Owner,s Manual Symetrix 572 SPL Computer

Owner,s Manual Symetrix 572 SPL Computer
!"
!"
#$
!"
Symetrix
572
SPL Computer
%&'()
Rev 2.0, 10/01/94
Part number: 530572
!"" # #$
%# " & #' (
) # # ### $
Production Information
This document was written using Microsoft Word for Windows V2.0 and 6.0. The drawings and graphs in
this manual were prepared using Corel Draw V2.0, Autocad V12, and Autoscript V5, then imported into
Word for Windows via encapsulated PostScript files. All page makeup occurred within Word for Windows.
Body text is set in Bookman 10pt and Section Heads are set in various sizes of Helvetica Bold. HelveticaNarrow was used for Figure and Table captions.
This manual was printed directly from PostScript files generated by Word for Windows on a Xerox
Docutech printer. This unique device is actually a laser printer, capable of 600 dpi resolution, with a
page throughput that rivals a high-speed photocopier. As a result, every page is a first-generation image.
Ain’t technology grand?
Table of Contents
1. Introduction.............................................................................................1-1
1.1 Do you have the right unit?.............................................................................. 1-2
1.2 About this manual............................................................................................ 1-2
1.3 Manual Sections.............................................................................................. 1-3
1.4 Operator Safety Summary............................................................................... 1-3
1.4.1 Terms........................................................................................................... 1-3
1.4.2 Equipment Markings..................................................................................... 1-4
1.4.3 Other Safety Information .............................................................................. 1-4
2. Basics......................................................................................................2-1
2.1 How Does It Work? ......................................................................................... 2-1
2.2 What About the Sensing Microphone? ............................................................ 2-1
2.3 Where Should I Put the Sensing Microphone? ................................................ 2-2
2.4 Where Shouldn’t I Put the Sensing Speaker(s)? ............................................. 2-2
2.5 What Does the Ratio Control Do? ................................................................... 2-2
2.6 Remember ...................................................................................................... 2-2
3. Technical Tutorial...................................................................................3-1
3.1 Matching Levels vs Matching Impedances ...................................................... 3-1
3.2 Signal Levels................................................................................................... 3-2
3.3 I/O Impedances............................................................................................... 3-2
3.4 XLR Polarity Convention ................................................................................. 3-2
3.5 Input and Output Connections......................................................................... 3-2
3.6 Condenser Microphones and the 572.............................................................. 3-4
4. Front Panel Overview.............................................................................4-1
4.1 Options, Options and More Options ................................................................ 4-2
5. Rear Panel Overview ..............................................................................5-1
5.1 Rear Panel Features and Connections............................................................ 5-1
5.2 Terminal Strip Connections ............................................................................. 5-2
6. Fast First Time Setup .............................................................................6-1
6.1 What you'll need.............................................................................................. 6-1
6.2 Overview ......................................................................................................... 6-1
6.3 Pre-installation considerations......................................................................... 6-1
6.4 Connections .................................................................................................... 6-2
6.5 Settings ........................................................................................................... 6-3
6.6 Calibration Checklist........................................................................................ 6-4
6.7 Calibration Procedure...................................................................................... 6-4
i
7. Using the 572 ..........................................................................................7-1
7.1 Installation ....................................................................................................... 7-1
7.2 Block Diagram................................................................................................. 7-1
7.3 Operating Mode .............................................................................................. 7-2
7.4 Bypass, CAL and Error Indicators ................................................................... 7-2
7.5 Options, options, options................................................................................. 7-2
7.6 Calibration ....................................................................................................... 7-3
7.7 Quick System Test. ......................................................................................... 7-3
7.8 Options, Options and More Options ................................................................ 7-3
7.9 What Could Go Wrong? .................................................................................. 7-4
7.9.1 The red MUSIC/PAGE lamp flashes during calibration................................. 7-4
7.9.2 The 572 does not accurately adjust the system level as ambient noise changes.
7.10 Using the 572 in High-noise Environments.................................................... 7-5
7.11 Low Frequency Sensitivity............................................................................. 7-5
7.12 Using the 572 With Horn Speakers ............................................................... 7-5
7.13 Using the 572 With Planar or Low Output Speakers...................................... 7-6
7.14 70V Systems ................................................................................................. 7-6
7.15 4, 8, and 16-ohm systems ............................................................................. 7-6
7.16 Using the External Relay Provisions.............................................................. 7-7
7.17 What Does the Ratio Control Do? ................................................................. 7-7
7.18 Monitoring the VCA Gain Via the Vc Terminal ............................................... 7-8
7.19 Calibration Issues.......................................................................................... 7-8
7.20 Effects Of Calibration Level On Performance. ............................................... 7-8
7.21 Summary Of Level Considerations: ............................................................... 7-9
8. Applications ............................................................................................8-1
8.1 Factories ......................................................................................................... 8-1
8.2 Restaurants, Bars & Theme Stores ................................................................. 8-1
8.3 Shopping Malls................................................................................................ 8-1
8.4 Auditoriums and Hotel Lobbies........................................................................ 8-1
8.5 Sports Facilities ............................................................................................... 8-2
8.6 Off-Track Betting Parlors and Casinos ............................................................ 8-2
8.7 Museums ........................................................................................................ 8-2
8.8 Airports, Train Stations, etc. ............................................................................ 8-2
8.9 Race Tracks .................................................................................................... 8-2
9. Troubleshooting Chart...........................................................................9-1
10. Repair and Warranty Information........................................................10-1
10.1 Return Authorization...................................................................................... 10-1
10.2 In-Warranty Repairs ...................................................................................... 10-1
10.3 Out-of-Warranty Repairs ............................................................................... 10-1
10.4 Symetrix 572 SPL Computer Limited Warranty ............................................. 10-2
10.4.1 Limitation of Liability ................................................................................... 10-2
11. Specifications .......................................................................................11-1
Appendix A. Architect’s and Engineer’s Specification ...........................A-1
Appendix B. External Sensing and Multi-unit Installations ....................B-1
ii
7-4
SAMPLE
INTERVAL
10
BYPASS
PAGE
MIC
GAIN
SENSE
GAIN
MUSIC/
SENSE PAGE
5
1.
LOW
HIGH
RATIO
S E NS E :
CALIBRATE
OU T P U T
26
MINUTES
LEVEL SET (dB)
-10
20
1
NORM
BYPASS
PAGE OVER
MUSIC
15
GAIN (dB)
0
15
(dB)
2:1
1:2
(dB)
2
5
9
15 20 26 30 40
MUSIC/PAGE ERROR
-15
-5
-20
0
MIN
SPL
COMPUTER
10
5
15
0
20
MAX
A BCD
1
2
3
4
OPTIONS
Introduction
The Symetrix 572 is an ambient noise sensing automatic level controller or SPL computer. The
572 does the following:
The sound system’s loudspeakers are used as microphones to sample the noise level in the
coverage zone of the sound system. Since the loudspeakers can’t be used simultaneously as
microphones and loudspeakers (not on this planet, at least), the 572 performs its ambient
noise sampling during silent periods in the incoming program.
If the incoming program material lacks silent periods, the 572 forces a sampling period that
interrupts the program audio. The frequency of the sampling period depends on the setting
of the unit’s sample interval control.
The 572’s microprocessor, running proprietary embedded software, computes how loud the
sound system should be given the current ambient conditions. The gain computation uses
combination of the current ambient and “experience” gained during the unit’s on-site
calibration procedure.
The 572 adds or subtracts enough gain to operate the sound system at the computed level.
Semi-automatic calibration makes the 572 very easy to set up. The calibration procedure
requires no test equipment1 and typically takes less than one minute. Internal non-volatile
memory stores the calibration parameters until they are changed and the memory will survive
indefinitely in the absense of ac power. Once calibrated, the 572 predicts how the environment
should respond under all possible operating conditions. Once calibrated, the SPL computer can
differentiate between environmental noise and music/paging signals, so there’s never a
problem with runaway gain or feedback.
You calibrate the SPL computer and its associated sound system when the room is at its
quietest. Pressing the mode switch tells the microprocessor to begin the calibration routine.
When the SET MIN indicator flashes, use the LEVEL SET MIN control to set the sound system’s
minimum output level. When the SET MAX indicator flashes, use the LEVEL SET MAX control to
set the sound system’s maximum operating level. The SPL computer puts those settings into
memory along with their respective SPL’s, then returns the unit to normal operating mode. No
test equipment is required for most situations.
The 572 also includes a mic-level paging input, a balanced line-level paging input, a balanced
input for background or foreground music, and page-over music capability (music ducking).
A multi-segment LED bargraph indicates the 572’s internal gain during operation and serves as
a prompting device during calibration.
For its inputs, the 572 uses a combination of XLR connectors and screw terminals. The output
connections are also screw terminals. All audio inputs and outputs are balanced. The mic-level
1
A sound level meter is helpful but not essential.
Rev 2.0, 10/01/94
1-1
page input accepts a 150-ohm balanced source. Line-level inputs are 10-kilohm balanced
bridging, +4 dBu signal level.
1.1 Do you have the right unit?
Symetrix makes two different SPL computers: the 571 and the 572. Although both units
perform essentially the same task, they are different.
The 571 requires an external sensing microphone(s) to monitor ambient conditions. The 571
works in real time; adjustments are made continuously, regardless of music, paging, or silence.
The 571 does not interrupt the signal path at any time.
The 572 uses the sound system loudspeaker(s) to monitor ambient conditions. Doing this
requires the 572 to monitor the incoming program material for silent sections. Once the 572
detects silence, it switches to sense mode, switching the loudspeaker(s) from the amplifier
output to its sense input. Sensing takes one to two seconds. Any signal applied to the paging
inputs during this time immediately terminates the sense period. If a silent period never
occurs, the 572 forces one. A front-panel control controls the forced sensing period. Sensing
may also be triggered externally. The 572 interrupts the signal path during sensing.
Table 1-1 provides a tabular comparison of the two units.
Table 1-1. 571 - 572 Feature comparison.
Feature
Uses dedicated microphone for ambient sensing
571
Y
572
N
Uses sound system speakers for ambient sensing
N
Y
Sound system loudness controlled by ambient noise
conditions
Y
Y
Continuous, real time operation
Y
N
Program silence sensing triggers ambient sense period
N
Y
Mic and line level paging inputs
Y
Y
Page over music (ducking)
Y
Y
Music + page mixing
Y
Y
Calibration required
Y
Y
Timed ambient sensing
N
Y
Interrupts signal path during sensing
N
Y
1.2 About this manual
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, both
technical as well as musical.
