Symetrix 527E User manual

527E Voice Processor
User’s Guide
527E

i
Table of Contents
Chapter 1 Introduction 1
Chapter 2 Operator Safety Summary 2
Chapter 3 Fast Setup 3
Chapter 4 Front Panel Overview 5
Chapter 5 Rear Panel Overview 7
Chapter 6 Using the 527E 8
Chapter 7 Applications 11
Chapter 8 Troubleshooting 13
Chapter 9 Specifications 14
Chapter 10 Block Diagram 16
Chapter 11 Warranty & Service 17
Appendix A Declaration of Conformity 19
Rev A.00, 1 September, 1999
Symetrix part number 53527-0A00
Subject to change without notice.
©1999, 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 photocopying,
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]
527E

527E
1
IntroductionChapter 1
Front panel
Rear panel
+15
POWER
0
dB
-15
1.5
OCT
HIGH EQ
.3 4
BANDWIDTH CUT/BOOST
Hz
6.8K
FREQUENCY
22K680
0
dB
+15
1.5
OCT
4.36.3K
BANDWIDTH
MID EQ
-15
CUT/BOOST
160
0
(dB)
-15 +15
CUT/BOOST
1.5
(OCT)
LOW EQ
4
.3
(Hz)
160
FREQUENCY
50016
BANDWIDTH
Hz
2.5K
FREQUENCY
42K
18K
65K
5K
50
FILTERS
3K
260
115
HIGH CUT (Hz)
22
6
8
GAIN
0
+15
FILTERS
EQ/
EXP/COMP
IN
BYPASS
BYPASS
LOW CUT (Hz)
0
CLIP
-15
-20
-10
10
RATIO
2
X:1
1
-10
6
3
-40
12
9
-25
0
GR
+20
COMPRESSOR
THRESHOLD
OUTPUT
6
3
GR
20
12
LINE
INPUT
MIC60
MUTE
MIX
(dB)
CLIP
20
E
MIC GAIN
VOICE
527
PROCESSOR
BYP
EXPANDER
THRESHOLD
-15dB
0dB
MIC
MIC PAD PHANTOM
ON
OFF
INPUTS
LINE
MUTE CONTROL
LINE
NC
MIC
LINE
LINE
MANUFACTURED BY SYMETRIX INC.
LYNNWOOD, WA USA
THIS PRODUCT CONTAINS NO
USER SEVICEABLE PARTS.
E
PROCESSOR
VOICE
527
FABRIQUÉ AUX E.-U. PAR SYMETRIX INC., LYNNWOOD, WASHINGTON.
RÉFÉREZ TOUTE RÉPARATION À UN TECHNICIEN QUALIFIÉ.
15 WATTS
MAXIMUM
AC INPUT
OUTPUTS
The Symetrix 527E traces its heritage back to the Symetrix 528, the first signal processor specifically
designed for voice applications. Revered as the rackmount equivalent of a studio console strip, the
classic 528E is still the most widely-used voice processor in the broadcast industry. To this
benchmark design, we added new controls and connections, and we refined it according to the
needs of installed sound applications. The result: An ideal product for installations requiring great
sounding key microphones. When used on announcement mics in stadiums and gymnasiums,
wireless and lapel mics in church systems, and paging mics in acoustically challenging
environments, the 527E provides voice-optimized processing from the company than invented it.
Simply stated, the 527E consists of a high-quality microphone preamp coupled to a three-band
parametric equalizer, high and low pass filters, and a dynamic range processor.
The dynamic range processor combines an interactive compressor/limiter and a downward
expander. Typically, the downward expander helps reduce background noise as well as the artifacts
of close miking. The compressor/limiter gives you overall control over the dynamic range of the
output signal and helps maintain a high overall signal level.
The filter section of the 527E features tunable low cut and high cut filters. These 12 db per octave
filters allow the user to remove objectionable low frequency noises, such as rumble and muddiness,
and high frequency noises, such as sibilance and air conditioning noise.
The three-band parametric equalizer is a reciprocal-curve design. Each band is connected in series
with the next to ensure that each filter band sums with its neighbors smoothly.
The 527E accepts both mic and line inputs. The microphone input uses a balanced transformerless
design. It works with any phantom-powered condenser microphone or any low-impedance micro-
phone having a balanced, floating output. The line input also uses a balanced transformerless
design and its matched resistors permit the 527E to attain a high, wideband, CMRR (common-mode
rejection ratio). Multistage RFI filters prevent radio frequency interference problems. The 527E’s
output section can drive balanced loads at line or mic levels.
We recommend that you read this manual from cover to cover. Somewhere between the confines of
the two covers you should find the answers to most (98%) of your questions. 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

