Mix Foundation 10/2008
Hillel Resner/Karen Dunn: "24th Annual Technical Excellence and Creativity Awards - elysia mpressor nominated for outstanding technical achievement in the category of signal processing technology. Presented by the Mix Foundation for excellence in audio in recognition of the outstanding achievement in the professional audio industry."
> TEC Award Nominees 2008

Sound On Sound 08/2008
Paul White: "The mpressor is one of the most versatile compressors I’ve ever come across. Its low distortion, ultra-transparent circuitry makes it perfectly suited to mastering and mixing in the traditional sense, while those weapons-grade extras make it invaluable for beefing up drums or bass – or just about anything else you want to energise."
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Réalisason 04/2008
Frank Ernould: "Mild settings make the mpressor be a well-behaved, efficient and transparent compressor, able to control the most tormented signals without being noticed. Tickle it a bit too much […] and you will reveal the beast within, turning an acoustic snare drum into an 8-bit drum-machine-snare, a Garage Band loop into a heavy-weight-beat."
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Audio Media 03/2008
Simon Tillbrook: "The elysia mpressor turned out to be quite an eye opener. This is far more than just another compressor with a few clever bits, this is a high-end sonically stunning and highly creative device, and the more time you have with the elysia mpressor the more you will understand and the harder it will be to let it go."
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Recording Magazin 03/2008
Stephan Kirschner: "The mpressor gives studio projects a creative push and invites to experiment. […] The unit takes a little bit of practice in order to understand all of its new possibilities, but all the more light bulb moments you will encounter. The mpressor will inspire anybody from the experimental electronic musician to the classic rock engineer."
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Sound & Recording 02/2008
Hannes Bieger: "If you are interested in a 'modern' all-round compressor that can also turn into a creative sound monster by all means, the mpressor is for you. Not only does it cover the 'standards', but it shines as a loud-maker and convinces with its spectacular sound effects that partly have never been heard before."
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Studio Magazin 01/2008
Fritz Fey: "The mpressor is […] an absolutely unique design that outranges the limits of conventional concepts by far. The complete circuitry layout is a true original. No matter if it is used for tracking or as a buss compressor or maybe even for mastering applications – the mpressor holds all the aces. Hats off!"
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Tape Op 01/2008
Joel Hamilton: "I can't recommend the mpressor highly enough. It truly is a glimpse at the future of compressors, and even fifty years from now I am not sure we will see an all-analog box that can do all the amazing things the mpressor can do… unless the geniuses at elysia figure out a way to outdo themselves."
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Amazona.de 12/2007
Hagen Fin: "The sound of the mpressor is an explicit antipode to clean digital compressors. Here the correlations between amplitude modulation and THD virtually seem to jump into your face, with the bottom line that everything simply sounds much more alive than a digital emulation. Extraordinary! A must-have item…"
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by Michael Nötges
Professional Audio (Germany) – November 2007

The mpressor by elysia keeps even most vehement signals in check. But who will tame this extroverted sound monster once it starts to surpass all expectations again?

Dominik Klaßen and Ruben Tilgner are out on business a lot. The reason: Their pro audio company with the epic name elysia demands full action. In 2005, Tilgner who is responsible for the development of the almost legendary Transient Designer or the Gain Station (review 6/2006) at SPL, and Klaßen whose expertise covers especially the marketing, communication and design sectors, had gotten up the nerve to go their own way. The starting point is the city of Nettetal which is situated closely to the Dutch border. The first project was the design and production of the alpha compressor, a very transparent sounding unit which is mainly aimed at mastering applications. Since the product launch in 2006 the two young entrepreneurs have been touring half the world untiringly in order to present their debut feature to the interested professional audience.

Just when the hype around the alpha abated a little, the next very promising elysia prototype was presented at this year’s Prolight & Sound show – the mpressor, a two channel compressor focused on profound sound design. It is equipped with discrete current feedback amplifier stages in class-A design, features a classic linear power supply with regular transformer and also the thermal control of critical components like its transconductance amplifiers. It addresses creative dynamic pros who are looking to use the numerous special innovative features in order to achieve punchy and crazy sounds as well as sound colorations full of character and lively compression results in general.

elysia’s ultimate goal for this unit was to create a modern instrument that meets the highest sonic demands for inspiring as well as real-world dynamics processing. The mpressor sells for a net price of 3,490 Euro and makes the creative sound freak’s mouth water at first sight.