If you're in a hurry (like most of us), or if you really don't believe that someone could write a
decent owners manual that you can read and understand, then do us both a favor and read the
remainder of this section and Section 6, "Fast First Time Setup." This section will help you get
connected, tell you what the knobs do, and send you on your way.
1-2
Rev 2.0, 10/01/94
1.3 Manual Sections
This manual contains the following sections:
Chapter 1. Introduction introduces the 572 and this manual. Describes important safety
information
Chapter 2. Basics lets you know what the 572 does, and how it does it.
Chapter 3. Technical Tutorial a basic and not-so-basic discussion of signal levels, input and
output impedances, and connection polarity.
Chapter 4. Front Panel Overview gives a brief look at the controls and switches of the 572.
Chapter 5. Rear Panel Overview gives a brief look at the connectors of the 572.
Chapter 6. Fast, First Time Setup is a section written especially for people who just can't wait to
get their hands on the knobs.
Chapter 7. Using the 572 describes the use of the 572 in detail.
Chapter 8. Applications describes some of the myriad uses for the 572.
Chapter 9. Troubleshooting tells what to do if the 572 doesn't work.
Chapter 10. Repair and Warranty Information tells how to get your 572 repaired and describes
the 572's Limited Warranty.
Chapter 11. Specifications lists the technical specifications of the 572's performance.
Appendix A. Appendix A contains the Architect’s and Engineer's specifications.
Appendix B. Appendix B tells how to use the external sense feature and how to connect
multiple 572s together in large installations.
1.4 Operator Safety Summary
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; they do not appear in this summary.
1.4.1 Terms
Several notational conventions are used in this manual. Some paragraphs may use Note,
Caution, or Warning as a heading. These headings have the following meaning:
Convention
Description
Caution
Identifies information that, if not heeded, may cause
damage to the 572 or other equipment in your system.
Note
Identifies information that needs extra emphasis. A Note
generally supplies extra information to help you use the
572 better.
Warning
Identifies information that, if ignored, may be
hazardous to your health or that of others.
In addition, certain typefaces and capitalization are used to identify certain words. These
situations are:
Convention
Meaning
CAPITALS
Controls, switches or other markings on the chassis.
Boldface
Strong emphasis.
Rev 2.0, 10/01/94
1-3
Finally, two symbols are used as visual hints. They are:
Symbol
Meaning
Helping hand. A hint to make your life a bit easier.
The Bomb. A visual way of saying, “Caution!”
1.4.2 Equipment Markings
The notational conventions used on the equipment itself are described in the following
paragraphs. These markings may also be used within this manual.
The lightning flash with
arrowhead symbol within
an equilateral triangle is
intended to alert the user
to 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.
CAUTION
RISK OF ELECTRIC SHOCK
DO NOT OPEN
DE CHOC ELECTRIQUE
ATTENTION: RISQUE
NE PAS OUVRIR
No user serviceable parts inside. Refer servicing to qualified service personnel.
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
S’adresser a un reparateur compétent.
The exclamation point
within an equilateral
triangle is intended to
alert the user to the
presence of important
operating and
maintenance (servicing)
instructions in the
literature accompanying
the appliance (i.e. this
manual).
Caution: To prevent electric shock, do not use the polarized plug supplied with this appliance
with any extension cord, receptacle, or other outlet unless the blades can be fully inserted to
prevent blade exposure.
1.4.3 Other Safety Information
The following paragraphs discuss other safety-related issues.
Power Source
This product is intended to operate from a power source
that does not apply more than 250V 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.
Danger from Loss of
Ground
If the protective ground connection is lost, all accessible
conductive parts, including knobs and controls that may
appear to be insulated, can render an electric shock.
1-4
Rev 2.0, 10/01/94
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.
Proper Fuse
The user accessible fuse is mounted on the rear panel.
For 117V ac operation, the correct value is 1/4A, 250V
ac, fast blowing (Bussman type AGC-1/4). The
fuseholder accepts American sized fuses (1/4 in dia.).
For 230V ac (export) operation, the correct value is
1/8A, 250V ac, fast blowing (Bussman type GDA125mA). The fuseholder accepts European 5 x 20mm
fuses.
Operating Location
Do not operate this equipment under any of the
following conditions: explosive atmospheres, in wet
locations, in inclement weather, improper or unknown
AC mains voltage, or if improperly fused.
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.
User-serviceable parts
There are no user serviceable parts inside the 572. In
case of failure, refer all servicing to the factory.
Rev 2.0, 10/01/94
1-5
Notes
1-6
Rev 2.0, 10/01/94
2.
Basics
An SPL computer periodically samples the ambient sound in a room. Having this information,
the SPL computer uses a combination of historical data and information stored during the
unit’s initial calibration to determine the optimum gain setting for the sound system.
How does it work? How do I get the best ambient samples? We’ll answer these questions, and
more, in this chapter.
2.1 How Does It Work?
The 572 uses the combination of analog circuitry and digital circuitry under the control of a
microprocessor. The microprocessor excels at following a set of instructions and making
decisions. Since really high-performance digital audio circuitry is still quite expensive, the 572
uses a recording studio-quality voltage-controlled-amplifier (VCA) to control audio levels.
In operation, the 572 monitors its input signals for silence. Anytime that silence occurs (an
option switch allows changing the silence threshold), the 572 switches to sense mode. In sense
mode, the 572 reduces the amplifier input by at least 30 dB, the loudspeakers are disconnected
from the power amplifier and connected to a high-gain differential amplifier (which cancels the
hum and other junk picked up by the unshielded speaker wires). The 572's microprocessor
monitors the output of the sense preamp and compares that signal to the calibration conditions
stored in the 572's parameter storage RAM, and at the last sample period. Based on this
information and the front-panel settings, the 572 decides how loud the sound system must
operate to restore audibility.
The 572 also has an internal timer, controlled by the front-panel SAMPLE INTERVAL control that
forces a sample if there haven't been any silent periods in the input signal. Anytime that the
input signal causes a sample period, the timer resets. If the input material has sufficient silent
periods, the timer-generated sample periods never occur.
In CAL mode, the 572 aquires a history of the environment’s sonic behavior. The 572 takes
three measurements: the environment’s minimum level, the sound system’s minimum level,
and the sound system’s maximum level. By running the system for about 8 seconds at the
desired minimum and maximum sound pressure levels, the microprocessor remembers these
three key performance parameters, which are automatically stored in non-volatile memory.
During calibration, the installer sets minimum and maximum levels—the 572 “reads” the
controls as they are changed, and stays in the appropriate calibration mode for about 8
seconds after the last change is made. This allows the installer time to re-set operating levels as
necessary.
When the system switches itself back to operate mode, the acoustical performance history
acquired during calibration becomes the baseline for gain change decisions. In operate mode,
the system goes about measuring environmental noise levels and internal signal levels. Because
the computer has already comitted to memory the parameters stored during calibration, it is
able to predict the gain setting required.
2.2 What About the Sensing Microphone?
Microphone? What microphone? The 572 doesn’t use sensing microphones. It does use the
sound system’s loudspeakers as microphones during sensing1. There aren’t many constraints
on your choice of loudspeakers. Horn-type speakers are more directional as well as being highly
efficient (both as speakers and as microphones). We have found that planar-type speakers do
not work well as microphones (but there is a workaround described in chapter 7). Internally,
1
There is no way to use a sensing microphone with the 572. The Symetrix 571 does, however,
use microphones for ambient sensing.
Rev 2.0, 10/01/94
2-1
the sense signal drives a bandpass filter (A-weighting approximation) before the 572 measures
its level (strength).
2.3 Where Should I Put the Sensing Microphone?
The sensing microphone needs to “hear” the ambient sound within the controlled space. In
large spaces it may be better to only use a few of the sound system speakers for sensing.
In the remainder of this manual, we’ll use the term “sensing speaker” to mean a speaker that is
connected to the 572’s TO SPEAKER terminals that is used during sensing periods as a
microphone.
2.4 Where Shouldn’t I Put the Sensing Speaker(s)?
Avoid the following situations:
Placing the sensing speaker(s) where it is within the noise field of a machine or other noise
source, unless you want the source’s noise contribution to more or less control the level of
the sound system. For example, how about a speaker in a newspaper plant near one of the
printing press(es).
Placing the sensing speakers where they always hear a nearby noise source. For instance,
how about a shopping mall near the kiddie area. You can work around this by connecting
these speakers to the TO AMP terminals so that they aren’t used for sensing.
2.5 What Does the Ratio Control Do?
The RATIO control acts much the same as the ratio control on a compressor or expander: it
affects the amount of change at the output for a given change at the input. In the 572, the
RATIO control determines how much the output changes for a given change at the sense input.
In the 12:00 position, the ratio is 1:1; a 1 dB sense change results in a 1 dB output change.
Turning the RATIO control clockwise results in expansion: in the 1:2 position (full CW), a 2 dB
change at the sense input results in a 4 dB output change. Turning the RATIO control
counterclockwise results in compression: in the 2:1 position, a 2 dB sense input change results
in only a 1 dB output change.
Use the RATIO control when you either want the 572 to more than keep up with the crowd
(expansion), or when you want it to lag behind when the crowd is loud (compression). Another
reason to use "compression" might be when the available amplifier power is limited. Last, you
must decide whether or not you want the sound system to be capable of "out-shouting" the
crowd.
2.6 Remember
2-2
Calibration must occur when the noise level in the controlled space is at it’s normal
minimum (which may or may not be dead quiet).
It helps if you have an estimate (SPL) of the maximum level required.
The sound system must be capable of attaining the maximum level required.
You can learn a great deal by listening to the sensing speakers. You’ll need an external
microphone preamp to do this.
You may need to create a second non-controlled zone to prevent the sound system level
from changing in spaces where the ambient condtions are stable (rest rooms, elevators,
break rooms, etc.)
Rev 2.0, 10/01/94
3.
Technical Tutorial
This section discusses a multitude of things, all related to getting signals in and out of the 572.
3.1 Matching Levels vs Matching Impedances
In any audio equipment application, the question of "matching" inevitably comes up. Without
digging a hole any deeper than absolutely necessary, we offer the following discussion to
(hopefully) clarify your understanding of the subject.
Over the years, we have all had impedance matching pounded into our heads. This is important
only for ancient audio systems, power amplifiers, and RF. Technically speaking, the reason is
power transfer, which reaches a maximum when source and load are matched. Modern audio
systems are voltage transmission systems and source and load matching is not only
unnecessary, but undesirable as well.
Ancient audio systems operate at 600 ohms (or some other impedance value), and must be
matched, both at their inputs and at their outputs. Generally speaking, if you are dealing
with equipment that uses vacuum tubes, or was designed prior to 1970, you should be
concerned about matching. These units were designed when audio systems were based on
maximum power transfer, hence the need for input/output matching.
