Symetrix 565E User manual

565E Dual Compressor/Limiter/Expander
User’s Guide
565E

i
Table of Contents
Chapter 1 Introduction 1
Chapter 2 Operator Safety Summary 2
Chapter 3 Fast Setup 3
Chapter 4 Tutorial 4
Chapter 5 Front Panel Overview 8
Chapter 6 Rear Panel Overview 10
Chapter 7 Connecting to Other Gear 11
Chapter 8 Applications 16
Chapter 9 Troubleshooting 19
Chapter 10 Specifications 20
Chapter 11 Warranty and Service 21
Chapter 12 Declaration of Conformity 23
Rev B, 19 August, 1998
Symetrix part number 53565E0B00
Subject to change at our whim and fancy without
notice.
©1998, Symetrix, Inc. All right reserved.
Symetrix is a registered trademark of Symetrix, Inc.
Mention of third-party products is for informational
purposes only and constitutes neither an endorsement
nor a recommendation. Symetrix assumes no
responsibility with regard to the performance or use
of these products.
Under copyright laws, no part of this manual may be
reproduced or transmitted in any form or by any
means, electronic or mechanical, including photo-
copying, scanning, recording or by any information
storage and retrieval system, without permission, in
writing, from Symetrix, Inc.
14926 35th Ave. West
Lynnwood, WA 98037 USA
Tel [phone]
Fax [phone]
Email: [email protected]
565E

565E
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IntroductionChapter 1
Front panel
Rear panel
CH2 OUTPUT
-10 0dBu CLIP
-3 -20
-12 -9 -6
CH2 COMPRESSOR
-6 -4 -2-12-15 -10 -8-2-6-18 -12
CH2 EXPANDER
-25
CH2 LIMITER
0
IN
+10-10
+13
BYPASS
+20
-20
GAIN (dB)
4 +5
-362.5
-10
-12
-25-250 +5
-12
10SLOW 1FAST
RELEASE RATIO (X:1)
-40 +20
SLOW
RELEASE
BYPASS
+10
THRESHOLD (dBu)
FAST
THRESHOLD (dBu) THRESHOLD (dBu)
BYPASS
CH1 OUTPUT
-10 0dBu CLIP
CH1 LIMITER
-12 -6-9 -3 -20-4-6 -2-15 -10-12 -8-25
CH1 COMPRESSOR
CH1 EXPANDER
-18 -2-12 -6
IN
+5 0
+10-10
-3 +13
BYPASS
4-10
62.5+5
+20
-20-12 BYPASS
THRESHOLD (dBu) GAIN (dB)
10
1
RATIO (X:1)
FAST-40 +20 SLOW
RELEASE
-12
-250
565
DUAL
EXPANDER
COMPRESSOR/
LIMITER/
E
SLOW
BYPASS FAST
RELEASE
+10
THRESHOLD (dBu) THRESHOLD (dBu)
-25
STEREO LINK
STEREO
DUAL MONO
CHANNEL 1 INPUTSIDECHAIN
INPUT
KEY
CHANNEL 1 OUTPUT
BALANCED/
UNBALANCED
BALANCEDBALANCED
OUTPUTS
BALANCED
TYPICAL CONNECTIONS
3
1
SIDECHAIN
31
GROUND=PIN 1
HIGH(+)=PIN 2
LOW(-)=PIN 3
22
INPUTS
BALANCED
CHANNEL 2 INPUT
1/4"BALANCED
SIDECHAIN OUT
KEY INPUT
GROUND
BALANCED
SLEEVE=GROUND
RING=LOW(-)
TIP=HIGH(+)
SIDECHAIN
INPUT
KEY
E
DUAL COMPRESSOR/
LIMITER/EXPANDER
BALANCED/
UNBALANCED
CHANNEL 2 OUTPUT
BALANCED
UNBALANCED
BALANCED/
AC INPUT
MAXIMUM
15 WATTS
FABRIQUÉ AUX E.-U. PAR SYMETRIX INC., LYNNWOOD, WA USA.
RÉFÉREZ TOUTE RÉPARATION À UN TECHNICIEN QUALIFIÉ.
MANUFACTURED IN LYNNWOOD, WASHINGTON USA
565
UNBALANCED
BALANCED/
Congratulations on your purchase of the
Symetrix565E:aone-boxanswertoyour
dynamics processing needs. The 565E Dual
Compressor/Limiter/Expanderofferstwo
channels of simultaneous, in-line controls for
compression,limitinganddownwardexpan-
sion. In addition, the 565E employs a new
circuitrydesign,DynamicsSquared™,for
dramatically reduced distortion during gain
reduction.
Compression,limiting,anddownwardexpan-
sion clear up different but related audio
problems. Whether you work with vocal tracks,
stage monitors, radio signals, paging systems
or playback systems, it's likely that your audio
needs more than one of these solutions.
The compressor and expander sections of the
565Efeaturenewly-developedcircuitry,
DynamicsSquared™.Thisproprietarydesign
addresses a key problem: most analog com-
pressors use conventional voltage-controlled
amplifier topography, which creates added
distortion when compressing mid-band
frequencies.DynamicsSquared™resolves
this problem by using circuitry that controls
gain while reducing distortion. As a result, the
565E allows you to apply high levels of
compression and expansion with much less
distortion.
If background noise, tape hiss, or pickup hum
isaproblem, eliminate itwiththe downward
expander. The 565E uses a true downward
expander, not a so-called “soft gate”. The
565E's downward expander won’t chop off the
transients and decays like a gate would, yet it
can work just as effectively for reducing those
noises between sounds.
While the downward expander quiets un-
wanted noise, the 565E’s compressor section
allows you to apply the right amount of
compression without pumping or breathing.
The separate limiter section guards against
peaks that lead to overload problems, freeing
the compressor section for settings specific to
compression and not protection. (Trying to set
a typical compressor for both compression and
peak protection usually results in less-than-
idealsettings.)The 565E'slimiterprotects
against sharp peak signals while the compres-
sor smooths out the audio program for a silky,
pleasing finish.
The 565E's sidechain allows users to alter all
three processing sections for special applica-
tions. Inserting an equalizer at the sidechain
can make the action of the 565E's compressor/
limiter/expanderfrequency-dependent.Empha-
size or de-emphasize a particular signal range to
make the 565E respond more or less to certain
frequencies.
Regardless of what your audio challenges may
be, the 565E offers a powerful variety of
solutions. In-line compression, limiting, and
expansion produce clean, clear audio in any
situation. Innovative circuitry permits users to
choose optimal settings without paying the
price of extra distortion.
We recommend that you read this manual
cover-to-cover. You will find the answers to
most of your questions inside. However, if you
are in a hurry, go directly to Chapter 3 (Fast
Setup). It will get you started quickly. Should
you have any comments or questions, please
do not hesitate to contact us at the numbers/
addresses below. Your calls are always
welcome.
Phone: [phone]
Fax: [phone]
Email: [email protected]
Website:www.symetrixaudio.com