The paint has only just dried as Klaßen hands over one of the first series production units to us personally – half a year after the exhibition of the prototype at the Musikmesse in Frankfurt. “The actual development took about one year”, the elysian explains, “and this splits into six months of developing the prototype and further six months for the following fine tuning.” In order to bring the circuitry to perfection in terms of sound, Tilgner states he had to keep exchanging certain components. “Time and again, it was really astounding how much influence single resistors or capacitors can have on the sound”. Klaßen adds: “We’re all about ears. Even the final inspection does not only rely on measurement equipment, but on our ears, too”.

But it is quite obvious that the elysians also know how to use their eyes, as the modern design of the eight kilo sound monster is very appealing. The looks are precious, have a true style of their own and are not based on trends of days long gone in order to evoke that nostalgic vintage feeling at all costs, like many of the new analog devices do. “We have 2007”, Klaßen says, “not 1960. We like to consider this when we design our products”. The nice powder coating of the housing directly catches the eye and is concurrently more rugged than anodized or painted surfaces. The specific name of this scratch-resistant coating is sparkling iron, which is a kind of twinkling grey. The front panel has a strictly symmetrical appearance, and its two channels which are accented in blue color bring the radiator grill design of classic sports cars to mind. The middle is dominated by a background-lit disk of frosted glass that shows the company logo and two accompanying LED chains. The well thought position of the eight aluminum knobs permit a comfortable operation.

Tilgner assures that the capsuled conductive plastic potentiometers are longer lasting than the conventional ones and – besides sounding better – should have a better resistance against scratching and other noise artifacts; even after years of use. The black push buttons have a precise pressure point and are back-lit in active mode, reminding of a solar eclipse with a small corona around the button. This ensures the easy control of all functions even in darker surroundings. Also in this regards the manufacturer has done an uncompromising job: All switching functions of the mpressor are coupled via capsuled relays, which have been placed at the best places to keep the audio path as short as possible. “We even did not use any internal audio cables”, Klaßen promises.

“If you want to make it right, make it discrete.”
This is something we want to see with our own eyes, and so we confront the designer piece with a screwdriver. Not often has opening a pro audio bolide been so worthwhile as in this case. The consequent symmetry is conspicuous. Even the ribbon cable for the LED display runs exactly through the middle of the unit. The audio and sidechain PCBs are stacked on top of each other in the front part of the housing. A cross brace shields them from the discrete power supply which occupies almost half of the housing. The oversized toroidal power transformer, Wima capacitors and the coppery T12 are evidences of the high grade and well though out construction. The PCBs are connected by the means of dedicated multi pin slots. “This also makes service very easy”, explains Tilgner, “because the modules can be exchanged in no time at all”. And indeed: the only existing cables are the ones for the power supply.

The back panel features six XLR connectors: two balanced inputs, two outputs plus a separate sidechain input per channel. The pin assignment for balanced as well as unbalanced operation is printed legibly above the specific connectors, which is a nice aid in practical use. If the external sidechain is activated, compression is no longer controlled by the input signals, but by the signals fed into the additional sidechain connectors. This allows frequency dependent compression (e.g. de-essing) as well as triggering the compressor with any audio signal, so that compression follows a dedicated bass drum signal only, for example. The sidechain path is equipped with a high pass filter (80 Hz with 6 dB per octave) in order to prevent the low frequencies from having too much influence on the overall compression process.

The link button couples both channels for stereo processing. The left channel becomes the master for the right channel and specifies the compressor and limiter settings for both sides. Equalizer and gain settings, however, still stay independent. For this reason, the stageless potentiometers for these two functions should be set at the same values when working in stereo mode. The mpressor has a hardwire bypass for each channel, meaning that the input signal is directly routed to the output when in bypass mode. This enables the user to perform direct A/B comparisons to control the applied settings and their effects. In a hectic studio situation, this is a useful and almost compulsory feature. Just as useful are the two LED chains for comfortably controlling the amount of gain reduction. A special circuit layout makes it possible to show indefinite interim values by modulating the brightness of the single LEDs. In doing so, elysia combines the advantage of analog VU meters (stepless display) with the benefits of fast and precise LED meters. The result is: you actually see what you hear. A nice-to-have addition would been a switching option to also control the input and output level in order to avoid unwanted distortion.