Power amplifiers are fussy because an abnormally low load impedance generally means a
visit to the amp hospital. Thus, it's important to know what the total impedance of the pile
of speakers connected to the amplifier really is.
RF systems are matched because we really are concerned with maximum power transfer
and with matching the impedance of the transmission line (keeps nasty things from
happening). Video signals (composite, baseband, or otherwise) should be treated like RF.
Some folks seem to believe that balanced/unbalanced lines and impedances are related; or
even worse that they are associated with a particular type of connector. Not so. Unbalanced
signals are not necessarily high-impedance and balanced signals/lines are not necessarily lowimpedance. Similarly, although 1/4-inch jacks are typically used for things like guitars (which
are high-impedance and unbalanced), this does not predispose them to only this usage. After
all, 1/4-inch jacks are sometimes used for loudspeakers, which are anything but highimpedance. Therefore, the presence of 3-pin XLR connectors should not be construed to mean
that the input or output is low-impedance (or high-impedance). The same applies to 1/4-inch
jacks.
So, what is really important? Signal level, and (to a much lesser degree), the impedance relation
between an output (signal source) and the input that it connects to (signal receiver).
Signal level is very important. Mismatch causes either loss of headroom or loss of signal-tonoise ratio. Thus, microphone inputs should only see signals originating from a microphone, a
direct (DI) box, or an output designated microphone-level output. Electrically, this is in the
range of approximately -70 to -20 dBm. Line inputs should only see signals in the -10 to +24
dBm/dBu range. Guitars, high-impedance microphones, and many electronic keyboards do not
qualify as line-level sources.
The impedance relation between outputs and inputs needs to be considered, but only in the
following way:
Always make sure that a device's input impedance is higher than the output
source impedance of the device that drives it.
Some manufacturers state a relatively high-impedance figure as the output impedance of their
equipment. What they really mean is that this is the minimum load impedance that they would
like their gear to see. In most cases, seeing a output impedance figure of 10,000 (10K) ohms or
higher from modern equipment that requires power (batteries or AC) is an instance of this type
Rev 2.0, 10/01/94
3-1
of rating. If so, then the input impedance of the succeeding input must be equal to or greater
than the output impedance of the driving device.
Symetrix equipment inputs are designed to bridge (be greater than 10 times the actual source
impedance) the output of whatever device drives the input. Symetrix equipment outputs are
designed to drive 600-ohm or higher loads (600-ohm loads are an archaic practice that won't go
away). You don't need to terminate the output with a 600-ohm resistor if you aren't driving a
600-ohm load. If you don't understand the concept of termination, you probably don't need to
anyway.
The two facts that you need to derive from this discussion are:
1.
2.
Match signal levels for best headroom and signal-to-noise ratio.
For audio, impedance matching is only needed for antique equipment and power amplifier
outputs. In all other cases, ensure that your inputs bridge (are in the range of 2 to 200
times the output source impedance) your outputs.
3.2 Signal Levels
The 572 is designed around studio/professional line levels: +4 dBu or 1.23 volts. The unit is
quiet enough to operate at lower signal levels such as those found in semi-pro or
musical-instrument (MI) equipment (-10 dBV or 316 millivolts).
3.3 I/O Impedances
The 572 is designed to interface into almost any sound reinforcement application or
background/foreground music application. This includes:
600-ohm systems where input and output impedances are matched.
Unbalanced semi-professional equipment applications.
Modern bridging systems where inputs bridge and outputs are low source impedances
(voltage transmission systems).
The 572's line input impedance is 40-kilohms balanced, and 40-kilohms unbalanced. The line
inputs may be driven from any source (balanced or unbalanced) capable of delivering at least 10 dBV into the aforementioned impedances.
3.4 XLR Polarity Convention
The 572 uses the international standard
polarity convention of pin 2 hot. The table at
the right shows the connections for each type of
connector.
XLR
Tip-RingSleeve
Signal
1
2
3
Sleeve
Tip
Ring
Ground
High
Low
3.5 Input and Output Connections
Figure 3-1 illustrates how to connect the 572 to various balanced and unbalanced sources.
To operate the 572’s balanced line inputs from unbalanced sources, run a 2-conductor shielded
cable (that's two conductors plus the shield) from the source to the 572. At the source, connect
the low/minus side to the shield, these connect to the source's ground; connect the high/plus
side to the source's signal connection. At the 572, the high/plus wire connects to the screw
terminal marked with a “+”, the low/minus wire connects to the screw terminal marked with a
“—”, and the shield (always) connects to screw terminal marked GND.. This is preferred as it
makes best use of the 572's balanced input (even though the source is unbalanced). The other
alternative shown in Figure 3-1 converts the 572's balanced input into an unbalanced input at
the 572’s input terminals. This works, but is more susceptible to hum and buzz than the
preferred method. There is no level difference either way.
3-2
Rev 2.0, 10/01/94
We do not recommend unbalancing the 572’s microphone input. Doing so makes these inputs
considerably more susceptible to hum and induced noise.
FROM BALANCED OUT
2 31
TO BALANCED IN
231
FEMALE XLR
PIN 1 = GROUND
PIN 2 = HIGH
PIN 3 = LOW
MALE XLR
PIN 1 = GROUND
PIN 2 = HIGH
PIN 3 = LOW
FROM BALANCED OUT
TIP
MALE TRS PLUG
TIP = HIGH
RING = LOW
SLEEVE = GROUND
RING
SLEEVE
TO UNBALANCED IN FROM
TRANSFORMER COUPLED OR
FLOATING BALANCED OUTPUT
MALE TS PLUG
TIP = HIGH
SLEEVE = GROUND +
LOW
FROM UNBALANCED OUT
MALE TS PLUG
TIP = HIGH
SLEEVE = GROUND +
LOW
TO BALANCED IN
FROM BALANCED OUT
TERMINAL STRIP
(+) = HIGH
(-) = LOW
= GROUND
TIP
RING
MALE TRS PLUG
TIP = HIGH
RING = LOW
SLEEVE = GROUND
SLEEVE
TO BALANCED IN
FROM UNBALANCED OUT
TERMINAL STRIP
(+) = HIGH
(-) = NOT USED
= GROUND
FROM NON-TRANSFORMER (ELECTRONIC)
BALANCED OUTPUT
(TYPICAL OF SYMETRIX PRODUCTS)
-
2 31
FEMALE XLR
PIN 1 = GROUND + LOW
PIN 2 = HIGH
PIN 3 = NOT USED
TERMINAL STRIP
(+) = HIGH
(-) = LOW
= GROUND
TO UNBALANCED IN
MALE TS PLUG
TIP = HIGH
SLEEVE = GROUND +
LOW
REV-B
Figure 3-1. Input and output connector wiring. These diagrams represent the majority of connectors used in
modern audio equipment. Locate the source connector in the left column and match it up with the
destination connector in the right column. Wire your cable according to the diagrams.
Rev 2.0, 10/01/94
3-3
3.6 Condenser Microphones and the 572
The 572’s paging microphone input is not equipped with phantom powering for condenser
microphones. If you wish to use a phantom powered microphone, you must provide a power
source externally.
Note. The microphone input is direct coupled; there are no dc blocking capacitors. If you use a
phantom powered microphone, the phantom supply voltage must be 15 volts or less1. If your
particular microphone operates at a higher supply voltage than 15 volts, the phantom power
supply must dc-block its output using capacitors or a transformer.
1
15 volts is the common-mode limitation of the microphone preamp.
3-4
Rev 2.0, 10/01/94
4.
Front Panel Overview
SAMPLE
INTERVAL
10
BYPASS
PAGE
MIC
GAIN
SENSE
GAIN
MUSIC/
SENSE PAGE
LOW
HIGH
RATIO
S E NS E :
CALIBRATE
OU T P U T
LEVEL SET (dB)
-10
SPL
COMPUTER
10
GAIN (dB)
5
20
-15
2
1
NORM
BYPASS
PAGE OVER
MUSIC
15
26
MINUTES
0
15
(dB)
2:1
5
9
5
15
A BCD
15 20 26 30 40
-20
1:2
(dB)
-5
0
0
20
MAX
MUSIC/PAGE ERROR
1
2
3
4
OPTIONS
MIN
Feature
Description
BYPASS switch
When depressed, resistively mixes the line level
music and page inputs and hardwires them to
the output terminals. The 572 will pass signal
regardless of it’s operational status. The 572
works just fine when it’s happy.
PAGE MIC GAIN trimpot
Screwdriver adjust level control provides up to
26 dB attenuation of signals from the page mic
input.
SENSE GAIN switch
Determines the gain of the sense preamp. When
the switch has been depressed, the sense
preamp’s gain is 40 dB higher. Use option switch
B to help you determine the correct setting for
this switch.
SENSE LED
LED indicator indicates that the 572 is sensing
the ambient conditions in the controlled area.
MUSIC/PAGE LED
LED indicator indicates that the 572 is in its
music/page mode.
SAMPLE INTERVAL control
This control sets the time period between forced
samples to compute sound pressure level
changes. If the 572 takes a silence-caused
sample during this time period, the sample
interval timer is reset. If the incoming program
material has enough silent periods, forced
sampling will never occur. This control is
disabled in external trigger mode.
PAGE OVER MUSIC control
Determines how much music signals are
attenuated (ducked) during paging, from 0 to 15
dB.
RATIO control
Sets the ambient gain ratio: from 2:1 to 1:2. This
determines whether the 572 makes a smaller
change than the ambient (2:1) or a larger change
than the ambient (1:2).
GAIN LED display
LED bargraph that indicates the amount of gain
being added to the sound system by the 572. In
cal mode, the display serves as an errorcondition indicator and as a prompting device.
LEVEL SET MIN control
Active only during calibration; sets the minimum
operating level of the sound system: from 0 to
-20 dB.
LEVEL SET MAX control
Active only during calibration; sets the maximum
operating level of the sound system: from 0 to
+20 dB.
Rev 2.0, 10/01/94
4-1
CALIBRATE switch
Momentary switch alternates the 572’s mode
from operate to calibrate. Operate is the initial
power-up state, and is indicated during use by
the LED display showing gain change and either
the sense or music/page LED being activated.
Depressing the CALIBRATE switch once alternates
states to calibration mode as indicated by
flashing SET MIN indicator on the LED bargraph
display.
Options DIP switch
These four switches allow several of the 572’s
operating parameters to be adjusted.
4.1 Options, Options and More Options
The option switches allow tailoring the 572 to different installation scenarios.
