Symetrix 581E User manual

581E Distribution Amplifier
User’s Guide
581E

i
Table of Contents
Chapter 1 Introduction 1
Chapter 2 Operator Safety Summary 2
Chapter 3 Fast Setup 3
Chapter 4 Front Panel Overview 4
Chapter 5 Rear Panel Overview 5
Chapter 6 Connecting to Other Gear 7
Chapter 7 Signal Flow Chart 10
Chapter 8 Troubleshooting 11
Chapter 9 Specifications 12
Chapter 10 Warranty and Service 13
Chapter 11 Declaration of Conformity 15
©April1999-2001Symetrix,Inc.
Allrightsreserved.
SymetrixPartNumber53581E0C00
Theinformationinthisguideissubjecttochange
withoutnotice.Symetrix,Inc.shallnotbeliablefor
technicaloreditorialerrorsoromissionscontained
herein;norisitliableforincidentalorconsequential
damagesresultingfromthefurnishing,performance,
oruseofthismaterial.
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oftheseproducts.
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maybereproducedortransmittedinanyformorby
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permissioninwritingfromSymetrix,Inc.If,
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permissiontoprintonecopyisherebygranted.
14926 35th Ave.West
Lynnwood, WA 98037 USA
Tel [phone]
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Email: [email protected]
581E

581E
1
IntroductionChapter 1
Front panel
Rear panel
TheSymetrix581EDistributionAmplifier
(4x4) is a four-input, sixteen-output distribu-
tion amplifier. In a typical configuration the
581E accepts four balanced input signals and
distributes each input to four independent
outputs. The volume of each of the sixteen
outputs may be individually trimmed via its
frontpanelpotentiometer.Similarly,the
volume of each of the four inputs may be
independently controlled. Associated with
each input is a four LED level meter to assist
the user in setting optimum operating levels.
The balanced input stages are designed for
highcommonmoderejectionandRFimmu-
nity. Output line drivers are stable short-
circuit protected and designed around
industry standard 5532 type op amps. The
581E operates from an internal power supply
built around a low magnetic field toroidal
transformer, resulting in a very low noise,
high performance product.
The 4x4 architecture of the 581E allows the
amplifier to fit the greatest possible number
of configurations. Each one input, four
output module is independent of the others.
Wiring the 581E’s inputs to four separate
audio sources provides four mono distribu-
tion channels with four outputs each. This
OUTPUT 4C OUTPUT 4D
POWER
CHANNEL 3
CLIP
OUTPUT 4A
+10
0
INPUT 4OUTPUT 3D
-10
OUTPUT 3B
CLIP
INPUT 3
+10
0
OUTPUT 3A
-10
OUTPUT 3C
CHANNEL 4
OUTPUT 4B
CHANNEL 2
OUTPUT 2DOUTPUT 2COUTPUT 2BOUTPUT 2A
0
INPUT 2OUTPUT 1C OUTPUT 1D
-10
+10
CLIP
CLIP
OUTPUT 1A
+10
0
E
INPUT 1
-10
581
AMPLIFIER (4x4)
DISTRIBUTION
CHANNEL 1
OUTPUT 1B
INPUT 1OUT 1AOUT 1C CHANNEL 1 OUT 1BOUT 2A INPUT 2 OUT 1DOUT 2BOUT 2D OUT 2CINPUT 3OUT 3B
CHANNEL 3 OUT 3A
OUT 3DINPUT 4OUT 4AOUT 4C OUT 4B
CHANNEL 4 OUT 3C
E 581
DISTRIBUTION
AMPLIFIER (4x4)
18 WATTS MAXIMUM
AC INPUT
OUT 4D
FABRIQUÉ AUX E.-U. PAR SYMETRIX INC., LYNNWOOD, WASHINGTON. RÉFÉREZ TOUTE RÉPARATION À UN TECHNICIEN QUALIFIÉ. THIS UNIT CONTAINS NO USER SERVICEABLE PARTS. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL. MANUFACTURED IN LYNNWOOD, WASHINGTON, U.S.A.
CHANNEL 2
configuration also accommodates two stereo
audio feeds.
Stereo audio can be distributed to eight
inputs by strapping the 581E’s inputs
together in pairs. Left channel audio is wired
to inputs #1 and #2, while the right channel
connects to inputs #3 and #4.
The 581E distributes a single mono audio
source to all 16 outputs when all inputs are
strapped together. Regardless of your audio
distributionrequirements,theSymetrix581E
solves the problem with minimum cost and
no wasted outputs.
Feel free to contact us if you have questions,
comments, or suggestions.
Phone [phone]
Fax [phone]
Email [email protected]
Website www.symetrixaudio.com
Ouroffice hours are 8:00am (800 hours)to
4:30pm Pacific Time.

