Each of both linkable channels offers a switchable Auto Fast function that allows very fast yet distortion-free compression without any artifacts. The Anti Log circuit generates explicit compression effects such as pumping and breathing. As the mpressor is a true feed forward design, it also allows negative ratios which result in the most ex-treme over-compression effects. The Niveau Filters can change the character of a track from subtle to striking with the possibility of a continuous frequency shift. The Gain Reduction Limiter is a novel feature that lets the user choose the maximum amount of Gain Reduction he wants to draw from the unit, and this at the twist of a knob. The switchable external sidechain inputs make for further flexibility in terms of compression behavior.
The circuit design of the mpressor is completely based on discrete analog technology. The entire signal processing is implemented with single transistors in permanent class-A mode, and even the sidechain and power supply are composed of fully discrete circuits. An oversized power transformer, capsuled conductive plastic potentiometers, internal temper-ature stabilizers for critical components as well as special current feedback amplifiers are part of the technical finesse. The combination of these elements aims at the maximum reachable signal quality and guarantees clean and powerful sound characteristics even when extreme settings are used.
The creative compressor
Compressors are absolute standard tools in daily studio work, but depending on the specific task they need to be used in lots of different ways. The range goes from mild changes of level during mastering to limiting the dynamic range in recordings to extreme compression to shape sounds envelopes.
Hence the various topologies and large range of compressors in the market today. The mpressor is a typical recording and mixing compressor that can handle a wide array of jobs because of its premium audio quality and precise control characteristics. On top of that, it offers a number of special functions that enable the user to create completely new and very spacy sounds.
This makes the mpressor a truly creative compressor that especially convinces with its elaborate and practical innovations. Reducing options to the essential makes it possible to achieve outstanding results for any audio material at first go.
The control characteristics of the mpressor offer a great spectrum of settings without generating any unwanted artifacts or noises. Even very fast attack and release settings can be used without any problems. Already known from the alpha compressor, the Auto Fast feature is a guarantee for very fast but undistorted gain reduction processes: if this function is activated, the attack time will automatically become shorter on input signals with fastly rising levels and intense changes of dynamics.
The novel Anti Log function generates an anti-logarithmic progress of the release curve. The release time will at first become slower when there is an ample increase of compression. As soon as the input signal returns to a noticeably lower amount, the release time will be shortened automatically. Depending on the other settings, compression will become much more audible than before as a result. This feature can be used to achieve BPM-dependent dynamic effects, manipulate the ambience parts of a reverb effect return, or process single sources such as vocals or bass.
Gain Reduction Limiter
Another specialty of the mpressor is its limiter for the control voltage. With it, one can set the maximum amount of gain reduction that will not be exceeded as long as the function is active. Normally the threshold and ratio parameters determine the amount of gain reduction which is adapted to the input signal in order to reduce the loudest parts as desired.
If the limiter is set to a maximum reduction value, threshold and ratio can have completely different settings without changing the maximum gain reduction. In this manner, very special variations of control characteristics can be achieved, e.g. applying a strong amount of compression while preserving the dynamics of loud passages at the same time.
Combining the Gain Reduction Limiter with the external sidechain transforms the mpressor into a true ducker. In this application, the music will automatically be turned down when a voice sets in (or just the other way round). Another option is to apply upward compression that only raises the volume of the quieter parts without changing the actual dynamics at all.
The mpressor provides a switchable external sidechain input per channel. Once it is activated, the compressor reacts to the fed in signals and opens up an enormous variety of additional potentials. A typical application is frequency-dependent compression, where an additional equalizer is used to give certain frequencies a stronger or weaker influence on the overall compression.
True ducking effects are also possible as well as very cool groovy sounds, e.g. controlling a stable synth pad with a drum beat fed into the sidechain. The combination of the Anti Log and Gain Reduction Limiter functions result in very unusual effects that sound like an inverted gate: the loud signals are reduced intensely while the quieter parts come in front more obviously.
In order to add flexible sonic stamps to compressed signal, there is a Niveau Filter placed after the compressor section which has been designed in the style of the audio EQ of the alpha compressor.
It also boosts the high frequencies beyond a selectable center frequency and cuts the low frequencies at the same time (or, depending on the individual setting, just the other way round). But according to the intended use of the mpressor, we have made the possible settings more extreme for more striking and dramatic effects. Only two controllers produce a great variety of different sounds.
These kinds of settings could not be generated by using standard parametric equalizers. The combination of this filter and the special control characteristics enable the mpressor to give a totally new character to the original signal which can vitally enhance a whole production.
Here is an old elysia saying: If you want to make it right, make it discrete! Of course this is also true of the mpressor, as the combination of very extreme control characteristics and an absolutely convincing quality of sound can only be achieved by using discrete circuitry. Therefore all signal stages were designed to use single transistors, resistors and capacitors, so each of the stages could be perfectly matched to its specific task as an important side effect.
Many parts of the circuitry do without negative feedback, and the complete unit works in constant class-A mode in order to ensure the best audio quality in any situation. Even the sidechain and the power supply are built with the exclusive use of single transistors, resulting in considerably lower noise compared to conventional ICs.
A look inside
The choice of components for the mpressor did not leave the slightest room for compromise – a great part of components which are used in the alpha compressor can also be found in the mpressor. All controllers use high-grade conductive plastic potentiometers. All switching functions are coupled via capsuled relays which are placed at the ideal places in the circuitry in order to keep the signal path reduced to the max.
A special input stage was trimmed to show a similar behavior to that of an input transformer. Furthermore, this stage distinguishes itself by a very good common mode rejection and an extra low capacity, preventing unwanted changes of the input signal effectively. A high-grade class-A output stage delivers adequate current to drive even long cable lines smoothly.
The power supply also benefits from the discrete design, as the voltage regulators produce such a low amount of noise that it can hardly be measured at all. A generously dimensioned toroidal power transformer provides enough current to charge the great number of quality electrolytic capacitors very quickly.
Certain critical components of the discrete circuitry are surrounded by special heating elements made of copper. This keeps important parameters constant and makes them independent from changes in temperature and operating time.
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