AUSTRALIAN MONITOR AM1600 User manual

Operation Manual
AM1600

!WARNING!
DO NOT EXPOSE TO EITHER
RAIN OR MOISTURE
!CAUTION!
RISKOFELECTRICALSHOCK
DO NOT OPEN
IMPORTANT!
Please read carefully.
Thisoperationmanualcontainsimportantinformationregarding
safetyprecautions,installation,performance,operationand
maintenance of your AM1600 power amplifier. You should
familiarize yourself with the contents of this
Safety Precautions
and Labelling
manual before operating your amplifier.
Therearpaneloftheunithasanumberofmarkingsand
internationally recognized symbols related to the
hazards and precautions that should be taken when
operatingMAINSconnectedequipment.
ThepresenceofaLIGHTNINGFLASHwithanarrowhead
containedwithintheboundariesofanequilateraltriangle
isintendedtoalerttheuserthatdangerousuninsulated
voltagesmayexistwithintheunit'senclosure.These
voltages may be of a sufficient magnitude as to
constitute the risk of an electrical shock.
This symbol is reinforced with the text:
ThepresenceofanEXCLAMATIONMARKcontained
within the boundaries of an equilateral triangle is
intended to alert the user that there is important
operatingandmaintenanceliteraturethataccompanies
the unit.
Theunitshouldnotbeoperatedinasituationwhereit
mayencountertheentryofwater,rain,oranyfluids.To
exposetheunittotheaboveconditionsmaymakethe
operationoftheunit hazardous and increasetherisk
of electrical shock.
The user should not attempt to service the unit. Only
qualified and knowledgeable personnel familiar with
the internal workings of the unit should attempt any
repair, servicing or authorized modification to the
unit. The unit does not contain any parts which the
usercanserviceorre-useinthisoranyotherproduct.
If you are in need of special assistance and the
information you require is outside the scope of this
manual,pleasecontactyournearestserviceagentor
Australian Monitor direct:
THE TECHNICAL OFFICER
AUSTRALIANMONITOR
C/-AUDIOTELEXCOMMUNICATIONSPTYLTD
PRIVATEBAG149,
SILVERWATER. N.S.W. 1811
AUSTRALIA.
Phone Fax
Local [phone] (02) 9748-2537
International 61-2-9647-1411 61-2-9748-2537
Email [email protected]
Internet www.australianmonitor.com.au
REFERSERVICINGTO
QUALIFIED PERSONNEL.
NO USER SERVICEABLE
PARTS INSIDE.

Features:
- Custom designed, 3RU heavy duty alloy chassis.
-Modularconstruction.
- Symmetrical layout - even weight distribution.
-Linear,well-regulating,highcurrentpowersupply.
-Highefficiencytoroidalmainstransformer.
-Continuoushighpowercapability.
- Lateral Mosfet Class AB output stage.
- Binding post and Neutrik "Speakon" output
connection.
-Inputsignalstrapping(loopthrough)connectors.
Protection Features
-Suppressionof inrush current atmainsturn-on.
- Side chain mains switching control.
-Inputmutingat turn-on.
-Inputovervoltageprotection.
-Radio-frequencyinterferencesuppression.
-Short-circuitprotectionand indication.
-Activebalancedinputs.
-21 Position detentedattenuators.
-Massiveheat-sink/heat-exchangers.
- Efficient front to back cooling.
- Quad, twin speed axial fans.
-Multi-rolelevel / fault indication.
-Frontandrear carry handles.
-Frontandrearmounting points.
-High-quality,close-tolerancecomponentsused
throughout.
-Thermaloverloadprotectionandindication.
- Mains Circuit Breaker.
-Individualhighcurrentrailfuses.
-Layout,grounding,decouplingandcomponentry
have been optimized to provide the user with
stability, reliability and longevity.