581E
2
Operator Safety Summary Chapter 2
Terms
Several notational conventions are used in this
manual. Some paragraphs may use Note, Caution,
or Warning as a heading. Certain typefaces and
capitalization are used to identify certain words.
These are:
Note Identifies information that needs
extra emphasis. A Note generally
supplies extra information to help
you to better use the 581E.
Caution Identifiesinformationthat,ifnot
heeded, may cause damage to the
581E or other equipment in your
system.
Warning Identifies information that, if
ignored, may be hazardous to your
health or that of others.
CAPITALS Controls, switches or other markings
on the 581E's chassis.
Boldface Strong emphasis.
Equipment Markings
AVIS:
NE PAS OUVRIR
Il ne se trouve a l’interieur aucune piece pourvant entre reparée l’usager.
SEE OWNERS MANUAL. VOIR CAHIER D’INSTRUCTIONS.
S’adresser a un reparateur compétent.
RISQUE DE CHOC ELECTRIQUE
No user serviceable parts inside. Refer servicing to qualified service personnel
.
CAUTION
WARNING:
TO REDUCE THE RISK OF FIRE OR
ELECTRIC SHOCK DO NOT EXPOSE
THIS EQUIPMENT TO RAIN OR MOISTURE
DO NOT OPEN
RISK OF ELECTRIC SHOCK
The lightning flash with arrowhead symbol within an
equilateral triangle is intended to alert the user of the
presence of uninsulated "dangerous voltage" within
the product's enclosure that may be of sufficient
magnitude to constitute a risk of electric shock to
persons. The exclamation point within an equilateral
triangle is intended to alert the user of the presence of
importantoperating andmaintenance (servicing)
instructions in the literature accompanying the
product (i.e. this manual).
Caution To prevent electric shock, do not use the
polarized plug supplied with the unit with
any extension cord, receptacle, or other
outlet unless the blades can be fully
inserted.
Important Safety Instructions
Please read and keep these instructions. Heed
and follow all warnings and instructions. Install
in accordance with the manufacturer’s instruc-
tions.
Power Source This product is intended to
operate from a power source that does not apply
more than 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 opera-
tion.
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
essentialforsafeoperation.Donotdefeatthe
safetypurposeofthegroundingplug.The
grounding plug has two blades and a third
grounding prong. The third prong is provided for
your safety. When the provided plug does not fit
your outlet, consult an electrician for replacement
of the obsolete outlet.
DangerfromLossofGround Iftheprotective
ground connection is lost, all accessible conduc-
tive parts, including knobs and controls that may
appear to be insulated, can render an electric
shock.
ProperPowerCord Useonlythepowercord
and connector specified for the product and your
operating locale. Use only a cord that is in good
condition.Protectthepowercordfrombeing
walked on or pinched, particularly at plugs,
convenience receptacles, and the point where
they exit from the apparatus.
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. Do not install near any heat source such
as radiators, heat registers, stoves, or other
apparatus (including amplifiers) that produce
heat. Unplug this apparatus during lightning
storms or when unused for long periods of time.
Stay Out of the Box To avoid personal injury
(or worse), do not remove the product covers or
panels. Do not operate the product without the
covers and panels properly installed. Only use
accessories specified by the manufacturer. Clean
only with a damp cloth.
User-serviceableparts Therearenouser
serviceable parts inside the 581E. In case of
failure,referallservicing tothe factory.Servicing
is required when the 581E has been damaged in
any way, such as when a power supply cord or
plug is damaged, liquid has been spilled or
objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture,
does not operate normally, or has been dropped.

581E
3
Fast First-Time Setup
Follow these instructions to get your 581E up-and-running as quickly as possible. The intent of this
section is fast setup. Refer to later chapters for explanation of the 581E’s controls and functions.
Connect audio inputs and outputs. If you do not know how to do this, forget Fast Set-Up
and read Chapter 5.
SetINPUT level trim controls straight up(12o’clock position).
SetOUTleveltrimcontrolsatmaximumlevel(clock-wiserotation).
Plug the 581E into an AC outlet using the IEC-type detachable power cord provided with
the unit.
Caution:Failure to connect the 581E to the proper AC mains voltage may
cause fire and/or internal damage.
Warning: Lethalvoltagesarepresentinside thechassis.Thereare nouser
serviceablepartsinsidethechassis.Referallservicetoqualified
servicepersonnelortothefactory.
Apply line level audio signal to the input(s). “Line level” means previously amplified
audio, i.e. not the output of a microphone or other unamplified audio transducer.
Turn up the INPUT level pot(s) until the red CLIP LED just barely lights. Then back the
level down just a bit until the CLIP LED doesn’t come on any more, or only occasionally
flashes.
Now read the rest of this user’s guide.



