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The information in this document is subject to
change without further notice and shall not be
deemed as an obligation or warranty of any kind by
the manufacturer. No warranties, express or implied,
are made with regard to the quality, suitability or ac-
curacy of this document.
The manufacturer reserves the right to change the
contents of this document and/or the associated
products at any time without the provision of prior
notice. The manufacturer shall not be held liable for
damages of any kind arising from the use, or the in-
ability to use this product or its documentation.
The information in this document is subject to copy-
right. All rights, technical changes and errata are re-
served. No part of this manual may be reproduced or
transmitted in any form or for any purpose without
the explicitly written permission of the copyright
holders.
elysia is a registered trademarks of elysia GmbH.
Other product and brand names contained in this
document are used for identication purposes only.
All registered trademarks, product designations or
brand names used in this document are the property
of their respective owners.
This product is manufactured accord-
ing to the 2002/95/EC directive. The pur-
pose of this directive of the European Union is the Re-
striction of Hazardous Substances (RoHS) in electron-
ic equipment in order to protect health and nature.
© 2006 elysia GmbH
2
WARNING: High Voltage
• Risk of electric shock.
• Do not open chassis.
• Refer service to qualied service sta only.
• Before connecting the device to the main power supply, check if the right
voltage is selected.
• Replace fuse with the same type and value only.
• This device must be connected to ground.
• Do not use a damaged power cord.
• Never place containers with liquid, e.g. beverages or a vase, on the unit.
• Do not expose this device to rain or moisture.
• Do not use this device near water, e.g. swimming pool, bathtub or wet base-
ment.
CAUTION: Temperature
• Surfaces of the device may become hot during operation.
• Do not install this device near any heat source such as radiators, stoves or
other heat sources.
• Always allow enough ventilation space around the unit for air circulation.
• Do not cover circulation vents.
CAUTION: Connecting & Mounting
• Never connect the output of a power amplier to this device.
• Place the unit on a rigid board or x it to an appropriate rack.
• Use the device according to this manual only.
CAUTION: Humidity
• If this device is moved from a cold place to a warm room, condensation can
occur inside the device. To avoid damaging the unit please allow it to reach
room temperature before switching on.
CE Conformity
elysia GmbH, Am Panneschopp 18, 41334 Nettetal, Germany, declares with sole
responsibility that this product complies with the following norms and directives:
• 2006/95/EG Low Voltage Directive (formerly 73/23/EWG or 93/68/EWG)
• 89/336/EWG EMC (Electromagnetic Compatibility) Directive
• DIN EN 55103-1 EMC of audio equipment - Emission
• DIN EN 55103-2 EMC of audio equipment - Immunity
This declaration becomes invalid by any unapproved modication of the device.
Nettetal, 01.06.2006 - Ruben Tilgner & Dominik Klaßen
3
Dear friend of audio culture,
First of all, we would like to thank you sincerely for choosing the alpha compressor as your new
mastering tool. From now on, you not only have the maximum possible audio quality in dynamics
processing at your disposal, but also a complete arsenal of exible and eective tools which will
shift the fruit of your work to a new level.
In short: You have opted for a product designed without the slightest compromise!
Please take a little time to read this manual thoroughly, as it will help you to entirely understand
the enormous potentials and to really push the envelope. We have attached great importance to
practical experience and fast results, which is also the reason for reserving the explanation of the
technological excesses realized in the alpha compressor to our website.
The Basics chapter contains essential information for the fundamental comprehension and quick
use of the specic functions and modules. After this, a couple of Scenarios are introduced in order
to illuminate just some of the versatile applications of your new favorite compressor. If you want
to go into further details, please have a look at the Reference chapter which elaborates on every
particular parameter.
If you have further questions or comments, please do not hesitate to contact us – we enjoy being
of your service. But for now, it is time to wish you lots of fun and pure audio pleasure with your
alpha compressor.
Use the Force…
the elysians
4
BASICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Getting Started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Signal Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Link Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Stereo Compression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Auto Fast. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Feed Forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
M/S Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Sidechain Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Audio Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Mix Controller. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Soft Clip Limiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
SCENARIOS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Stereo Linked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
M/S Linked. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
M/S Unlinked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Upward Leveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
M/S Leveling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Groove Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Vocal Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
DeEssing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Parallel Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Stereo Enhancer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
LoFi Compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Extreme Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
REFERENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Threshold Oset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Threshold . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Auto Fast Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Auto Fast Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Ratio Feedback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Ratio Feed Forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
EQ Gain Low. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
EQ Gain High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
EQ Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
SC Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
SC Low Pass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
SC High Pass. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Mix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Soft Clip . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Level Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Recall Sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
INDEX
5
Mix
Gain
EQ Freq
SC Gain
dB
EQ Gain
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
Compressed
On
Thresh
AttackmsReleasemsRatio
1:X
Soft Clip
SC Freq
BASICS
Controls
Both channels of the alpha compressor are absolutely identical regarding their electronic design.
Therefore both sides of the front panel have exactly the same controls and switches. Continuative
information on the specic functions can be found on the pages in brackets.
Thresh Attack Release Ratio
EQ Freq
On
Mix Gain
Hz
Auto Fast
x10 On
Auto FastFeed Forward
SC GaindBSC FreqEQ Gain
Soft Clip
TransformerDirect Compressed On
Soft Clip
Gain Reduction
M/S Mode Active Channel Link
Threshold: the operating point of the compressor. If the input level exceeds the value set
with this controller, the compression process will start. (p. 26)
Feed Forward: switches the junction of the sidechain alternatively behind (feedback) or in
front (feed forward) of the actual compressor section. (p. 14)
Attack: the transient response of the compressor. It determines the time the alpha compressor needs to reach 10 dB of gain reduction. (p. 27)
Auto Fast: a semi-automation. This function shortens the attack time automatically on fast
and loud signal impulses. (pp. 13, 27)
Release: the return phase of the compressor. It controls the period of time between when
the input signal falls below the threshold and the compressor’s return to unity gain. (p. 28)
Auto Fast: similar to the Auto Fast feature for the attack parameter, this function automatically shortens the release time and then returns to the set value. (pp. 13, 28)
Ratio: the relation between the input level and the output level. In feed forward mode, the
actual ratios become signicantly higher than the printed values. (p. 29)
Gain Reduction: the display for the gain reduction. Shows the amount of compression measured in dB as an optical support for the acoustic events. (p. 12)
Soft Clip LED: indicates the activity of the Soft Clip Limiter. This LED should only light up
shortly from time to time in order to avoid audible distortion. (p. 19)
EQ Gain: the characteristic of the Niveau Filter. Between the mid and fully counter-clockwise
position, bass is boosted and treble is cut (vice versa in the other direction). (pp. 17, 30)
BASICS – Controls
6
EQ On: activates the Niveau Filter. In the signal path, this special EQ is placed after the com-
pressor section, thus it will not inuence this section’s behavior. (p. 17)
EQ Freq: the center frequency of the Niveau Filter. Around this reference point, bass is boosted and treble is cut or vice versa. (pp. 17, 31)
x10: shifts the frequency range of the Niveau Filter. The printed values from 20 Hz to 2.0 kHz
are multiplied by 10 to 200 Hz and 20 kHz. (pp. 17, 31)
SC Gain: inuences the character of the sidechain lter. It can be blended from high pass to
low pass with lots of expedient interim values. (pp. 16, 31)
SC On: activates the sidechain lter which allows frequency-dependent shaping of the compression process. (p. 16)
SC Freq: sets the highest/lowest frequency which – dependent of the SC Gain controller –
you want the compressor to react to/not to react to. (pp. 16, 32)
Direct: makes the direct signal routed directly from the input stage audible in its respective
channel or mutes it when inactive. (p. 18)
Mix: if both the Direct and Compressed knobs are active in their respective channel, the Mix
controller blends between them for onboard parallel compression. (p. 18, 33)
Compressed: makes the compressed and/or ltered signal audible in its respective channel
or mutes it when inactive. (p.18)
Gain: compensates for the level reduction caused by the compression process. The controller oers up to 12 dB of amplication. (p. 9)
Transformer: switches an additional transformer into the signal path as an additional means
of sound shaping. (p. 14)
Soft Clip: helps to limit short, loud transients to subsequent A/D converters from clipping by
rounding the signal peaks. (pp. 19, 33)
Soft Clip On: activates the Soft Clip limiter. The limiter modules for both channels should
always be activated or deactivated at the same time. (p. 19)
M/S Mode: enables to process the middle and the side signals separately, and nally decodes both channels back to left and right/stereo. (p. 15)
Active: enables the processing modules of the alpha compressor. In deactivated state, the
input is directly routed to the output by a hardwire bypass. (p. 10)
Channel Link: both channels can be operated in combination with the left control panel as
master. Note: Filter, mix, gain and limiter stages will not be linked in this mode. (p. 11)
BASICS – Controls
7
BASICS
Connectors
Voltage
220 - 240 VAC ~ 50 Hz
110 - 120 VAC ~ 60 Hz
Power Consumption 100 W
Made in Germany
WARNING!