Contents Page
1. Introduction 5
2. Controls,ConnectorsandIndicators 6
2.1FrontPanel 7
2.2RearPanel 9
3. Installation 11
4. Operation 13
5. Bridge Mode 15
6. TwoOhmorNotTwoOhm 16
7. Maintenance 17
8. Warranty 18
9. Specification 19
List of Illustrations Page
Figure 1. Block Diagram 5
Figure2.FrontPanelLayout 6
Figure3.RearPanelLayout 8
Figure 4. Case Dimensions 10
Figure 5. "Speakon" Connector Wiring 12
Figure 6. Bridge Mode Speaker Wiring 15

1. Introduction
Congratulations on choosing Australian Monitor for
yourprofessionalamplificationrequirements.
The design of your AM1600 Audio Power Amplifier
embracesalltheaspectsofawelldesignedunit.The
visual design, mechanical, electrical and sonic
parameters,alongwithourdedicatedmanufacturing
process, have all been optimized to provide a
professional tool that exhibits quality, reliability and
longevity.
TheAM1600amplifiersare3unit(5.25")tall,19"wide
rack mountable units.
Each channel of the amplifier comprises a balanced
active input with an attenuator driving a differential
classA drivestage which in turn drives a fan-cooled,
class AB MOSFET output stage configured as a
sourcefollower.Theunitoperatesfromahighcurrent
capablelinearpowersupply.
Theseunitshavebeenspecificallydesignedtodeliver
their high power output with minimal distortion, and
providethecriticaldegreeofcontrolrequiredbyyour
speakers, at high duty cycles for extended periods.
Figure 1 Amplifier Block Diagram
Introduction 5

6 Controls & Connectors
Figure 2 Front Panel Layout
2. Controls,
Connectors
& Indicators
Insert - 1 VU Meter / Satus Indicator

Front Panel
Figure 1 shows the panel layout of the AM1600. The
functionsofthecontrolsandindicatorsareasfollows:
1.Attenuator
Levelcontrol foryouramplifierisprovidedbya21
positiondetentedpotentiometerandindicatesgain
reduction in decibels from the 0 dB position
(maximumgain,noattenuation).
2. VU Meter - Status Indicator
LevelIndication(seeinsert-1)
Eachchannelfeaturesavariable10segmentdisplay
showing the actual power/volume level available
beforeclipping(takingmainssupplyandloadduty
intoaccount).
Thedisplayiscolourcoded,andcalibratedin3dB
increments.
The10LEDs are:
Green = -27dBto-21dB
Yellow = -18dBto-6dB
Red = -3dBandthetwoLEDsindicating
the clipping point.
PowerOnIndication
Two Green LEDs either side of the mains switch
(above the "ON" legend) are used to indicate that
theunitison.Thefirst GreenLEDindicatesthe15
Volt preamp supply is present (the left hand side
displayshows-15V,andtherighthandsideshows
the+15V).
The next LED outwards is also a supply indicator
and shows that the Positive High Current Output
Railisavailabletothecorrespondingchannel.
NOTE:Theamplifierisnotdamagedbyrunninginto
clipping,butspeakersmaybe.Tomaximisethelife
of your speakers, try to keep clipping infrequent.
3. Power Switch
PresstheswitchDOWN forpowerON andUP for
power OFF. At start-up (turn-on) the input to the
amplifier is muted by 30dB for approximately two
seconds.
4. Thermal Indicator
Whenswitching the amplifieron, this redLED will
flash momentarily, indicating correct operation of
the Mains In-Rush Current Suppression circuit.
AfterestablishmentofInrushCurrentSuppression
circuit the LED will extinguish. This LED will not
illuminateduringnormaluseoftheamplifier.
In the advent of a thermal overload this LED will
illuminateredindicatingthattheinternaloperating
temperatureofoneorbothamplifierchannelshas
exceededasafelevelofoperationandthe amplifier
willbeshutdown.Thefanswillcontinuetorunand
oncetheamplifierhascooleddownsufficiently,the
amplifierwillstartupautomaticallyprovidingInrush
CurrentSuppressionandinputsignalmutinguntil
establishment of the amplifier after which it will
returntonormaloperatingmode.
NOTE:Youshouldalwaysensurethatthefangrille
iskeptcleanandfreefromthebuildupofdustand
lint.Thiswillensurelongeroperationofyouramplifier
and reduce the possibility of it prematurely going
intothermalshutdownmode.
5. Fault Indicator
ThisamberLEDwillilluminatewhenafaultcondition
exists.
The fault detection circuit monitors the difference
betweendriveandoutputinyouramplifier.
Ifyouhaveashortonthespeakeroutput(orablown
negativerailfuse)theLEDwillflashbrightlyinsync
with the programme. This LED will also flash with
programmepeaksforgrossoverloadsoriftheload
is 2 ohms or less.
The circuit has two stages of operation:
1.Itwillprovideindication(e.g.grossoverload)but
does not affect the input signal (a faint flash).
2. It will indicate and mute the input signal (e.g.
shorted output) (brightly flashing or permanently
on).
Intheadventofafailurethedisplaypanelrevertsto
a fault display to assist in diagnosis of the fault.
- The VU meter will light up fully and the Positive
Output Rail LED will extinguish if the positive
supplyrailisnotavailable(checkrear+verailfuse).
- The fault Led will glow brightly if the Negative
OutputRailisnotavailable(checkrear-verailfuse).
- Failure of the pre-amp supply will cause the
amplifier to be muted and indicator LEDs to be
extinguished.
Controls & Connectors 7

