The mpressor by elysia keeps even most vehe

The mpressor by elysia keeps even most vehe
TEST COMPRESSOR elysia mpressor
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
By Michael Nötges
ominik Klaßen and Ruben Tilgner are
out on business a lot. The reason: Their
pro audio company with the epic name elysia demands full activity. 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 mainly aims at mastering applications. Since the product launch in
2006, the two young entrepreneurs have
been touring half the world untiringly in
Professional audio Magazin 11/2007
elysia mpressor
Huge, transparent sound
Inspiring design and entire
musical concept
Build quality and construction
Analog-dynamic LED display
Negative ratios possible
Semi-automation for the attack time
Antilogarithmic release
characteristic possible
External sidechains
Gain Reduction Limiter
Effective Niveau Filters
Common mode rejection
The mpressor is a creative instrument for
extravagant dynamics processing: analog,
up to date and technical state of the art.
order to present their debut feature to the
interested professional audience. Just when
the hype around the alpha abated a little, the
next and already very promising elysia prototype was presented at this year’s Prolight
& Sound show – the mpressor, a two channel compressor focused on sophisticated
Professional audio Magazin 11/2007
sound design. It is equipped with discrete
current feedback amplifier stages in class A
design, features a classic linear power supply with transformer and also the thermal
control of critical components like the temperature compensated transconductance
amplifiers (see tech box). It addresses cre-
ative 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
TEST COMPRESSOR elysia mpressor
On top of the standard features of a compressor, the mpressor offers effective Niveau Filters, Gain Reduction Limiters, negative ratios as well as the innovative Anti Log
and Auto Fast functions.
the highest sonic demands for inspiring as
well as real-world dynamics processing. The
mpressor sells for a net price of 3,490 Euro
[Germany] and makes the creative sound
freak’s mouth water at first sight already.
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 hunk 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 are 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 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 preci-
The pin assignment illustration for the connectors in balanced and unbalanced operation is easy to read.
se 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
positions 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.”
That 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 like 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 (see tech box) are evidences of the
high grade and well thought out construction. The PCBs are connected by the means
of dedicated multi pin slots. “This also
makes service very easy”, explains Tilgner,
Professional audio Magazin 11/2007
“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
good help 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
the unit is 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
These two characteristic curves of the compression show both the
hard knee characteristic
of the mpressor at a ratio of 1:10 (red) and the
effect of negative ratios
Because of the Gain
Reduction Limiter, loud
parts keep their dynamics, as the control
voltage of the compression module is limited
to a specified amount
(blue). The red curve
shows the effect of
negative ratios.
Professional audio Magazin 11/2007
TEST COMPRESSOR elysia mpressor
Harmonic distortion is around 0.25 percent and is part of the intended basic
The harmonics k2 and k3 earmark the sound of the mpressor and move forward
into audible regions with increasing gain.
Common mode rejection could be better: at a frequency of 18 kHz it extends the
-40 dB mark.
The frequency response is reduced smoothly beyond 10 kHz for sonic reasons. The
Niveau Filters do a fantastic job in customizing the sound.
precise LED meters. The result is: you actually see what you hear. A nice-to-have
addition would have 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 fourth coupled circuit
analyses the input voltage very precisely
in order to generate the optimal value
for the 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 control36
ler. The threshold covers a range from +16
to -18 dB. The attack time varies between
0.01 and 150 milliseconds and therefore
offers very effective compression even of
fast transients. The release time can be set
between 5 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 also adds harmonics to the signal, 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
Professional audio Magazin 11/2007
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,
because the Auto Fast function reacts as
quickly as a flash. After that, 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 they will not be compressed any
further above the fixed GRL value. The
Gain Reduction Limiter makes ducking
and upward compression effects possible
without changing the proper dynamics.
As always, 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
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
The two channels can be linked for stereo operation.
The analog dynamic LED displays are an exact optical
counterpart of what is happening acoustically.
-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 combination possibilities. 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
TEST COMPRESSOR elysia mpressor
A look behind the scenes of the mpressor
Ruben Tilgner did not leave any aspect of the construction of the mpressor to chance, and thus it became a rich
source of technical innovations and finesse. It starts with
the discretely built power supply that, as Tilgner states,
fundamentally determines if a unit behaves dynamically
and openly or if its sound is more on the calm and reserved
side. After all, the developer explains, the power supply
feeds all active stages and therefore has a noticeable influence on all parts of the circuitry. Background information:
Processing loud and dynamic signal impulses demands
great amounts of current for a short time. Therefore the
power supply must have a sufficient capacity at all times.
In the mpressor, a special placement of the electrolytic capacitors in the circuitry keeps the high charging currents
away from the signal ground in order to ensure an optimal
voltage supply. Additional MKP capacitors are placed at
many positions for the same reason. An improved noise
and hum rejection builds the basis for clear and clean
sound characteristics. “Even the rectifier diodes have an
influence on the sound”, Tilgner explains and proceeds:
“They charge the electrolytic capacitors in the power supply for a short moment and then provide electric current
for the complete circuitry. For this reason, we use very
fast diodes that we chose as a result of listening tests.
