Behringer Denoiser SNR2000 User manual

DENOISER® SNR2000
Version 2.3 June 2002
Users Manual
www.behringer.com
ENGLISH

2
DENOISER SNR2000
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Heat:
The appliance should be situated away from heat sources such as radiators, heat registers, sto es, or other
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All other ser icing should be referred to qualified ser ice personnel.

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DENOISER SNR2000
FOREWORD
Dear Customer,
Welcome to the team of DENOISER users and thank you ery much for expressing your confidence in
BEHRINGER products by purchasing the SNR2000.
It is one of my most pleasant tasks to write this letter to you, because it is the culmination of many months of
hard work deli ered by our engineering team to reach a ery ambitious goal: making an outstanding de ice
that will become a standard tool used by studios and P.A. companies. The task to design the DENOISER
certainly meant a great deal of responsibility, which we assumed by focusing on you, the discerning user and
musician. It also meant a lot of work and night shifts to accomplish this goal. But it was fun, too. De eloping a
product usually brings a lot of people together, and what a great feeling it is when e erybody who participated
in such a project can be proud of what we e achie ed.
It is our philosophy to share our joy with you, because you are the most important member of the BEHRINGER
family. With your highly competent suggestions for new products you e greatly contributed to shaping our
company and making it successful. In return, we guarantee you uncompromising quality (manufactured
under ISO9000 certified management system) as well as excellent technical and audio properties at an
extremely affordable price. All of this will enable you to fully unfold your creati ity without being hampered by
budget constraints.
We are often asked how we are able to produce such high-grade de ices at such unbelie ably low prices. The
answer is quite simple: its you, our customers! Many satisfied customers mean large sales olumes enabling
us to get better conditions of purchase for components, etc. Isnt it only fair to pass this benefit back to you?
Because we know that your success is our success too!
I would like to thank all people whose help on Project DENOISER has made it all possible. E erybody has
made ery personal contributions, starting from the designers of the unit ia the many staff members in our
company to you, the user of BEHRINGER products.
My friends, its been worth the trouble!
Thank you ery much,
Uli Behringer

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DENOISER SNR2000
SNR2000
DENOISER®
Professional and all-purpose single-ended noise reduction system
sTAC (Transient Attack Control) dynamic filters respond accurately to signals with fast attacks
sAuto-filter circuitry for automatic sliding filters
sIRC (Interacti e Ratio Control) downward expander for inaudible noise reduction during signal pauses
sAccurate gain reduction and cut-off frequency meters
sDual mono or true stereo couple function
sSer o-balanced inputs and outputs on XLR and 1/4" TRS connectors
sRelay-controlled hard bypass with auto-bypass function during power failure (failsafe relay)
sCut-in delay to a oid switch-on thumps
sUltra low-noise audio operational amplifiers offer outstanding sound performance
sHigh-quality detented potentiometers and Illuminated switches
sHigh-performance output transformer BEHRINGER OT-1 retrofitable
sManufactured under ISO9000 certified management system

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DENOISER SNR2000
TABLE OF CONTENTS
1. INTRODUCTION..................................................................................................................... 6
1.1 The design concept ......................................................................................................................... 6
1.2 Before you begin ............................................................................................................................. 7
1.3 Control elements ............................................................................................................................. 7
1.3.1 Front panel ........................................................................................................................... 8
1.3.2 Rear panel ............................................................................................................................ 8
2. OPERATION ............................................................................................................................ 9
2.1 Operation of the filter section........................................................................................................... 9
2.1.1 The masking effect ................................................................................................................ 9
2.1.2 The dynamic low-pass filter ................................................................................................... 9
2.2 The TAC filter of the DENOISER .................................................................................................... 10
2.2.1 SENSITIVITY control ............................................................................................................ 11
2.2.2 CUT OFF control .................................................................................................................. 11
2.2.3 RELEASE control ................................................................................................................ 11
2.2.4 AUTO switch....................................................................................................................... 12
2.2.5 FREQUENCY meter ........................................................................................................... 12
2.3 Operation of the expander section ................................................................................................. 12
2.4 The IRC expander of the DENOISER ............................................................................................. 13
2.4.1 THRESHOLD control .......................................................................................................... 14
2.4.2 RELEASE control ............................................................................................................... 14
2.4.3 RATIO control ..................................................................................................................... 14
2.4.4 GAIN REDUCTION meter .................................................................................................... 14
