change their functions between expander mode and pump up compressor mode. However, with compression, the attack time is still the reaction time on a higher input level, but, in difference to expander mode, the output level is reduced in this case. The release control ranges from 0.1 sec to 2.5 sec; the range of the attack control is 0.2 ms to 10 ms.
The range of the Threshold control that determines the upper limit of the regulation, reaches from - 40 dB to + 15 dB, which is sufficient for any application.
Ratio and GR-LIMIT
The Ratio control determines the operation mode. The inactive, 1 : 1 setting is at the center position. Turning the ratio to the right causes compression while the range to the left causes expansion or de-compression, respectively. The maximum Ratio is 2 for both modes.
The GR-LIMIT control determines that maximum gain (with compressor mode) or gain reduction (with expander/de-compressor mode). The range from 3 dB to 50 dB (full range, no limitation) allows all settings that are needed for the different operation modes. The law of the control pot is double logarithmic, which allows precise adjustment of the small values that are mainly necessary. The GR-limit control is very important for both the pump-up compressor mode and the de-compressor mode. With de-compressor mode, it makes possible to determine the level range of the de-compression precisely. With the pump-up compression mode, this control determines the maximum possible gain. If this would not be limited to an appropriate value, the gain would constantly raise down to a level below - 80 dB which would result in extremely high noise values at low input levels.
DeCompressor and Expander
Both applications are not really different. Only the threshold setting is entirely different. While the expander is supposed to suppress noise and other interferences at low levels and leave the levels above this noise floor unchanged, the de-compressor is used to reverse a prior compressor setting. In both cases, expansion takes place. To compensate an overcompression the original compression parameters will be unknown in almost all cases and have to be figured out. The best way to do this is to start with an expansion ratio of 1.5 and a GR-limit setting of 10 dB. Now, the threshold control is used to find the range of the over-compression. As soon as the threshold setting results in an improvement, fine tuning of GR-limit and threshold should be the next step. When these settings are optimized, the fine tuning of attack and release is necessary to get closer to the compensation of the original setting. The final step repeats everything to get closer to an satisfactory setting.
When used as Expander the theshold should be adjusted to a level that leaves the wanted level range unchanged but reduces the noise or any other disturbance. The ratio control determines the steepness of the suppression while the GR-limit control limits the maximum attenuation. The fade down speed is controlled by the release pot. To avoid loosing transients and audible fade-in the attack control should be set all to the left.
When the ratio control is set to the right, the signal below threshold is not expanded but compressed. This features results in a 'reversed compression', which is entirely different from the 'normal' compression. The normal compressor reacts on an increase of the level with a gain reduction that is timed by the attack setting while the pump-up compressor raises the gain when the level drops down. The advantage of this principle is the low distortion even with fast release and attack times and low frequencies, since the regulation is high at low levels and vice versa. It is possible to achieve high density and high loudness gain of the signal using this principle. Since the regulation takes place only below threshold it is possible to combine both, the conventional compressor and the pump-up compressor. While the compression is used with a slow attack, short release setting to maintain transients and natural sound performance, the pump-up compressor can add density in the low level range with very fast attack and release times.
A separate LED chain with 10 LEDs shows the gain reduction or gain - depending on the setting of the ratio control - with a range of 12 dB.
- go to Limiter Section