The class-A output stages are push-pull-amplifier designs,
which means that one is handling the positive half cycle
and another one the negative half cycle. As both of them
are supplied with a quiescent current, they will stay conductive even when there is no signal present. If this was
not the case, the amplifier would work in class-B mode
which would cause crossover distortion, occurring because
of a small glitch at the joins between the two halves of
the signal at the zero point. The manufacturer states that
the mpressor has a quiescent current of 14 milliampere,
which is an unusually high value for an audio device. As
a result, the transistors always stay conductive – even
when a low resistor load causes a high amount of current.
Thus, crossover distortion will not appear in the first place.
The amplifier stages of the mpressor are also discrete
designs, which means that they are composed of single
transistors, resistors, diodes and capacitors. This enables
the developer to realize his sound conception in every detail by selectively exchanging components – provided that
he has the needed experience. Additionally, elysia runs all
amplifier stages in current feedback mode. The reason for
this: Conventional amplifiers for audio applications use
voltage feedback designs. These op-amps are based on
a two transistor differential amplifier concept. Input and
output are compared with each other in order to make corrections if necessary, but this also produces a slight delay.
This changes the phasing and results in an oscillation at
very high frequencies and causes the negative feedback
to become positive. Often small capacitors are used to
avoid this effect by deliberately reducing the speed of the
amplifiers and decreasing high frequency amplification.
“These capacitors have a negative influence on the
sound quality of a signal”, says Tilgner. His logical consequence was to create an amplifier circuit that would
not need any capacitors that interact with the frequency
response. In the amplifier stages of the mpressor, the
Just like its exterior, the inside of the
mpressor is a great
show: the coppery
T12 Heater keeps
critical components
at a stable operating
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 –
Not least it is the symmetrical consistency of the
mpressor that points out the accurate and well
thought out concept.
negative feedback directly modulates the current and
therefore avoids the delay in the differential amplifier.
This reduces the delay of the signal significantly and
keeps the phasing even of high frequencies stable. The
manufacturer states that their amplifiers can process
frequencies up to the megahertz range and that they
have a fast slew rate as well as a high impulse constancy.
On top of that, elysia uses a so called T12 heater in order
to make heat sensitive components work constantly. This
keeps temperature fluctuations of the integrated components at a minimum degree. Up to twelve discrete
transistors are integrated into a massive copper ring
which is warmed up to a defined temperature. After
a short start up phase, only a small amount of current is needed to keep the working temperature at
a stable level. An electronic control circuit ensures
that the possible tolerance is only a few degrees.
The gain reduction cell of the compression module is not
off-the-peg either. The mpressor employs a discrete and
temperature compensated Transconductance Amplifier
(TCA). The core of this circuit is a difference transistor pair
with a modulated current source regulating the amplification. Further transistors reduce noise and the influences
of the control voltage to the signal. One advantage of a
TCA is that it can react fast to the control voltage – an
important condition for fast attack and release times. The
make up gain already happens in the input stage and runs
in parallel with the sidechain. Thereby it does not influence the compression process, and even strong amounts
of compression will not result in an increasing noise floor.
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 to appear 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
Professional audio Magazin 11/2007
a cat of prey on the qui vive: In the right
moment, it hits smoothly yet relentlessly at
the same time. The very short attack times
will not even let 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 creativity
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 here as well.
After this, 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 reProfessional audio Magazin 11/2007
duction 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 sidechains come 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, has its compression triggered by
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 that. Because
of its innovative features, the mpressor
elysia GmbH
Ringstraße 82
41334 Nettetal
Tel: +49 2157 126040
Fax: +49 2157 126312
info[email protected]
Price (net, Euro)
3,490 [Germany]
Dimensions WxDxH (mm)
483 x 377 x 89
Weight (kg)
2 balanced XLR
2 balanced XLR
13 segment LED for gain
reduction, LED for GRL
Input controller
0 to 20 dB
16 to -18 dB
Attack time
0.01 to 150 ms
Release time
5 to 1,200 ms
1:1.2 to 1:-4 (negative ratios
can be applied)
Equalizer gain
Up to 6 dB
Equalizer frequency
26 Hz to 2.2 kHz
Equalizer frequency (x10)
260 Hz to 22 kHz
Gain Reduction Limit
0 to 21 dB (control
voltage limit)
Sidechain Ext.
Auto Fast
Semi automation attack
Anti Log
release curve
Bypass compression
Separate for left and
right channel
Stereo link
Auto Fast, Anti Log, Gain Reduction Limiter, negative ratios,
analog dynamic LED meter, discrete power supply design,
Niveau Filters, current feedback amplifiers, thermal control
of critical components, transconductance amplifiers (TCA)
Maximum input level (dBu)
Maximum output level (dBu)
Noise floor (dB)
External voltage floor (dB)
Maximum THD (%)
very good
very good / outstanding
very good
very good
very good / outstanding
Final grade
Top class very good
Value for money
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 warranted to be worth every Cent.
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