8 Controls & Connectors
Figure 3 Rear Panel Layout

Rear Panel
6. Balanced Input
A female 3-pin XL type connector is provided on
eachinput:
Pin 1 = Signal Ground;
Pin2=Hot(non-inverting or in phase);
Pin3=Cold(invertingorreversephase).
6a.SignalStrapping
A male 3-pin XL type connector is provided and
wired in parallel with the female input XLR for
strapping/loopingsignalbetweenamplifiers.
7. SPEAKON Output Connector
TheNEUTRIK(NL4MP)4waySPEAKONconnector
isprovidedasthemainspeakeroutputtermination.
Thisemergingstandardofloudspeakertoamplifier
connection allows access to both channels of the
amplifier via the one connector for bi-amp
applications.Channel-Aisconsideredthedominant
channelandhasbothchannelswiredtotheSpeakon
connector. See the installation section of this
manualfordetailedinformationonSpeakonwiring.
7a.Binding Post Outputs
Binding posts (banana jacks) are provided for
speaker output termination with banana plugs or
barewire.Theredpostisusedaspositiveandthe
black post is used as negative.
8. Mains Lead
Youramplifierissuppliedwithaheavydutymains
lead(powercord)appropriatelyratedforthemains
supply voltage marked on the rear panel of your
amplifier.
The wires in the mains lead are coloured in
accordancewiththefollowingcode:
BROWN = ACTIVE;
BLUE = NEUTRAL;
GREENANDYELLOW = EARTH.
Controls & Connectors 9
! CAUTION !
Your amplifier must always be earthed!
9.Mains CircuitBreaker
A “push to reset” thermal acting circuit breaker is
suppliedonyouramplifierprovidingoverallprotection
of your amplifier’s power supply and the
interconnectingmains.Thebreakerwillisolatethe
"active" mains conductor in the event of a high
current internal fault or in continued overload
conditions.
Thebreakerwillnotbeabletoberesetimmediately
after tripping. A cool down period of around 30
seconds is required before the breaker will reset
backintocircuit.Ifthebreaker"trips"immediately
afterareset,thenafaultmayhavedevelopedwithin
theamplifier.
10. D.C. Rail Fuses
YourAM1600 amplifierisfitted with10Ampfuses
perrail-perchannel,asoverloadprotectionforthe
outputstageof youramplifier.
These fuses are in series with the high current
supply railstotheamplifier'soutputstageandwill
blowwhen:
1) An internal fault exists;
2)Thereisasustainedoverload;
3) There is a sustained short circuit;
4)Sustainedloadfault.
Front Panel Indication will result if one of the
corresponding Rail Fuses is to "blow".
- The VU meter will light up fully and the positive
Output Rail LED will extinguish if the positive
supply Rail Fuse "blows".
-TheFaultIndicatorwilllightupandpulseinsync.
withtheprogramsourceifthenegative supplyRail
Fuse "blows".
Replace only with 10 Amp, 3AG fast acting type
fuses.