Fast Setup
Chapter 3





581E
4
Input Level Controls
Thefour inputlevel controlsonthe 581EaremarkedINPUT1, INPUT2,INPUT 3and INPUT4.
Each control adjusts it’s corresponding input signal over a 30dB range. With signal applied to
input(s) turn up the INPUT level pot(s) until the red CLIP LED just barely lights. Then back the
level down just a bit until the CLIP LED doesn’t come on any more, or only occasionally flashes.
This is the optimum setting and will provide the greatest signal-to-noise ratio without distortion.
If your incoming signal positions are unpredictable then we suggest a straight up (12 o’clock)
setting. Since the 581E’s input has 18dB of headroom above +4dBu, this setting should work well
under most conditions.
If you find that your input signal is very low (the output of a “-10” consumer level device, such as
a CD player, for example), turn the INPUT level control clockwise to boost the signal. Conversely,
if you're feeding a “+8” broadcast level signal to the 581E then turn the INPUT level control
counterclockwise until the proper LED display is achieved.
Output Level Controls
Thesixteen outputlevelcontrols onthe581E are markedOUT1A, OUT1B,OUT 1C,OUT1D,
OUT 2A, OUT 2B, etc. Use these controls to attenuate the output level over a 20dB range. Start by
turning all controls fully clockwise (unity gain). This will create equal levels from all outputs. If for
some reason you wish to reduce the level of certain outputs then turn the appropriate control(s)
counterclockwise. Otherwise, for better overall system performance it’s best to leave the controls
wide open (full clockwise) for the hottest possible output signals.
Front Panel Overview Chapter 4
Front panel drawing
-10
OUTPUT 1DOUTPUT 1A
CLIP
+10
OUTPUT 1B
CHANNEL 1
0
INPUT 1 OUTPUT 1C

581E
5
Rear Panel OverviewChapter 5
The 581E is fitted with removable terminal blocks for both input and output connections. While not
absolutely necessary, it is usually much easier to unplug the removable block before making or
changing connections.
INPUTS
The four 581E inputs are balanced. Of course, they may be used in unbalanced configurations but
for optimum system wide performance (best noise rejection) balanced operation is highly recom-
mended, whenever possible. Be sure and use shielded cable for both input and output connec-
tions. The wire should always be two-conductor plus shield, even for unbalanced connections.
For balanced input signals:
1. Connect the incoming signal “+” (high) to the “+” INPUT terminal of the 581E.
2. Connect the incoming signal “-” (low)tothe“-”INPUT terminal of the 581E.
3. Connect the incoming signal ground (shield) to the ground terminal of the 581E. Repeat
for all inputs.
For unbalanced input signals, using two-conductor shielded cables:
1. Connect the incoming signal “+” (high) to the “+” INPUT terminal of the 581E. Use
the red wire.
2. Connect the incoming signal ground to the “-” INPUT terminal of the 581E. Use the
blackwire.
3. Connect the cable shield at the ground connection of the 581E only.
If you experience hum or noise, make sure that both the 581E and the device which you are feeding
are grounded on the same AC mains circuit. If this is not the source of the noise problem, you must
isolate the unbalanced output from the balanced input with an audio transformer or “matchbox.”
WIRING THE 581E IN 2x8 or 1x16 CONFIGURATION
To connect the 581E as a 2 input, 8 output distribution amplifier proceed as follows:
1. Connect the two incoming signals to INPUT 1 and INPUT 2 as per the instructions above.
2. Connect (4) additional short pieces of #20 or #22 gauge wire as follows:
INPUT1“+”toINPUT3 “+”
INPUT1“-” toINPUT3“-”
INPUT2“+”toINPUT4 “+”
INPUT2“-”toINPUT4“-”.
To connect the 581E as a 1 input, 16 output distribution amplifier proceed as follows:
1. Connect the single incoming signal to INPUT 1 as per the instructions above.
2. Connect (6) additional short pieces of #20 or #22 gauge wire as follows:
INPUT1“+”toINPUT2 “+”
INPUT2“+”toINPUT3 “+”
INPUT3“+”toINPUT4 “+”
INPUT1“-” toINPUT2“-”
INPUT2“-” toINPUT3“-”
INPUT3“-” toINPUT4“-”