565E
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The information in this summary is intended
for persons who operate the equipment as well
as repair personnel. Specific warnings and
cautions are found throughout this manual
wherever they may apply.
The notational conventions used in this
manual and on the equipment itself are
described in the following paragraphs.
The lightning flash with arrowhead symbol
within an equilateral triangle is intended to
alert the user of the presence of uninsulated
"dangerous voltage" within the product's
enclosure that may be of sufficient magnitude
to constitute a risk of electric shock to per-
sons.
Theexclamation pointwithinanequilateral
triangle is intended to alert the user of the
presence of important operating and mainte-
nance (servicing) instructions in the literature
accompanyingthe565E(i.e.thismanual).
Caution To prevent electric shock, do not
use the polarized plug supplied
with the 565E with any extension
cord, receptacle, or other outlet
unless the blades can be fully
inserted.
Terms
Several notational conventions are used in this
manual. Some paragraphs may useNote,
Caution, or Warning as a heading. Certain
typefaces and capitalization are used to
identify certain words. These are:
Note Identifies information that needs
extra emphasis. A Note generally
supplies extra information to help
you to better use the 565E.
Equipment Markings
Operator Safety Summary Chapter 2
Caution Identifies information that, if not
heeded, may cause damage to the
565E or other equipment in your
system.
Warning Identifiesinformationthat,if
ignored,maybehazardousto
yourhealthorthatofothers.
CAPITALS Controls, switches or other
markings on the 565E's chassis.
Boldface Strong emphasis.
Power source - This product is intended to
operate from a power source that does not
apply more than 255Vrms between the power
supply conductors or between either power
supply conductor and ground. A protective
ground connection, by way of the grounding
conductor in the power cord, is essential for
safe operation.
Dangerfromloss ofground-Iftheprotective
ground connection is lost, all accessible
conductive parts, including knobs and controls
that may appear to be insulated, can render an
electricshock.
Properpowercord-Useonly thepowercord
specified for the product. Use only a power
cord that is in good condition.
Operatinglocation-Do not operate this
equipment under any of the following condi-
tions: explosive atmospheres, in wet locations,
ininclementweather, improperorunknown AC
mainsvoltage,or if improperlyfused.
Stayoutofthebox-Toavoidpersonalinjury or
injury to others, do not remove the product
covers or panels. Do not operate the product
without the covers and panels properly
installed.
AVIS:
NE PAS OUVRIR
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
SEE OWNERS MANUAL. VOIR CAHIER D’INSTRUCTIONS.
S’adresser a un reparateur compétent.
RISQUE DE CHOC ELECTRIQUE
N
o user serviceable parts inside. Refer servicing to qualified service personnel
.
CAUTION
WARNING:
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO RAIN OR MOISTURE
DO NOT OPEN
RISK OF ELECTRIC SHOCK

565E
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Fast First-Time Setup
Follow these instructions to get your 565E up-and-running as quickly as possible. The intent of this
section is fast setup. Refer to later chapters for explanation of the 565E’s controls and functions.
Connect the line-level signal source for Channel 1 to either the female XLR input jack (pin 2
hot) or the 1/4-in. TRS (tip-ring-sleeve, stereo, 3-conductor) input jack for Channel 1.
Connect the line-level signal return to either the male XLR output jack or to the 1/4-in. TRS
output jack for Channel 1. If you use the 1/4-in. jack, use a TRS plug for balanced
circuits or use a TS plug for unbalanced circuits. Additional information on the signal
connections may be found on pages 13-14 of this manual.
If necessary, repeat for Channel 2. Ignore the SIDECHAIN (KEY INPUT) connections for now.
Connect the AC input to an AC power source of the proper voltage and frequency, as
marked on the rear of the unit.
Caution:Failure to connect the 565E to the proper AC mains voltage may
cause fire and/or internal damage.
Warning: Lethalvoltagesarepresentinsidethechassis.Therearenouser
serviceablepartsinsidethechassis.Referallservicetoqualified
servicepersonnelortothefactory.
Make your initial switch and control settings as follows:
SWITCH/CONTROL SETTING
CHANNEL 1
EXPANDER THRESHOLD CONTROL BYPASS
RELEASE CONTROL 12O’CLOCK
COMPRESSOR THRESHOLD CONTROL -10(12O’CLOCK)
RELEASE CONTROL 12O’CLOCK
RATIO CONTROL 2:1(APPROX.10O’CLOCK)
LIMITER THRESHOLD CONTROL BYPASS
OUTPUT GAIN CONTROL 0(12O’CLOCK)
STEREO LINK STEREO/DUAL MONO SWITCH DUAL MONO (“OUT” POSITION)
CHANNEL 2 REPEAT SETTINGS SHOWN FOR CHANNEL 1
With the 565E’s controls and switches now set according to the preceding section, the 565E
should pass signal. Fast setup is complete.
Refining Your Settings
Refine the EXPANDER THRESHOLD setting so that the expander reduces the gain of background noise
when the desired input signal is not present, but does not reduce the gain when the desired signal
is present and does not trigger excessively on short pauses in the program material. Adjust the
COMPRESSOR THRESHOLD control so that two or three of the compressor gain reduction LEDs light
when normal level program material is present. Set the LIMITER THRESHOLD control so that the -3
LED just lights on the highest peaks in the audio program material. Remember these settings are
just guidelines; you can use whatever settings work best for you.



Fast Setup
Chapter 3



565E
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Dynamics Processing Tutorial and 565E Functional Basics
Audio signals possess several basic properties: amplitude or volume (measured in volts or dB),
frequency or pitch (measured in Hertz), duration (measured in hours:minutes:seconds) and
waveform(describedgraphically,likesine,square,triangle,orpulse).Complexsignalslikemusical
sounds are made up of simpler waveforms such as sine waves, mixed in the proper proportions.
Signal processors allow you to manipulate various parameters of an audio signal. Equalizers change the
amountofamplification giventodifferent frequencies(aperfect amplifier increasesthegain ofall
frequencies by the same amount). Dynamics processors change the dynamic range of audio signals.
The dynamic range of an audio signal is the difference between its loudest and softest moments. For
audio equipment, this is the difference between the noise floor (residual noise output, with no input
signal) and peak clipping (the point at which the output clips or distorts). A hypothetical black-box
havinganoisefloor of -90 dBuandamaximum peak output levelof+24dBu would have adynamic
rangeof114dB (+24 minus -90).Audiostoragedevices like tape machineshaveamuch narrower
dynamic range; a typical professional analog two-track tape machine may have a dynamic range of 65 to
70dB.
If you’ve used an analog tape recorder before, then you are already familiar with the problem of
setting recording level. Record too hot and you get distortion; record too cold and get noise in
return. Many musical instruments have dynamic ranges that exceed that of most tape recorders. So,
how do we squeeze a 80 or 90 dB signal into a 60 or 70 dB window?
The answer lies in a common audio signal processor: the compressor.
Compressors and Limiters
A compressor or limiter monitors the level (or amplitude) of a signal and reduces the amplitude
according to a rule whenever the signal level exceeds a predetermined level. The predetermined
level is known as the threshold level and is usually set by a front-panel control. The amount by
which the compressor lowers the level is the compression ratio, and this parameter is usually set
via a front-panel control as well.
Compression ratio refers to the ratio of a change at the input versus the change at the output of
the device. Thus, if we apply an above-threshold signal that changes 10 dB to the input of a
hypothetical compressor, and measure a 2 dB change in the output signal, that compressor would
have a compression ratio of 10:2, or 5:1 (reduce the fraction). Different compression ratios have
differentuses.Use lower ratios (6:1orless) for levelcontrol,intermediateratios (8:1 to12:1)for
leveling (making the signal level more or less constant), and higher ratios for limiting (putting an
absolute ceiling on the signal level).
Limiters are nothing more than compressors, but are possessed of much higher compression ratios
(20:1 or higher). Limiters are typically used to stop occasional peaks which would otherwise cause
overload or distortion. Typically a limiter is set (via its threshold control) so that it “stays out of
the way” until a peak comes along.
Expanders and Gates
While a compressor or limiter reduces the dynamic range of a signal by reducing its level once it
has exceeded a threshold level, an expander does the opposite (well, almost). The easiest way to
visualize an expander is to think of it making loud signals louder. This is fine, except that in the real
world, the device following the expander (such as a processor or an amplifier) would go into
terminaloverload.
The solution is to make soft signals softer, a.k.a. downward expansion. This is what the 565E’s down-
ward expander does. When the signal level falls below the level set by the threshold control, the
expander reduces its gain by the amount dictated by its expansion ratio. Thus, for a below-threshold
signal, a 10 dB output change results from a 5 dB change in the input signal, if the expansion ratio is 1:2.
Tutorial Chapter 4

565E
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A gate is similar to an expander except that its ratio is much higher; thus the action is more like a
switch once the signal falls below threshold. Some expander applications for the 565E may be quite
similar to a gate, like tending a lone announce microphone, but downward expanders generally are
not well-suited to typical gate applications such as removing leakage from drum microphones,
where very tight control is desired.
Ratio
The compression ratio of the 565E determines how much the output changes for a change in the
input. A linear amplifier (like a simple preamp) has a ratio of 1:1 because a change of 1 dB at its
input results in a 1 dB change at its output. A compressor alters the input/output relationship by
its compression ratio. Thus a 20:1 ratio means that a 20 dB above-threshold change at the input
results in a 1 dB change at the output. In other words, a very audible change at the input (20 dB)
turns into a barely discernible change at the output (1 dB).
Compressors are not the only devices to have an input/output ratio. Any device that is capable of
changing the input/output relationship can be said to have a ratio. Thus expanders, gates, com-
pressors and limiters all fit this category.
An expander magnifies output changes for a given input change. Thus, once the input signal falls
below threshold, the expander changes the output by the amount of the ratio. The 565E’s down-
ward expander has an expansion ratio of 1:1.5, which means that a below-threshold input signal that
gets 10 dB quieter turns into an output signal that gets 15 dB quieter.
A gate can be looked at as an expander with an infinite expansion ratio. Thus the slightest peak in
the input signal from below-threshold to above-threshold switches the gate from closed to open.
Gain versus Output Level
The GAIN control compensates for signal level lost to compression. As an example, set the THRESH-
OLD control counter-clockwise and set the RATIO control of the 565E for a 4:1 ratio. Now adjust the
THRESHOLD control for 10 dB of gain reduction as viewed on the compressor’s gain reduction
display. The output level should be significantly lower than it was when the Threshold control was
counter-clockwise (i.e. when no compression was being applied). You supply the additional gain
(make-up gain) by adjusting the GAIN control until the input and output signal levels match.
Release Time
Most dynamics processing equipment has a control marked RELEASE on the front panel. This
control refers to release time, and it affects the length of time required for the gain to recover to the
no-signal state (when no signal is applied to the input). The release time control allows tailoring
the expander’s or compressor’s recovery time to the program material.
For compressors, the no-signal state is unity gain (passing the signal straight through the compressor,
with no change in gain). Compressors pass any signal whose level is below threshold at unity gain.
The release time control determines how long it will take for the compressor to return to unity gain, once
the input signal has fallen below the compression threshold. Generally, peak limiting is associated with
short release times and compression or leveling associated with longer release times.
For expanders, the no-signal state is determined by the amount of gain reduction applied when no
signal is present at the expander’s input. The amount of gain reduction is set by the threshold
control and by the ratio of the expander, and this applies to any signal whose level is below-
threshold. In this case, the release time control governs how long it takes for the expander to
reduce the gain when the signal disappears. Typically, smooth expansion of speech or music is
associated with longer release times, and gating-type functions, such as feedback suppression, are
associated with short release times.

565E
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Setting the Threshold Control
The THRESHOLD control sets the audio signal level where the compressor/expander/limiter begins
working. In the case of the compressor or limiter, the processor begins working once the signal has
exceeded the threshold level. For the expander, it begins working once the signal has fallen below
the threshold level.
For any of the three processors, the THRESHOLD control setting also determines the degree or
amount of gain reduction. Thus, for the compressor, rotating the control counter-clockwise
(towards -40) results in increasing amounts of compression. For the expander, counter-clockwise
rotation raises the level that the signal must exceed to pass through the expander untouched. This
has the effect of “shutting off” the signal once you reach and then pass the threshold level.
For most compressor applications, moderate amounts of gain reduction are all that is required, 3-9
dB at the most. If you are using the compressor to minimize level changes of a wide range of
program material (automatic level control), then higher amounts of gain reduction are needed. In
typical compressor applications, program material with a very wide dynamic range calls for higher
amounts of gain reduction than program material with less dynamic range.
Note With higher amounts of gain reduction, slower release times are recommended.
Interpreting the Displays
The 565E has one display per processing section. The three displays associated with the expander,
compressor and limiter indicate a parameter called gain reduction. Simply stated, the gain reduction
indication shows how far the gain or amplification was reduced from unity. Another way of looking
at this is: if the gain reduction display says 10 dB of gain reduction, switching the unit to bypass
will result in a 10 dB increase in the output level.
The output display indicates output level in dBu. For most applications, just make certain that you
neverseetheCLIPLEDilluminate.
Using the Sidechain
The sidechain is a patch point in the control circuit of a dynamic range processor. It provides
access to the part of the circuitry that tells the VCA (voltage controlled amplifier) what to do. The
565E’s sidechain is routed through a TRS jack labeled “KEY INPUT”. This jack is located on the
rear panel, and it provides both a send and return via the same jack. The sidechain connection
affects all three processors in the 565E.
The 565E’s sidechain connections are derived from the balanced input stage, and they allow
access to the control circuit’s input signal. The control signal is derived from, but kept totally
separate from, the audio signal path. This means that the control signal can be processed outside
the 565E without actually processing the signal that’s going through the VCA (the audio signal
itself). This presents some very interesting possibilities for changing or improving the operation of
the dynamic range processor.
The most common use of the sidechain is to make the action of the 565E’s compressor/limiter/
expander frequency dependent, that is, to make it respond more (or less) to certain frequencies, by
inserting an equalizer in the sidechain path. Because the audio signal and the control signal remain
completely separate (even while the control circuit tells the VCA whether to turn the gain up or
down), you can equalize just the sidechain without changing the EQ in the main audio path.
This allows you to emphasize a frequency portion of the audio program so that this portion
dictates the behavior of the processing (for example, you can boost the appropriate high frequen-
cies to make the compressor behave like a de-esser), or to de-emphasize a frequency portion that is
controlling the audio more than you would wish (for example, with beat-heavy dance music, cutting
the low end can prevent the compressor from “pumping and breathing” with every kick drum beat).

565E
7
Keep in mind that the threshold level becomes a function of the amount of overall gain through the
equalizer, including the boost. This technique can be used with any frequency that can be con-
trolled by the equalizer.
One occasion for using an EQ in the sidechain is when low frequency signals transmitted through
a desk or podium are triggering the 565E’s expander unnecessarily. You can solve this problem by
using an equalizer in the sidechain to remove the low frequencies from the control signal or to
boost the voice-range frequencies in the control signal.
When the offending frequencies are removed or minimized, the relative level of the desired frequen-
cies increases. The expander can now tell the difference between the wanted and unwanted signals.
Use this technique in any situation where levels are nearly the same, but the fundamental frequen-
cies involved are different.
Note The ability of the expander to discriminate between wanted and unwanted signals is
partially determined by mic technique. Be particularly careful of high frequency sounds
entering the side or rear pattern of a cardioid mic. Most cardioid mics exhibit a sharply
rising off-axis response characteristic at higher frequencies. Check the off-axis curve (the
lower one) in the manufacturer’s literature. If there’s only a 3dB to 6dB difference between
the on-axis (frontal) response and the off-axis (side or rear) response in the 5kHz to 10kHz
reason, high frequency sounds will be picked up by the side or back of your mic.
Use the mic’s directional pattern to keep other sources as far off-axis as possible - do everything
you can do to extract all the source-to-source discrimination possible through good mic technique.
The sounds picked up by individual mics must be primarily the sound of the desired signal, or the
expander won’t be able to tell the difference.
Hint You can save time, and make life easier, by listening to the output of the equalizer (instead
of the 565E’s output) that you’re using in the sidechain. Doing this allows you to hear the
signal that will control the 565E, and perhaps to find the range that you wish to emphasize
orde-emphasizemoreeasily.

565E
8
Expander Section
THRESHOLD control - The THRESHOLD control varies the
downwardexpanderthresholdfrom+10dButoBYPASS.
The downward expander will engage when the audio
signal present at the input of the expander drops below
this threshold, or when there is no signal present at the
expander’s input. The downward expander gently lowers
below-threshold signals at a ratio of 1:1.5 (a 1dB below-
threshold drop in signal at the expander’s input results
in a 1.5dB drop in signal at the expander’s output).
RELEASE control - The RELEASE control allows the user to
varythedownwardexpander release time from250
milliseconds to 5 seconds. The release time is the
amount of time that it takes for the downward expander to push the output signal down to the
level determined by the 1:1.5 ratio, in response to an instantaneous below-threshold drop in
the input signal level. Shorter release time settings cause the expander to act more quickly,
and longer release time settings cause the expander to act more slowly and smoothly.
LED display - The LED display indicates the amount by which the expander has reduced the
level of the input signal.
The Compressor Controls
THRESHOLD control-The THRESHOLD
control varies the compressor threshold
from -40 dBu to +20 dBu. The compres-
sor threshold is the level that the input
signal must reach before the compressor
becomes active. When the input signal
exceeds this threshold, the compressor
will reduce the output gain by the
amount determined by the compressor
RATIO control setting.
RELEASE control - The RELEASE control
allows tailoring of the compressor’s
recoverytimetothe program material.
Generally, peak limiting is associated with short release times and compression, or leveling, is
associated with longer release times.
The 565E’s release circuitry has a unique dual-release time feature designed to make life easier.
The dual-release feature makes the release time partially program-dependent, giving you the
best of both worlds: fast release for short-duration peaks and a longer release time for longer-
duration peaks. The RELEASE control adjusts the speed of the longer of the two. The
compressor release time can be varied from 180 milliseconds to 2.5 seconds.
RATIO control - The RATIO control determines the amount of compression that occurs for a
given above-threshold change in the input level. The ratio that is being controlled is the ratio
between an above-threshold change in the input level and the resulting change in the output
level. If the RATIO control is set to 10:1, then a 10 dB above-threshold change in the input
level would result in only a 1 dB change in the output level. Higher ratios are used where
tighter control is desired, such as when you want to control peaks in the audio signal, and
lower ratios are used for gentle smoothing of levels.
LED display - The LED display indicates the amount by which the output level has been
reduced by the compressor.
Front Panel Overview Chapter 5
CH1 EXPANDER
-2-6-18 -12
-12
-250
SLOW
BYPASS FAST
RELEASE
+10
THRESHOLD (dBu)
-4-6 -2-15 -10-12 -8-25
CH1 COMPRESSOR
4-10
62.5+5
10
1
RATIO (X:1)
FAST-40 +20 SLOW
RELEASETHRESHOLD (dBu)
-25