RISK OF ELECTRIC SHOCK - DO NOT OPEN!
Fuse Type
1.5 A Slo-Blo @ 220 - 240 VAC
3.0 A Slo-Blo @ 110 - 120 VAC
elysia GmbH • D-41334 Nettetal • Germany
Mains module
This module combines the line cord connector, the on/o switch, the fuse holder with integrated 230/115 VAC voltage selector and a line lter for providing the transformer with
clean current. Note: Some export version have a xed voltage of e.g. 100 or 115 VAC and
cannot operate at 230 VAC.
Controller Brightness Button Brightness
Gnd1Hot
2
3
Gnd
Right Out Right In Left InLeft Out
Hot2Gnd
Cold
1
3
Gnd1Hot
2
3
Gnd
Hot2Gnd
1
3
Cold
WARNING: High voltage
Make sure to disconnect the line cord before replacing eventually blown fuses or changing
the operating voltage of the unit!
In order to change the operating voltage, the fuse holder has to be taken out and re-inserted so that the desired voltage can be read correctly (and is not standing upside down).
The white triangular arrow that belongs to the chosen voltage setting points at the small
rectangular mark on the mains module.
WARNING: Fuses
Always make sure to use the correct fuses for the chosen voltage: 230 VAC 1.5 A Slo-Blo or
115 VAC 3.0 A Slo-Blo. Incorrect or missing fuses are dangerous safety hazards for both the
unit and yourself!
Audio outputs (+4 dBu)
Pin assignment balanced: 1 ground 2 hot (+) 3 ground
Pin assignment unbalanced: 1 ground 2 hot (+) 3 idle
Audio inputs (+4 dBu)
Pin assignment balanced: 1 ground 2 hot (+) 3 cold (-)
Pin assignment unbalanced: 1 ground 2 hot (+) 3 ground
Note: If a device that is placed before the alpha compressor in the signal chain has an unbalanced output stage, a complete muting can eventually occur when the compressor is
activated. If this happens, please follow the advice on page 34.
LED brightness dimmers
Controller brightness: light intensity of blue LEDs
Button brightness: light intensity of white LEDs + logo disc
BASICS – Connnectors
8
Getting Started
Never fear! With its many options and quite a lot of controllers the alpha compressor might look a
little tricky at rst sight. In practical experience, however, it is a clearly structured and easy to use
tool.
The control elements are divided into three layers, whereas the left and the right channel sides are
completely identical.
Thresh
+11
+15
+18
+4
0
-3
-6
-9
-12
+20
-13
dB
Attack
13
7.0
2.0
24
28
50
70
110
130
0.01
150
ms
Release
150
100
75
300
430
570
1k5
60
1k8
ms
Ratio
800
1.4
1k1
1.3
1.2
Auto FastFeed Forward Auto Fast
1.7
1.6
1.8
1.9
2.1
2.2
1.1
2.4
1:X
Compressor section
The upper array contains the dynamic section with the classic parameters threshold, attack, re-
lease and ratio. Furthermore, there are some interesting special functions like feed forward and
Auto Fast that will be explained later.
0.3
0.3
1.0
1.6
2.2
2.7
Lo
EQ Gain
1.6
2.2
2.7
Hi
dB
On x10 On
EQ Freq
40
30
22
20
140 170
Hz
-0.3 -0.3
220
300
500
1k0
2k0
-1
-2
-5
-12
LP
SC Gain
-2
-5
-12
HP
dB
SC Freq
80
50
40
30
280 340
Hz
430
580
900
2k0
3k3
Filter section
Firstly, the middle array features the audio lter, which enables you to perform subtle changes
on the overall tonal character. Secondly, it consists of the sidechain lter which allows frequency-
dependent compression when it is switched into the detector path.
50
Mix
30
20
10
60
70
80
90
100
Dir
Com
%
2.0
1.5
Gain
0.5
3.5
4.5
0
12
dB
Soft Clip
6.0
8.0
10
11
TransformerDirect Compressed On
16
14
11
19
21
24
25
dB
8.0
5.5
4.0
3.0
Level section
The lower array starts with the mix controller that allows blending between the unprocessed and
the compressed, ltered and amplied signals. Next in line is the gain controller for making up the
gain of the reduced signal. Last comes the Soft Clip limiter which allows catching fast transients.
BASICS – Getting Started
9
BASICS
In the middle of the unit, right below the gain reduction meters, there are three buttons to set the
distinct operating modes of the alpha compressor:
M/S Mode Active Channel Link
M/S Mode
If this button is pressed, the alpha compressor will work in M/S mode in which the controls on the
left side aect the middle channel and those on the right side belong to the side channel. Other-
wise the unit will work in stereo mode.
Active
If this button is pressed (LED glows), the incoming signals will be processed by the alpha compres-
sor. Otherwise there is a hard bypass, whereas the gain reduction meters will still stay active.
Channel Link
If this button is pressed, the left upper array will act as a master for the dynamic sections of both
channels. All other parameters (lter, mix, gain, limiter) are not linked, though, and therefore have
to be set manually. In this mode the gain reduction is identical for both channels.
Signal Flowchart
The schematic shows the signal ow from the input through the specic modules to the output.
M/S matrix, sidechain lters, audio lters, mix stages, transformers and Soft Clip limiters can be
optionally switched into the signal path via relays, which is also true of the Auto Fast and feed
forward functions.
Left
Input
Input
Transformer
Input
Buer
Sidechain
Filter
Sidechain
Compressor
Gainreduction
Meter
Audio
Filter
Transformer
Mix
Stage
Gain
Stage
Soft Clip
Limiter
Output
Amp
Left
Output
10
Input
Buer
Input
Transformer
Right
Input
M/S Encoder
Compressor
Sidechain
Sidechain
Filter
Audio
Filter
Gainreduction
Meter
Gain
Stage
Mix
Stage
Transformer
M/S Decoder
Right
Output
Output
Amp
Soft Clip
Limiter
BASICS – Signal Flowchart
Thresh Attack Release Ratio
Auto Fast
Feed ForwardOnAuto Fast
Thresh
AttackmsReleasemsRatio
1:X
Soft Clip
EQ Freq
On
Mix Gain
Hz
Auto Fast
x10 On
Auto FastFeed Forward
SC GaindBSC FreqEQ Gain
Soft Clip
TransformerDirect Compressed On
Gain Reduction
M/S Mode Active Channel Link
EQ Freq SC Gain
EQ Gain
Mix
x10 On
Gain
SC Freq
dB
Soft Clip
TransformerDirect Compressed On
Link Mode
In link mode, both channels of the alpha compressor can be coupled and operated with the con-
trollers and switches of the left control panel. Please consider the following important notes:
Both sides of the alpha compressor utilize exactly identical electronic modules that could even be
interchanged with each other in principle. This grants a high equality of signal processing in the
left and right channel, which is especially important in stereo mode. Another result is the excellent
isolation of both channels from each other, and the audio quality will not decline because there
are no lossy to and fro signal routings in the circuitry.
As an eect of this design approach, only the control functions of the compressor (marked green
in the gure) are combined in link mode. The left control panel becomes the master, that is the
settings for the left channel are transferred to the right channel – therefore the settings of the
particular controllers on the right side are not relevant in link mode.
At the same time this means that the audio functions of the compressor (marked orange) are not
combined. In linked stereo mode please pay attention to set the controllers and switches for both
EQ, mix and gain sections identically. Otherwise an audible drift between the left and the right
channel might occur.
In linked M/S mode, however, you can set the EQ, mix and gain stages to dierent values to achieve
certain eects. For example, you can use dissimilar settings of the gain controllers to alter the ste-
reo width (more information on page 24) or you can employ the EQ stages for mid and side signals
separately.
In the signal path, the Soft Clip limiters are located after the M/S decoder. This means that the lim-
iters are completely independent from the operation mode of the alpha compressor – they always
work in stereo. The limiters are also not aected by the status of the link function and therefore
have to be set at the same values every time they are engaged.
BASICS – Link Mode
11
M/S Mode
Mix
EQ FreqHzSC Gain
dB
SC Freq
EQ Gain
Feed Forward
On
x10
On
Transformer
Direct
On
Soft Clip
Mix
EQ Freq
SC Gain
dB
EQ Gain
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Thresh
AttackmsReleasemsRatio
1:X
Soft Clip
SC Freq
BASICS
Thresh Attack Release Ratio
Auto Fast
Gain
Compressed
Auto Fast
Soft Clip
Gain Reduction
Active Channel Link
Gain
Compressed
Stereo Compression
In order to get a rst impression of the sonic qualities and the control characteristics of the alpha
compressor, only the controllers highlighted in the gure are used. The functions that are cur-
rently not needed should be deactivated (related LEDs do not glow). Et voilà: We have a classic
linked stereo compressor!