Figure 4 Dimensions
10 Installation

3.Installation
Mains Lead Wiring
WARNING
Your amplifier must be earthed at all times!
When you first receive your amplifier it may not have
a mains plug attached. You must ensure that an
appropriate plug is used and corresponds with the
amplifier’scurrent(ampere)requirementsandmeets
the approval of your local energy authority.
Please refer termination of this lead to qualified
personnel. Australian Monitor takes no
responsibility for any damage or harm resulting
from improper termination of this lead!
Thewiresinthemainsleadarecolouredinaccordance
withthefollowingcode:
GREEN AND YELLOW = EARTH
ConnecttotheterminalmarkedwiththeletterE,with
theEARTHSYMBOL orcolouredGREEN.
BLUE = NEUTRAL
Connect to the terminal marked with the letter N (or
coloured WHITE in USA and Canada, or coloured
BLACK in the United Kingdom).
BROWN = ACTIVE (LIVE)
Connect to the terminal marked with the letter A or L
(orcolouredBLACK in USAandCanada or coloured
RED in the United Kingdom).
Power Requirements
Mains Voltage Circuit Breaker Rating
100to120 volts 20 Amps
220to240 volts 10 Amps
PowerConsumptionatidle = 350 Watts
Consumptionatrated4ohmpower = 2700 Watts
Ensurethatyourmainsvoltageisthesameastherear
panelmainsvoltagemarker(+/-10%).
Mounting
Your amplifier is designed for standard 19" rack
mounting and occupies 3 EIA rack units (5.25"). The
mountingcentresare:
Vertical: 2.25" (57.15mm)
Horizontal: 18.15" (461.1mm)to18.62"(473.0mm).
The slots in the mounting flange will accept bolt
diameters up to 1/4" (6.35mm).
Werecommendthatyouprovideadditionalsupportfor
theamplifier,especially ifroaduseisplanned,asthe
weightcanbendsomeracksotherwise.Thissupport
canbeprovidedbysecureshelving,supportrailsora
rearrackmountingstriptomatchupwiththerearrack
mountpointsprovidedonyouramplifier.
Cooling
EachchannelofyourAM1600amplifieriscooledbyan
axialfanwhichdrawscoolairfromthefrontoftheunit
andexpelstheheatedairviatherearoftheunit.These
units offer two speed fans which run at half speed,
switching to full speed when the internal heatsink
temperatureexceeds600 C(1280F).
Anunrestrictedairflowintoandoutfromtheunitmust
be provided. Any restriction of the air flow will cause
heat to build up within the unit and possibly force the
unit into its thermal shutdown mode.
If the units are to be operated in an environment
wheretheairflowisrestrictedsuchassealedracksor
even when running 2 ohm loads, the cooling should
be supplemented by extra cooling fans to evacuate
the heated air and aid the flow of cool air through the
unit.
Input Wiring
IMPORTANT! Do not directly connect pin 1 on the
amplifier’s input or strapping XLR, to the amplifier’s
chassis, speaker ground or power ground!
NOTE: Input signal ground is not to be used as
a safety ground (earth).
Theinputtoyouramplifierisabalanced3-pinsystem
andrequiresallthreepinstobeconnected.Onlyhigh
quality twin-core shielded cable should be used.
When wiring for a balanced source the connector
goingtotheinputofyouramplifiershouldbewiredas
follows:
Pin 2 = HOT(InPhase-noninverting).
Pin 3 = COLD(ReversePhase-inverting).
Pin 1 = GROUND/SHIELD.
When wiring from an unbalanced source you must
ensurethatpin3isconnectedtopin1(inputground),
either by linking the pins in the input connector or by
the source equipment's output wiring.
When wiring for an unbalanced source:
Pin 2 = HOT(inphase withtheamplifier’soutput),
Pin 3 = GROUND/SHIELD(joinstopin1).
Pin 1 = GROUND/SHIELD
Installation 11