527E
2
Operator Safety Summary Chapter 2
Terms
Several notational conventions are used in this
manual. Some paragraphs may use Note, 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 527E.
Caution Identifies information that, if not
heeded, may cause damage to the
527E or other equipment in your
system.
Warning Identifies information that, if
ignored, may be hazardous to your
health or that of others.
CAPITALS Controls, switches or other markings
on the 527E’s chassis.
Boldface Strong emphasis.
Equipment Markings
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
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
persons. The exclamation point within an equilateral
triangle is intended to alert the user of the presence of
important operating and maintenance (servicing)
instructions in the literature accompanying the
product (i.e. this manual).
Caution To prevent electric shock, do not use the
polarized plug supplied with the unit with
any extension cord, receptacle, or other
outlet unless the blades can be fully
inserted.
Important Safety Instructions
Please read and keep these instructions. Heed
and follow all warnings and instructions. Install
in accordance with the manufacturer’s instruc-
tions.
Power Source This product is intended to
operate from a power source that does not apply
more than 120V rms 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.
Grounding The chassis of this product is
grounded through the grounding conductor of
the power cord. To avoid electric shock, plug the
power cord into a properly wired receptacle
before making any connections to the product. A
protective ground connection, by way of the
grounding conductor in the power cord, is
essential for safe operation. Do not defeat the
safetypurposeofthegroundingplug.The
grounding plug has two blades and a third
grounding prong. The third prong is provided for
your safety. When the provided plug does not fit
your outlet, consult an electrician for replacement
of the obsolete outlet.
DangerfromLoss ofGround Ifthe protective
ground connection is lost, all accessible conduc-
tive parts, including knobs and controls that may
appear to be insulated, can render an electric
shock.
Proper Power Cord Use only the power cord
and connector specified for the product and your
operating locale. Use only a cord that is in good
condition.Protectthepowercordfrombeing
walked on or pinched, particularly at plugs,
convenience receptacles, and the point where
they exit from the apparatus.
OperatingLocation Donotoperatethisequip-
mentunderanyofthefollowingconditions:
explosive atmospheres, in wet locations, in
inclement weather, improper or unknown AC
mains voltage, or if improperly fused. Do not
install near any heat source such as radiators,
heat registers, stoves, or other apparatus
(including amplifiers) that produce heat. Unplug
this apparatus during lightning storms or when
unused for long periods of time.
Stay Out of the Box To avoid personal injury (or
worse), do not remove the product covers or
panels. Do not operate the product without the
covers and panels properly installed. Only use
accessories specified by the manufacturer. Clean
only with a damp cloth.
User-serviceable parts There are no user
serviceable parts inside the 527E. In case of
failure, refer all servicing to the factory. Servicing
is required when the 527E has been damaged in
any way, such as when a power supply cord or
plug is damaged, liquid has been spilled or
objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture,
does not operate normally, or has been dropped.

527E
3
Fast Setup
Fast Setup
Chapter 3
Connections
Connect your input source to the appropriate XLR or Euroblock connector. Connect the 527E’s
output to line-level input using the line-level XLR or Euroblock output connector. If you need to
feed a mic-level input, use the mic-level XLR output connector.
If you are using a condenser microphone, refer to “Phantom Powering Condenser Microphones” in
Chapter 6 before depressing the PHANTOM POWER switch.
Caution Failure to connect the 527E to the proper AC mains voltage may cause fire and/or
internal damage. There are no user serviceable parts inside the chassis. Refer all
service to qualified service personnel or to the factory.
Warning Lethal voltages are present inside the chassis. There are no user serviceable parts
inside the chassis. Refer all service to qualified service personnel or to the factory.
Connect the AC input to an AC power source of the proper voltage and frequency, as marked on the
rear of the unit.
Settings for Initial Setup
Set the controls and switches on the front and rear panel as follows:
Follow these instructions to get your 527E up-and-running as quickly as possible. The intent of
this section is fast setup. If you need something clarified, then you’ll find the answer elsewhere in
this manual.
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527E
4
The 527E’s controls and switches are now set
according to the preceding section. The 527E
should now pass signal. The OUTPUT LEVEL LED
display and the POWER LED should be illuminated.
Depending upon the signal levels, the
compressor’s gain-reduction display may be
illuminated.
Refining Your Settings
Temporarily put the Exp/Comp and EQ sections
into bypass mode, set the MIC GAIN control so that
the OUTPUT LED display indicates a signal level
between -10 and 0 VU. The CLIP LED should almost
neverilluminate.
Use the downward expander to reduce background
noise and/or mouth noises. Set the THRESHOLD
control to allow low level speech sounds to pass
while still blocking unwanted sounds which are at a
lower level than the lowest-level speech audio.
Use the threshold control to vary the amount of
gain reduction, as indicated on the compressor’s
gain-reduction display. Generally, 3 to 6 dB is
sufficient, unless you are using a low compression ratio (below 2:1), or you want a special effect.
Pick a ratio suited to the task at hand: low ratios and low thresholds for unobtrusive level control,
medium ratios for overall level control and consistency, high ratios (> 8:1) for limiting or in-your-
face sorts of sounds.
The frequency settings given will work well with male voices. For women, the low-EQ range shifts
up to 200 or 300Hz, the mid-EQ range shifts up to 3-5 kHz.
If you are using a microphone that exhibits proximity effect when you close-talk it, then you’ll
probably need to reduce (cut) the bass (low) response somewhat. 3-6 dB should be fine (don’t do
this if you want a big, ballsy sound). A bit of mid-EQ will help make voices cut and seem loud. The
high-EQ adds brightness and intimacy.
If you are using a microphone that has minimal proximity effect (like the ElectroVoice RE-20), then
you’ll probably need to increase (boost) the bass response somewhat. 3 to 6 dB should do the job.
The same mid- and high- EQ recommendations given previously still apply.
For many applications, setting the output GAIN control at 0 dB (12:00 o’clock) works fine. If you are
adding a bunch of EQ (which tends to cause an overall level increase), then you may need to
decrease the GAIN setting. On the other hand, if you are using a fair amount of compression, you
may need to add some gain to compensate for the level lost in compression. Pick a setting that
gives you enough signal downstream, yet still keeps the CLIP LED from illuminating. The output
display is peak responding, so you can’t quite set levels as if it were a VU meter (which responds
moreslowly).
The output CLIP LED monitors the output stage. Large amounts of boost and/or high signal levels
can cause CLIP indications. If this occurs, lower the signal level via the GAIN control.
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527E
5
Chapter 4 Front Panel Overview
Input
MIC GAIN Sets the gain of the mic preamp for best compromise between signal-to-noise ratio
and headroom.
MIX Selects between the Mic input and Line input, or allows a mix of both inputs.
CLIP LED Monitors mic inputs for clipping. Illuminates 3 dB below the actual clip point.
MUTELED Lights when the output of the 527E has been muted by a remote switch connected to
the 527E’s rear panel MUTE CONTROL Euroblock connector.
Downward Expander / Compressor
EXPANDER THRESHOLD Sets the threshold level for the downward expander. Signals below this
threshold are downward expanded (reduced in level).
COMPRESSOR THRESHOLD Sets the threshold level for the compressor. Signals above this
threshold cause gain reduction in the compressor.
COMPRESSOR RATIO Sets the compression ratio of the compressor. This determines the
amount by which above-threshold signals will be compressed.
DOWNWARD Indicates the amount of downward expander activity (gain reduction) at
EXPANDER any instant in time.
LEDDisplay
COMPRESSOR Indicates the amount of compressor activity (gain reduction) at any
LEDDisplay instant in time.
Output Section
GAIN Sets the overall gain of the 527E’s output over a ±15 dB range. The actual adjustment
point is in the expander/compressor’s VCA, which is pre-EQ.
OUTPUT LED Indicates the peak output level of the527E relative to the balanced output. 0 VU
Display on the display corresponds to +4dBu at the balanced output. For unbalanced
applications, the actual output level is 6 dB lower than that shown by the display.
Note The 527E’s mic output will have an output level of -36dBu when the display
indicates0VU.
Bypass
EXP/COMP Defeats the downward expander/compressor. This is not a hard-wire
IN/BYPASS Switch bypass.
EQ/FILTERS Disengages the EQ and Filter section when set to the Bypass (Out)
IN/BYPASS Switch position. This is a hardwire bypass.
+15
POWER
0
dB
-15
1.5
OCT
HIGH EQ
.3 4
BANDWIDTH CUT/BOOST
Hz
6.8K
FREQUENCY
22K680
0
dB
+15
1.5
OCT
4.36.3K
BANDWIDTH
MID EQ
-15
CUT/BOOST
160
0
(dB)
-15 +15
CUT/BOOST
1.5
(OCT)
LOW EQ
4
.3
(Hz)
160
FREQUENCY
50016
BANDWIDTH
Hz
2.5K
FREQUENCY
42K
18K
65K
5K
50
FILTERS
3K
260
115
HIGH CUT (Hz)
22
6
8
GAIN
0
+15
FILTERS
EQ/
EXP/COMP
IN
BYPASS
BYPASS
LOW CUT (Hz)
0
CLIP
-15
-20
-10
10
RATIO
2
X:1
1
-10
6
3
-40
12
9
-25
0
GR
+20
COMPRESSOR
THRESHOLD
OUTPUT
6
3
GR
20
12
LINE
INPUT
MIC60
MUTE
MIX
(dB)
CLIP
20
E
MIC GAIN
VOICE
527
PROCESSOR
BYP
EXPANDER
THRESHOLD