Option A sets the music silence threshold. This threshold is the signal level at the MUSIC LINE
INPUT that the 572 considers silent. Signals below this threshold are considered silent, and are
fair game for sense intervals.
In installations where the ambient noise level is fairly low, and where the background music
has a great deal of dynamic range (like classical music from a CD player), you may need to keep
the signal level through the 572 quite high, as well as using the lower silence threshold, and
reducing the gain at the power amplifier input to put the music back to a comfortable level.
This prevents the 572 from punching holes in the program material during quiet passages.
Option B enables sense view which forces the 572 to sense mode and displays
the sense preamplifier on the front-panel bargraph. Use
option B to view the signal level returned from the
Option
loudspeakers in sense mode and to verify that the signal level
switch A
falls within the 572's limits for proper operation. The ideal
indication should fall between the 5 dB and 26 dB LEDs on
UP
the calibration display. If necessary, use the SENSE GAIN
DOWN
switch on the front panel. Don't leave SENSE VIEW engaged as
Option
it prevents normal operation!
Switch B
Option C enables sample averaging. If option switch C is
UP
down, the 572 computes the gain change solely on the basis
DOWN
of the current sample. If option switch C is up, the 572
computes the gain change based on the average of the current
Option
sample and the running average level (the 572 then squirrels
Switch C
away the new average for the next sample period).
UP
Option D enables the EXTERNAL SENSE feature accessed from
TB2-3 on the rear panel. Use this feature as described in
DOWN
Appendix B of the manual, or to force a sense period based on
Option
an external contact closure (sense triggering occurs whenever
Switch D
TB2-3 is connected to TB2-4/ground). Option D, when
enabled, disables the SAMPLE INTERVAL timer and the 572 will
UP
only enter sense mode when TB2-3 is grounded.
Down
the output of
Silence
Threshold
-20 dBu
-35 dBu
Sense View
Enabled
Disabled
Sample
Averaging
Running
Average
No Average
External
Sense
Enabled
Disabled
Table 4-1.
Option Switch Settings
4-2
Rev 2.0, 10/01/94
5.
Rear Panel Overview
FUSE:
1/2 AMP (100VAC)
1/2 AMP (117VAC)
1/4 AMP (220/240VAC)
FROM
TO
SPEAKER AMP
EXT
RELAY
CNTRL
EXT
SENSE
TRIG
SPARE
LINE
OUTPUT
P RE S S
LINE INPUTS
PAGE
MUSIC
Vc
PAGE
MIC
FUSE
S/N
THIS PRODUCT CONTAINS NO USER SERVICABLE PARTS
MANUFACTURED BY SYMETRIX INC, SEATTLE, WA, USA
T B2 1 0
9
8
7
6
5
4
3
2
1
T B1 1 0
9
8
7
6
5
4
3
2
1
5.1 Rear Panel Features and Connections
Feature
Description
Serial Number
Do yourself a favor and write this number down somewhere
safe, and while you’re at it, please send us the completed
warranty card?
AC Power Input
Power cord. Connect only to appropriate AC power source.
Refer to rear-panel marking for correct AC source value.
FUSE
AC mains fuse. Replace only with same type of fuse, as noted
on the rear of the chassis.
Domestic: 1/4A, 250V ac, fast blowing (Bussman type AGC1/4)
Export: 1/8A, 250V ac, fast blowing (Bussman type GDA125mA)
PAGE MIC INPUT
Rev 2.0, 10/01/94
Balanced, mic level input for paging microphone. Phantom
powering is not present. If using a phantom powered
microphone, ensure that the phantom voltage does not exceed
15V. Higher voltages may be used if the powering device
contains blocking capacitors or isolation transformers to
prevent the phantom supply voltage from appearing at the
mic input of the 572.
5-1
5.2 Terminal Strip Connections
Feature
Term. #
Description
TO SPEAKER
TB2(10,9)
Connect speakers used for sensing and sound system usage
here. Speakers may be speaker impedance or constant voltage.
FROM AMP
TB2(8,7)
Connect amplifier here. Amplifier output may be speaker
impedance or constant voltage.
GROUNDS
TB2(6,4,2)
Connect to circuit ground inside the 572.
EXT RELAY
CNTRL
TB2(5)
NPN open collector output for driving external relay. You must
supply power for the relay coil. Remember to connect a diode
across the relay coil to absorb the back EMF generated by the
relay coil. The maximum voltage at this point is 40 V dc at 625
mA.
EXT SENSE
TRIG
TB2(3)
Active low input. When option switch D is up, grounding this
terminal forces a sense operation. The unit remains in sense
mode for as long as this terminal is grounded. The terminal
must remain grounded for at least one second in order to
perform sensing.
SPARE
TB2(1)
Not used, not connected.
GROUNDS
TB1(10,6,3)
Connect to circuit ground inside the 572.
LINE OUTPUT
TB1(9,8)
Balanced (differential) output of the 572.
For unbalanced usage, use TB1(9) and TB1(10). TB1(8) should
float.
VC
TB1(7)
Monitor point for the control voltage for the VCA. The gain
relationship is -159mv/dB. Use this voltage to verify that the
VCA is actually being told to change the gain or to connect a
stereo-slave unit.
PAGE INPUT
TB1(5,4)
Balanced line-level input for paging signals. Signals at these
terminals cause signals applied to the music inputs to
attenuate (duck). For unbalanced signals, use TB1(5) for signal
and connect TB1(6,4) to ground.
MUSIC INPUT
TB1(2,1)
Balanced line-level for music signals. Normally used for
background music. Signals applied to these terminals are
attenuated (ducked) whenever signals are present at either of
the page inputs.
5-2
Rev 2.0, 10/01/94
6.
Fast First Time Setup
Follow these instructions to get your 572 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.
6.1 What you'll need
To install a 572, you'll need the following items:
1.
2.
3.
4.
5.
6.
The 572.
Access to the power amplifier input (line level), mixer output (line level), power amplifier
output (speaker level), speaker line connections.
Background music feed (usually the mixer line output).
Paging feed (line or mic level or both) preferably separate from the background music feed.
A time where the ambient noise level in the loudspeaker coverage area is at its normal
minimum. This is the level at which the 572 begins raising the level. Thus, it should NOT
be when the space is dead quiet, unless that is the normal minimum.
Program audio and paging signals during calibration.
6.2 Overview
The following points of information must be considered during system design and installation.
Place the 572 in the signal chain as the final level controlling device.
Equalizers following the 572 are acceptable IF their controls (both EQ and level) will not be
changed after calibration.
It is imperative that any gain or level controls used in the signal chain after the 572 remain
unchanged once the unit has been calibrated. This includes wall mounted autoformer and
L-pad speaker-level controls used for zone balancing.
Level controls in the signal chain before the SPL Computer are acceptable, because the unit
“reads” input level changes.
Calibrate the 572 when the coverage zone’s ambient noise level is it’s nominal
minimum.
“Nominal minimum” means whatever ambient noise level is the minimum for that
particular environment, no matter what the actual level may be. It should not be dead silent
unless that is normal.
The ambient noise level measured by the 571 during the calibration procedure is used by
the microprocessor to calculate gain changes. As a result, the unit doesn’t care what the
actual ambient noise level is during calibration. However, the overall control range may be
inadequate if the noise level is too high during calibration.
During calibration, run normal program signals through the system.
This allows the SPL Computer to develop an acoustical performance history of the
environment based upon the type of material that will ordinarily be run through the
system. No extra test equipment is required for normal calibration. However, to set the
system up for specific operating levels, a noise source and SPL meter are needed
6.3 Pre-installation considerations
Before installing the 572, be sure that you've considered the following items:
1.
Ambient noise sources in the loudspeaker coverage area. Are there any noise sources near
any of the speakers used for sensing?
2.
It is not necessary to use all speakers for sensing.
Rev 2.0, 10/01/94
6-1
3.
If the speakers are wired using the "home run" method1, then you'll have extra flexibility in
excluding specific speakers from the speakers used for ambient sensing (if needed).
4.
The speaker wiring should be separate from any AC or other EMI-noisy wiring. Neither side
of the wiring can be grounded, except at the amplifier.
5.
Horn speakers may require modification of the 572, especially if the ambient noise level is
high.
6.
There can be no user adjustable level controls in the speaker lines.
7.
Once calibrated, it is not permissible to alter the settings of any level controls that are
electrically located after the 572.
8.
If there are multiple loudspeaker zones, there probably ought to be a separate 572 for each
zone.
9.
If the power amplifier is larger than 300 watts (70-volt systems), 200 watts (8-ohm
systems), or 100 watts (4-ohm systems), then the internal 5-amp relay can't handle the
load current. You must use an external relay.
10. It is good to know the minimum and maximum ambient levels (dB SPL) that the system is
expected to handle. Of course, the sound system should be able to exceed the maximum
ambient by 3-6 dB (unless it's in the design that the system can't out-shout the crowd).
11. It's preferable that the 572 mix the paging signals with the background music or other
signals internally through its separate paging and music inputs (as opposed to supplying
the 572 with a mix of everything). The 572 monitors its paging inputs and immediately
terminates a sense period when a paging signal is present. This is not true for the music
input.
12. Loudspeakers from "alien" systems (sound systems located within the sensing zone of the
572, but not under control of the 572) can cause unwanted gain changes.
6.4 Connections
A drawing of a typical music with paging system is shown in . Make all of the following
connections:
1. Paging microphone (or mic-level mixer output) to the PAGE MIC XLR connector. Remember
that mic or line paging sources duck the signal connected to the MUSIC input.
2. Line-level paging source (or other source) to the PAGE terminals on TB1. Remember that
mic or line paging sources duck the signal connected to the MUSIC input.
3. Background or foreground music source to the MUSIC terminals on TB1. Signals connected
to this input are ducked (attenuated) by signals present on either of the PAGE inputs.
4. SPL Computer output from TB1 to your sound system’s amplifier(s).
5. Your sound system’s amplifier output to the 572’s FROM AMP terminals on TB2.
6. The speaker output of the 572 to the sound system speakers in the controlled zone.
1 The home run method of wiring brings each speaker (or sometimes a sub-group of speakers)
to the amplifier on its own pair of wires. The usual method is to wire from speaker to speaker,
which saves wire at the expense of flexibility.
6-2
Rev 2.0, 10/01/94
Figure 6-1. 572 generic hookup diagram.
Connect the powerline 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 572 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.
6.5 Settings
Set the controls and switches on the front and rear panel as shown in Table 6-1.
Table 6-1. Front and rear panel control and switch settings.