2.5 The COUPLE function ................................................................................................................... 15
3. APPLICATIONS ..................................................................................................................... 15
3.1 Initial settings of the DENOISER ................................................................................................... 15
3.2 Studio applications ........................................................................................................................ 16
3.2.1 Noise reduction during playback ......................................................................................... 16
3.2.2 Noise reduction during recording ......................................................................................... 16
3.2.3 Reducing noise on subgroups, monitor and effects buses ................................................... 17
3.2.4 Noise reduction for effects de ices ...................................................................................... 18
3.2.5 Noise reduction during tape duplication ............................................................................... 18
3.2.6 Noise reduction for instruments ........................................................................................... 18
3.2.7 Reducing noise in P.A. systems ......................................................................................... 19
3.2.8 Noise reduction in Hi-Fi and ideo applications .................................................................... 19
4. TECHNICAL BACKGROUND .............................................................................................. 20
4.1 What are audio dynamics? ........................................................................................................... 20
4.2 Compressors/limiters .................................................................................................................... 21
4.3 Expanders/noise gates ................................................................................................................. 21
4.4 Downward expansion .................................................................................................................... 22
4.5 Noise as physical phenomenon..................................................................................................... 22
4.6 Companders ................................................................................................................................. 22
4.7 The single-ended principle ........................................................................................................... 23
5. INSTALLATION ..................................................................................................................... 23
5.1 Rack mounting .............................................................................................................................. 23
5.2 Audio connections ........................................................................................................................ 23
6. SPECIFICATIONS ................................................................................................................. 24
7. WARRANTY ........................................................................................................................... 26

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DENOISER SNR2000
1. INTRODUCTION
Thank you ery much for expressing your confidence in BEHRINGER products by purchasing the BEHRINGER
DENOISER SNR2000.
Electrical noise is still one of the most unpleasant problems in the field of electro-acoustics. The basic noise
produced by a single unit is not considered to be annoying. The combination of se eral instruments, effects
de ices and tape machines, howe er, results in a drastic increase in noise le el. This requires the use of a
noise reduction system.
Conventional noise reduction systems
Con entional noise reduction systems often suffer from se eral percei able drawbacks: either the noise
reduction process deteriorates the signal by cutting the high-frequency portions, or the dynamic filter reacts
too slowly, which makes percussi e signals lose its bite. Last but not least, there are systems which
function as simple noise gates and produce unnatural on/off effects.
The interactive technology of the DENOISER
With the DENOISER we offer one of the most efficient noise reduction systems using single-ended technology.
BEHRINGERs unique filter circuitry in conjunction with the new built-in BEHRINGER audio detectors
represents a technical breakthrough in the field of noise reduction systems. Effecti e noise reduction with
minimal signal interference is the result.
The noise reduction capabilities of the BEHRINGER DENOISER are based on bandwidth limiting by means
of a dynamic low-pass filter and broadband noise reduction during music pauses by a downward expander.
The need for both a professional and all-purpose noise reduction system was the basis for the de elopment of
the BEHRINGER DENOISER. Many years of experience in the field of noise reduction technology enabled us
to design a system particularly suited to the highest demands.
The TAC (Transient Attack Control) circuitry, a new BEHRINGER de elopment, opens the filter e en when
processing percussi e material, without e.g. cutting a drums kick.
A newly de eloped IRC (Interacti e Ratio Control) expander has been integrated into the DENOISER. The
ratio of which is automatically adjusted, dependent on the program material. The result is an expander which
can be adjusted without deteriorating your audio. Furthermore, the expander is more tolerant of those signals
which appear slightly abo e the background noise.
DENOISERthe professional noise reduction system
The BEHRINGER DENOISER pro es to be an excellent tool for the professional sound engineer. Furthermore,
the extensi e control features pro ide specific and successful processing of all sortes of program material.
The unit can be used in broadcasting and TV, professional studios, CD mastering studios and for P.A. and
intercom systems etc. It is useful for cleaning up studio tracks, tape duplications, motion picture sound
tracks, during mixdown, and more.
Be it noise reduction for instruments (guitars, keyboards, etc.) or for effects de ices (flangers, distortion units,
phasers, chorus units, digital delays, compressors, equalizers, pedal board de ices, analog delays, psycho-
acoustic effects units, pitch shifters, etc.) the BEHRINGER DENOISER is the no-compromise answer when
the situation demands a no-compromise solution.