The compression stage works with a permanent hard knee characteristic (see curve) and furthermore in the so-called Feed Forward mode. This forward coupled circuit analyses the input voltage very precisely in order to generate the optimal control voltage from the result of this measurement. In a manner of speaking, this elaborate circuit kind of predicts what is going to happen next concerning the development of the level. This is also the basis for the optimal implementation of the possibility to set negative ratios and the external sidechain feature. The make up gain of the compressor already happens in the input stage, which is also the reason for the absence of an additional output controller. The threshold covers a range from +16 to -18 dB. The attack time varies between 0.01 and 150 milliseconds and therewith offers very effective compression even of fast transients. The release time can be set between five and 1,200 milliseconds, thus it covers a great range that opens the door to extreme effect compression. The ratio controller initially makes it possible to set conventional compression rates (1:1.2 to 1:10). But the extensive range of the mpressor transcends the usual standard functions and additionally offers negative ratios (1:-0.3 to 1:-4). These result in very loud input signals being extremely low at the output.

The mpressor hits like a cat of prey
This compression effect results in a great amount of reduction for snare drum beats or other very dynamic signals, while weaker impulses stay untouched. In addition to the gain controller that not only raises the level but adds harmonics to the signal, too, the Niveau Filters also influence the basic sound of the mpressor. If this equalizer module is active, the special filters affect the frequency response like a pair of scales: One controller determines the center frequency between 26 Hz and 2.2 kHz, and another one controls the change in amplitude. An additional push button shifts the frequency range by factor ten (260 Hz to 22 kHz). Frequencies ‘left’ of the center frequency are boosted up to 6 dB by turning the EQ Gain controller counter clockwise, while the area to the ‘right’ is attenuated correspondingly. If the controller is turned clockwise, though, the changes in amplitude happen just the other way round. In the exact middle position, the scales are even and the frequency range stays untouched. Therefore a boost of low end frequencies always goes with a simultaneous cut of the treble. But this is not the end of it by far. With its Auto Fast and Anti Log functions as well as the Gain Reduction Limiter, the mpressor has a couple of further interesting special features on board.

The semi automation called Auto Fast automatically shortens the attack time on fast and loud signal impulses. With it, the newcomer can cope with sudden changes in dynamics without the constant need to use extremely short attack times which could potentially produce audible distortion. This also ensures that abrupt level peaks will not be able to escape the compression process, as the Auto Fast function reacts quickly as a flash. Afterwards the compressor works with the dedicated setting of the attack controller again and is virtually on the qui vive to catch the next peak reliably. The Anti Log function changes the release characteristic of the mpressor. Linear or logarithmic release curves usually build the basis for subtle compression results. Hence it needs an antilogarithmic pendant in order to create striking and creative compression.

The return line becomes the exact opposite of a logarithmic curve: the release time is longer at the beginning and then accelerates its speed while the signal level goes down. A special trick in the circuit ensures that this function works independently from the specific gain reduction value. The Anti Log function gives the user completely new sounds at the push of a button; resulting in exceptional reverse effects or vivid breathing of the compressor. Another specialty of the mpressor is the Gain Reduction Limiter which defines the control voltage to a chosen value. As this happens independently from the input level as well as ratio and threshold values, no further compression goes on beyond the limit of the GRL. The result: Loud passages maintain their dynamics, because above the fixed GRL value they will not be compressed any further. The Gain Reduction Limiter makes ducking and upward compression effects possible without changing the proper dynamics.

As usual, the measurements from the Professional audio Magazin test laboratory are consulted for an objective quality control. Noise floor and external voltage floor are at good 82.6 and 76.7 dB respectively. The harmonic distortion stays under 0.25 percent when no input amplification is used. The FFT analysis shows k2 and k3 that clearly reach the -50 dB mark when +4 dB of amplification are applied. They are should contribute to the special sound character. “At first, the mpressor sounded much too neutral and clean”, explains Tilgner, “so that we started to try lots of different options to add that certain dirt with the help of added harmonics.” He also claims that the frequency response was attenuated above 10 kHz for sound reasons. The corresponding diagram confirms this characteristic (see curve). With values better than -60 dB the channel crosstalk is good as expected. The common mode rejection could be better, though: at 10 kHz it is only -45 dB.

This time, the extensive practice and listening test of Professional audio Magazin seems to go on forever with no end in sight. The reason for this lies especially in the great diversity of settings and combinations. The basic sound of the mpressor alone (with the threshold controller fully counter clockwise in order to idle the compression module) has a character of its own. The sound impression appears considerably larger and more direct as the original. The stronger the input amplification gets, the fuller and livelier the signal appears – the additional k2 and k3 contingents (see FFT analysis) certainly have their share in this. But for all that, the mpressor always stays bright and transparent and seems to further enlarge the sound characteristics. The additional Niveau Filters are an outstanding feature to adapt or bend the basic sound. If the filter is used subtly, the signal appears a little freshened and somehow leaner by boosting the treble and cutting the bass. The other way round, the sound will become fuller and darker with the high frequencies reduced and the lows raised. But extreme high and low pass filter settings are also possible on top of those subtle changes, as well as effective modifications of the mid frequencies.