When using the NEUTRIK SPEAKON (NL4MP)
connector for speaker output, use only the mating
NEUTRIKNL4FCin-lineconnector.Thisconnectoris
designed so that both channels can be fed from a
singleconnector.
Two SPEAKON connectors are provided on the
amplifier. The "Channel A" SPEAKON actually
carries both Channel-A & Channel-B outputs (see
Figure5:SpeakonConnectorWiringDiagrams).
The "Channel-B" SPEAKON carries the Channel-B
outputonly.
Thisarrangementallowsyoutheoptionofconnecting
to the outputs separately or together. Connecting
through a single connector has the advantage of
minimising connections, preserving phasing and
simplified channel allocation, which is particularly
important when bi-amping or in bridge mode.
IMPORTANT
Do not overload your amplifier by connecting the
Channel-Boutputtwice!
Channel-A is used as the “dominant” channel and
when sourcing a dual output from Channel-A the
followingstandardshouldbeused:
Channel-A=LeftorLowFrequencies.
Channel-B=RightorHighFrequencies.
When in bridge mode:
Pin 1+ = Bridge Output Positive
Pin2+ = Bridge Output Negative.
NOTE:In-lineXLRconnectorsoftenhaveatermination
lugthatconnectsdirectlytothechassisoftheconnector.
Do not link this lug to pin 1 at the amplifier’s input as
it will defeat the amplifier’s input grounding scheme.
Thislugisoftenreferredtoasa"drain”andisusedto
provide a termination to the chassis for shielding
purposes when a floating signal ground is required
between the source and destination, or when
disconnectingthesignalgroundisrequiredtoreduce
earthloopnoise,ornoiseinducedintosignalgrounds
fromstray magneticfields.
OutputWiring
Whenwiringtoyourspeakers always use thelargest
gaugewireyourconnectorwillaccept.Thelongerthe
speakerleadthegreaterthelosseswillbe,resultingin
reduced power and less damping at the load. We
recommendusingaheavydutytwocoreflex(fourcore
flexif bi-amping) 10to 12 gauge(2mm2to 2.5mm2or
50/0.25orequivalent)asaminimum.
Binding Post Outputs
When terminating to the 4 mm binding post (banana
jack) output connectors, banana plugs or bare wires
canbeused.Theredterminalispositiveandtheblack
terminal is negative (ground).
If running in BRIDGE mode, only the red binding
posts are used. Channel A provides the positive
output to the load and channel B provides the
negativeoutput to the load.
SPEAKON Outputs
12 Installation
SINGLE CONNECTION BRIDGED CONNECTION
DUAL CONNECTION
Figure 5. "Speakon" Connector Wiring Diagram
BI-AMP CONNECTION

4. Operation
IMPORTANT
All signal source equipment should be adequately
earthed. This not only ensures your safety but
everybody else's as well. Faults can and do occur in
mains connected equipment where the chassis can
become “live” if it is not properly earthed. In these
instancesthefaultina“floating”(un-grounded)pieceof
equipment will look for the shortest path to ground
which could possibly be your amplifier's input. If the
faultcurrentislargeenoughitwilldestroytheinputto
your amplifier and look for the next available path,
which may be you!
Before making any connections to your amplifier
observethefollowing:
Ensurethemainsvoltagesupplymatchesthelabel
ontherear panel of youramplifier(+/- 10%).
Ensure that the power switch is OFF (UP)
Ensure that all system grounds (earths) are
connectedfrom a common point. Avoid powering
equipment within a system from multiple power
sourcesthatmaybeseparatedbylargedistances.
Checkthecontinuityofallinterconnectingleadsto
your amplifier, ensure that there are no open or
short circuited conductors.
Ensure that the power handling of your load
(speakers) can adequately cope with the power
outputoftheamplifier.
Very Important
DuetothehighpowerabilityoftheAM1600 youneed
to be aware that certain precautions need to be
followedtoensurelongevityofyouramplifier:
-Neverturnyouramplifieronunlessallconnections
(inputsandspeakers)havebeenmade!
- Neverplug in a signal lead after the amplifier has
beenturnedon!Turntheunitofffirst.
- Never drive the output into clipping if the load is
open circuit or there is no speaker load connected!
PoweringUp
REMEMBER
Theamplifiershouldbethelastpieceofequipmentthat
youturnon andthefirstpieceofequipmentthatyou
turnoff.
We recommend turning the attenuators on your
amplifier down when turning the unit on.
When you power up your amplifier, your amplifier
goesthroughanestablishmentperiodbeforeitwill
acceptsignal.TheInrushCurrentSuppression(ICS)
circuitisinoperation for thefirst0.5seconds. This
limitsthemainscurrenttoprevent"nuisancetripping"
of circuit breakers.
During this period the THERMAL LED will flash red
whilst the mains voltage gradually charges up the
power supply. You will then hear a relay “click”,
indicatingmainsisnowdirectlyappliedtotheamplifier.
While the ICS circuit operates there is also a 30dB
muteonthesignalinput.Aftertwosecondsthismute
will release, allowing any applied signal to pass
unattenuated.
When switching the amplifier off, wait a couple of
secondsbeforeswitchingtheunitonagain.Thisallows
the ICS circuit to reset.
Level Matching
Thenormaloperating position for theattenuatoris
the"0dB"position(fullyclockwise,noattenuation).
In this position the amplifier operates at full gain.
Turningtheattenuatorback(anticlockwise)reduces
the input sensitivity by the amount marked on the
attenuatorscale(dial).
NOTE: If full power output is required you should
operateyouramplifierwiththefrontpanelattenuator
abovethe-15dB position,otherwiseclippingofthe
input circuitry and its resultant distortion will occur
beforefulloutputpowerisachieved.
Sensitivity
Youramplifierisalineardeviceoperatingwithafixed
input to output voltage gain (less attenuation). The
maximum output voltage swing is determined by the
applied mains voltage, load, load type and the duty
cycle of the applied signal.
Thevoltagegainfactorofyouramplifieris:62.0times
or35.8dB.
The input sensitivity for your amplifier when the
attenuator is at the “0” dB attenuation position (fully
clockwise) is nominally:
+2.2dBu(1.00voltsin)forratedpowerintoa8ohm
load.
+1.5dBu(0.92voltin)forratedpowerintoa4ohm
load.
Operation 13
1.
2.
3.
4.
5.