+This manual first describes the terminology used, so that you can fully understand the SNR2000
and its functions. Please read the manual carefully and keep it for future reference.
1.1 The design concept
The philosophy behind BEHRINGER products guarantees a no-compromise circuit design and employs the
best choice of components. The operational amplifiers which are used in the DENOISER are exceptional. They
boast extreme linearity and ery low distortion characteristics. To complement this design the choice of
components includes high tolerance resistors and capacitors, detented potentiometers and se eral other
stringently selected elements.
1. INTRODUCTION

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DENOISER SNR2000
1.2 Before you begin
Your DENOISER was carefully packed in the factory and the packaging is designed to protect the unit from
rough handling. Ne ertheless, we recommend that you carefully examine the packaging and its contents for
any signs of physical damage, which may ha e occurred during transit.
+If the unit is damaged, please do not return it to BEHRINGER, but notify your dealer and the
shipping company immediately, other ise claims for damage or replacement may not be granted.
Shipping claims must be made by the consignee.
The BEHRINGER DENOISER fits into one standard 19" rack unit (1 3/4"). Please allow at least an additional
4" depth for the connectors on the back panel.
Be sure that there is enough space around the unit for cooling and please do not place the DENOISER on high
temperature de ices such as power amplifiers etc. to a oid o erheating.
+Before you connect your DENOISER to the mains, please make sure that your local voltage
matches the voltage required by the unit:
The fuse holder on the female mains connector has 3 triangular markings, with two of these triangles
opposing each other. The DENOISER is set to the operating oltage printed next to these markers and can be
set to another oltage by turning the fuse holder by 180°. CAUTION: This instruction does not apply to
export models exclusively designed, e.g. for 115-V operation!
The mains connection of the DENOISER is made by using the enclosed mains cable and a standard IEC
receptacle. It meets all of the international safety certification requirements.
+Please make sure that all units have a proper ground connection. For your o n safety, never
remove or disable the ground conductor of the unit or of the AC po er cable.
As standard, the BEHRINGER DENOISER features electronically ser o-balanced inputs and outputs.
The circuit design features automatic hum rejection for balanced signals, permitting trouble-free operation
e en at highest operating le els. Externally induced power-line hum, etc. is thus suppressed effecti ely. The
automatic ser o function recognizes the presence of unbalanced connectors and adjusts the nominal le el
internally to a oid le el differences between the input and output signals (6dB correction).
You will find additional information in chapter 5 INSTALLATION.
1.3 Control elements
Fig. 1.1: Front panel of the DENOISER
The BEHRINGER DENOISER features two identical channels. Each channel is equipped with four push button
switches, six rotary controls and 16 LEDs. The COUPLE switch is for stereo tracking.
1. INTRODUCTION

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DENOISER SNR2000
1.3.1 Front panel
Fig. 1.2: Front panel control elements
1
The IN/OUT switch acti ates the relay and, consequently, the corresponding channel. The unit is
bypassed when the switch is not depressed.
2
By depressing the OUPLE switch you will tie channel 1 and 2 together for stereo tracking.
+If using the COUPLE s itch, it is recommended that all controls be set identically on both
channels to ensure proper tracking.
3
The EXPANDER IN/OUT switch acti ates the expander section.
4
Use the THRESHOLD control to set the threshold at which low le el downward expansion starts. Once
the signal falls below this threshold, the amount of expansion increases as the signal le el decreases.
5
The RELEASE control allows to adjust the desired release time of the expander section.
6
Use the RATIO control to adjust the ratio of the downward expansion. Low ratios, from 1.2:1 to about
3:1 produce a more or less slight downward expansion. When, howe er, the ratio is set to 6:1, the
DENOISER functions as noise gate.
7
This eight-segment GAIN REDU TION meter indicates the amount of expansion.
8
The FILTER IN/OUT switch acti ates the filter section.
9
The SENSITIVITY control allows you to set the operating le el of the dynamic filter relati e to the le el
of the input signal.
10
The RELEASE control allows to adjust the desired release time of the filter.
11
The UT OFF control allows to adjust the filter -3 dB point. Thus, the filter can be adapted perfectly to
arious noise conditions.