Front Panel Control
BYPASS switch
Setting
out (NORM)
PAGE MIC gain
12:00 o’clock
SENSE GAIN switch
SAMPLE INTERVAL
PAGE OVER MUSIC
RATIO
LEVEL SET MIN
LEVEL SET MAX
OPTION switches
out (HIGH)
Rev 2.0, 10/01/94
8:00 o'clock
Rear Panel
OUTPUT
PAGE MIC
MUSIC IN
PAGE IN
Setting
Connect to power amplifiers.
Connect balanced, low-impedance
page microphone here.
Connect line-level music source here.
Connect line-level paging source here.
8:00 o'clock
12:00 o’clock
9:00 o’clock
8:00 o’clock
All down
6-3
6.6 Calibration Checklist
You initiate the calibration procedure by pressing the MODE switch once (from OPERATE mode).
Complete the following checklist before beginning the calibration procedure.
Complete all input and output connections.
Apply power to the 572.
Verify that the unit passes signal in the BYPASS mode. Enter BYPASS mode by depressing
the BYPASS switch. Return the BYPASS switch to the OUT position. You should still have
audio.
Set option switch B to the UP position (sense view). Observe the LED bargraph. There
should be at one LED on, up to a maximum of 7 LEDs on. If no LEDs are on, depress the
SENSE GAIN switch. Leave the switch in whatever position results in a reading between the
first and last LEDs in the bargraph.
Set the front and rear panel controls as shown in Table 6-1.
Caution
The 572 resistively mixes its line inputs in Bypass mode. This can cause
attenuation whose amount depends upon the actual source devices as well as the
amplifier(s) conncected to the unit’s outputs.
The 572 delivers unity gain when the output is operated unbalanced, and the gain
is +6 dB wshen the output is operated balanced.
6.7 Calibration Procedure
1. Apply program or paging signals to the 572’s input(s).
2. Press the MODE switch once to enter CALibration mode.
3. Using the 572’s LEVEL SET MIN control, adjust the control for the minimum desired
operating level when the LED bargraph indicator marked SET MIN flashes.
4. Using the 572’s LEVEL SET MAX control, adjust the control for the maximum desired
operating level when the LED bargraph indicator marked SET MAX flashes.
The 572 “listens” to the sound system for about 8 seconds at the minimum level (after it detects
the last adjustment of the MIN control), and then for about 8 seconds at the maximum level
(after the last adjustment of the MAX control). Then the microprocessor returns the unit to
OPERATE mode under the new calibration values.
When the calibration procedure is completed, the acoustic performance record of the room is
placed in non-volatile memory along with the minimum and maximum level settings. The unit
will operate under these calibration settings until the calibration procedure is run again.
The calibration procedure may be run as many times as necessary. If for any reason the
procedure is interrupted before completion, the unit returns to operate mode under the
previously stored values. If the procedure is run to completion with no changes, the unit
calculates the same values as it did under the previous calibration procedure, and puts those
new values into non-volatile memory. Only when the level set max or LEVEL SET MIN setting is
changed does the unit put new operating values into memory.
You can force sensing by turning the sample interval control to 1 and then quickly returning it
to 5. You can also force sensing by using option switch D and TB2-3.
6-4
Rev 2.0, 10/01/94
7.
Using the 572
This section is intended for more advanced users. If you are a first-time user, we recommend
that you start out by using the procedure found in "Fast, First-Time Setup."
7.1 Installation
The 572 may be installed free-standing or rack mounted. There no special ventilation
requirements for single or multiple units.
Installation Requirements
Mechanical
One rack space (1.75 inches) required, 12.5 inches depth (including
connector allowance).
Electrical
105-125 VAC, 18 Watts maximum.
Domestic fuse: 1/4A, 250V ac, fast blowing (Bussman type AGC-1/4)
Export (230V ac) fuse: 1/8A, 250V ac, fast blowing (Bussman type
GDA-125mA)
Connectors
XLR-3 female and screw terminals for inputs. Pin 2 of the XLR
connectors is "Hot." Screw terminals for outputs and other
connections.
7.2 Block Diagram
On the following page you will find the block diagram for the 572. Please take a moment and
take note of the following:
The balanced input amplifiers (mic and line) are direct coupled. This is only noteworthy if
there is significant common-mode dc voltages present on the signal lines (greater than 15V).
Phantom powering for condenser microphones falls into this category.
The EXT RELAY CNTRL terminal is the open collector of a 2N4401 NPN transistor . You must
supply power for any external relay used. The transistor’s limits are: VCEO = 40V and Icmax =
625 mA.
In when the BYPASS switch is pressed, the line-level MUSIC and PAGE inputs are resistively
mixed and sent to the outputs. There is no automatic hard-wire bypass in the event of a
power failure.
Paging signals (mic and line) are mixed and drive the ducker (PAGE OVER MUSIC) circuitry.
The EXT SENSE TRIG input is not edge driven. The 572 remains in sense mode as long as
this input is held low.
Option switch B switches the LED bargraph to read the output of the sense preamplifier
and forces the 572 into sense mode. This allows you to make sure that you have enough
signal level for proper ambient sensing. The correct reading is more than one LED lit and
less than all LEDs lit under all ambient conditions. The sense gain switch located on the
front panel changes the gain of the sense preamp. Use either setting as long as the LED
bargraph reads as described earlier.
The relay contacts used to switch the speakers to and from sense have a 5 ampere rating. If
your load requires more current than this, use the EXT RELAY CNTRL terminal (TB2-5) to
control an external high-current relay.
Rev 2.0, 10/01/94
7-1
TB1
PAGE MIC
GAIN
10
9
LINE
OUTPUT
8
PRESS
TB2
VCA
PAGE MIC
10
9
TB1
8
PAGE 4
LINE 5
INPUTS 6
7
TO
SPEAKER
FROM
AMP
HARDWARE BYPASS
PAGE OVER
MUSIC
+5V
PAGE
DETECTOR
RATIO
SAMPLE
INTERVAL
MIN
MAX
SENSE
GAIN
A
B
JP1
MULTIPLEX AND A/D CONVERTER
TB1
MUSIC 1
LINE 2
INPUT 3
MUSIC
VCA
BYPASS
VCA
TB1
"GAIN" DISPLAY
TB2
Vc
7 OUT
D/A
CONVERTER
2
5
9
15
20
25
30
4 EXTERNAL
RELAY
5
CONTROLL
40
MICROPROCESSOR
+5V
REV-B
+5V
+5V
A
1 2
MODE
PUSHBUTTON
B
3 4
OPTIONS
TB2
JP2-A.G.C.
THRESHOLD
3 2
EXT SENSE
TRIGGER
Figure 7-1. 572 Block Diagram.
7.3 Operating Mode
The 572 has three operating modes: OPERATE, CALIBRATE, and BYPASS. You access these
modes by sequentially operating the MODE switch or by pressing the BYPASS switch. Each push
of the mode switch toggles the operating mode between CALIBRATE and OPERATE.
7.4 Bypass, CAL and Error Indicators
The front-panel LED bargraph also serves as a status indicator. Two of
the LEDs serve as prompts during calibration, one other LED serves as
an error indicator during calibration.
If the error indicator flashes during calibration, the calibration
procedure automatically aborts and the 572 returns to operate mode
using the calibration values previously stored in non-volatile memory.
The 572 cannot be recalibrated until the problem causing the error is
corrected.
Figure 7-2 LED Bargraph
7.5 Options, options, options
The 572 has many operational options, mostly controlled by a 4-wide DIP switch located on the
front panel. The microprocessor scans the switches continuously; any changes in their settings
are acted upon almost instantaneously.
7-2
Rev 2.0, 10/01/94
The four option switches set the music silence threshold level, sense view (displays sense level
on front panel bargraph), ambient sample averaging, and external sense control.
7.6 Calibration
must be performed when the ambient noise in the loudspeaker coverage area is at
☞ Calibration
its normal minimum level for the area. (NOT dead quiet, unless that is normal.)
1.
Complete all input and output connections. There must be program audio present at a
LINE INPUT connection before calibration can be completed. If the system is used for paging,
activate the paging system by having an assistant count or recite the alphabet during the
entire calibration procedure. The audio input level must be greater than -35 dBu or the
572 will not recognize the presence of audio and the MUSIC/PAGE ERROR light will flash.
2. Warn any people present that sound system may get momentarily loud.
3. Set the front panel controls as described in Table 6-1..
4. Verify that program audio is audible in the system speakers.
5. Set the system power amplifier's volume control to a comfortably loud level. Do not
readjust this control after calibration of the 572 or your calibration will be invalid.
6. Set the BYPASS switch to the OUT position.
7. Use a pencil to push the CALIBRATE button in and then release it.
8. The red MIN lamp lights. Adjust the MIN CALIBRATE knob to a comfortable listening level.
The system audio level will stay at this level for 10 seconds. This level is the minimum level
that the 572 allows in the space, regardless of how quiet the ambient noise level may be or
get.
9. When the red MAX lamp lights adjust the MAX CALIBRATE knob to set the system level to as
loud as you ever want the volume to go during noisy times. Check that the power
amplifier(s) aren't clipping. The system audio level will return to normal in 10 seconds. It
may be helpful to monitor the acoustical level in the space with a sound level meter.
10. Calibration is complete. The 572 will adjust the system level as the ambient noise in the
area increases.
7.7 Quick System Test.
❒
While talking loudly or making noise near a system speaker turn the SAMPLE INTERVAL
control to "1" and then quickly return it to "5". This forces the system to sense. The
system level should increase in response to the increase in ambient noise.
❒
While remaining quiet, turn the SAMPLE INTERVAL control to "1" and then quickly return it to
"5". This forces another sense. The system level should return to the minimum level.
7.8 Options, Options and More Options
The option switches allow tailoring the 572 to different installation scenarios. There are four
option switches.
Option A sets the music silence threshold. This threshold is the signal level at the MUSIC LINE
INPUT that the 572 considers silent. Signals below this threshold are considered silent, and are
fair game for sense intervals.
In installations where the ambient noise level is fairly low, and where the background music
has a great deal of dynamic range (like classical music from a CD player), you may need to keep
the signal level through the 572 quite high, as well as using the lower silence threshold, and
reducing the gain at the power amplifier input to put the music back to a comfortable level.
This prevents the 572 from punching holes in the program material during quiet passages.
Option B forces the 572 to sense mode and displays the output of the sense preamplifier on
the front-panel bargraph. Use option B to view the signal level returned from the loudspeakers
in sense mode and to verify that the signal level falls within the 572's limits for proper
Rev 2.0, 10/01/94
7-3
operation. The ideal indication should fall between the 5 dB
and 26 dB LEDs on the calibration display. If necessary, use
the SENSE GAIN switch on the front panel. Don't leave SENSE
VIEW engaged as it prevents normal operation!