527E
6
Filters
LOW CUT Selects the cutoff frequency of the LOW CUT FILTER (variable from 6 Hz to 260 Hz).
This filter will uniformly pass frequencies above the cutoff frequency.
HIGH CUT Selects the cutoff frequency of the HIGH CUT FILTER (variable from 3kHz to 65 kHz).
This filter will uniformly pass frequencies below the cutoff frequency.
Parametric EQ Low
FREQUENCY Varies the center frequency of the low-frequency equalizer from 16Hz to 500 Hz.
BANDWIDTH Varies the bandwidth of the low-frequency equalizer from 0.3 to 4 octaves.
(Q=4.8to0.27).
CUT/BOOST Sets the degree of boost or cut; ±15 dB.
Parametric EQ Mid
FREQUENCY Varies the center frequency of the mid-frequency eq from 160 Hz to 6300 Hz.
BANDWIDTH Varies the bandwidth of the mid-frequency eq from 0.3 to 4 octaves.
(Q=4.8to0.27).
CUT/BOOST Sets the degree of boost or cut; ±15 dB.
Parametric EQ High
FREQUENCY Varies the center frequency of the equalizer from 680 Hz to 22 kHz.
BANDWIDTH Varies the bandwidth of the high-frequency equalizer from 0.3 to 4 octaves.
(Q=4.8to0.27).
CUT/BOOST Sets the degree of boost or cut; ±15 dB.
POWER LED Indicates the presence of AC power.