A track with a broad dynamic range is the best material for a rst test. Just start playing with the
threshold, attack, release and ratio parameters of the left channel in order to get to know the con-
trol behavior of the compressor. Allow yourself to take some time for this, as the understanding of
the basic control characteristics is the most important condition for perfect results.
Keep having a look at the gain reduction meters from time to time. No doubt: the ear is the de-
cisive benchmark. Just consider the optical information as a supporting means to evaluate the
compression process (fast/slow, strong/weak, etc.).
The levels of the compressed signals can be made up by adding an appropriate amount of ampli-
cation with the gain controllers. Since the link function will only aect the control voltage of the
compressor, the gain controllers of both channels should be set to the same values in stereo link
mode. For instant A/B comparisons just push the active button.
Note: If the threshold controller produces too little gain reduction when turned hard right or too
much of it when turned hard left, please go to page 26 and see how to adjust the internal thresh-
old.
Left
Input
Compressor
Gain
Stage
Left
Output
BASICS – Stereo Compression
12
Right
Input
Compressor
Sidechain
Gain
Stage
Right
Output
Auto Fast (Attack)
The Auto Fast function causes an automatic shortening of the attack time on fast and loud signal
peaks. This eect is easy to comprehend when compressing a preferably dynamic drum loop, for
example.
Please set the following values as a starting position:
• Attack: 50 ms
• Release: 300 ms
• Ratio: 1:1.8
• Threshold: Set to a position that results in approx. 3-4 dB of gain reduction
Because of the quite long attack time the snare and bass drum will be processed very moderately.
If now Auto Fast is engaged, the compressor will react to the fast and loud peaks, resulting in a
noticeably higher amount of gain reduction.
And here is the trick: Directly after this process the attack time will return to the value that was
originally set, and on ‚slower‘ signals the original value will not be changed at all. The compressor
will only become very fast in case it is really needed!
Auto Fast (Release)
The same example is suitable to use the Auto Fast function for the release parameter, too.
The following values are useful to get started:
• Attack: 30 ms + Auto Fast
• Release: 300 ms
• Ratio: 1:1.8
• Threshold: Set to a position that results in approx. 7-8 dB gain reduction
Now press the Auto Fast button of the release controller and keep your ears open as well as an eye
on the meter: the area between 4-8 dB is reduced very fast now, whereas the set value of 300 ms
stays valid between 0 and 4 dB.
Note: If you use very long release times, the eectiveness of this function will decrease. Very long
attack times will also reduce the intensity of this circuit.
This function can be a great help especially for applications with dicult dynamic structures, as it
counteracts the danger of clippings caused by too short values and the loss of loudness and pres-
sure caused by too slow settings at the same time.
13
BASICS – Auto Fast
BASICS
Feed Forward
This function makes it possible to switch the junction of the sidechain alternatively behind (feed-
back) or in front (feed forward) of the actual compressor section. This has an enormous eect on
the character of the compressor.
Again, our drum loop can be used for demonstration: While processing in feedback mode is
smooth and even, switching into feed forward mode will result in a clearly more aggressive and
harder kind of compression.
From the technical point of view this function mainly inuences the characteristic curve of the
ratio value. In feedback mode it goes up to a moderate Ratio of 1:2.5. In contrast, the feed forward
mode provides much higher values that also allow limiter settings and even negative ratios (i.e.
loud signals will be reduced even more). Thus, small changes in dynamics can generate a high
amount of gain reduction.
The values of the attack controller will also change noticeably in feed forward mode, as they will
become almost twice as high as the value shown on the scale.
Transformer
Each of the two channels features an additional transformer that can be switched into the signal
chain after the mix stage. In principle, these are classic output transformers, but here they are not
used for balancing and galvanic isolation, but as an additional means of sound shaping.
If you like to add that certain amount of ‚iron‘ to your sound, just push the transformer button and
there you are. Because of the mastering approach of the alpha compressor this feature is much
more a subtle audio shaping feature than a glaring sound eect.
In stereo mode, the buttons for both channels should be activated or deactivated at the same
time. Depending on the source material and personal taste, you can, however, add the transform-
er sound to single channels when working in M/S mode.
14
Left
Input
Right
Input
M L
M/S Encoder
S
Compressor
Sidechain
Sidechain
Compressor
Gain
Stage
Gain
Stage
R
M/S Decoder
Left
Output
Right
Output
BASICS – Feed Forward & Transformer
Channel Link
Mix
EQ FreqHzSC Gain
dB
SC Freq
EQ Gain
Feed Forward
On
x10
On
Transformer
Direct
On
Thresh Attack Release Ratio
Soft Clip
Mix
EQ Freq
SC Gain
dB
EQ Gain
Feed Forward
On
x10
On
Transformer
Direct
On
Soft Clip
SC Freq
Soft Clip
Thresh Attack
Release
Ratio
Compressed
Gain
Auto Fast
Auto Fast
Gain Reduction
M/S Mode Active
ms
Gain
Compressed
Auto Fast
ms
Auto Fast
1:X
M/S Matrix
One of the most powerful features of the alpha compressor is its switchable M/S matrix. By acti-
vating it, the incoming stereo signal is encoded into a middle channel (mono) and a side channel
which contains the stereo parts of the left and right channel (but not the common mono part).
This enables you to process the middle and the side signals separately, and nally both channels
are decoded back to left and right (stereo). A practical example helps to understand the general
idea.
The ideal song for this would be the following: Important elements like voice, drums and bass are
placed in the middle whereas the remaining instruments are mixed stereophonically.
Switch the alpha compressor into M/S mode and leave the link function deactivated for now. The
left side of the compressor now controls the middle channel and the right side the side channel.
By using the compressed switches, you can listen to both channels separately, so that you will be
able to hear what is instantly happening in the particular channel.
Now you can process the mono and side parts separately from each other. Depending on the mix,
sometimes it is only the middle channel that needs compression whereas the side channel stays
unprocessed. Other mixes have a lot of stereo information; in these cases both middle and side
channels are processed, the settings of which can be completely dierent from each other.
At the beginning, both gain controllers should be set at the same values, but this can change in
the progress of optimization by all means. You can use dierent settings of the gain controllers in
M/S mode for specic changes of the stereo width, for example.
Of course the link function also works in M/S mode. In this case, signals in the M and S channels
are reduced evenly so that the result of the compression is the same as if working in stereo mode.
However, you will still be able to adjust the level proportion between M and S with the gain con-
trollers.
BASICS – M/S Matrix
15
Mix
EQ Freq
Hz
EQ Gain
Feed Forward
On
x10
Transformer
Direct
On
Soft Clip
Mix
EQ Freq
SC Gain
dB
EQ Gain
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Thresh
AttackmsReleasemsRatio
1:X
Soft Clip
SC Freq
BASICS
Thresh Attack Release Ratio
Auto Fast
Gain
Compressed
Auto Fast
SC GaindBSC Freq
On
Soft Clip
Gain Reduction
M/S Mode Active Channel Link
Gain
Compressed
Sidechain Filter
The sidechain lter allows frequency-dependent shaping of the compression process by giving
specic frequency areas a stronger or weaker inuence on the detection circuit.
The linked M/S mode is most suitable to demonstrate the eect: Since the largest amount of signal
energy can be found in the middle as a general rule (bass drum etc.), the lter will have its greatest
impact here. A track with a balanced proportion of bass, middle and treble frequencies should be
chosen to give this function a try.
If the SC gain controller is set to HP (High Pass), the lter will act like a 6 dB high pass and the
reaction of the compressor on bass frequencies decreases. The setting LP (Low Pass) turns the
lter into a 6 dB low pass and the compressor reacts primarily on low frequencies. Again, the gain
reduction meter is a reliable aid to evaluate the distinct modes of operation.
The combination of sidechain lters, M/S matrix and dierent attack settings enables you to make
very selective changes and – depending on the source material – even to process single instru-
ments or voices in nished mixes. Details on that can be found in the Scenarios chapter.
Note: When working in linked stereo mode, the sidechain lters of both channels should be set to
identical values. In linked M/S mode, however, only the sidechain lter of the middle channel is
active, and in unlinked M/S mode the SC lter of the side channel is available, too.