producesavoltagedropduetothewire’sresistance.
Thisvoltagedifferencebetweentheampearthand
source equipment earth appears to the amplifier's
input as a signal and is amplified as hum.
Therearethreethingsyoucandotoavoidearthloop
problems:
Ensureyourmainspowerfortheaudiosystemis
“quiet” i.e. without equipment on it such as air-
conditioning,refrigerationorlightingwhichmay
generate noise in the earth circuit.
Ensure all equipment within the system shares
a common ground/ safety earth point. This will
reducethepossibilityofcirculatingearthcurrents
astheequipmentwillbereferencedtothesame
groundpotential.
Ensure that balanced signal leads going to the
amplifierareconnectedtoearthatoneendonly.
SignalGroundLifting
Whenpropersystemhook-uphasbeencarriedout,
youmaystillhavesomehumorhumrelatednoise.
Thismaybeduetoanyofthepreviouslymentioned
gremlins.
Oneofthemosteffectivewaystoreduceearthloop
orelectromagneticallyinducedhumistodisconnect
input signal ground at the input connector of your
amplifier.Thiseffectivelybreakstheearthlooppath
or open circuits the input ground path so no
electromagnetically induced currents can flow
throughtheamplifier.
NOTE: If the input signal ground is lifted you must
ensureadequateshieldingoftheinputwiring.Ifthe
signalsourceequipmentdoesnotprovideadequate
shielding(i.e.adefinitiveconnectiontoground)you
mustdisconnecttheshieldfromtheinputconnector's
ground pin (Pin-1) and reconnect it to the "drain"
contactontheinputconnector.Thiswillensurethe
shield on your input wiring actually goes to the
amplifier chassis and subsequently to earth.
DONOTCONNECTPIN-1DIRECTLYTOTHE
DRAINCONNECTION.
You will defeat the amplifiers internal grounding
scheme and possibly cause instability within the
amplifier.
This should only be done when the amplifier is
operated from a balanced signal source.
NOTE:Bewaryofquasi-balanced outputs,these
areoftennomorethanfloatingunbalancedoutputs.
14 Operation
1.
2.
Each channel of your amplifier has a nominal
balancedinputimpedanceof18kOhms(@1kHz)
andshouldnotpresentadifficultloadforanysignal
source.
Your signal source (i.e. the equipment feeding the
amplifier) should have an output impedance of
600Ohmsorlowertoavoidunwantedhighfrequency
loss in the cabling.
Inputoverload occursat+20.5dBu(8.25volts).
See the specification section for more detailed
information.
Hum Problems
Mostequipmentisdesignedforminimumhumwhen
used under ideal conditions. When connected to
otherequipment,andtosafetyearthinanelectrically
noisy environment however, problems will often
occur.
Thethree"E"sofhumandhumrelatednoisewhich
can plague your audio system are:
a) Electrostatic radiation,
b)Electromagneticradiation,and
c) Earth loops
Electrostatic radiation capacitively couples to
system elements causing an interference voltage
that mainly affects higher impedance paths, such
asamplifierinputs.Thesourceisgenerallyanearby
highvoltagesuchasamainsleadoraspeakerlead.
Theproblemcanusuallybereducedbymovingthe
offending lead away, or by providing additional
electrostatic shielding (i.e. an earthed conductor
which forms a barrier to the field).
Electromagnetic radiation induces interference
currents into system elements that mainly effect
lowerimpedancepaths. Radiotransmittersorstray
magneticfields frommains transformersare often
the cause of this problem. It is generally more
difficult to eliminate this kind of interference, but
again, moving the source away or providing a
magnetic shield (i.e. a steel shield) should help.
Earth loops can arise from the interfacing of the
variouspiecesofequipmentandtheirconnections
to safety earth.
Thisis byfar the most common cause of hum, and
it occurswhensourceequipmentandtheamplifier
are plugged into different points along the safety
earth where the safety earth wiring has a current
flowing in it. The current flowing through the wire
3.