527E
7
SERIAL NUMBER [Please send us the completed warranty card.]
AC POWER INPUT IEC-power connector. Connect only to appropriate AC power source. Refer to
rear-panel marking for correct AC source voltage.
Outputs
LINE OUTPUT XLR connector or a Euroblock connector. Balanced, line-level output.
Connections are:
XLR Euroblock
Pin 1 Ground
Pin2 + High
Pin3 - Low
To feed an unbalanced load, connect the Ground (shield) side to Pin 1 (ground)
only, and the Hot (center conductor) side to Pin 2 (+).
MIC OUTPUT XLR connector. Balanced, mic-level output. Connections are Pin 1 ground, Pin
2 high (+), and Pin 3 low (-).
Mute Control
MUTE CONTROL Euroblock terminal connector. Unbalanced muting port for “cough switch”
control. A simple contact closure between the + and ground terminals of the
MUTE connector will silence the output. Any SPST switch or relay contact will
work.
If you would like to use the mute feature as a “push-to-talk”function, use a
normally-closed relay or switch contact. When the switch is pushed (or the relay
is energized), the contacts will open and un-mute the audio signal.
The open-circuit voltage at the + terminal is about 15 volts DC, limited by a 20,000
Ohm resistor. Take care not to apply any foreign voltage potential to these
terminals.
Inputs
LINE INPUT XLR connector or Euroblock connector. 10-kilohm balanced bridging line input
intended for signals ranging from -10 dBu to +4 dBu. Connections are Pin 1
ground, Pin 2 high (+), and Pin 3 low (-). For unbalanced connection to the LINE
INPUT, we recommend connecting the input cable shield to both Pins 1 and 3, and
the center cable conductor to Pin 2.
MIC INPUT XLR connector. Balanced input suitable for low-impedance microphones.
48V phantom powering available. Connections are Pin 1 ground, Pin 2 high (+),
and Pin 3 low (-). We do not recommend feeding the MIC INPUT from an
unbalanced source.
MIC PAD Pushbutton switch inserts a 15dB pad for strong mic signals.
PHANTOM POWER Pushbutton switch enabling phantom power on MIC INPUT.
Rear Panel OverviewChapter 5
-15dB
0dB
MIC
MIC PAD PHANTOM
ON
OFF
INPUTS
LINE
MUTE CONTROL
LINE
NC
MIC
LINE
LINE
MANUFACTURED BY SYMETRIX INC.
LYNNWOOD, WA USA
THIS PRODUCT CONTAINS NO
USER SEVICEABLE PARTS.
E
PROCESSOR
VOICE
527
FABRIQUÉAUX E.-U. PAR SYMETRIX INC., LYNNWOOD, WASHINGTON.
RÉFÉREZ TOUTE RÉPARATION ÀUN TECHNICIEN QUALIFIÉ.
15 WATTS
MAXIMUM
AC INPUT
OUTPUTS

527E
8
Using the 527E
Following are some tips and techniques for using the 527E. You should consider any settings
given as starting points for developing your own settings.
Metering
The 527E has several LED bargraphs that serve as gain reduction and output meters. The gain-
reduction meters indicate the change, from unity gain, for their respective function and the LEDs
read (and move) from top to bottom. When operating as a level meter, the LEDs read (and move)
from bottom to top. Each meter has its own scale markings, as shown on the front panel.
Gain Setting
There are two places to adjust the gain of the 527E: at the mic input, before any processing, and at
the output.
First, the mic input gains. You make best use of the 527E’s signal-to-noise ratio by ensuring that
your mic-level input signals are adjusted to fit within the headroom of the mic preamp. Doing so
ensures optimum dynamic range through the mic preamp and succeeding processors. With the
Expander/Compressor, Filter, and EQ sections temporarily set to BYPASS and the OUTPUT GAIN
control set to 0 dB (12:00 o’clock), set the MIC GAIN control so that the OUTPUT LEVEL display
indicates levels in the -10 to 0 VU range. The CLIP LED should never illuminate on signal peaks.
Remember to restore the settings of the various bypass switches.
Finally, the OUTPUT GAIN. After adjusting all of the other processors, set this control so that the 0
VU LED on the OUTPUT LEVEL meter illuminates. The red CLIP LED should never illuminate.
The output CLIP LED also monitors the EQ section. If the CLIP LED illuminates, reduce the OUTPUT
GAIN control setting slightly and/or reduce the amount of boost that you are applying in the EQ
section. You may need to increase the gain of some device following the 527E to achieve the same
overalllevel.
Downward Expander
Expander operation is easily misunderstood unless it’s remembered that what’s being expanded is
the dynamics, or changes, of signals passing through the circuit. Expanders come in two very
different types: linear, and downward.
Linear expanders increase the dynamic range of all signals, no matter what their actual level. The
linear expander simply makes all changes greater by some ratio, which is sometimes user adjust-
able. In the real world, linear expanders aren’t too practical because clipping occurs when signals
just below maximum output level are expanded.
For instance, an unprocessed signal 3 dB below clipping that increases 2 dB won’t distort, because
it’s still 1 dB below maximum. But if that same signal is passed through an expander operating at a
1:2 ratio, the same 2 dB change at the expander’s input becomes a 4 dB change at its output.
However, that signal would be 1 dB over maximum, causing distortion. Linear expanders must be
used with care, because very few systems have enough headroom to handle the upward dynamic
range increase they produce.
The kind of processor most commonly called an expander is really a downward expander, because
it only affects signals below threshold. This gives the operator control over the expander’s
activities, allowing it to be used to expand the usable dynamic range of the system without running
out of headroom. The 527E uses a downward expander.
The lower limit restriction of a system is the noise floor, which is usually well below the 527E’s
lowest expander threshold. It’s important to keep in mind that while the signal levels may change
greatly, the noise usually doesn’t change very much. The action of the expander increases the
dynamic range of all signals below threshold. This action increases the apparent loudness of
signals, while decreasing the apparent loudness of the noise.
Chapter 6

