Activating the THD Boost function raises the level in front of the gain control element. This generates additional harmonics inside the input stage of this amplifier, which has a significant influence on the sonic structure of a signal. The mpressor 500 is a pure feed forward compressor, and the gain potentiometer is placed before the control element. This means that the intensity of the saturation can be raised or lowered by different settings of the gain controller.
What’s special: The detector in the sidechain of the compressor runs in parallel and is therefore not influenced by the THD Boost at all. The actual compression does not change, it is only the sound which is being influenced. You generate a saturated signal which as a result is also reduced in dynamics, but the actual control of the compressor itself is always based on the original dynamics including all transients, impulses and so on.
The custom discrete gain reduction cell of the mpressor 500 provides low noise, extremely fast time constants and all the punch in the world.
A crucial part in the development process of a compressor is to design its control element that reduces the audio signal controlled by voltage. This is also where the main technological concepts show the most obvious differences. The mpressor 500 uses elysia’s special Transconductance Amplifier (TCA). A differential pair of transistors that uses a modulated current source to affect the amount of amplification builds the core of this module. A few extra transistors were added in order to further decrease noise and unwanted influences of the control voltage.
Another advantage of the TCA topology is the very fast response to the control voltage. This is the basis for a compressor that can even handle rapid changes in dynamics and which provides extremely fast time constants. Also remarkable is the fact that the make up gain was designed as an amplification of the input signal. This is running parallel to the sidechain path and therefore does not have any unwanted influence on the processing itself. The essential advantage of this arrangement is that the background noise always stays at the same level, no matter how much amplification is applied.