Figure 6 Bridge Mode Speaker Connection
Bridge Mode 15
5. Bridge Mode
The term BRIDGE is used when two independent
amplifierchannelsareusedtodrivethesameload.The
load is in series (a bridge) between the two amplifier
channels.
Channel A is used as the "dominant" channel and its
output is in phase with the input signal, and channel
B has to have its phase reversed so it is exactly 1800
out of phase with the input signal.
As two amplifiers with a phase difference of 1800are
now driving the load you will now have double the
voltageintotheload.Thismeansyouwillnowhavefour
timesthepowerintothatload.Theoutputcannowbe
considered as an active balanced output.
AcommonuseofanamplifierinBRIDGEmodeisfor
driving70volt&100voltdistributionlines.InBRIDGE
mode,TheAM1600canproduceinexcessof114volts
into a line impedance of 8 ohms (1600 watts) and in
excess of 90 volts into a line impedance of 4 ohms
(2100watts).
Equallytheunitscanbeusedinbridgemodetoprovide
thecorrectvoltage/powerrequirementsforanapplica-
bleload.
AsshowninFigure6,therearefourstepsinsettingup
yourAM1600amplifierforrunningitinBRIDGEmode.
Whilst the amplifier is off,
1. ConnectthesignalsourcetotheChannel-Afemale
inputXLR.
2. Loopfrom Channel-A male XLRto Channel-Bfe-
maleinputXLRwithaReversePhaseLead.
AreversePhaseLeadiswired:
Channel-A Channel-B
Pin-1 to Pin-1
Pin-2 to Pin-3
Pin-3 to Pin-2
3. Connect your load between the red binding post
output terminals, where the positive side of the
loadisconnectedtotheChannel-Aoutput andthe
negative side of the load goes to the Channel-B
output.Therearenofurtherconnectionsrequired.
4. Turntheattenuators onbothchannelsfullyclock-
wise(0dB- no attenuation).
You can also source the output from the Channel-A
SPEAKONoutputconnectorwhereChannel-Awillbe
onthepinmarked1+andChannel-Bwillbeonthepin
marked2+.
NOTE:Youshouldcheckaftermarketmanufactured
Speakon interconnecting speaker leads before
connecting them to your amplifier. Some leads are
manufactured for specific purposes, or specific use,
andmayhavepinsshortedinsidetheconnector.Any
speakonleadwithshortedpinswillobviouslyshortthe
outputofyouramplifier(eithertoground,oroutputto
output-becareful).