527E
9
For example, an expander operating at a ratio of 1:2 will cause an input signal that falls 10 dB below
threshold to fall 20 dB at its output. The downward action of the expander reduces the noise floor
by the same ratio applied to the signal. Since the relationship between the signal and the noise
stays the same, the noise is reduced 20 dB by the action of expander, which is responding to a 10
dB drop in the signal with its 1:2 ratio.
Think about using the expander when you are faced with a noisy signal (not necessarily hiss) or
when heavily compressing a voice and you want to remove some of the less desirable artifacts
(false teeth rattling, lip smacking, tongue noise, etc.) You can also use the expander to help remove
microphone leakage from a signal.
Start by setting the threshold so that the expander causes gain reduction (left LED meter) as the
signal falls in level. Increasing threshold levels (less negative numbers) cause further reductions in
the overall gain as the signal level falls.
Compression
The compressor generally controls peak levels and helps to maintain a high overall average signal
level. Used in this manner, the compressor’s action is generally inaudible. Compressors can also be
used creatively, to make a source sound louder than it really is, or to create a special effect.
For most level control applications, moderate settings yield the best results. We recommend a
starting point of: COMP THRESHOLD control setting sufficient to cause about 6 to 8 dB of gain
reduction on peaks using a COMP RATIO setting of 4:1.
For a highly compressed sound (you know, the used car salesman during the 3AM movie), use a
10:1 ratio setting and 10 dB or more of gain reduction.
Filtering
The filter section of the 527E features a low cut filter, useful for cleaning up muddiness and
eliminating rumble, and a high cut filter, for removal of objectionable high frequency noises, such
as sibilance and tape hiss. The low cut filter is tunable and reduces frequencies below the user-
selected cutoff frequency by 12 dB per octave. The high cut filter is tunable and reduces frequen-
cies above the user-selected cutoff frequency by 12 dB per octave.
Equalization
The 527E’s parametric equalizer has three overlapping bands. Each band can operate as a peaking
or dipping equalizer. The boost and cut range for each band is ±15 dB. The bandwidth may be
varied from 0.3 to 4-octaves wide.
Since the bands overlap, it is possible to apply equalization at the same frequency in two places.
Doing so could conceivably increase the signal level by 30 dB at one frequency. You may need to
reduce the INPUT or OUTPUT GAIN to avoid distortion. Likewise, large amounts of boost in any one
band may require reducing the setting of the OUTPUT GAIN control to prevent overload. Let the
OUTPUT CLIP LED be your guide.
A parametric equalizer offers perhaps the greatest flexibility of any type of equalizer, however it can
be more difficult to arrive at a setting than with other equalizers. A good strategy for setting any
equalizer is to set the level control for maximum boost, then vary the Frequency and Bandwidth
until you locate the portion of the spectrum that you wish to modify. Then refine the setting of the
Level control for that band. Next refine the setting of the Bandwidth control. You may have to go
back and forth between Level and Bandwidth to find the magic setting. Toggling the EQ Bypass
switch between in and out can help too.
As a rule, it is much easier to hear changes in amplitude (level) than it is to hear bandwidth
changes. It is also easier to hear the abundance of something rather than the absence of the same
thing. Even if you intend to apply cut (negative level) to a particular frequency, it is still easier to
find that frequency by boosting first, tuning second, and resetting the boost/cut last according to

527E
10
taste or need. Finally, you may find that more natural sounds result when you use wider band-
widths for boosting, narrower bandwidths for cutting. Regardless, there are no hard and fast rules
and in the end, whatever works for you is best.
It’s generally easier to apply boost to a sound for shaping (and that’s how many engineers start).
Many times, however, you may want to experiment with removing an offending sound (as opposed
to drowning it out with something else). In a complex mix, this may work better because it may
require less overall EQ to remove the offending sound; the end result will sound more natural.
Phantom Power
In a nutshell, here are the do’s and don’ts of phantom powering:
DO: Verify that your microphone can be phantom powered (if it is a condenser mic).
Ensure that your microphone’s output is low impedance, balanced and floating. This is
especially important for ribbon mics.
Turn the phantom power off when connecting vintage ribbon microphones.
Mute your monitor speakers or headphones when turning the phantom power on or off.
If you don’t, there will be a loud, nasty pop.
Mute your monitor speakers or headphones whenever you plug in or unplug a phantom
powered microphone. If you don’t, there will be a loud, nasty pop.
DON’T: Plug in an A-B powered microphone without a suitable adapter.
Worry about your dynamic or ribbon microphones, as long as they are wired so that the
output is balanced and floating.
Use the microphone input for line-level sources, especially those that are transformerless.
Use the microphone input with unbalanced sources. Use a direct box to convert the
unbalanced source to balanced. Then, connect the balanced direct box output to the
527E’smicrophoneinput.
Worry about your tube condenser mics. They are compatible (although they cannot be
phantom powered).
Mute Control
A contact closure between the positive and ground terminals of the 527E’s rear-panel MUTE
CONTROL will mute the output by at least 60dB. Any SPST switch or relay contact will work.
Note Do not apply any external power source to the mute connector. Do not use the ground
terminal for any purpose other than mute switching.
The open-circuit voltage at the positive terminal is 5 V (DC limited by approximately 20k Ohms).

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11
Applications
The 527E Voice Processor was designed to make the same kind of specialized processing that’s
applied to voice-overs and vocal tracks in recording studios available for use in paging, public
address and sound reinforcement. Typical applications will include a range of installations from
stadiums to churches. For example, use the 527E on stadium announcement mics where extra vocal
processing is required to help overcome the inherent acoustic problems that hinder intelligibility in
large venues. Churches often have key mics needing extra processing, such as lapel or wireless
mics. Adding the 527E to a key mic prior to the automatic mixer in churches yields significant
control advantages.
The following discussions illustrate some of the more useful applications for the 527E. As a result
of its versatility, combinations of the applications described here will normally be used.
Microphones - Compressing, Limiting, Expanding
The 527E’s dynamic range processor is used to control both over-modulation and noise. Noise, in
this case, may be electrically induced (hum, buzz, etc.), or acoustically transferred (paper rattling,
air conditioning, etc.), since the downward expander attenuates all below-threshold signals without
regard to origin. Careful adjustment of the two threshold controls allows the operator to put the
527E to work on any portion of the dynamic range. The expand threshold control governs the
527E’s activity in the lower part of the dynamic range, while the comp threshold governs activity in
the upper part of the range.
For smooth overall dynamic range processing that will tend to “homogenize”the sound and
remove only very low level noises, use a gentle compression ratio with a relatively high comp
threshold, and a relatively low expand threshold.
The soft-knee transition characteristic of the interactive processor allows the use of much higher
compressor/limiter ratios with much lower thresholds. The expander’s rapid rise below its thresh-
old, combined with the compressor’s smooth transition through its threshold, makes processing go
unnoticed. Use this application to “tighten up”voice signals. The expander eliminates noise and
adds “punch.”
Use the expander to remove background noise whether or not the compressor is being used. Be
sure the expander threshold is set low enough to allow even the lowest level speech sounds to
pass. If set correctly, the threshold will attenuate whenever a mic is not in use, eliminating extrane-
ous pickup of stage sounds and reducing feedback. To remove the compressor, set the compres-
sion ratio to 1 (essentially out of the circuit).
Likewise, the compressor/limiter may be used without the expander to control only the upper end of
the dynamic range. For general purpose overall gain control, use compression. Set the ratio
between 2:1 and 3:1, with a comp threshold setting that results in 6dB to 10dB attenuation.
Limiting is used for very definite control of the maximum level. As the name implies, limiting sets
the upper limit, but is not intended for general purpose overall gain control. For limiting, set the
ratio at 10:1, with the comp threshold control set to provide no more than 3dB to 6dB attenuation.
Bear in mind that limiting is an extreme dynamic control action intended to prevent overload farther
down the line. Limiting may be more pleasing to the ear than clipping distortion, but it doesn’t
generally sound good enough to be used for more than 6dB attenuation.
Increasing Gain Before Feedback
To optimize a PA system’s response for minimum feedback, tune out the feedback using the
parametric equalizer. To find and eliminate resonances that can become feedback problems, turn the
system on, with the microphone(s) and speaker(s) in place as they will normally be used, then
follow the sequence below. Gain before feedback should increase about 6dB (perhaps as much as
15dB) with this technique.
Chapter 7