Option
switch A
Silence
Threshold
UP
DOWN
-20 dBu
-35 dBu
Option
Switch B
Sense View
UP
DOWN
Enabled
Disabled
Option D enables the EXTERNAL SENSE feature accessed from
TB2-3 on the rear panel. Use this feature as described in
Appendix B of this manual, or to force a sense period based on
an external contact closure (sense triggering occurs when TB23 is connected to TB2-4/ground). The 572 remains in sense
mode for the duration of the contact closure. This option also
disables the SAMPLE INTERVAL timer and the 572 will only enter
sense mode when TB2-3 is grounded.
Option
Switch C
Sample
Averaging
UP
DOWN
Running
Average
No Average
Option
Switch D
External
Sense
7.9 What Could Go Wrong?
UP
Down
Enabled
Disabled
Option C enables sample averaging. If option switch C is
down, the 572 computes the gain change solely on the basis of
the current sample. If option switch C is up, the 572 computes
the gain change based on the average of the current sample
and the running average level (the 572 then squirrels away the
new average for the next sample period).
Here are the two most common situations and some things to
look for.
Table 7-1.
Option Switch Settings
7.9.1 The red MUSIC/PAGE lamp flashes during
calibration
1.
2.
3.
There is no audio at the LINE INPUT from the program source. In a PAGING ONLY system
there must be a page in progress during the entire calibration procedure.
The audio input level to the 572 is too low. With the OPTIONS dip switch "A" in the up
position the input level must be greater than -20 dBu. If the switch is in the down position
the input level must be greater than -35 dB.
There are no speakers connected to terminals 9 and 10, TO SPEAKER. The 572 uses the
system speakers as microphones when sensing.
7.9.2 The 572 does not accurately adjust the system level as ambient noise
changes.
1.
2.
3.
4.
7-4
Repeat the calibration procedure. Calibration must be made during times of minimum
background noise or the minimum system level will be inaccurate.
If the maximum level was set too high during calibration the system will get too loud as
the background noise level increases.
If the maximum level was set too low the system will not be loud enough when the
ambient noise level reaches its peak.
Ensure that all speakers are operating in-phase.
Rev 2.0, 10/01/94
5.
☞ 6.
7.
8.
If hum is being induced in the
speaker wiring the 572 will treat
this noise as "sense" audio when
sensing. Make sure that the
speaker wiring is not routed next to
AC wiring or unrelated 70V speaker
wiring. Disconnect the speakers
from the system and using a
microphone preamplifier connected
to the speaker(s), listen in
headphones to what the 572
"hears" when it is sensing. Listen
Figure 7-3 Using a microphone preamp to hear the
for any noises that could falsely
sense speakers.
trigger a gain change. Listen for
any hum or buzz.
The accuracy of the 572 is only as good as the sample audio that your speakers
provide when the unit is sensing. If any of the system speakers are located near noisy
equipment such as vending machines, ice machines, air conditioning blowers, or separate
paging speakers the level of the 572 system will increase disproportionately with the noise
level of the noisy equipment. Disconnect the speakers from the system, connect them to
the input of a balanced, low-impedance microphone preamp (like the Symetrix SX202) and
listen in headphones to what the 572 "hears" when it is sampling!
Check Chapter 9 in this manual.
If all else fails, call Symetrix.
7.10 Using the 572 in High-noise Environments
In noisy locations, it's important to locate the speakers where they do the most good, both for
the listener as well as the 572. Remember that if the speaker is next to a noisy machine, the
machine's noise output will probably cause the 572 to raise the level when the machine is
operating. If this isn't desirable, then exclude that particular speaker from the speakers used
for sensing by connect the offending speaker(s) directly to the amplifier output, bypassing the
572. In other cases, directional (horn) speakers may help by directing the sound to the listener.
Horns are also more efficient, making your amplifier power go further. You can also put a
sensing speaker somewhere where the noise level is more representative of the average noise
level in the space even though there may not be anyone who can hear it. On the other hand,
this may be a more appropriate application for the 571 (which uses a sensing microphone).
Be sure to read the Appendix B in the manual before embarking on a multi-zone, multi-572
system design.
7.11 Low Frequency Sensitivity.
The sensing circuit of the 572 includes a 3-pole high pass filter. The 572 will not respond to
background noise below 300 Hz. This design makes the system insensitive to building rumble
and air handling noise. The sense circuit responds to signals between 500 Hz and 15 kHz.
7.12 Using the 572 With Horn Speakers
Several users have had difficulty getting the 572 to calibrate and operate properly when
connected to strings of high gain horn speakers in high noise environments. The horns
returned too much signal to the 572 when it was sampling, which overloaded the A/D
converter. In one case we were able to get the system to operate by increasing R13 and R14 to
91K0. If you set option switch B UP and the sense level indication exceeds the 26 dB LED in
both positions of the SENSE GAIN switch, you need to increase R13 and R14.
In other cases using a single speaker as the sensing transducer was the only answer. In these
cases the output of the power amplifier connects directly to the speaker string and the single
Rev 2.0, 10/01/94
7-5
sampling speaker is wired to TB2-9 and TB2-10 (TO SPEAKER terminals) of the 572. Terminals
TB2-7 and 8 (FROM POWER AMP) are not connected. When the 572 samples it only looks at the
single speaker for a reference level of ambient noise. In these cases the Symetrix 571 should
have been specified for the job!
7.13 Using the 572 With Planar or Low Output Speakers
Some speakers make lousy microphones. In a situation like this, we recommend using a
separate speaker(s) for sensing. To do this, connect all of the speakers used to produce sound
to the amplifier output. Connect all of the speakers used for sensing to the 572’s TO SPEAKER
terminals. If you wish these speakers to produce sound, then connect the 572’s FROM AMP
terminals to the amplifier output, otherwise leave the FROM AMP terminals unconnected.
During sensing, the 572 sets the VCA to about 30 dB attenuation, so the speakers connected
directly to the amplifier outputs are effectively silenced.
7.14 70V Systems
The 572 has been designed with both 70V (or other constant-voltage system) and speakerimpedance systems. Aside from the amount of current flowing through the 572's sense relay,
the only other difference arises from the signal level returned by the speakers when the 572
switches to sense mode. In 70V systems, the signal level is higher, because of the step-up
action of the line transformers. With highly-efficient speakers, this may present a problem
because the sense input of the 572 may be overloaded. Use option switch B to check the level
coming back. Refer also to section 4.2. in this document. The sense relay's 5A contact current
limit forces a 300-watt wattage limit for 70V systems.
70V systems, it is common practice to provide autotransformers or L-pads after the line
Intransformer
to allow local volume control. NOT! Allowing any sort of level control after the 572
invalidates the settings made during calibration. If you must provide a local level control, then
ensure that the controlled zone is a minor part of the entire system, that the users understand
that the volume level of the system may not always be ideal, and (finally) that the locally
controlled zone is not used for sensing.
Finally, it is imperative that every speaker and transformer in the system operates in-phase.
7.15 4, 8, and 16-ohm systems
In 4, 8, and 16-ohm systems (speaker-impedance
systems), the levels returned to the 572 are low; you'll
probably need to use the high-gain position of the SENSE
GAIN switch. The 5A contact current limit forces the
following limitations:
Impedance
16-ohms
8-ohms
4-ohms
Limit
400 watts
200 watts
100 watts
Refer also to the paragraph regarding zone volume controls in the preceding section.
7-6
Rev 2.0, 10/01/94
7.16 Using the External Relay Provisions
When controlling
amplifiers larger than
200 watts (8-ohms)
you really should be
using the Symetrix
571. If you insist on
using the 572, you
must use an external
DPDT relay. The 572's
internal relay cannot
handle more than 5amps of load current.
This corresponds to
300 watts at 70V, 200
watts at 8-ohms, and
100 watts at 4-ohms.
The 24-volt version of
the Potter & Brumfield
PRD11DGO works
well. Its DPDT
contacts are rated at
30 amps. Figure 7-4
shows how to connect
everything.
The 572 provides a
contact closure
through a transistor
switch to operate the
external relay. This
closure can be found
on the rear panel
barrier strip TB2-5
which is labeled EXT
RELAY CNTRL. Terminal
TB2-6 is ground. Wire
the negative output of
Figure 7-4 Using the External Relay connections.
your external power
supply to TB2-6 (Ground). Connect the positive output of the power supply to one side of the
external relay coil. Connect the other side of the relay coil to TB2-5. The user supplied power
supply and external relay coil circuit is closed whenever the 572 goes into the SENSE mode. Be
sure to put a back-biased diode (1N4002 or better) across the relay coil.
7.17 What Does the Ratio Control Do?
The ratio control acts much the same as the ratio control on a compressor or expander: it
affects the amount of change at the output for a given change at the input. In the 572, the
RATIO control determines how much the output changes for a given change at the sense input.
In the 12:00 position, the ratio is 1:1; a 1 dB sense change results in a 1 dB output change.
Turning the RATIO control clockwise results in expansion: in the 1:2 position (full CW), a 2 dB
change at the sense input results in a 4 dB output change. Turning the ratio control
counterclockwise results in compression: in the 2:1 position, a 2 dB sense input change results
in only a 1 dB output change.
Rev 2.0, 10/01/94
7-7
Use the ratio control when you either want the 572 to more than keep up with the crowd
(expansion), or when you want it to lag behind when the crowd is loud (compression). Another
reason to use "compression" might be when the available amplifier power is limited. Last, you
must decide whether or not you want the sound system to be capable of "out-shouting" the
crowd.
☞ 7.18
Monitoring the VCA Gain Via the Vc Terminal
You can monitor what the VCA is doing via the VC terminal on TB1-7. The gain relationship is
-159 mv/dB. Don't worry about what the actual value of the gain or loss (it's unity gain @ 0 V),
it's the change in gain and the actual starting/stopping values that count. For instance, after
calibration, the VCA control voltage is sitting at 1 volt (-6.289 dB loss through the VCA). After
the first sense interval, the control voltage now sits at -1 volt (about 6.289 dB gain). The VCA
gain has changed by 12.58 dB (overall gain increase). The front panel gain display will read 9.
☞ 7.19
Calibration Issues
If you want the 572 to operate correctly then proper calibration is an absolute necessity. The
calibration procedure establishes the high and low limits (level-wise) for the sound system. It
also establishes the baseline noise level for the space. Therefore, it is imperative that the
calibration be performed at a time when the space is at or near its nominal minimum and that
you have the ability to operate the sound system at its maximum desired level for short periods
of time.
