Discrete Class-A Topology
As a true elysia specialty, the audio path of the xpressor is completely based on discrete circuitry and does not use any integrated circuits at all.
To explain the advantages of discrete circuitry we'd like to present a comparison that might seem a little odd at first: audio technology vs. cooking! If somebody uses instant meals exclusively, he will have to accept whatever comes out of the box. A creative cook, however, focuses on his own special recipes and ingredients.
In this respect, integrated circuits (ICs) are pretty similar to packet soups: they are cheap, mainstream and they simply do not match haute cuisine. So if you want to design an analog audio device 100 % according to your own demands and ideas without any compromise, there will be no way around a discrete design.
The xpressor follows this philosophy consequently. Its complete audio path is a new design which is based on the exclusive use of high grade discrete components. A truly unique recipe!
In addition, our universal compressor operates in permanent class-A mode. This means that the transistors are always conductive, resulting in the absence of crossover distortion and providing a pristine sonic base: the general sound character is always wide, open and punchy.
Inspired by its big brothers: the switchable semi automation for a perfect attack on the basis of the value set by the user.
The attack parameter is a very crucial factor for the operations of a compressor. Choosing the right time settings is very important, but depending on the dynamic progress of the source material this can be a difficult task - no matter if single tracks or complete mixes are processed.
If a very short attack time is chosen, the compressor is able to catch the short peaks, but on the other hand the sustaining signal will also be processed, which might result in audible distortion. Longer settings reduce distortion significantly, but then the compressor is too slow for catching fast impulses.
This is where the Auto Fast function comes into play. For example, if you set the attack to 80 ms and then engage the Auto Fast mode, the attack time will be shortened automatically on fast and loud signal impulses. The compressor reduces the signal quickly and prevents it from slipping through.
Then the attack time directly and automatically returns to its original setting. In Auto Fast mode the compressor can be very fast, but only when it is really needed. This function influences the attack parameter on short and loud impulses only; in all other cases the original setting of the controller has priority.
This alternative characteristic of the release curve follows a logarithmic course instead of the standard linear progress and results in a very gentle kind of compression.
It is the time constants and especially the release parameter that decide if the processing of a compressor is obvious or unobtrusive to the ear. As it is difficult to achieve perfect results for all kinds of different material with only one type of release curve, the xpressor offers two different options to chose from: logarithmic and linear.
It is characteristic of a logarithmic release that the time constant shortens when the amount of gain reduction increases. The advantage of this behavior is that short and loud peaks (e.g. drums) have a fast release time, while the remaining material is processed with a slower release. Its smooth performance makes the Log Release especially useful for mastering and stereo buss compression.
The linear mode, however, has a straight release profile, without the slower tapering release characteristic of the Log mode. The linear mode is a good choice for more aggressive dynamics control of dry signals, and it is especially useful when you want to process signals which do not have a long decay period.
The characteristic curve bends and goes back down! Heavy pumping, backward sounds, etc. - perfect for very cool compression effects.
Negative ratios - what exactly does this mean To get a better understanding of this function, it makes sense to realize what the ratio control of a 'normal' compressor does:
1:1 The signal remains linear, there is no compression going on.
1:2 After crossing the threshold, an increase of 2 dB at the input will be compressed to an increase of 1 dB at the output.
1: After crossing the threshold, the output signal is constantly held at the threshold level without reacting to further increases at the input (limiter).
At a negative ratio, the characteristic curve bends and returns back down after crossing the threshold. The louder the input signal, the lower the output signal - perfect for groovy compression effects. To get a grip on the extreme 'destruction' this can cause, engaging the Gain Reduction Limiter is just the right idea.
Beyond infinity - made possible by the xpressor ;-)
Available directly on the unit: the direct and the compressed signal can be blended in any desired relation by simply turning the mix controller.
Parallel compression, also known as 'New York' compression, is a technique based on mixing a dry signal with a heavily compressed identical signal. It is thought to maintain the subtleties of a performance while stabilizing the dynamics.
The mix controller of the xpressor makes it possible to cross-fade between the unprocessed and the compressed signals. This allows parallel compression right in the box and supersedes additional routings in favor of a better signal quality.
Now you can use even extreme compression settings without killing a track by winning the loudness war. By mixing just a part of the compressed signal to the original, the major portion of the initial dynamic structure remains intact.
A tunable low cut filter in the sidechain of the xpressor avoids overcompression and pumping when there is a lot of low end energy in the mix.
The xpressor has a low cut filter with a selectable frequency which is located in the sidechain. This means that it will not affect the the audio signal itself, but the way in which it will be compressed. The keyword here is 'frequency selective compression'.
Let's say you are processing a mix which has a very prominent kick drum. If you used the traditional approach of full range compression, you'd probably end up overcompressing the whole mix because everything is reduced too much.
The reason for this is the great lot of low end energy the kick produces, causing high amounts of gain reduction on the complete mix. And what makes it even worse is that your mix can start to pulsate in the beat of the kick - cool for some electronic music, but certainly not always welcome.
The low cut filter of the xpressor reduces the influence that the low frequencies have on overall compression - a very easy way to apply the desired amount of gain reduction without the side effect of the track starting to pump.
This technique is especially useful in mastering or when complete mixes are to be compressed, but it can also be a handy tool for processing subgroups or even single signals, too.
You want to create frequency dependent compression or have it accented by the groove The external sidechain input makes nearly everything possible!
The external sidechain enables the compressor to control its processing totally independent from the audio material running through it. If the SC Extern switch is active, compression will not be triggered by the signals from the regular audio inputs anymore, but by different signals which are fed into the additional sidechain input connectors.
If, for example, a duplicate of the input signal is processed with an equalizer and then fed into the sidechain input, the result will be frequency-dependent compression. Another example is to send the bass drum of a drum machine into the sidechain input in order to achieve nice groovy compression that is pumping in sync with the music.
The creative options are almost infinite. Compression can be exactly on time or totally against it, which can of course be varied on the fly. Single instruments can be given more space in a mix according to its rhythm. All of a sudden, static sounds become vivid and sound really interesting!
In addition to the external sidechain input the xpressor features a send output, which can be used to feed a summed copy of the input signals e.g. to an EQ and then into the sidechain input - additional sends from the DAW or the console are no longer needed.
Gain Reduction Limiter
This novel limiter is not placed in the audio path as usually, but restricts the control voltage of the compressor instead.
A specialty of the xpressor is the Gain Reduction Limiter for the control voltage. This limiter is not placed in the audio path where you would usually find it, but in the control path of the compressor. When it is activated, it limits the control voltage according to the setting of the GR Limit controller. This means: No matter how high the input level might become - the amount of gain reduction will never exceed the value which you have set.
For comparison, imagine a fader on a mixing console with your hand moving the fader to 'play compressor'. If now the fader was limited by a piece of duct tape at -10 dB, for example, it could only reduce the signal up to this value. If the input level dropped below this limit, the fader would be moved up correspondingly.
However, if the input signal got even louder, the fader could not be moved down any further because of the duct tape limit, and then the output signal would become louder again in correspondence with the input signal.
Loud parts in an arrangement can keep their dynamics, as they will not be compressed beyond the limit of the Gain Reduction Limiter. Some very nice special effects like ducking or upward compression can be achieved with this easily by only reducing the quieter parts without changing the original dynamics at the same time.
The xpressor offers a second switchable sound flavor by altering its frequency spectrum, harmonics and transient response.
This function is basically a slew rate limiter that reduces the speed of the output amplifier stages. This affects the frequency spectrum, the harmonics and the transient response at the same time.
Fast transients are slowed down a bit and the overall sound appears more round and merged. As this function influences the behavior of the output stages, the effect it creates has an impact on the complete processing results of all EQ stages.
In this way the xpressor offers two different sound characters at the push of a button: the powerful transparency of the discrete class-A circuitry and the saturated richness of the Warm mode.
Analog Dynamic LED Meter
The gain reduction meter modulates its LEDs in their brightness in order to show the action of the compressor in an analog way: fast and with smooth transitions.
The gain reduction meter is a very important visual tool for evaluating the operation of the compressor in addition to what your ears tell you. A lot of devices make use of sometimes more, sometimes less precise VU meters. But because of the inertia of the needle these meters are only useful with moderate time parameters.
Another popular form of meter is the LED chain. Unfortunately it has a disadvantage, too: When the standard driver units are used, the change between two values always happens abruptly. A single LED in the chain can therefore only show an imprecise value in a defined interval. Hectic flicker indicates that the actual value must be somewhere in between.
The xpressor solves these problems by using an analog dynamic variant that combines the benefits of both VU meters and LED chains. This meter is based on LEDs, too, but a special circuit design makes it possible to show intermediate values by modulating the brightness of the LEDs.
This means a true analog way of showing the operation of the compressor: very fast, but with smooth transitions. The user gets an important tool for precise gain reduction monitoring - finally the relationship between acoustic and visual perception feels just right.
All potentiometers in the xpressor have 41 steps which are a great help for recalling your previous sessions fast and precisely.
The xpressor features stepped potentiometers for all its parameters throughout. The 41 steps make a precise recall very easy, and they provide a useful range of possible settings at the same time. And you will just love the feel of them, too ;-)
<10 Hz - 400 kHz (-3.0 dB)
@ 0 dBu, 20 Hz - 22 kHz, Mix 0 % : 0.002 %
@ 0 dBu, 20 Hz - 22 kHz, Mix 100 % : 0.006 %
@ +10 dBu, 20 Hz - 22 kHz, Mix 0 % : 0.003 %
@ +10 dBu, 20 Hz - 22 kHz, Mix 100 % : 0.056 %
20 Hz - 20 kHz : -94 dBu
20 Hz - 22 kHz : 115 dB
Input : +21 dBu
Output : +21 dBu
Input : 10 kOhm
Output : 68 Ohm