527E
12
1. Note the settings of each of the compressor controls.
2. Temporarily set the compressor ratio to 10:1. Increase system gain very carefully until a
feedback frequency becomes slightly audible.
3. With the bandwidth set at about .3 octave, and the cut/boost control set for about -15dB, tune
the frequency control of one section until the feedback is no longer audible.
4. Increase system gain until feedback becomes slightly audible again.
A. If it’s the same frequency that was heard first, readjust the same frequency and bandwidth
controls until it again subsides.
B. If it’s a new frequency, repeat Step 2 using another of the EQ sections.
5. Increase gain again to find the third most prominent feedback frequency. Repeat Step 2 using
yet another of the EQ sections.
6. Reduce system gain to normal operating levels.
The high cut and low cut filters may also be used to eliminate feedback that falls within their
ranges. However, using the filters in this manner may result in a larger amount of the frequency
spectrum being removed than if you used the parametric EQ (depending on the setting of the
parametric EQ’s bandwidth controls).
High Level Paging and Public Address Systems - Dynamic Processing
Public address and sound reinforcement situations that require compression/limiting are often
plagued by feedback problems. Usually the “make up gain”used with compression causes an
overall increase in level which in turn, can cause feedback in the absence of signal, when the
compressor releases and brings the gain back up to normal.
The 527E’s interactive dynamics processor allows the use of large amounts of comp/limiting
without serious side effects. When compression is applied to “normal”signal levels, the compres-
sor returns to unity gain when the signal goes away. This action increases overall system gain.
The 527E’s expander, on the other hand, decreases gain whenever signals fall below threshold.
Careful setting of the two threshold controls tells the 527E how and when to adjust the gain.
Pages and announcements can be made much “tighter”with compression, but in high-sound-level
situations, feedback problems may make even gentle, low-ratio compression impossible. The
527E’s interactive processor performs exceedingly well in this situation, because the expander
decreases gain to compensate for the gain increase that results from compression.
Careful adjustment of the expander threshold control will prevent feedback in the absence of
signal, even with substantial compression. Note that in most cases the expander threshold must be
set lower than the compressor threshold.

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13
Troubleshooting
Troubleshooting Chart
SYMPTOM PROBABLECAUSE
No output Check cables and connections.
Are inputs driven by outputs, and outputs driving inputs?
Verify cables, source and load by patching input and output
connections together at the unit.
Check for AC power presence. Power LED on?
Check output by plugging headphones into output connector
(use an adapter).
Are the LED displays operating?
Did you use the correct output (mic or line-level)?
Is the MIX CONTROL set correctly?
Hum or buzz in output Check input and output connector wiring.
Ground loop. Check related system equipment grounding. Are
all system components on the same AC ground?
Distortion Check input signal. Is it too hot, or is it already distorted?
Is the OUTPUT display indicating clipping ?
Is the input clipping?
Check output loading. Should be above 600 ohms.
Are the power amplifiers clipping?
Is something else clipping?
Noise (hiss) Check input signal levels and level control settings.
The OUTPUT display should indicate signal up to but not
including the CLIP LED.
Check gain settings on upstream equipment.
Is the input signal already noisy?
The system gain structure should be such that the 527E
operates at or near unity.
Is the 527E set for mic-level output, driving a line-level input,
with the 527E’s gain set fairly high and upstream devices
contributing a significant amount of gain?
No LED displays Is the unit plugged in and turned on?
Is the AC outlet OK?
No nothing If you are using a condenser microphone, is the phantom
power switched on?
Did you connect to the proper input and output?
Is everything downstream really live?
Is the DOWNWARD EXPANDER THRESHOLD set too high?
Chapter 8