581E
6
OUTPUTS
The 581E’s four outputs are active balanced circuits and should be used to feed balanced audio
inputs. Use two-conductor shielded audio cable for all connections.
Feeding balanced inputs:
1. Connect the “+” (high) OUTPUT terminal of the 581E to the “+” (high) of the input
of the device which you are feeding.
2. Connect the “-” (low) OUTPUT terminal of the 581E to the “+” (high) of the input of
the device which you are feeding.
3. Connect cable shield to the ground of the 581E and the ground connection of the
device which you are feeding.
Feeding unbalanced inputs:
WEDON'TRECOMMENDIT.Ifyoumustfeedanunbalancedinputwiththe581E,youshould
isolate the two devices with either an audio transformer or an interface matching device (a “match-
box”). The 581E follows the AES standards for balanced audio circuits. The ground connections of
the amplifier are chassis ground.
If you must connect the output of the 581E directly to an unbalanced input, try this procedure. Use
two-conductor shielded audio cable.
1. Connect the “+” (high) OUTPUT terminal of the 581E to the “+” (high) of the
unbalanced input.
2. Make no connection tothe“-” (low) OUTPUT terminal of the 581E.
3. Connect the cable shield at the 581E’s ground and at the input connector of the
unbalanced input.
The output signal level of the 581E will be 6 dB lower when driving an unbalanced input without a
transformer or matching interface device.
If you experience hum or noise, make sure that both the 581E and the device which you are feeding
are grounded on the same AC mains circuit. If this is not the source of the noise problem, you must
isolate the balanced output from the unbalanced input with an audio transformer or “matchbox.”

581E
7
Connecting to Other GearChapter 6
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 (hope-
fully) clarify your understanding of the subject.
Over the years, we have all had impedance matching pounded into our heads. This is important
only for vintage 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.
HVintage 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.
HPower 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.
HRF 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 low-impedance.
Similarly,although 1/4 inch jacks are typically used for thingslikeguitars (which are high-imped-
ance 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 high-impedance. 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-to-noise 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 signalsin the -10 to +24 dBm/dBurange. 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 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 the output of whatever device drives the input
(i.e. to be greater than 10 times the actual source impedance). 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.)

581E
8
The two facts that you need to derive from this discussion are:
HMatch signal levels for best headroom and signal-to-noise ratio.
HFor audio, impedance matching is only needed for vintage equipment and power amplifier
outputs. In all other cases, ensure that your inputs bridge your outputs (meaning the
inputs are in the range of 2 to 200 times the output source impedance).
Signal Levels
The 581E is designed around studio/professional line levels: +4 dBu or 1.23 volts RMS. The unit is
quiet enough to operate at lower signal levels such as those found in semi-pro or musical instru-
ment(MI)equipment(-10dBuor300millivolts).
I/O Impedances
The 581E is designed to interface into almost any recording studio or sound reinforcement applica-
tion. This includes:
H600-ohm systems where input and output impedances are matched.
HModern bridging systems where inputs bridge and outputs are low source impedances
(voltage transmission systems).
The 581E’s input impedance is greater than 20-kilohms balanced. The inputs may be driven from
any balanced source capable of delivering at least -10 dBu into the aforementioned impedances.
The 581E’s output impedance is 600 ohms balanced, 300 ohms unbalanced. The output line driver
delivers+22 dBm into600-ohmbalancedloads or +18dBminto600-ohm unbalanced loads.
Input and Output Connections
The illustration on the next page shows how to connect the 581E to balanced and unbalanced
sources and loads.
To operate the 581E from unbalanced sources, run a 2-conductor shielded cable (that’s two
conductors plus the shield) from the source to the 581E. 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 581E, the high/plus wire connects to pin 2, the low/minus wire connects
to pin 3, and the shield (always) connects to pin 1. This is the preferred method as it makes best
use of the 581E’s balanced input (even though the source is unbalanced). The other alternative
shown in the illustration converts the 581E’s balanced input into an unbalanced input at the input
connector. This works, but is more susceptible to hum and buzz than the preferred method. There
is no level difference between either method.
You can drive unbalanced loads with the 581E’s outputs by using the XLR connector with pin 3
left open. In an emergency (the show must go on), you can ground pin 3, but if you have the
choice...leave it open. If you must ground pin 3, it is must be grounded at the 581E, rather than at
the other end of the cable. The price, regardless of whether or not pin 3 is grounded is 6 dB less
output level. If your system is wired with pin 3 hot, and you are driving an unbalanced load, pin 2
mustfloat.