Left
Input
M L
Compressor
Sidechain
Filter
Sidechain
M/S Encoder
Gain
Stage
M/S Decoder
Left
Output
16
Right
Input
S
Compressor
Gain
Stage
R
Right
Output
BASICS – Sidechain Filter
Mix
SC Gain
dB
SC Freq
Feed Forward
On
Transformer
Direct
On
Thresh Attack Release Ratio
Soft Clip
Mix
SC Gain
dB
Auto Fast
Feed ForwardOnAuto Fast
On
Transformer
Direct
On
Thresh
AttackmsReleasemsRatio
1:X
Soft Clip
SC Freq
Soft Clip
EQ Gain
EQ Freq
On
Hz
Compressed
Gain
Auto Fast
x10
Auto Fast
Gain Reduction
M/S Mode Active Channel Link
EQ Gain
EQ Freq
Compressed
Gain
x10
Audio Filter
The audio lter is placed behind the compressor in order to avoid unwanted inuences on the
detection circuit of the dynamic section.
If the EQ gain controller is turned hard right, the signal rates above the selected center frequency
will be boosted by 3 dB and the part below the center frequency will be cut by 5 dB [Fig. A]. Turn-
ing the controller hard left reverses the eect: Below the center frequency there is a boost and
above it there is a cut [Fig. B].
Gain
A
+
-
+
Gain
-
B
Center Frequency
Center Frequency
The EQ frequency controller comprehends an array from 20 Hz - 2 kHz which can be shifted to 200
Hz - 20 kHz by pushing the x10 button.
In linked M/S mode as explained above it is possible to make dierent settings with the audio
lters in the M and the S band. Again, the results can be listened to separately by using the com-
pressed switches for each channel. However, in stereo mode, both audio lters should be set to
the same values in order to avoid unwanted shifts in the stereo spectrum.
Note: Depending on the settings of the audio lters it might be necessary to adapt the volume
with the gain controllers.
Left
Input
Compressor
M
Sidechain
Audio
Filter
Gain
Stage
L
Left
Output
Right
Input
S
M/S Encoder
Compressor
Audio
Filter
Gain
Stage
M/S Decoder
R
Right
Output
BASICS – Audio Filter
17
EQ FreqHzSC Gain
dB
SC Freq
EQ Gain
Feed Forward
On
x10
On
Transformer
On
Soft Clip
EQ Freq
SC Gain
dB
EQ Gain
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
On
Thresh
AttackmsReleasemsRatio
1:X
Soft Clip
SC Freq
BASICS
Thresh Attack Release Ratio
Auto Fast
Mix Gain
Direct Compressed
Auto Fast
Soft Clip
Gain Reduction
M/S Mode Active Channel Link
Mix
Direct Compressed
Gain
Mix Controller
The mix controller makes it possible to cross-fade between the unprocessed and the compressed/
ltered signals. This allows parallel compression right in the alpha compressor and renders addi-
tional routings unnecessary in favor of a better signal quality.
Now you can use even extreme compression settings without killing the 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.
The control logic of this feature is also worth mentioning. If only the compressed button is pushed,
you will hear the compressed signal only. Otherwise, if only the direct button is pushed, only the
unprocessed signal routed from before the compressor section will be audible. If both buttons are
pushed, the mix controller will become active, and if none of the buttons is pushed, the channel
will be muted.
In practice you can switch between unprocessed, compressed or mixed signals very fast without
having to change the position of the mix controller.
In this way, the left and right channels (stereo mode) respectively the middle and side channels
(M/S mode) can be listened to separately – here you again have the choice between the original,
the compressed or the mixed signal. To mute the other channel, just deactivate the associated
direct and compressed buttons.
Left
Input
Right
Input
M
S
M/S Encoder
Compressor
Compressor
Sidechain
Gain
Stage
Gain
Stage
Mix
Stage
Mix
Stage
L
R
M/S Decoder
Left
Output
Right
Output
BASICS – Mix Controller
18
Soft Clip
M/S Mode
Channel Link
Mix
Gain
EQ FreqHzSC Gain
dB
SC Freq
EQ Gain
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Compressed
Thresh
Attack
Release
Ratio
Mix
Gain
EQ Freq
SC Gain
dB
EQ Gain
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Compressed
Thresh
AttackmsReleasemsRatio
1:X
SC Freq
Soft Clip
Gain Reduction
Direct
On
Active
Direct
Soft Clip
On
Soft Clip Limiter
The Soft Clipper was designed to limit short, loud transients to prevent subsequent A/D converters
from clipping. However, the circuit does not behave like a classic brick wall limiter, but more like an
analog tape machine driven into saturation: it rounds the peaks instead of making hard cuts.
The Soft Clip modules are placed directly in front of the output stages. Their settings are not inu-
enced by the mix and gain controllers. This is also the case in M/S mode, because the limiters are
located after the M/S decoder and therefore are always assigned to the left and right stereo chan-
nels. Note that the channel link does not aect the circuit either – because of this the settings of
the Soft Clip controllers for both channels should always be identical!
If the alpha compressor is the last unit in the signal path before the A/D converter, it is only once
that the setting of the Soft Clip limiter has to be adapted to the converter. It is best to use a fast,
sample-accurate PPM meter to nd the right setting, because it is an accurate method of bench-
marking the resulting change in level.
The Soft Clip LEDs located on top of the gain reduction meters should only light up shortly, as
noticeable distortion appears if you drive this circuit too hard. Particularly with regard to acoustic
and classical music, this feature should be used with care and moderate settings only.
Left
Input
Right
Input
Soft Clip
Limiter
Soft Clip
Limiter
Left
Output
Right
Output
BASICS – Soft Clip Limiter
19
M/S Mode
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
SCENARIOS
Thresh
+15
+4
0
+11
+18
+20
-13
dB
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
ms
Gain
2,0
1,5
Compressed
300
50
70
110
130
150
3,5
0,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
Soft Clip
Gain Reduction
Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
7,5
8,5
9,5
11
12
14
16
18
20
Compressed
3,5
4,5
Gain
6,0
2,0
1,5
8,0
0,5
10
11
0
12
dB
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Stereo Linked
This setting is especially useful for tracks in which the instruments are not placed straight in the
middle of the stereo spectrum – when a recording has been made by using classic stereo miking
like in Jazz, for example. In order to come up to such styles of music, one should make sure to create an unobtrusive and smooth kind of compression. This can be achieved by setting a long attack
time and a ratio value in the lower control range, at which only a very few dB of gain reduction
are required. If necessary, you can use the mix controllers to apply the eect of the compressor
in even ner doses (both direct and compressed buttons have to be activated for this). Moreover,
you can kick in the audio lters to make additional sonic corrections. Note: Look after setting the
mix, gain and lter controllers at the same values when working in stereo mode. The link function
only aects the control mode of the actual compressor section. Of course the linked stereo mode
can also be used for many other styles of music, but then you will often be able to achieve even
better results in M/S mode.
20
Thresh
+15
+4
0
+11
+18
+20
-13
dB
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
ms
Gain
2,0
1,5
Compressed
300
50
70
110
130
150
3,5
0,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
Soft Clip
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Gain Reduction
M/S Mode Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
7,5
8,5
9,5
11
12
14
16
18
20
Compressed
3,5
4,5
Gain
6,0
2,0
1,5
8,0
0,5
10
11
0
12
dB
M/S Linked
The function of the compressor in linked M/S mode is quite similar to its function in linked stereo
mode, and the resulting gain reduction in the middle and the side channel is exactly the same.
An attack time of 30-40 ms ensures that transients from percussion instruments are hardly compressed, while the release time of 250 ms lets the compressor decrease its gain reduction fast
enough. Variations of the release time are especially eective in controlling the amount of loudness. Here, activating the Auto Fast function should be preferred to setting a very fast release time.
The generated gain reduction is primarily aected by matching the threshold and ratio parameters. A ratio of 1:1.7 has often proved to be a good start. But what is the essential advantage of
the linked M/S mode compared to the linked stereo mode? The levels of M and S can be set dierently, which makes it very easy to perform changes of the stereo width (Mix too narrow? More gain
to the side channel. Not enough punch? Add gain to the middle). Furthermore, a left/right drift
SCENARIOS – Stereo Linked & M/S Linked
caused by possible unequal settings of the gain controllers is impossible in this mode.
Channel Link
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Thresh
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
M/S Mode
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
On
Auto Fast
x10
On
Transformer
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
+15
+4
3,0
14
Thresh
+11
+15
4,0
5,0
11
12
0
+18
-13
+20
dB
6,0
7,5
8,5
9,5
+4
0
+11
+18
+20
-13
dB
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
150
ms
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
3,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
2,1
1,2
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
1,5
2,0
3,0
4,0
12
14
16
18
M/S Mode Active
1,0
20
Soft Clip
Gain Reduction
1,0
1,5
2,0
16
18
20
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
150
ms
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
3,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
1,1
2,4
1:X
M/S Unlinked
The true strengths of an M/S compressor will not be revealed until it is switched into unlinked M/S
mode. Depending on the mix and the style of music, the dynamics and loudness in the middle
and side channel can be completely dierent from each other. Take a heavily pumping bass drum
right in the middle and 100 % stable strings in the sides, for example – just try this with any other
compressor ;-) Thus it can make perfect sense to set strongly diering values of threshold, attack,
release and ratio for the middle and the sides. In order to achieve a better evaluation of the results,
it is advisable to listen to the processed channel solo for a start. Please remember to deactivate the
direct and compressed buttons of the other channel for this. Using the audio lters, which can also
be set completely dierent from each other now, can help to additionally enhance the tonal balance of a mix. Once you have discovered the potentials of the M/S mode, lots of formerly dicult
mixes can be controlled much better, resulting in audibly better eects.
+4
0
Thresh
+11
+15
+18
+20
dB
30
20
Direct Compressed
-13
Mix
-3
10
-6
-9
-12
Feed Forward
50
Dir
%
Attack
7,0
60
24
28
13
2,0
0,01
150
ms
Gain
70
80
2,0
90
1,5
100
0,5
Com
300
50
70
110
130
3,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
2,1
1,2
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
Soft Clip
Gain Reduction
Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
7,5
8,5
9,5
11
12
14
16
18
20
50
60
Mix
70
30
20
Direct Compressed
80
90
10
100
Dir
Com
%
3,5
4,5
Gain
6,0
2,0
1,5
8,0
10
0,5
11
0
12
dB
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Upward Leveling
Upward Leveling – this describes the possibility to make only the low signal parts louder and leave
the louder changes in dynamics unprocessed. The settings shown above are suitable for classical
music, for example, where ‚typical‘ compression is objectionable. The compressor works in linked
stereo mode, the attack time is set at maximum and the release time is at 150 ms. Under these
conditions the alpha compressor will function as a leveler. In feed forward mode the attack time
is twice as long compared to feedback mode and therefore amounts to 300 ms. The ratio characteristic corresponds to a limiter, and the make up gain is about 6 dB. The result of these settings:
Quieter passages that do not produce any gain reduction will be boosted by 6 dB, whereas loud
signals will be limited by the compressor. Now the special trick is to set the mix controller to 50 %.
By adding the original signal the initial dynamics will be saved, and the bottom line is that only the
quieter signals will be turned up.
SCENARIOS – M/S Unlinked & Upward Leveling
21
Channel Link
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
On
Auto Fast
x10
On
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
On
Auto Fast
x10
On
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
On
Auto Fast
x10
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
SCENARIOS
Thresh
+15
+4
+4
0
+11
+18
+20
-13
dB
-3
-6
-9
-12
Feed Forward
Attack
7,0
24
28
13
2,0
0,01
ms
Gain
2,0
1,5
Compressed
300
50
70
110
130
150
3,5
0,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
1,5
2,0
3,0
4,0
12
14
16
18
M/S Mode Active
1,0
20
Soft Clip
Gain Reduction
1,0
1,5
18
20
0
Thresh
+11
2,0
+15
3,0
4,0
+18
5,0
-13
+20
dB
6,0
7,5
8,5
9,5
11
12
14
16
-3
-6
-9
-12
Feed Forward
Attack
7,0
24
28
13
2,0
0,01
150
ms
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
3,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
1,1
2,4
1:X
M/S Leveling
As with Upward Leveling, long attack times are the secret of M/S Leveling. Here the compressor reacts primarily to the complete signal energy and less to single rhythmic accents. If this principle is
now used on the side and the middle channel separately, a stereo mix will become more compact
in an unobtrusive way and everything will sound a little more vivid. This method is especially interesting to enhance rock and pop tracks in a discreet but eective way. Here the feed forward mode
is active again. The ratio is set at about 1:1.5 and the gain controller at about 3 dB. The threshold is
adapted to a value that results in approx. 3-4 dB.
Thresh
+15
+4
0
+11
+18
+20
-13
dB
-3
-6
-9
-12
Feed Forward
Attack
7,0
24
28
13
2,0
0,01
ms
Gain
2,0
1,5
Compressed
300
50
70
110
130
150
3,5
0,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
-0,3 -0,3
SC Gain
-1
-2
-2
-5
-5
-12
-12
LP
HP
dB
6,0
8,0
10
11
12
430
Release
Ratio
1,4
1,3
1,2
SC Freq
On
1,7
1,6
1,8
1,9
2,1
2,2
5,0
1,1
2,4
1:X
6,0
280 340
430
7,5
80
8,5
50
9,5
40
2k0
11
30
3k3
Hz
Soft Clip
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Gain Reduction
M/S Mode Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
7,5
8,5
9,5
11
12
14
16
18
20
Compressed
3,5
4,5
Gain
6,0
2,0
1,5
8,0
0,5
10
11
0
12
dB
Groove Compression
Sometimes it would be great to be able to just emphasize the rhythmical elements of a mix in
order to bring out the groove with the aim of giving the track the right kick. The gure shows how
the alpha compressor can help you to cope with this challenge. The bass drum is used as a trigger
for the compressor; therefore the sidechain lter is of special importance in this application. It is
set to low pass, with a center frequency of approx. 70 Hz. Now the threshold and ratio controllers
are used to set the intensity of the gain reduction, and the groove will be controlled by the release
parameter, which has merely to be adapted to the speed of the track. Depending on the song and
the style of music, the gain reduction can be higher by all means; usually 5-6 dB will do very good.
The linked M/S mode makes sense in this application, because the inuence of the bass drum on
the control process is enhanced as well as the resulting sonic eect.
22
SCENARIOS – M/S Leveling & Groove Compression
Channel Link
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
On
Auto Fast
x10
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
Channel Link
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
Transformer
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
3,0
14
Thresh
+11
+15
4,0
5,0
11
12
0
-3
-6
-9
-12
+18
-13
+20
dB
6,0
7,5
8,5
9,5
3,5
4,5
Gain
6,0
2,0
1,5
Compressed
8,0
10
0,5
11
0
12
dB
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
1,1
2,4
1:X
Thresh
+15
+4
0
+11
+18
+20
-13
dB
-3
-6
-9
-12
Feed Forward
Attack
7,0
24
28
13
2,0
0,01
150
ms
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
3,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
-0,3 -0,3
SC Gain
-1
-2
-2
-5
-5
-12
-12
LP
HP
dB
6,0
8,0
10
11
12
430
Release
Ratio
1,4
1,3
SC Freq
On
1,7
1,6
1,8
1,9
2,1
1,2
2,2
5,0
1,1
2,4
1:X
6,0
280 340
430
7,5
80
8,5
50
9,5
40
2k0
11
30
3k3
Hz
1,5
2,0
3,0
4,0
12
14
16
18
M/S Mode Active
1,0
20
Soft Clip
Gain Reduction
1,0
1,5
2,0
16
18
20
Vocal Down
If you have a track in which the vocals are too loud, the compressor can be set in a way that it
mainly reacts to the lead vocals placed in the middle, resulting in a better integration into the mix.
For this purpose, switch it into the unlinked M/S mode. Again, the specialty here lies in combining
the sidechain lters with suitable attack parameters. The SC lter of the middle channel is set to
high pass at a center frequency of about 270 Hz with the eect that the compressor hardly reacts
to bass impulses anymore. The attack time lies between 70-100 ms. Thus, transient-like signals like
a snare drum also only have a minor inuence on the compression process. The release time is set
at about 100 ms so that the compressor can return to its idle status fast enough. In the side band,
both the controller for the threshold and the ratio parameters should be turned hard left if you
do not wish any further processing there. An equal setting of the middle and side channel gain
controllers is also advised.
Thresh
+15
3,0
14
Thresh
+11
+15
4,0
5,0
11
12
0
-3
-6
-9
-12
+18
-13
+20
dB
6,0
7,5
8,5
9,5
3,5
4,5
Gain
6,0
2,0
1,5
Compressed
8,0
10
0,5
11
0
12
dB
+4
0
+11
+18
+20
-13
dB
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
150
ms
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
3,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
-0,3 -0,3
SC Gain
-1
-2
-2
-5
-5
-12
-12
LP
HP
dB
6,0
8,0
10
11
12
430
Release
Ratio
1,4
1,3
SC Freq
On
1,7
1,6
1,8
1,9
2,1
1,2
2,2
5,0
1,1
2,4
1:X
6,0
280 340
430
7,5
80
8,5
50
9,5
40
2k0
11
30
3k3
Hz
1,5
2,0
3,0
4,0
12
14
16
18
M/S Mode Active
1,0
20
Soft Clip
Gain Reduction
1,0
1,5
2,0
16
18
20
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
1,1
2,4
1:X
+4
DeEssing
A variation of the Vocal Down scenario is DeEssing which is used for reducing unwanted ess and
hiss sounds. The sidechain lter of the middle channel is set to approx. 2 kHz, which is even higher than in the previous application, so that only the high frequencies can inuence the detection circuit. At about 100 ms, the attack time is also quite long and the release time is set to fast
50 ms. Now threshold and ratio are used to set the trigger point and the intensity of the processing. Again, this application is run in unlinked M/S mode to assure that only the middle channel is
processed (but of course you can still additionally process the sides separately if needed).
SCENARIOS – Vocal Down & DeEssing
23
M/S Mode
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Feed ForwardOnAuto Fast
x10
On
Transformer
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
Channel Link
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Transformer
Direct
On
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
Auto Fast
Feed ForwardOnAuto Fast
On
Transformer
Direct
On
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
SCENARIOS
+4
0
Thresh
+11
+15
+18
+20
dB
20
Direct Compressed
-13
Mix
30
10
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
ms
50
60
Gain
70
80
2,0
90
1,5
100
Dir
Com
%
300
50
70
110
130
150
3,5
0,5
0
dB
570
150
100
4,5
800
1k1
1k5
75
60
1k8
ms
Auto Fast
6,0
8,0
10
11
12
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
Soft Clip
Gain Reduction
Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
7,5
8,5
9,5
11
12
14
16
18
20
50
60
Mix
70
30
20
Direct Compressed
80
90
10
100
Dir
Com
%
3,5
4,5
Gain
6,0
2,0
1,5
8,0
0,5
10
11
0
12
dB
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Parallel Compression
If it should (or must) become really loud, you can also use the alpha compressor to drive a track
against the wall – but without the negative eects this usually entails. For this procedure it is preferable to work in the classic linked stereo mode. The time parameters are set very fast here; especially the attack time at only 10 ųS. The release parameter is set at 150 ms, while the corresponding
Auto Fast function is also activated and the ratio is at maximum. With these settings everything
will be compressed very intensely – even fast transients and impulses, resulting in an intense limitation of the output peak levels. Now the mix controller comes into play: If the just created ‚at‘
signal is mixed to the original signal in moderate rates, it is possible to achieve an increase in loudness while still saving a great part of the initial dynamics.
Thresh
+15
+4
0
-3
+11
-6
-9
-12
+18
+20
-13
dB
4,5
3,5
Gain
6,0
2,0
1,5
Compressed
8,0
10
0,5
11
0
12
dB
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
1,5
2,0
3,0
4,0
12
14
16
18
M/S Mode Active
1,0
20
Soft Clip
Gain Reduction
1,0
1,5
18
20
0
Thresh
-3
+11
2,0
+15
3,0
4,0
+18
5,0
11
12
14
16
-6
-9
-12
-13
+20
dB
6,0
0,3
0,3
1,0
7,5
8,5
9,5
2,7
Lo
dB
EQ Gain
Hi
140 170
EQ Freq
220
40
30
22
20
Hz
Compressed
300
500
1k0
2k0
x10
3,5
4,5
Gain
6,0
2,0
1,5
8,0
0,5
10
11
0
12
dB
1,6
2,2
2,7
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
1,2
2,1
2,2
1,1
2,4
1:X
+4
Stereo Enhancer
Even when there is nothing to compress from time to time, your productions can still benet from
the alpha compressor, as the combination of the M/S matrix and the audio lters makes a very nice
tool for inuencing the stereo spectrum. For this purpose the compressor is switched into M/S
mode and the audio lter of the side channel adds 1.0-1.5 dB at a center frequency of approx. 1
kHz. The gain controllers of both channels are at 0 dB. These settings cause a boost of all frequencies above 1 kHz in the side channel, which intensies the spatial perception as the room reections become more distinct. The lower frequencies, however, are not of that great importance for
spatial perception. Of course simply increasing the level in the side channel can be used to achieve
a (broadband) change in the stereo spectrum, too, but this variant oers much more dierentiated
options because it is frequency-dependent.
24
SCENARIOS – Parallel Compression & Stereo Enhancer
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
Auto Fast
Feed ForwardOnAuto Fast
On
Direct
On
Thresh
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
Auto Fast
Feed ForwardOnAuto Fast
On
Direct
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
EQ Gain
Lo
2,7
2,2
1,6
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
On
x10
On
Direct
On
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
Mix
Dir
10
%
20
30
60
70
80
90
Com
100
50
EQ Freq
Hz
20
22
30
40
140 170
500
220
300
2k0
1k0
SC Gain
dB
LP
-12
-5
-2
-1
-0,3 -0,3
-2
-5
-12
HP
EQ Gain
Lo
2,7
1,0
0,3
1,6
2,2
2,7
Hi
dB
0,3
Auto Fast
Feed ForwardOnAuto Fast
x10
On
Direct
On
Thresh
+20
+18
dB
+15
+11
0
-3
-6
-9
-13
-12
+4
Attack
0,01
2,0
ms
7,0
13
28
50
70
110
150
130
24
Release
60
75
ms
100
150
430
570
800
1k1
1k8
1k5
300
Ratio
1,1
1,2
1:X
1,3
1,4
1,7
1,8
1,9
2,1
2,4
2,2
1,6
Soft Clip
25
24
dB
21
19
14
11
8,0
5,5
3,0
16
4,0
SC Freq
Hz
30
40
50
80
280 340
430
2k0
3k3
500
800
+15
+4
0
+11
+18
+20
-13
dB
0,3
0,3
1,0
1,6
2,2
2,7
Lo
dB
-3
EQ Gain
Hi
24
28
Attack
-6
13
-9
7,0
-12
2,0
0,01
150
ms
140 170
EQ Freq
40
1,6
30
2,2
2,7
22
20
2k0
Hz
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
220
300
500
1k0
3,5
0
dB
570
150
100
x10
4,5
75
6,0
12
60
8,0
10
11
Transformer
800
1k1
1k5
1k8
ms
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
2,1
1,2
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
Soft Clip
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Gain Reduction
M/S Mode Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
0,3
0,3
1,0
7,5
8,5
9,5
2,7
11
Lo
Hi
12
dB
14
16
18
20
EQ Gain
1,6
2,7
140 170
EQ Freq
220
40
300
30
22
20
Compressed
500
1k0
2k0
x10
Hz
3,5
4,5
Gain
6,0
2,0
1,5
8,0
10
0,5
11
0
12
dB
Transformer
2,2
LoFi Compression
Can the alpha compressor also sound really bad? Of course not, but sometimes it just loves being,
well … dierent. In this LoFi Compression scenario, the use of the audio lters is the crucial point.
By reducing the high frequencies from 4 kHz on, everything sounds a little darker, while, at the
same time, the bottom experiences a great degree of additional punch. The chosen time parameters result in loud and twangy compression eects. The high ratio settings create a great amount
of compression, so that gain reduction values of 8-12 dB are absolutely normal. In this application
the mix controllers give you the option to blend this extreme sound with the original at will.
Thresh
+15
+4
0
+11
+18
+20
-13
dB
24
28
Attack
-3
-6
13
-9
7,0
-12
2,0
0,01
150
ms
Gain
2,0
1,5
0,5
Compressed
300
50
70
110
130
Auto Fast
3,5
0
dB
570
150
100
4,5
75
6,0
12
60
8,0
10
11
Transformer
800
1k1
1k5
1k8
ms
Auto FastFeed Forward
430
Release
Ratio
1,3
1,7
1,6
1,8
1,4
1,9
2,1
1,2
2,2
5,0
1,1
2,4
1:X
6,0
7,5
8,5
9,5
11
Soft Clip
1,0
1,5
2,0
3,0
4,0
12
14
16
18
20
Gain Reduction
M/S Mode Active Channel Link
1,0
1,5
2,0
3,0
4,0
5,0
6,0
7,5
8,5
9,5
11
12
14
16
18
20
Compressed
3,5
4,5
Gain
6,0
2,0
1,5
8,0
10
0,5
11
0
12
dB
Transformer
Extreme Settings
Even though the main focus of the alpha compressor lies on mastering applications, you can also
use it to nd interesting and sometimes extreme settings for single channels or subgroups. Here is
just one of many examples. It is especially suitable for processing drum tracks eectively: The time
parameters with the additionally activated Auto Fast functions are very fast. The high ratio in feed
forward mode causes an extreme characteristic curve so that loud signals will be reduced signicantly. By doing so, very high gain reduction values of 20 dB and more can occur by all means. The
spatial elements now come into the foreground more articulately – it somehow sounds as if the
microphones had been placed a little bit further away during recording.
SCENARIOS – LoFi Compression & Extreme Settings
25
REFERENCE
Threshold Oset
The analog audio level of the alpha compressor depends on the studio environment it is used in. In the majority of cases it depends on the D/A converter used, because the output stages of the converter determine
the analog level. As there is no binding norm for it, this level can be at +4 dB, +6 dB, +10 dBu, +12 dBu or
even +15 dBu. To make sure that the threshold controller actually covers its complete adjustment range it
can be adjusted to those dierent levels.
When is an adjustment necessary?
1. At low Ratio values (1:1.3), the threshold controller is almost completely turned clockwise and the gain reduction
is still too low
2. At higher Ratio values (1:2.5), the threshold controller is
turned completely counter-clockwise, but nevertheless gain
reduction already sets in
In order to adjust the internal threshold oset, the rst thing
to do is to open the top cover with the adequate Torx screwdriver. Before the adjustment can be done the unit has to be
powered up for at least 15 minutes to reach a stable working
temperature. Please make sure to disable the M/S and link
functions. Now send an audio signal into the compressor
and set the attack to approx. 24 and the release to 300 ms.
On the upper circuit board there is a blue trimmer labeled THRESHOLD OFFSET placed directly behind the
threshold potentiometer (yellow arrow in the gure). In the rst case (too little gain reduction) the trimmer
has to be turned clockwise to raise the amount of gain reduction. In the second case (too much gain reduction) the trimmer has to be turned counter-clockwise. In order to reassure that the adjustment range now
really ts, it is recommended to repeat the above-mentioned test with the threshold controller in extreme
left/right position. The same procedure should also be applied to the right channel, of course.
Threshold
The diagram shows dierent threshold settings in feedback mode. The threshold and the ratio are
always interdependent: On high ratios the threshold is usually set to lower values in order not to
produce too much gain reduction, and on lower ratio settings the threshold controller is turned
more to the right. The complete threshold range covers 33 dB which enables the user to make very
sensitive settings in reasonable steps at any time.
26
REFERENCE – Threshold Offset & Threshold
Attack
Here a burst signal (a sine tone that is boosted by 12 dB for a period of 100 ms) is used to demon-
strate the eectiveness of the attack controller. The dierent curves show how fast this level jump
is reduced by 4 dB. On fast settings the reduction takes only a few milliseconds, on longer settings
the reduction does not only take longer, but it is also smaller. Therefore the amount of gain reduc-
tion is always higher on fast attack settings than on longer settings.
Auto Fast Attack
Utilizing a burst signal again, this diagram shows a comparison between a normal attack time of
50 ms (dark curve) and the later added Auto Fast function (light curve). This reveals how fast this
circuit reacts: Even the rst waves of the burst are already reduced by 2.3 dB. The whole gain re-
duction now happens much faster, too. Note: This function starts working at -3 dB; on lower gain
reduction values the changes in dynamics are too small to trigger it accurately.
27
REFERENCE – Attack & Auto Fast Attack
REFERENCE
Release
This gure is based on a very fast attack time; the gain reduction is about -7 dB. The burst lasts for
25 ms and then follows the release phase with time parameters of dierent length. The linear char-
acteristic of the release curve is very easy to see here. Because of the utilized circuit, the attack time
must always be added to the release time. The advantage is that in combination with long attack
settings you can use even the fastest release settings without generating unwanted artifacts.
Auto Fast Release
In this case the Auto Fast function was added to a release time of 400 ms (light curve). It is easy
to see that directly after the burst the release time becomes very fast (only 20 ms) and then re-
turns to its original setting. This has two eects: Firstly, the level in a period of 500 ms after the
burst becomes 2.5 dB louder, and secondly the release phase is already completed after 250 ms.
In practice this means an apparent increase in loudness without the distortion usually generated
by constantly fast release times.
28
REFERENCE – Release & Auto Fast Release
Ratio Feedback
The alpha compressor works with a soft knee characteristic with rising gain reduction values at
increasing ratios. The scale on the front panel is based on a measured gain reduction of 6 dB.
Strictly speaking, the ratio values become noticeably higher on stronger reductions: If there is
17 dB of gain reduction the ratio value will shift from the printed 1:2.5 to actual 1:4.5 after all.
Anyhow, the scale is optimized to the lower gain reduction settings as these are the ones most
frequently used in mastering applications.
Ratio Feed Forward
In feed forward mode the ratio characteristics dier strongly from those in feedback mode. Al-
though they remain quite comparable up to a value of 1:1.5, the dierences become extremely
obvious at higher settings. The lower curve shows the radical eects: An input level of 0 dBu is re-
duced to -8.3 dBu, and an input level of +10 dBu is reduced to -15 dBu (!) after processing. Extreme
settings like these can only be achieved with a feed forward compressor, and they can result in
very wild eects.
29
REFERENCE – Ratio Feedback & Ratio Feed Forward
REFERENCE
EQ Gain Low
For this measurement the center frequency was set to 1.8 kHz and the EQ gain controller was set
to dierent positions between 0 and full left (-3 dB). The diagram shows the eectiveness of the l-
ter: The lower frequencies are boosted up to 3 dB, at the center frequency they cross zero, and the
higher frequencies are cut up to 4.5 dB. Depending on the setting of the EQ gain the level might
need some make up with the gain controller.
EQ Gain High
Now let’s have a look at the opposite scenario. In this gure the EQ gain controller was turned
from 0 to full right at a center frequency of 1.1 kHz. Contrary to the previous example, the high
frequencies are now boosted up to 3 dB and the lower frequencies are reduced by up to 5 dB. The
ne-tuned interim values make it possible to apply very subtle sonic changes.
30
REFERENCE – EQ Gain Low & EQ Gain High
EQ Frequency
This diagram shows a variation of center frequencies with the EQ gain controller turned fully clock-
wise (HI). The x10 button shifts the complete frequency area by a factor of 10. With settings in the
border areas of the covered frequencies it is also possible to realize ‘almost’ shelving lters, but in
these cases the level has to be adapted with the gain controllers.
SC Gain
The green curve shows an almost linear compression with a constant gain reduction across the
complete frequency spectrum. If the SC gain controller is set to high pass (HP – yellow curve),
however, the low frequencies will not inuence the detection circuit and the gain reduction sets
in only on higher frequencies. In low pass mode (LP – orange curve) just the low frequencies are
fully processed and the intensity of the gain reduction decreases with rising frequencies. Of course
there are a lot of useful interim values between the linear and the extreme positions.
31
REFERENCE – EQ Frequency & SC Gain
REFERENCE
SC Low Pass
This diagram shows some settings of the sidechain frequency controller (SC Freq) in low pass
mode (LP). If the lter is set at 100 Hz for example, full gain reduction will still occur at these 100
Hz and the high frequencies will have lesser inuence the higher they get. Therefore in this mode
of operation the lter should always be set to the highest frequency you just about want the com-
pressor to react to.
SC High Pass
Here the controller was turned completely the other way round. In high pass position (HP) the ap-
proach of the sidechain lter is slightly dierent. At 100 Hz the compressor now hardly reacts to
just this frequency and only the higher frequencies will have an increasing inuence on the gain
reduction. In practice the controller should therefore be set to the lowest frequency you just about
want the compressor not to react to.
32
REFERENCE – SC Low Pass & SC High Pass
Mix
This measurement diagram shows a fade from the original to the compressed signal (direct and
compressed buttons active). The gain controller was set at 8 dB, which is also the reason for de-
creasing levels in the more clockwise areas of the controller range. In case that only the direct or
alternatively only the compressed signal is switched in, the mix controller does not have any inu-
ence on the level.
Soft Clip
These characteristic curves show the smooth processing of the Soft Clip limiter. Even though this
gure employs huge amounts of level reduction to demonstrate the eect clearly, the limiter val-
ues should not exceed 6 dB as a general rule. After all, this function aims at rounding the peaks of
a signal and not at reducing the complete level. Too heavy use of the Soft Clip limiter can cause
audible distortion.
33
REFERENCE – Mix & Soft Clip
APPENDIX
Level Problems
No Signal
This problem might be caused by balanced wiring. If the signal almost completely drops when the
alpha compressor is activated, it is probable that a pin of the XLR connector at the input is not con-
nected. As the input stages feature transformers, both pins have to be connected. The classic case
for this problem would be a balanced XLR connection that is connected to an unbalanced output
that only uses ground and pin 2. Connecting pin 3 to ground should solve this problem.
Slight Level Jump
Under certain circumstances, pushing the active switch may cause a small change of level. If there
is no noticeable dierence between bypass and active when in stereo mode with activated di-
rect buttons and mix controllers fully turned counter-clockwise, everything is OK. But if there is
a small change of level somewhere between 0.5 - 1 dB, the input and output impedances of the
devices preceding and succeeding the alpha compressor might be the reason. A high output im-
pedance (approx. 1 kOhm) of the preceding device and a low input impedance (<4700 Ohm) of
the succeeding unit are especially critical. If the compressor is in bypass, the preceding device
will be loaded with the input impedance of the alpha compressor itself plus the input impedance
of the succeeding unit. This cumulative load might result in a decrease of level. If now the alpha
compressor is activated, the preceding device only “sees” the alpha compressor and no longer the
following unit. Therefore the load decreases and the level rises as a consequence. Especially tube
equipment tends to produce this phenomenon. Generally speaking, output impedances smaller
than 150 Ohm are recommended for a trouble-free signal chain.
Large Level Jump
The output stages of certain audio processors are designed in a way that the level will always
stay the same – no matter if they are hooked up with a balanced or an unbalanced connection. If
pin 3 is connected to ground, for example, the level at pin 2 will automatically become twice as
loud as before. These kinds of output stages are usually unproblematic. But there are also stages
that cannot compensate for that. In these cases the level at pin 2 stays as it is, even if pin 3 is con-
nected to ground. If the alpha compressor is placed between a device with that kind of output
stages and a device with unbalanced inputs and with pin 3 connected to ground, it is possible that
the level jumps up by 6 dB when the compressor is activated. As a general rule, input stages with
balanced connectors are always the best choice. In case these are not available, the rst attempt
to solve this problem should be to disconnect pin 3 at the XLR inputs of the alpha compressor
and then connect it to ground. This generates an unbalanced signal that should not shift the level
anymore.
34
APPENDIX – Level Problems
Technical Data
Frequency Response: <10 Hz – 200 kHz (-0.5 dB)
THD+N @ +15 dBu, 20 Hz - 22 kHz:
Stereo Mode (Direct) 0.0039 %
Stereo Mode (Compressed) 0.009 %
M/S Mode (Direct) 0.014 %
M/S Mode (Compressed) 0.034 %
Noise Floor, 20 Hz - 20 kHz (A-weighted):
Stereo Mode (Direct) -95.8 dBu
Stereo Mode (Compressed) -89.3 dBu
M/S Mode (Direct) -95.6 dBu
M/S Mode (Compressed) -92.3 dBu
Dynamic Range, 20 Hz - 22 kHz:
Stereo Mode 122 dB
M/S Mode 118 dB
Maximum Input Level:
Stereo Mode +28 dBu
M/S Mode +23 dBu
Maximum Output Level:
Stereo Mode +27 dBu
M/S Mode +23 dBu
Input Impedance: 10 kOhm
Output Impedance: 68 Ohm
Pin Assignment Input: 1. GND
2. Positive (transformer balanced)
3. Negative (transformer balanced)
Pin Assignment Output: 1. GND
2. Positive
3. With 68 Ohm to GND
Power Consumption: 100 W max
Fuse Type: 115 VAC 3 A Slo-Blo/230 VAC 1.5 A Slo-Blo
Dimensions (W x H x D): 483 mm x 133 mm (3 U) x 405 mm
19“ x 5.3“ (3 U) x 16“
Weight: 16.0 kg/35 lb
APPENDIX – Technical Data
35
APPENDIX
Warranty
Conditions and limitations
The alpha compressor is covered by a limited warranty for a period of 5 years against defects in parts and
labor from the date of purchase. Natural wear is not covered by this warranty. elysia will remedy problems
caused by material or workmanship either by repair or replacement to restore the product to full performance without charge for parts and labor. Repairs or replacements will not extend the warranty period.
The warranty is given to the original purchaser only and is not transferable. elysia will only give warranty on
products purchased through authorized elysia dealers. The warranty will only be valid in the country of the
original purchase unless otherwise pre-authorized by elysia.
All warranties become void when the product has been damaged by misuse, accident, neglect, modication, tampering or unauthorized alteration by anyone other than elysia authorized service personnel.
The warrantor assumes no liability for property damage or any other incidental or consequential damage
whatsoever which may result from failure of this product. Any and all warrantees of merchantability and tness implied by law are limited to the duration of the expressed warranty.
This warranty gives you specic legal rights and you may also have other rights which vary from state to
state. Some of the above limitations may not apply to you.
Registration and return
To conrm your warranty please register your elysia product shortly after purchase. The easiest and fastest
way is to use the online form you will nd in the service section of our website www.elysia.com. If you cannot
or do not want to use this option, please contact us via the address you will nd at the end of this warranty
statement. You will be provided with registration documents suitable for fax or mail use free of charge.
In case you notice any defect, please contact elysia for technical support directly. You can nd the correspondent contact data at the end of this warranty statement. You will receive a return authorization which
enables you to send your product to the elysia factory where it will be repaired and then sent back to you.
Packaging and shipping
All returns to the factory must be in the original packaging, accompanied by the return authorization, and
must be shipped via insured freight at the customer‘s own expense. A new original packaging can be ordered from elysia. The customer will be charged for new factory original packaging if he fails to ship the
product in the original factory packaging.
In case that a product must be returned to the factory from a country outside Germany, the customer shall
adhere to specic shipping, customs, and commercial invoicing instructions given with the return authorization as elysia will not be responsible for transportation costs or customs fees related to any importation or
re-exportation charges whatsoever.
After repair, the product will then be returned to the customer via prepaid, insured freight, method and
carrier to be determined by elysia. elysia will not pay for express or overnight freight service or pay for shipments to locations outside Germany. All damages caused by transport are not covered by this warranty.
36
Contact data
For technical support please contact:
elysia GmbH
Am Panneschopp 18
41334 Nettetal
Germany
info@elysia.com
Version 1.2
Printed in Germany
APPENDIX – Warranty
1.7
1.6
Ratio
430
300
Release
28
24
Attack
0
+4
Thresh
2.1
1.9
1.8
570
50
-3
2.2
2.4
1.1
1.2
1.4
1.3
1k1
800
1k5
1k8
60
75
150
100
110
70
130
150
0.01
2.0
13
7.0
-9
-6
-12
-13
+20
+18
+11
1.0
5.0
+15
4.0
3.0
2.0
1.5
800
500
2k0
430
1:X
280 340
SC Freq
Auto FastFeed Forward
SC Gain
ms
-0.3 -0.3
-1
Auto Fast
220
ms
140 170
EQ Freq
EQ Gain
0.3
dB
0.3
1.0
7.5
6.0
3k3
Hz
30
40
80
50
-5
-2
-12
HP
dB
LP
-2
-12
-5
x10 On
500
300
1k0
2k0
Hz
20
22
40
30
On
2.2
1.6
2.7
Hi
dB
Lo
2.7
8.5
9.5
11
12
5.5
8.0
11
14
16
4.0
3.0
dB
25
24
19
21
Soft Clip
10
8.0
6.0
4.5
3.5
2.0
Gain
80
70
60
50
Mix
30
14
16
18
20
TransformerDirect Compressed On
11
12
dB
0
0.5
1.5
90
100
Com
%
Dir
10
20
1.7
1.6
Ratio
430
300
Release
28
24
Attack
0
+4
Thresh
Song . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Soft Clip
1.0
1.5
2.0
3.0
4.0
5.0
2.1
1.9
1.8
1.4
800
570
150
70
50
13
-6
-3
+11
6.0
2.2
2.4
1:X
280 340
1.1
1.2
1.3
1k1
100
110
7.0
-9
+15
SC Freq
Auto FastFeed Forward
1k5
SC Gain
1k8
ms
-0.3 -0.3
60
75
Auto Fast
130
150
ms
140 170
0.01
2.0
EQ Freq
-12
EQ Gain
-13
0.3
dB
0.3
+20
+18
11
9.5
8.5
7.5
2k0
430
40
80
50
-5
-2
-12
-1
-2
-12
-5
500
300
1k0
220
22
40
30
2.2
1.6
2.7
1.0
2.7
1.6
2.2
Gain Reduction
20
18
16
14
12
3k3
Hz
8.0
30
11
14
16
HP
19
dB
Soft Clip
8.0
LP
6.0
4.5
x10 On
3.5
2k0
2.0
Gain
Hz
80
20
70
60
On
50
Hi
Mix
30
dB
Lo
M/S Mode Active Channel Link
5.5
4.0
3.0
dB
25
24
21
10
TransformerDirect Compressed On
11
12
dB
0
0.5
1.5
90
100
Com
%
Dir
10
20
Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Right Channel Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engineer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Left Channel Track . . . . . . . . . . . . . . . . . . . . . . . . . . .
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
37
Download the PDF at www.elysia.com
„Let there
be sound“
And there
38
was sound.
(AC/DC)
TCHAIKOVSKY‘S NEWS
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