12
By depressing the AUTO switch, the RELEASE and CUT OFF controls are deacti ated. Thus, release
time and corner frequency of the filter are automatically deri ed from the input signal.
13
This eight-segment FREQUEN Y meter indicates the bandwidth of the filter.
1.3.2 Rear panel
Fig. 1.3: Rear panel connectors
14
SERIAL NUMBER. Please take the time to complete and return the warranty card within 14 days of the
date of purchase, otherwise you will lose the right to the extended warranty. Or just use our online-
registration (www.behringer.com).
1. INTRODUCTION

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DENOISER SNR2000
15
FUSE HOLDER / VOLTAGE SELE TOR. Please make sure that your local oltage matches the oltage
indicated on the unit, before you attempt to connect and operate the DENOISER. Blown fuses may only
be replaced by fuses of the same type and rating. Some models allow for inserting the fuse holder in two
different positions, in order to switch o er from 230 V to 115 V operation, and ice ersa. Please note that
for 115 V operation outside Europe, you need to use a fuse of a higher rating (see chapter 6
SPECIFICATIONS).
16
Use the enclosed power cord to connect the unit to the mains.
17
These are the balanced 1/4" TRS and XLR AUDIO INPUTS of your DENOISER.
18
These are the balanced AUDIO OUTPUTS of the DENOISER, a ailable as 1/4" TRS and XLR connectors.
2. OPERATION
The need for an all-purpose and professional noise reduction system was the basis of the de elopment of our
DENOISER.
The system design has to meet the following criteria:
1. All-purpose application: the noise reduction design is aimed to operate with both all types of instruments
as well as with all composite signal sources.
2. Most effecti e noise reduction while influencing the signal to the least possible extent. The signals original
sound as well as its attack response remains unaffected.
3. No side effects such as pumping, noise tails, etc. known from con entional circuitries.
4. Simple operation through comprehensi e automation of control processes.
To obtain maximum performance, it is necessary to understand what is achie ed by each of the separate
filter and expander sections and how they perform together. Once you understand how these circuits
work, it will be easier to set up the controls correctly to suit any application.
The noise reduction effect of the expander section is acti e only when signal le els are low. The filter section,
on the other hand, is acti e at all times o er the complete dynamic range. Since the filter section is always
acti e, let us look at what is happening in that circuit first:
2.1 Operation of the filter section
2.1.1 The masking effect
The function of the BEHRINGER DENOISER is based on the masking effect: noise will be masked and
thus becomes inaudible, as soon as considerably louder sound signals are added.
One of the basic components of BEHRINGER circuitry is a dynamically controlled low-pass filter which allows
low frequencies to pass but filters the high-frequency information, depending on the music material. In
contrast to con entional noise filters with fixed cut off frequencies, the DENOISER shifts the cut off frequency
between 800Hz and 20kHz, depending on the program material. This is the range where noise is considered
most annoying. The cut off frequency of the filter depends on both the input le el and the frequency range of
the audio signal.
2.1.2 The dynamic lo -pass filter
The filter section features a dynamic low-pass filter which operates as follows: With no audio signal present,
the dynamic filter will close down to a user selectable cut off point. This cut off point is adjustable between
800 Hz and 6 kHz. If the cut off was set for 1kHz, the bandwidth of the filter would be from 20 Hz to 1 kHz. If
an input signal had a bandwidth from 20 Hz to 2 kHz, the filter would open far enough to pass up to the 2 kHz
frequency and its harmonics, while reducing any noise present from approximately 2 kHz to 20 kHz. If a broad-
band signal with frequency components up to 20 kHz appears at the input, the dynamic filter would open all the
way to 20 kHz.
2. OPERATION

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DENOISER SNR2000
Fig. 2.1: Operation of the dynamic filter
With a low-frequency input signal present, the dynamic filter will reduce any mid or high-band noise as well as
any disturbing noise tails. If the input signal is dominated by high-frequency components, howe er, the
dynamic filter will open to its full extent to let the signal pass, maintaining high-frequency information.
2.2 The TAC filter of the DE OISER
Our main goal was to create a filter which cuts off high frequencies during pauses but lets the signal pass
without modification as soon as a usable signal is present. Howe er, its realization poses many problems.
Apart from intelligent program recognition, the filter has to meet the following criteria:
1. The control times of the dynamic filter must be fast enough so that high frequencies will not be cut off. Thus,
the sound of signals with a high slope, such as percussi e instruments, will not be modified.
2. Howe er, if the control times are too fast, flutter may occur, i.e. intermodulation distortion could be produced.
The new BEHRINGER TAC (Transient Attack Control) filter circuit gurantees extremely fast control times
without producing audible intermodulation distortion. In contrast to con entional units based on so-called RMS
rectifiers, the TAC circuitry uses a peak detector. While the RMS rectifier calculates the a erage or mean
alue of the signal, i.e., requires a so-called integration time, the peak detector exactly traces the input
signal response. Thus, the TAC circuit is capable of reacting much faster to abrupt le el changes produced by
percussi e signals. The delay which the integration time causes in RMS rectifiers is eliminated in a peak
detector, i.e, the kick of the instrument remains almost unaltered.
2. OPERATION

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DENOISER SNR2000
Fig. 2.2: omparing the BEHRINGER TA filter circuitry and the conventional RMS characteristic curve
2.2.1 SENSITIVITY control
This control determines the sensiti ity of the filter. If the input le el exceeds the alue adjusted with the
SENSITIVITY control, the dynamic filter begins to open. If the adjusted alue is, for example, -30 dBu, high-
frequency signals with a le el abo e -30 dBu cause the filter to open.
+The SENSITIVITY setting depends on the type of noise and the application on hand. If the
control is set to a value hich is above the noise floor level of the input signal, there is the risk
of muting the signals high-frequency portions. It is therefore necessary to set the SENSITIVITY
control very carefully.
2.2.2 CUT OFF control
The CUT OFF control sets the lower cut off frequency of the dynamic filter. Under most conditions, this
control should be set at 800 Hz, allowing for the maximum possible amount of noise reduction. The cut off
frequency should be increased if you want to affect noise in the upper portion of a signal only or if too
drastic noise reduction leads to unwanted side effects.
For example, if you wish to only eliminate noise in the upper frequency range, say from 2 to 20 kHz, set
the CUT OFF control at 2 kHz. Frequencies below 2 kHz will not be affected.
2.2.3 RELEASE control
We recommend fast release settings on indi idual instruments or ocals. This is because there is no real
ambience to the signal. Release times about 0.06 to 0.2 seconds would be perfect.
Howe er, with mastered signals or composite music, slower release times should be used. Release times
slightly greater than 0.2 seconds are generally ideal. A oid using ery long release rates in this application to
reduce the risk of audible noise tail effects.
Using longer release rates (around one second) allows the DENOISER to denoise effects returns. Audible
and unnatural cutting-off of the re erb will thus be a oided.
2. OPERATION

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DENOISER SNR2000
2.2.4 AUTO s itch
The AUTO switch allows to automatically control release time and cut off frequency of the TAC filter. Thus, by
depressing the AUTO switch, the RELEASE and CUT OFF controls are deacti ated. Release time and cut off
frequency of the filter are now automatically deri ed from the input signal.
Generally, good results will be achie ed with the AUTO function. Howe er, with complex sound sources
e.g. classical music featuring a great amount of disturbing noise fine tuning should be done with the
RELEASE and CUT OFF controls.
2.2.5 FREQUENCY meter
A precise 8-digit LED meter indicates the current operating point of the filter. The LEDs keep you informed
regarding lower cut off frequency, release time and frequency range of the audio signal. If no LED lights up, the
cut off frequency is set to 800 Hz. If, on the other hand, all LEDs light up, the bandwidth is abo e 20 kHz
and the filter has no influence on the usable signal.
It pro es quite useful to set the SENSITIVITY control in that way that the noise floor causes the first LEDs
to light up.
+Please note that this meter is merely supposed to help you adjust the controls. It is re-
commended to perform A/B comparisons ith the FILTER IN/OUT s itch to find out hich
setting suits your demands!
+Please also note that after po er-up the unit needs a fe minutes to arm up. While the unit
calibrates automatically, the LEDs might indicate values that deviate from the values stated
by the controls and scales on the front panel!
2.3 Operation of the expander section
The noise reduction system of the DENOISER is based on two signal processing techniques, which can be
used separately but may also be combined with each other: in addition to the dynamically controlled low-pass
filter mentioned abo e, the DENOISER features a so-called downward expander which uses a second noise
reduction process to eliminate remaining interference noise.
A downward expander automatically reduces the o erall le el for all signals below an adjustable threshold and
therefore extends the dynamic range of the program material.