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527E Specifications
Specifications Chapter 9
Note The maximum operating ambient temperature is 25 degrees C.
Specifications subject to change without notice.
Inputs
Microphone Input Clip LED Fires at 1 dB
below clipping of mic preamp
Microphone Input Type BalancedTransformerless,
Low Impedance
Phantom Power +48V nominal
Microphone Preamp Gain 20 to 60 dB (pad out),
5 to 45 dB(pad in)
Microphone Input Maximum Input Level 0 dBu (pad out)
Equivalent Input Noise (EIN) -126 dBu
(60 dB gain, 20 kHz noise bandwidth)
THD+Noise(Preamponly) 0.02%
(1 kHz, 50 dB gain, +10 dBu output)
MicrophonePreampCMRR > 60 dB (40 dB gain, 20 Hz to 20 kHz)
Line Input Type and Impedance 10k Ohms Transformerless,
Balanced Bridging
Line Input Maximum Input Level +20 dBu
Line Input Nominal Input Level +4 dBu
Line Input CMRR > 50 dB (0 dBu, 20 Hz to 20 kHz)
Filters
Low Cut Filter Slope 12 dB/octave
Cutoff Frequency Range 6 Hz to 260 Hz @ -3dB
High Cut Filter Slope 12 dB/octave
Cutoff Frequency Range 3 kHz to 65 kHz @ -3dB
Parametric Equalizer
Type Three-band Parametric Equalizer
Frequency Ranges of Bands Low: 16 to 500 Hz
Mid: 160 to 6300 Hz
High: 680 Hz to 22 kHz
Peak/Dip Bandwidth 0.3 to 4 octaves,
measured at maximum boost
Maximum Boost/Cut ±15 dB
Metering
Type Multi-segment LED bar graph
Output Level -20, -10, 0, Clip (0 VU = +4 dBu),
VU calibrated, peak responding
Expander Gain Reduction 3, 6, 12, 20 dB
Compressor Gain Reduction 3, 6, 9, 12 dB
Overall Performance Data
Frequency Response 20 Hz to 20 kHz (+0, -0.5 dB), EQ out
compressor out, downward expander out
THD+Noise <0.08%, 20 Hz to 20 kHz, +4 dBm output
NoiseFloor -89 dBu (all functions enabled)
-95 dBu (with EQ function bypassed)
Dynamic Range Processor
Type Interactive Comp/Limiter-Downward Expander
Comp/Limiter Ratio 1:1 to 10:1
Downward Expansion Ratio (max) 1:1.8
Outputs
Output Section Type Balanced,Transformerless
Maximum Output Level +21 dBu Balanced
Output Clip LED Fires 3 dB below clipping
Output Source Impedance 200 Ohms, Balanced
Minimum Load Impedance 600 Ohms Balanced or Unbalanced
Output Gain ±15 dB
Physical
Size (hwd) 1.72 x 19 x 6 inches,
4.37 x 48.26 x 15.24 centimeters
Weight 5.1 lbs (2.3kg) net
Electrical
Power Requirements 115V nominal, 105 to 125V AC,
50 to 60 Hz, 15 watts maximum
230V nominal, 205 to 253V AC,
50 to 60 Hz, 15 watts maximum

527E
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527E Architects and Engineers Specifications
The voice processor shall be capable of microphone signal preamplification, line input buffering,
downwardexpansion,compression/limiting, filtering, andparametric equalization.
The unit shall have a low-noise, low distortion microphone preamplifier with variable gain (20 dB to
60 dB) and switchable (on/off) +48V phantom power. A 15 dB pad shall be provided to accommo-
date high output microphone signals. A balanced-bridging line input suitable for +4 dBu input
signals shall also be provided along with a mix control to select either the microphone or line
inputs, or a combination of both inputs.
The dynamics processing section shall contain an interactive compressor/limiter and downward
expander. There shall be front panel controls for compression ratio (1:1 to 10:1), compressor
threshold (-50 dBm to +20 dBm), expander threshold (-30 dBm to 0 dBm), and a bypass switch.
There shall be a 12 dB/Oct high cut filter with a user-adjustable cutoff frequency range 3 kHz to
65 kHz, and a 12 dB/Oct low cut filter with a cutoff frequency range from 6 Hz to 260 Hz.
There shall be a three-band parametric equalizer. Each band shall have ±15 dB maximum boost/cut,
and continuously variable bandwidth (.3 octaves to 4 octaves). The equalizer bands shall have
substantially overlapping frequency ranges, with a combined range of 16 Hz to 22 kHz. There shall
be a front panel bypass switch.
The voice processor shall be equipped with the following LED displays: A four-segment LED
display that monitors the overall output level, a four-segment LED display that monitors the
compressor/limiter, and a four-segment LED display that monitors the downward expander. All
displays shall be independent. There shall also be a single LED clip indicator to indicate clipping
withinthemicpreamplifiers.
The microphone input shall be an active balanced bridging design terminated with 3-pin XLR-
female connector (AES/IEC standard wiring). The microphone preamp shall be capable of an
equivalent input noise specification of at least -126 dBu (60 dB gain, 20 kHz noise bandwidth). The
line input shall be a balanced, transformerless design using a 3-pin XLR-female connector (AES/
IEC standard wiring) and a Euroblock terminal connector. All input circuitry shall incorporate RFI
filters of the LC or RC low-pass type.
The line output shall be an active balanced design terminated with a 3-pin XLR-male connector
(AES/IEC standard wiring) and a Euroblock terminal connector. The mic output shall terminate with
a3-pinXLR-maleconnector (AES/IEC standardwiring).
The voice processor shall be capable of operating by means of its own built-in power supply
connectedto 115V ACnominal (105 to 130V), 50to 60 Hzor 230VAC nominal (207to 253V),50 to
60Hz.
The unit shall be a Symetrix Incorporated model 527E Voice Processor.