It is not possible to calibrate the 572 properly at other than the lowest normal ambient for the
space. Do not calibrate when the space is dead quiet, unless that is the lowest normal ambient
level.
7.20 Effects Of Calibration Level On Performance.
The calibration procedure sets two gain values (MINL and MAXL), and establishes a baseline
SPL threshold level (BTL). The baseline SPL threshold is the lowest SPL that the 572 will
respond to. Below the BTL, there will be no gain changes. Thus, the level set by the MIN pot
during calibration becomes the minimum output level (MINL) of the 572. If the room ambient
falls below the BTL, the output of the 572 remains at MINL.
The MAXL corresponds to the maximum output level of the 572, regardless of the setting of the
RATIO control, or the ambient noise level. The rule here is the change in ambient level times the
slope may not exceed MAXL. If the computed gain change passes the test, then that value
drives the VCA, if not, then the change is limited to MAXL.
If the BTL level is too low, relative to the actual minimum ambient level (AMAL), then the 572
could run out of control range. This is what would occur if you tried to use silence to set the
BTL. If the AMAL level is marginally too low, then simply ensure that there is a low enough MIN
setting to allow the sound system to track this minimum level. On the other hand, you could
establish a minimum level (to ensure that the sound system is always heard) by making this
the difference between the BTL and MINL.
If the BTL level is higher than the AMAL, then the sound system is likely to be too loud when
the space is at its quietest. Reducing the amplifier gain will work, but you must ensure that
there is enough gain-change range (difference between MIN and MAX controls) to keep up with
a noisy environment.
7-8
Rev 2.0, 10/01/94
☞
7.21 Summary Of Level Considerations:
1. It is best to try to hit the Baseline SPL Threshold Level on the head, or certainly within 6
dB.
2. Be sure that you have more Maximum Level than you need, which will help compensate if
the
3. Baseline SPL Threshold Level is higher than the Actual Minimum Ambient Level.
Rev 2.0, 10/01/94
7-9
Notes
7-10
Rev 2.0, 10/01/94
8.
Applications
Here are a few applications that the 572 lends itself to. It’s important in every one of these
applications (actually, any 572 application) that the unit has been properly calibrated and that
the program material has sufficient silence periods for ambient sensing.
8.1 Factories
In this application, the 572 monitors the ambient noise level within a factory and adjusts the
sound system’s operating level to ensure that it is always audible. Ensure that all speakers that
are used for sensing are installed so that they receive an average of the noise sources within
the space to ensure that a loud, localized noise source does not dominate the control of the
sound system. For speakers that are near a noise source, you may need to wire these speakers
directly to the power amplifier, bypassing the 572. If the sound system needs to be heard
consistently in spite of the localized noise source, you may need to create a controlled zone at
the source by dedicating a 572, speaker(s) and an amplifier to that purpose.
Speakers serving “quiet zones,” such as break rooms, offices, and restrooms, should probably
be on their own amplifier, fed from the input of the 572 (so that they are unaffected by the
572).
8.2 Restaurants, Bars & Theme Stores
All of these establishments have one thing in common: they all use background or foreground
music as an integral part of their ambiance. The volume level of the music is important;
audible, but not too audible. How audible is not the judgement of the kid that works the
counter. It’s a management decision. The 572 helps guarantee the audibility of the music
regardless of actual conditions during operation.
Again, picking the right speaker locations is the key. In a restaurant, avoid using speakers near
the kitchen, entry areas, and espresso machines for sensing.
In bars and lounges, keep any speakers mounted near the blenders and dishwashers behind
the bar out of the sensing circuit. Remember that any extraneous sound sources (like the TV in
a sports bar) will be regarded as extra ambient noise by the 572 and the sound system level will
increase as a result. You can try to avoid this by running the TV sound through the 572 so that
the TV sound becomes part of the 572’s throughput. The 572 will force a sample if it doesn’t see
silent periods that are long enough to use for sensing in the TV programming. This could be a
problem during “Monday Night Football.”
8.3 Shopping Malls
In this application, the 572 ensures that announcements within the public spaces are always
audible, but never too loud. In mall applications, it’s a good idea to wire speakers mounted near
localized noise sources (like the kiddie area) directly to the power amp so that they are not used
for sensing. Like the factory application, you want the sense speakers to average out all of the
various noise sources within the mall.
For high-noise areas, it’s a good idea to create separate coverage zones each with their own
572.
8.4 Auditoriums and Hotel Lobbies
Here the 572 keeps track of the ambient conditions in the outer areas such as the lobbies and
foyers. If you have speakers in the rest rooms, these speakers should probably not be under the
572’s control since these areas are generally more subdued than the outer areas and you
wouldn’t want flushing a toilet to raise the SPL in the lobby (or maybe you do...).
Rev 2.0, 10/01/94
8-1
8.5 Sports Facilities
Sports facilities, like auditoriums, can benefit from the 572. Again, the 572 tracks the ambient
conditions on the concourses, other access areas, and the refreshment stands. Consider using
multple 572s to isolate specific noise sources and their environments from each other, such as
the refreshment stands from the concourse environment. Since the 572 uses the existing
speakers, this could be an aftermarket add-on.
8.6 Off-Track Betting Parlors and Casinos
In these facilities, the crowd reaction is likely to be sudden and intense. If the program material
doesn’t have long enough silent spots for sensing, the 571 is a better idea since it works in real
time.
In casinos, be sure to place the to average the crowd and the machines, especially the dollar
machine with the 20-jillion dollar jackpot.
8.7 Museums
Now why would you want to put a 572 into a museum? When the museum has an overall
paging system. That when.
What about when the museum has automated exhibits? That’s not when. Use a 571 instead
because the 571 works in real time. The time delays between sensing periods and operating
periods would most likely result in sound systems that are too loud for the current ambient
condition.
8.8 Airports, Train Stations, etc.
The 572 is ideally suited to managing the SPLs within airports and other transportation hubs.
Within airports, use at least one 572 per paging zone.
In subway stations, pick a speaker location that favors the crowd but still ‘hears’ the trains.
Doing so ensures that the level increases when a train is present.
Make sure that there are sufficient silent periods for sensing. You can use the mic-level page
input for the local paging mic and the line-level paging input for facility-wide paging. Use the
music input for background music, if any.
8.9 Race Tracks
Different race tracks have different noise sources. In auto racing, the cars usually make more
noise than the spectators. If you’re going to apply a 572 to a speedway, position the speakers so
they are in a good spot to pick up the cars as well as the crowd.
If this isn’t practical, consider using a small paging speaker(s), with a 70V transformer1 that is
only used as a microphone. Use a moderate transformer tap, like 10 watts. You may even be
able to do away with the transformer. Use shielded twisted-pair cable and don’t forget to tie the
shield to the case of the speaker (or float it if it’s plastic or to avoid a ground loop.). Position the
speaker so it has a nearby view of the stands and connect it to the 572’s TO SPEAKER
terminals. Do not connect the amplifier to the FROM AMP terminals. Instead, connect the
amplifier directly to the other loudspeakers.
In horse (and dog) racing, the spectators make more noise than the animals. In this case, the
spectator area speakers serve as expected, both for paging as well as for sensing.
1
The ElectroVoice PA15BT-7 or PA30-AT are both suitable units.
8-2
Rev 2.0, 10/01/94
Use a short AVERAGING TIME. Ensure that the program material has enough dead spots to
ensure frequent sensing. Definitely use a live mic when calibrating. Beware of acoustic
feedback, especially when calibrating the MAX level.
Rev 2.0, 10/01/94
8-3
Notes
8-4
Rev 2.0, 10/01/94
9.
Troubleshooting Chart
Symptom
Probable Cause
No output
Check cables and connections.
Are inputs driven by outputs, and outputs driving
inputs?
Are all of the cables good?
Is there signal coming out of the source?
Is the signal chain after the 572 functioning?
Check for AC power presence. Power LED on?
Is the fuse OK?
Unit won’t calibrate
Are input levels normal?
Use Option Switch B to check sense gain. Change
setting of SENSE GAIN switch.
MUSIC/PAGE LED flashes during
No audio at either line input or the page mic input.
Input signal level too low. Change Option Switch A to
the UP position.
Speakers not connected at TO SPEAKERS terminals.
calibration.
Music always plays too loud
MIN and/or MAX levels set incorrectly during
calibration.
Unit seems to have no effect
Check the RATIO control. At 2:1, the gain changes are
very subtle.
Bad calibration. Repeat calibration procedure during
quiet time.
MAX level set too low.
Unit never senses, even during
silence
Option switch D up. Change switch setting.
Unit loses the beginnings of
paging messages
Paging signals should always drive the PAGE LINE INPUT
or the PAGE MIC INPUT.
Unit does not accurately adjust
system as ambient noise changes
Bad calibration. Repeat procedure during quiet time.
Hum induced in speaker wiring. Ensure that speaker
wiring is not routed adjacent to ac wiring.
Disconnect speakers from 572 and connect to low-Z
balanced mic preamp (such as the Symetrix SX202)
and listen on headphones.
Speaker mounted near continuous noise source. Take
the speaker out of the sensing system by connecting it
directly to the amplifier output.
The accuracy of the 572 is only as good as the sample
audio that the speakers provide during sensing.
Unit interrupts the program
audio
Yes. It sure does. Since the 572 uses the system
speakers to sense ambient noise, it must break the
circuit in order to sample.
Unit interrupts paging.
Use either of the PAGE inputs. They have a higher
priority than the music input.
Rev 2.0, 10/01/94
9-1
Unit senses during paging.
Caused by long silent pauses during paging. If it
REALLY is a problem, increase the value of C32. This
also increases the recovery time for the music input
after a page.
You can guarantee NO INTERRUPTIONS by specifying a
Symetrix 571.
Music does not duck enough
during paging
Replace R64 (PAGE OVER MUSIC control) with 1megohm fixed resistor.
Need to duck music/program in
response to external signal.
Feed music/program audio to MUSIC LINE INPUT.
Remove C40 (4.7F/50V). Connect external signal to
PAGE LINE INPUT terminals.
Hum or buzz in output
Check input connector wiring (refer to Figure 3.3).
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?
Line input signal may be too hot.
Page mic signal may be too hot.
Does the sound system have sufficient power for the
SPL that you’re trying to attain? Reduce MAX setting.
Is something else clipping?
Noise (hiss)
Check input signal levels, and level control settings.
Check gain settings on downstream equipment.
Is the input signal already noisy?
Blows fuses
Replace fuse, turn unit on. If the fuse blows again, call
the doctor.
No nothing
Is the unit plugged in?
Is the unit in BYPASS mode?