During our next test run, the mpressor has to prove its capabilities on compressing a drum submix. One thing is obvious very fast: the mpressor is no easygoing exponent of its kind, but an agile creative tool that does not want to hide what it is doing, but loves to show it candidly instead – and we are talking about great potentials here. Slight compression with a low threshold and small ratios are always possible, but the hard knee characteristic still makes the mpressor work effectively and uncompromisingly. This is a major difference to unobtrusive sound refiners like Universal Audio’s 1176LN (Test 4/2007) or Drawmer’s S3 (Test 8/2007) that treat the audio material at hand much more deliberately and gently. The mpressor is like a cat of prey on the qui vive: In the right moment, it hits smoothly but relentlessly at the same time. The very short attack times will not let even the fastest of transients produced by heavy snare beats escape – even those are reduced mercilessly.

As a result, drum signals are very direct and controlled and sound as if they were processed with a brickwall limiter leaving almost no dynamics at all if increased ratios (1:10) and long release times are used. By activating the Auto Fast function the mpressor becomes extra fast just in the right moment without unwanted distortion. The result: Drums sound like far away, the transients are eliminated and the quieter ambience and fading instruments come to the fore noticeably.

Without the Auto Fast function and humane attack times and ratio (10 to 20 milliseconds and 1:5), the drums almost seem to attack you, and the room becomes more audible and present in addition. By shortening the release time, the groove appears more and more punchy and aggressive. From a certain point on, the mpressor starts to pump rhythmically. Equipment and signal form a perfect team with the right setting, making the groove much more vivid. Now we activate the Anti Log function: Because of the antilogarithmic characteristic in combination with a short release time, the drums suddenly sound extremely dense, expressive and start gasping for air violently. A longer release, however, results in intense effect compression and generates completely new ideas for interesting drum loops.

Unlimited creative fun
In search of more crazy effects, we test the negative ratios with a complete house track. The result is a reverse effect: loud signals are suddenly reduced by extreme amounts and then return to their original level slower or faster (depending on the specific release time). Here the Anti Log function has a very interesting effect on the release as well, behaving like a reverb decay played backwards. In order to achieve a preferably fast but still distortion-less control process, experimenting with the Auto Fast function can be of great benefit as well.

Now we insert the mpressor as an external effect into Cubase 4 and use it on a couple of different single instruments. A slap style electric bass produces gain reduction values of 15 and 20 dB quickly. The GR Limiter helps to keep the reduction at a fixed value which is completely independent from threshold and ratio settings. Even if a very strong compression is set, the reduction can be limited to e.g. 4 dB. The transients come to the fore very obviously. The electric bass sound has more freshness now, punch and even extreme variations in dynamics cannot irritate the mpressor anymore, because the applied limiter value will not be exceeded at any time. The output stays at an even level.

Now the sidechain comes into play: We trigger an eighth groove of the electric bass with a corresponding bass drum signal. The compressor works with a ratio of 1:3 and a threshold of about 1 dB. The attack controller is set to 21 and the release time amounts to 150 milliseconds. Instantly, both signals melt into a compact entity and appear to be more powerful. Setting a negative ratio of 1:-1 makes the electric bass pulsate and gives it a vivid groove. Now our pioneering spirit is aroused for good. We copy a snare track in the sequencer, provide it with an eights delay and use the clone as the trigger signal. The effect is set to 100 percent wet so that only the echoes are fed into the sidechain of the mpressor. Applied to a synth pad, this results in a dynamically wafting sound structure that keeps changing its characteristics all the time with new settings of the delay and the mpressor. From extremely cutting to slightly wavy – everything is possible. 

Feeding the pure effect signal into the inputs of the mpressor and the dry original into the sidechain also produces very interesting results. This time the effect, no matter if it is a chorus, flanger, phaser or reverb, is compressed subject to the original signal. A phaser which is applied to a snare signal disappears on the actual hit and then starts to increase until it is choked again by the next snare hit. Experimenting with the different parameters and special features opens up new sound worlds and provides unlimited creative fun.

Analog does not necessarily mean vintage, and elysia’s new creative compressor is the best proof for this. Because of its innovative features, the mpressor is as modern as it is state of the art concerning its concept and construction. It sounds excellently and leaves nothing to be desired in terms of flexible dynamics processing and fancy sound design. The designer piece costs 3,490 Euro net, but to the modern sound aficionado, the mpressor is obviously worth every Cent.