527E
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Block Diagram
EQ
LINE
0 CLIP
-20
BYPASS
OUTPUT
-10
OUTPUT
MIC OUTPUT LINE
HI CUT
HIGH CUT
FILTER
CIRCUIT
CUT/BOOSTFREQUENCY
BANDWIDTH
REMOTE
MUTE
NC
CONTROL
OUTPUT GAIN
LO CUT
MUTE
CIRCUIT
CUT/BOOSTFREQUENCY
BANDWIDTH
PARAMETRIC FILTER
CIRCUIT
MID EQ
CIRCUIT
PARAMETRIC FILTER
FILTER
CIRCUIT
VCA
MIX
BYPASS
EXP/COMP
LOW CUT LOW EQ
MIC GAIN
MIC
PREAMP
+V
MIC
INPUT
PHANTOM
MIC PAD
EXPANDER
LINE
INPUT
LINE
INPUT
CLIP
CUT/BOOSTFREQUENCY
PARAMETRIC FILTER
HIGH EQ
BANDWIDTH
CIRCUIT
GR
3 6 12
9
RATIO THRESHOLD COMPRESSOR COMPRESSOR
GR
3 6 20
12
THRESHOLD
VOLTAGE
CONTROL
CIRCUITRY
Chapter 10

527E
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Warranty & ServiceChapter 11
527E Limited Warranty
Symetrix, Inc. expressly warrants that the product will be free from defects in material and workman-
ship for one (1) year. Symetrix’s obligations under this warranty will be limited to repairing or
replacing, at Symetrix’s option, the part or parts of the product which prove defective in
material or workmanship within one (1) year from date of purchase, provided that the Buyer
gives Symetrix prompt notice of any defect or failure and satisfactory proof thereof. Products
may be returned by Buyer only after a Return Authorization number (RA) has been obtained
from Symetrix. Buyer will prepay all freight charges to return the product to the Symetrix
factory. Symetrix reserves the right to inspect any products which may be the subject of any
warranty claim before repair or replacement is carried out. Symetrix may, at its option, require
proof of the original date of purchase (dated copy of original retail dealer’s invoice). Final
determination of warranty coverage lies solely with Symetrix. Products repaired under warranty
will be returned freight prepaid by Symetrix via United Parcel Service (surface), to any location
within the Continental United States. At Buyer’s request the shipment may be returned via
airfreight at Buyer’s expense. Outside the Continental United States, products will be returned
freight collect.
The foregoing warranties are in lieu of all other warranties, whether oral, written, express,
impliedor statutory. Symetrix,Inc. expressly disclaimsany IMPLIED warranties,including
fitnessfor a particularpurpose or merchantability. Symetrix’swarranty obligation and
buyer’sremedies hereunder are SOLELY and exclusively as stated herein.
This Symetrix product is designed and manufactured for use in professional and studio audio
systems and is not intended for other usage. With respect to products purchased by consum-
ers for personal, family, or household use, Symetrix expressly disclaims all implied warran-
ties, including but not limited to warranties of merchantability and fitness for a particular
purpose.
This limited warranty, with all terms, conditions and disclaimers set forth herein, shall extend
to the original purchaser and anyone who purchases the product within the specified warranty
period.
Warranty Registration must be completed and mailed to Symetrix within thirty (30) days of the
date of purchase.
Symetrix does not authorize any third party, including any dealer or sales representative, to
assume any liability or make any additional warranties or representation regarding this product
information on behalf of Symetrix.
This limited warranty gives the buyer certain rights. You may have additional rights provided
by applicable law.
Limitation of Liability
The total liability of Symetrix on any claim, whether in contract, tort (including negligence) or
otherwise arising out of, connected with, or resulting from the manufacture, sale, delivery,
resale, repair, replacement or use of any product will not exceed the price allocable to the
product or any part thereof which gives rise to the claim. In no event will Symetrix be liable for
any incidental or consequential damages including but not limited to damage for loss of
revenue, cost of capital, claims of customers for service interruptions or failure to supply, and
costs and expenses incurred in connection with labor, overhead, transportation, installation or
removal of products or substitute facilities or supply houses.

527E
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If you have determined that your 527E requires repair services and you live outside of the
United States please contact your local Symetrix dealer or distributor for instructions on how
to obtain service. If you reside in the U.S. then proceed as follows:
At the Symetrix factory, Symetrix will perform in-warranty or out-of-warranty service on any
product it has manufactured for a period of five years from date of manufacture.
Before sending anything to Symetrix, contact our Customer Service Department for a return
authorization (RA) number. The telephone number is [phone], Monday through Friday,
8AM (800 hours) though 4:30 PM (1630 hours), Pacific Time.
In-warranty Repairs
To get your 527E repaired under the terms of the warranty:
1. Call us for an RA number.
2. Pack the unit in its original packaging materials.
3. Include your name, address, daytime telephone number, and a brief
statement of the problem.
4. Write the RA number on the outside of the box.
5. Ship the unit to Symetrix, freight prepaid.
We do not accept freight collect shipments.
Just do these five things, and repairs made in-warranty will cost you only one-way freight
charges. We’ll prepay the return (surface) freight.
If you choose to send us your product in some sort of flimsy packaging, we’ll have to charge
you for proper shipping materials. If you don’t have the factory packaging materials, then do
yourself a favor by using an oversize carton, wrap the unit in a plastic bag, and surround it
with bubble-wrap. Pack the box full of Styrofoam peanuts. Be sure there is enough clearance in
the carton to protect the rack ears (you wouldn’t believe how many units are returned with
bent ears). We won’t return the unit in anything but Symetrix packaging for which we will have
to charge you. Of course, if the problem turns out to be operator inflicted, you’ll have to pay
for both parts and labor. In any event, if there are charges for the repair costs, you will pay for
the return freight. All charges will be COD unless you have made other arrangements (prepaid,
Visa or Mastercard).
Out-of-warranty Repairs
If the warranty period has passed, you’ll be billed for all necessary parts, labor, packaging
materials, and freight charges. Please remember, you must call for an RA number before
sending the unit to Symetrix.