Unit not plugged in, but works
anyway
Need schematics?
Call us
Call the factory at (800) 288-8855.
Note: Repeated fuse blowing is a sure sign of electronic distress. If you replace the fuse once
and it blows again, it's time to get the unit repaired. Replacing the fuse with one of greater
amperage is an invitation to an expensive disaster (not to mention a fire hazard!).
9-2
Rev 2.0, 10/01/94
10.
Repair and Warranty Information
Should you decide to return your 572 to Symetrix for service, please follow the following
instructions.
10.1 Return Authorization
Symetrix will service any of its products for a period of five years from the date of manufacture.
However, no goods will be accepted without a Return Authorization number.
BEFORE SENDING ANYTHING TO SYMETRIX, CALL US FOR AN RA NUMBER.
JUST ASK, WE'LL GLADLY GIVE YOU ONE! CALL (206) 787-3222 WEEKDAYS, 8AM
TO 4:30 PM PACIFIC TIME.
10.2 In-Warranty Repairs
To get your unit 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, etc. and a brief statement of the problem. Your daytime
telephone number is very useful if we can't duplicate your problem.
4.
Put the RA number on the outside of the box.
5.
Ship the unit to Symetrix, freight prepaid.
Just do those five things, and repairs made in-warranty will cost you only the one-way freight
fee. We'll pay the return freight.
If you choose to send us your product in some sort of flimsy, non-Symetrix 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. Use additional
bubble-wrap if you must ship more than one unit per carton. Be sure there is enough clearance
in the carton to protect the rack ears (you wouldn't believe how many units we see here with
bent ears). We won't return the unit in anything but original Symetrix packaging. 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 return freight. All charges
will be COD unless you have made other arrangements (prepaid, Visa or Mastercard).
10.3 Out-of-Warranty Repairs
If the warranty period has passed, you'll be billed for all necessary parts, labor, packaging
materials, and any applicable freight charges.
Remember, you must call for an RA number before you send the unit to Symetrix.
This Symetrix product is designed and manufactured for use in professional and studio audio
systems. Symetrix, Inc. (Symetrix) warrants that this product, manufactured by Symetrix,
when properly installed, used, and maintained in accordance with the instructions contained in
the product's operator's manual, will perform according to the specifications set forth in the
operator's manual.
Rev 2.0, 10/01/94
10-1
10.4 Symetrix 572 SPL Computer Limited Warranty
Symetrix expressly warrants that the product will be free from defects in material and
workmanship for one (1) year. Symetrix' obligations under this warranty will be limited to
repairing or replacing, at Symetrix' 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 and Buyer will prepay all freight charges to return any products 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 via United Parcel Service by Symetrix, to any location
within the Continental United States. 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,
implied or statutory. Symetrix, expressly disclaims any IMPLIED warranties, including
fitness for a particular purpose or merchantability. Symetrix's warranty obligation and
buyer's remedies 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 consumers
for personal, family, or household use, Symetrix expressly disclaims all implied warranties,
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.
10.4.1 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.
10-2
Rev 2.0, 10/01/94
11. Specifications
Input/Output
Inputs
All inputs are balanced, transformerless.
Page Mic: XLR-female, balanced low impedance, 40 dBu nominal level..NOT phantom powered.
Music: screw terminals, 40-kilohms balanced
bridging, -10 dBu nominal level.
Page: screw terminals, 40-kilohms balanced
bridging, 0 dBu nominal level.
Output
Balanced, transformerless.
Screw terminals, +24 dBm maximum into 600 ohm
balanced load. 100-ohm source impedance.
Control Voltage output
Unscaled drive signal to the VCA. V = -156 mV/dB
Gain (VCA at unity)
Balanced input to unbalanced output: 0 dB
Unbalanced input to balanced output: 6 dB
Balanced input to balanced output: 6 dB
CMRR
Page Mic: greater than 60 dB @ 1 kHz
House Page (line): greater than 40 dB @ 1kHz
Music: greater than 40 dB @ 1 kHz
Maximum input levels
Mic input: -30 dBu
Line inputs: +18 dBu
Performance Data
Maximum control range
40 dB ( 20dB)
Ambient Noise-to-Gain ratio
Variable, 2:1 to 1:2
Sample Interval
Forced: Variable, 1 min to 26 min
Auto: Silent periods < -30 dBu, > 800 ms
Frequency Response
20-20kHz +0, -1 dB
Noise floor (30 kHz bandwidth)
Better than -85 dBu @ unity gain.
Distortion (THD+N)
< .05% @ 1 kHz, unity gain, music input to line
output.
Page-Over Music
Variable, 0 to 15 dB
Physical
Size (hwd), in & cm
1.75 x 19 x 7.5 in
4.45 x 48.3 x 19.5 cm
Weight, lbs & kg
8 lbs (3.6 kg) net
11 lbs (5 kg) shipping
Electrical
Power requirements
117V ac, 50-60 Hz, 12 watts
230V ac, 50 Hz, 12 watts.
In the interest of continuous product improvement, Symetrix Inc. reserves the right to alter, change, or modify these
specifications without prior notice.
Rev 2.0, 10/01/94
11-1
Notes
11-2
Rev 2.0, 10/01/94
Appendix A.
Architect’s and Engineer’s Specification
The ambient sensing automatic level controlling device shall regulate the operating level of a
sound system in proportion to changing noise levels in the sound system’s operating area. The
device shall be capable of adjusting gain control over 40 dB overall (max) range, and shall be
governed by a microprocessor which shall be controlled by embedded software. The device shall
vary its gain based upon measurements of the sound pressure level of ambient noise in the
environment. These sound level measurements shall be made by the level controlling device
through the loudspeakers otherwise used for the system’s output.
To facilitate the use of the system’s loudspeakers as noise measuring “microphones,” the device
shall provide relay switching of the speaker line circuit so as to disconnect the speakers from
the amplifier output and to connect the speakers to its own sensing input.
The device shall provide inputs for paging signals at microphone level (nominal -40 dBu) or line
level (nominal 0 dBu), and for music signals at line level (nominal -10 dBu).
The device shall have a ratio control to vary the ambient-noise-to-gain ratio continuously from
2:1 to 1:2, and a front panel switchable hard-wired bypass. Calibration of the automatic level
controlling device shall be semi-automatic, and shall require switching the device to CAL mode,
and adjusting the minimum desired operating level and the maximum desired operating level.
Calibration settings shall be continuously maintained in non-volatile memory without the need
for battery back up power.
In addition to the various functions and general specifications mentioned above, the ambient
sensing automatic level controlling device shall meet or exceed the following overall
performance criteria: frequency response 1 dB 20 Hz to 20 kHz, total harmonic distortion less
than 0.05% at any attenuation from -40 dB to 0 dB (2 kHz), maximum paging microphone
input level -30 dBu, maximum line input level +18 dBu, maximum output level +24 dBm into
600-ohms balanced. Minimum impedance at the microphone inputs shall be 1800 ohms,
minimum impedance at the line inputs shall be 40 kilohms.
The device shall be housed in an all steel chassis designed to be mounted in a 1U (1.75”) space
in a standard 19” rack.
The ambient sensing automatic level controlling device shall be the Symetrix model 572 SPL
Computer.
Rev 2.0, 10/01/94
A-1
Notes
A-2
Rev 2.0, 10/01/94
Appendix B.
External Sensing and Multi-unit Installations
Option switch D enables the external sense input and prevents both periodic sensing and
silence-based sensing. When option switch D is UP, sensing only occurs when TB2-3 is held
low (grounded). The unit remains in sense mode for as long as TB2-3 is grounded and you must
ground the external sense line for a minimum of one second.
You use this feature when it is inappropriate to interrupt the program material based on either
time or silence. Of course, you must have some other means of telling the 572 when to sense
(electronic wizardry, slave labor, etc.).
Option switch D has one additional use: forcing multiple 572s to sample simultaneously. There
are two reasons for doing this:
1. Adjacent sound systems to the controlled area are noise sources as far as the 572 is
concerned. Their acoustical output influences the ambient sampling of other units.
Simultaneous sampling removes adjacent systems from consideration as noise sources.
2. During sampling, the sampling speakers are connected to an extremely high-gain amplifier.
Adjacent speaker wiring, in the same conduit or raceway, may cause crosstalk into the
speaker wiring connected to the sampling speakers, which will cause erroneous results in
the controlled zone.
Figure B-1 shows what is necessary for externally controlled sampling. Figure B-2 shows how
to interconnect multiple 572s for simultaneous sampling.
A BC
1
2
D
FROM
TO
SPEAKER AMP
UP
EXT
RELAY
CNTRL
EXT
SENSE
TRIG
SPARE
LINE
OUTPUT
P RE
LINE INPUTS
PAGE
MUSIC
Vc
3
OPTIONS
TB2 10
9
8
7
6
5
4
3
2
1
TB1 10
9
8
7
6
5
4
3
2
1
MASTER UNIT
P
U
SH
E
SAMPLE
T O SA M
PL
MOMENTARY SPST
PUSHBUTTON SWITCH
Figure B-1. Using option switch D and a remote momentary pushbutton for externally
controlled sampling.
Rev 2.0, 10/01/94
B-1
A BC
1
2
D
DOWN
FROM
TO
SPEAKER AMP
EXT
RELAY
CNTRL
EXT
SENSE
TRIG
SPARE
LINE
OUTPUT
P RE
LINE INPUTS
PAGE
MUSIC
Vc
3
OPTIONS
TB2 10
9
8
7
6
5
4
3
2
1
TB1 10
9
8
7
6
5
4
3
2
1
MASTER
A BC
1
2
D
UP
FROM
TO
SPEAKER AMP
EXT
RELAY
CNTRL
EXT
SENSE
TRIG
SPARE
LINE
OUTPUT
PRE
LINE INPUTS
PAGE
MUSIC
Vc
3
OPTIONS
TB2 10
9
8
7
6
5
4
3
2
1
TB1 10
9
8
7
6
5
4
3
2
1
SLAVE UNIT #1
A BC
1
2
D
UP
FROM
TO
SPEAKER AMP
EXT
RELAY
CNTRL
EXT
SENSE
TRIG
SPARE
LINE
OUTPUT
P RE
LINE INPUTS
PAGE
MUSIC
Vc
3
OPTIONS
TB2 10
9
8
SLAVE UNIT #2
7
6
5
4
3
2
1
TB1 10
9
8
7
6
5
4
3
2
1
TO ADDITIONAL
SLAVE 572’S
Figure B-2. Multiple 572 master-slave connections for simultaneous sampling.
B-2
Rev 2.0, 10/01/94
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement