The Universal Analog Compressor
The xpressor is a discrete class-A stereo compressor with a pristine sound and an incredibly flexible feature set. It gives you an enormous amount of control over dynamics while still being comprehensive and easy to use. Achieve professional compression results in no time at all!
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Every single of its many aspects – sound, features, circuitry, components, design, materials, manufacturing – has been thought over and over until there was just nothing left to improve. Basically, every single part of our fine products is custom, and most of these are made according to our own designs and specs.
Only the best components the market has to offer are good enough for the xpressor, and it shows. Each of our product is manually built to order and tested by ourselves, here at our headquarters in Germany.
Our product benefits sum up in an audio quality that is beyond all doubt. Even when extreme settings are used, the sound always stays clean and powerful. The xpressor achieves perfect processing results for all different styles of music and assures the ‘this is it’ feeling of a finished song. Its enhanced functions exceed the potential of normal compressors by far and give you unimagined options for mastering and mixing.
This feature is from his bigger Brother, the alpha compressor.
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.
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 choose 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.
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:
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
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.
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 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.
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.
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.
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 compression 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.
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.
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.
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.
<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 (A-weighted): -94 dBu
20 Hz – 22 kHz: 115 dB
Input: +21 dBu
Output: +21 dBu
Input: 10 kOhm
Output: 68 Ohm
19″ x 1.75″ x 8.4″ (W x H x D)
482,6 mm x 44,45 mm x 214 mm (W x H x D)
“The xpressor is my go-to bass comp. I just used it on an electric bass track where notes were jumping out all over the place. I was able to crush it with up to 15 dB of reduction. There was plenty enough gain to bring it up, and even being crushed like that, it was punchy as hell!
Slap on the Warm Mode and it just adds this fantastic grit and body to the bass! However, this truly flexible compressor suits my other instruments just as nicely, and it does a great job on the mix buss as well. A fantastic companion for my museq…“
Frank Perri | Musician & Composer | New York
“I honestly can’t see a situation where an engineer, from a beginner to pro, would NOT benefit from having an xpressor in the rack, it does exactly what it says on the tin and much, much more… A lot of times compressors are more or less one or two trick ponies and this one seems to be a full-blown horse circus!
It’s like a transient-shaping-lava-lamp, I just get mesmerized playing loops through it and thinking I’m the shit, haha!!! It’s one of the most versatile and creative yet easy to understand pieces of gear I’ve ever seen or heard…“