Changing the ariable release time and the expansion ratio enables the expander to operate as a noise gate.
Expanders generally function with a flat ratio cur e, so that the signal continually fades. Noise gates howe er,
can be seen as a special type of expander. They normally work with a more exaggerated ratio and radically
attenuate the signal if it falls below the threshold.
+The follo ing explanations also apply to the gate function, because the gate is a special form of
the expander.
2. OPERATION

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DENOISER SNR2000
Fig. 2.3: The function of an expander
2.4 The IRC expander of the DE OISER
The response characteristics of con entional expanders tend to cut the signal abruptly and the result is
generally unacceptable, since the effect is clearly audible. Inaudible expansion, howe er, requires a gentle
Soft Knee characteristic due to a continuous transition of the straight lines at the threshold.
A newly de eloped IRC (Interacti e Ratio Control) expander has been integrated into the DENOISER. The ratio
cur e characteristic automatically adapts itself, dependent on the program material.
With low ratios and a slight expansion, the transition is gentle, whereas higher ratios and increasing
expansion will result in harder transitions within the cur e.
The IRC expander is therefore equipped with a soft, interacti e non-linear ratio cur e which is best suited to
the human hearing. Critical signals around the threshold le el are processed with low expansion ratio
settings, whereas low signals will be subjected to an increasingly higher ratio which will result in greater
attenuation.
Fig. 2.4: IR curve characteristic of the expander
The result is an expander which can be adjusted without the risk of alienating the o erall sound. Furthermore,
the expander is more tolerant towards those usable signals which appear slightly abo e the noise floor.
2. OPERATION

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DENOISER SNR2000
2.4.1 THRESHOLD control
The THRESHOLD control of the expander defines the operating le el. It stretches across a ery wide range and
therefore applies to all working le els. Input le els abo e the adjusted threshold point do not experience any
change. Howe er, if the le el falls below the threshold the dynamic process is acti e.
For example, if the THRESHOLD control was set at 0 dBu and the input signal drops below 0 dBu, downward
expansion will begin. In typical applications the setting of the threshold control should be between 5 and 20dB
abo e the quiescent noise floor of the input signal. For example, if the quiescent noise floor was
-40dBu, a setting between -35 to -20 dBu will produce the desired expansion.
+With the RATIO control set to maximum and the THRESHOLD control set at +10 dBu, an input
signal level ould have to exceed approximately +5 dBu to produce an output signal.
2.4.2 RELEASE control
The RELEASE control determines the time the downward expander requires to decrease the le el of the
output signal. The RELEASE control is ariable from 0.2 to 4 seconds and refers to a 20 dB gain change. The
ultimate setting of the RELEASE control depends on your demands: When the expander sections are
supposed to function as gates, settings between 0.2 and 0.5 seconds are recommended.
For indi idual instruments or ocals use a setting between 0.2 and 0.5 seconds. For composite music a
setting between 0.6 and 2 seconds is recommended. If you want to use the expander section to reduce subtle
background noise from effects de ices, a ery slow release time (2 to 6 seconds) would be perfect.
2.4.3 RATIO control
The ratio between input and output le el for all signals that fall below the threshold is called expansion
ratio. It is adjustable ia the RATIO control. This control adjusts an important parameter: It determines whether
the section functions as expander or gate.
A ratio of 1:1 indicates that the output signal will correspond to the input signal, i.e. the le el does not change.
A ratio of 1:2 indicates that for e ery 1 dB decrease in input le el below the threshold, there will be resultant
corresponding decrease in the output le el of 2 dB. A ratio of 1:6 indicates, that for a 1 dB decrease in input
le el below the threshold, there will be a corresponding decrease in the output le el of 6 dB etc.
Low ratios from 1:1 to about 1:3 produce precisely controlled downward expansion. At more pronounced
settings up to 1:6 the DENOISER functions as gate.
The scale of the ratio is calibrated in dB on the front panel. It indicates the decrease in output le el, resulting
from a 1 dB decrease in input le el.
The DENOISER works as an IRC expander. The interacti e control function defines the soft onset of the
expander, according to the characteristics of human hearing during the fade out process. This allows for a
natural and thus inaudible elimination of interference noise. This means that, as the input le el drops slightly
below the threshold point, the expander ratio will start at 1.1:1 and increase to an ultimate ratio selected with
the RATIO control. The correct setting of the ratio control depends on your demands: In order to achie e a
flat expansion cur e, we recommend settings of 1:1 to 1:3. This pro ides soft and limited expansion for
difficult and noisy audio applications. Higher settings up to 1:6 are recommended for gating applications
which allow for noise reduction of more than 70 dB.
2.4.4 GAIN REDUCTION meter
The eight GAIN REDUCTION LEDs on the front panel of the BEHRINGER DENOISER function as follows:
If the input le el falls below the threshold, the expander starts working with the current le el reduction factor
being indicated by the GAIN REDUCTION LEDs.
Let us consider, for example, a specific signal that falls by 2 dB below the threshold: with a ratio setting of
1:6, the output signal is attenuated by 12 dB; in comparison to the input signal the output signal has been
reduced by 12 dB, which is indicated by the 10 dB LED.
Although the VCA of the BEHRINGER DENOISER pro ides a control range of 80 dB, it is not ery useful to
display the entire range, since such drastic control processes are performed ery rarely in practice. The
displayed range of the GAIN REDUCTION indicators is 40 dB.
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2.5 The COUPLE function
The couple switch links channel 1 and channel 2. This includes each channels expander detection and filter
detection circuits. Although this allows the two channels to track each other for stereo applications, it should
be pointed out that this is not a master/sla e setup, but rather a link and for true stereo tracking it is
necessary to set both channels controls identically.
In master/sla e operation one channel exclusi ely go erns both channels, whereby in couple mode both
channels are combined resulting in a common control oltage.
+When using the COUPLE s itch, a high-level, high-frequency signal present in one channel
ill cause the expander and filter of both channels to open at the same point. Accordingly,
both channels expanders and filters are supposed to close at the same point. Therefore, it is
recommended that both channels are set identically. (The most critical controls are the
expander THRESHOLD and the filter SENSITIVITY controls.) If the t o channels are not set
identically, a predominant setting in one channel ill affect the other channel.
The only two controls that operate separately when the COUPLE switch is on are the expander RELEASE
and the expander RATIO controls. It is recommended to set these controls identically on both channels.
Howe er, if one channel re eals more noise than the other, the expander RELEASE/RATIO controls of the
respecti e channel can be used to let the expander close quicker for effecti e noise reduction while still
tracking in stereo.
+If using the COUPLE s itch, it is recommended that all controls are set identically to ensure
proper tracking.
3. APPLICATIONS
In this section se eral typical applications of the DENOISER are discussed. The following basic settings can
sol e most dynamic problems. They are the ideal starting point.
Please take the time to study the application examples carefully, in order to be able to make full use of the
DENOISER's capabilities in future.
The main applications of the DENOISER can be di ided into three categories:
1. The DENOISER is used to eliminate interferences from acoustic instruments such as guitars etc. as
well as keyboards, samplers or other line le el instrument signals.
2. The DENOISER is used to eliminate interferences in effects de ices, tape machines, mixers or other
studio equipment.
3. The DENOISER can be used for remo ing noise from records and any tape recordings.
3.1 Initial settings of the DE OISER
The subsequent settings of the front panel controls will be based on the respecti e input le el and noise floor.
Due to the fact that it would be impossible to demonstrate e ery application you can think of, we recommend
to carefully read this manual and the function of its controls, as the unit has a certain complexity due to the
extensi e setting ariations. Once familiar with the functions of the indi idual controls, you will be able to
purposefully and creati ely operate the unit.
The following chart shows a typical setup and can be used as a guide for a ariety of applications:
Example:
Type of music composite (e.g. mixdown)
Reference level -10 dBu
Noise floor -60 dBu
Tab. 3.1: Example for a standard application
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We recommend the following control settings:
Controls Settings
IN/OUT switch IN
EXPANDER switch IN
THRESHOLD control -50 dBu
RELEASE control 2 second
s
RATIO control 3:1
FILTER switch IN
SENSITIVITY switch -30 dBu
AUTO switch IN
Tab. 3.2: Initial settings of the DENOISER
3.2 Studio applications
3.2.1 Noise reduction during playback
For this standard application, the DENOISER is inserted after the master or multitrack machine, i.e. between
tape machine and mixer (or amplifier). A cassette recorder or similar machine may also be the signal source.
Fig. 3.1: Noise reduction during playback
1. Set up your equipment as usual, while bypassing your DENOISER.
2. Turn on the BEHRINGER DENOISER and adjust the controls as desired (if necessary, read chapter 1.3
Control elements once again).
3. Check your settings by making A/B comparisons using each channels IN/OUT switch.
3.2.2 Noise reduction during recording
The noise reduction effect may be increased by using the DENOISER not only during playback but also when
recording. For this purpose, insert the unit directly after the master output of the mixer into the recording path
of the master or multitrack machine. Set up the unit as described in the pre ious section Noise reduction
during playback.
In particularly difficult cases, we recommend using the DENOISER both during recording and playback.
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Fig. 3.2: Noise reduction during recording
If the mixer features a line le el insert (either pre or post equalizer), the DENOISER should be inserted here.
Fig. 3.3: Noise reduction using the line insert
3.2.3 Reducing noise on subgroups, monitor and effects buses
For this application there are se eral options:
1. If your mixer features subgroup inserts, you can reduce noise in subgroups separately.
2. You can also connect monitor or effects buses (aux sends) to the BEHRINGER DENOISER and route the
signal back to a channel input. For this purpose, the respecti e signals ha e to be taken pre fader, while
the respecti e channels must be muted. We recommend to use the DENOISER as the last component in
the chain of effects de ices. The o erall signal will then be processed by the DENOISER and sent
back to the mixers master section ia the effect returns.
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Fig. 3.4: Noise reduction in the effects bus
3.2.4 Noise reduction for effects devices
Effects de ices such as flangers, phasers, distortion or chorus units, delay and re erb de ices,
compressors, equalizers, exciters, etc. can considerably increase the o erall noise le el. The DENOISER
will also be useful here. Simply insert the unit after the effects de ice that causes noise problems. If there are
se eral de ices, insert the DENOISER as the last unit in the signal chain.
3.2.5 Noise reduction during tape duplication
The noise produced by magnetic tapes can be significantly reduced with the DENOISER. Tape/cassette
copies will pro ide low noise and higher dynamics.
Particularly old and noisy tapes can be new lease of li e with the DENOISER. If adjusted properly, it will
produce copies that sound better than the original.
Simply insert the BEHRINGER DENOISER between the line outputs of the master machine and the inputs of
the recorder.
Machines with tape return monitor function allow you to check the quality of the copy while duplicating the
tape.
Fig. 3.5: Reducing noise during tape duplication
3.2.6 Noise reduction for instruments
Digital instruments (synthesizers, samplers, etc.) often produce quantization noise, which can be ery
annoying. The DENOISER can be inserted directly after the instrument and will remo e typical noise tails
etc.
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Fig. 3.6: Noise reduction on keyboards
+Please note that lo level signal sources such as guitars must be pre-amplified beforehand, as
the BEHRINGER DENOISER only processes line level signals (-10 dBV to +10 dBu).
3.2.7 Reducing noise in P.A. systems
The noise produced by P.A. systems is particularly annoying. Hum induced in the microphone cables
combined with high gain settings results in a drastic increase of noise.
The DENOISER can sol e these problems, too. Insert the unit into the indi idual microphone channels (line
inserts) or into the master, monitor or effects buses.
Fig. 3.7: Reducing noise in a P.A. system
3.2.8 Noise reduction in Hi-Fi and video applications
The DENOISER can also be used in Hi-Fi and ideo applications. The unit is simply placed between the
signal source (cassette player, tuner, VCR, etc.) and the power amp. We recommend using the so-called
tape monitor connections that most preamplifiers offer. Thus, the DENOISER can be inserted into any
signal source.
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Fig. 3.8: Noise reduction in Hi-Fi systems
The BEHRINGER DENOISER can be used for:
sdisc and tape recordings
sideo and audio cassette playback purposes
sTV reception
sradio reception
4. TECHNICAL BACKGROUND
4.1 What are audio dynamics?
A remarkable feature of the human ear is that it can detect the widest range of amplitude changesfrom
the slightest whisper to the deafening roar of a jet-plane. If one tried to record or reproduce this wide
sound spectrum with the help of amplifiers, cassette recorders, records or e en digital recorders (CD, DAT,
etc.), one would immediately be restricted by the physical limitations of electronic and acoustic sound
reproduction technology.
Fig. 4.1: The dynamic range of various devices
4. TECHNICAL BACKGROUND