6. Two Ohm or
Not Two Ohm
NOTE: Ensure adequate ventilation and monitor the
FAULTindicatorstoguardagainstthermalshutdown
whendrivingtwoohmloads.
A preamble.
Theloadthataloudspeakerpresentstoanamplifieris
very complex and at different frequencies can be
inductive, capacitive, resistive, or a combination of
these(reactive).Withthecomplexinteractionofthese
attributes,whichalterfromloudspeakertoloudspeaker,
adefinitive load foran amplifier doesnot really exist.
Loudspeakers operating within an enclosure are
specified with a nominal impedance. This nominal
impedanceisonlyaroughguidetotheloaditpresents
toanamplifier.
Asanexample,aloudspeakerwithanominalimpedance
of say 8 ohms, may have an impedance of over 50
ohms at resonance (bass frequencies), drop to less
than6ohmsaftertheresonancepeak(throughitsmid
bandarea)andthenincreasetoover16ohmsforhigher
frequencies.
A4ohmloadmakesanamplifierwork"harder"thanan
8ohmloadatthesamevoltage,asdoublethecurrent
isrequired.
Thoughvariousloudspeakersmaybemarkedwiththe
samenominalimpedance,someloadsaremoredifficult
thanothers.
Bassfrequenciesusuallyexhibithigherimpedances
and require higher voltages to achieve the desired
result. They also reflect higher energy back to the
amplifiersimplyduetotheamount of cone excursion
involvedatlowerfrequencies.
The Mid frequency band usually offers the lowest
impedancesandthehighestdutycyclesrequiringboth
highvoltageandhighcurrent.
TheHighfrequencyregionusuallyoffersamoderate
impedance and usually does not need much voltage
but the instantaneous current demand can be much
greaterthan youthink.
As well as this burden on the amplifier, the transient
waveformsfoundinactualusecandemandalotmore
current than the "steady-state" sinewaves used in
most amplifier bench tests.
ThepoweroutputofyourAM1600amplifierquotedon
the specification sheet is derived from a voltage
excursionintoaresistiveloadforasinewaveatagiven
frequency. Though this method is in line with the
variousstandardsthatexist,itonlygivesanindication
to the maximum voltage swing (before clipping) for a
givenload.Thismethodofratingpowerdoesnotgive
anindicationofthecurrent(Ampere)capabilityofthe
amplifier, nor does it show the amplifier’s ability to
sustainhighenergywaveforms.
YourAM1600amplifierhasbeenspecificallydesigned
tobe ableto delivermore than twice the current than
that shown on the specification sheet to cope with
difficultloadsand/orhighenergywaveforms.
Thisextracurrentreserveistheresultofoverengineering
andistheheadroomtheamplifierutilizestocontrolthe
loudspeakeranddealwiththe“reactiveenergy”from
theloudspeaker load that has to be dissipatedwithin
theamplifier.
YourAM1600 amplifierisabletodrive2ohmloadsor
operate in BRIDGE mode into 4 ohms. The operator
mustbeawarethatwhendriving2ohmloadsorbridged
4 ohm loads that the currents running in the output
stagearevery largeandwillcausegreaterheatbuild
upwithin theamplifierthanhigherimpedance loads.
The Front Panel FAULT Indicators can be used to
provideanindicationof the "difficulty"oftheloadand
willgivetheoperatoranindicationoftheheatbuildup
in the output stage.
Ifthefaultindicatorsflashwiththe"clip"LEDsordonot
illuminate until well into clipping then the load can be
consideredas normal or easy.
If the fault indicator starts to flash before the "clip"
LEDs then the load should be considered complex
and/ordifficult.
For the more complex and/or difficult loads, the
illumination of the "fault" LED on programme peaks
shouldbeinterpretedastheoutputlevellimit.Driving
the output continuously past this point could result in
muting of the output stage, breakers tripping or
prematurethermalshutdown.
The fault detection circuit is also thermally
compensated,andfaultindicationwilloccurearlier
when the unit is hot. If the "fault" LED continually
lights earlier than normal, then the unit is heating
up.Ifthesignallevelisnotreducedtocompensate
for the heating of the unit then thermal shutdown
may occur.
16 Two Ohm or Not Two Ohm

7.Maintenance
Your AM1600 amplifier will need minimal
maintenance. No internal adjustments need to be
madetotheunittomaintainoptimumperformance.
Toprovideyearsofunhinderedoperationwesuggest
amaintenanceinspectionbecarriedoutonaregular
basis, say every 12 months or so.
Fans
Due to the openness of the air path through your
AM1600 amplifier, very little dust should settle
withintheamplifier.Theunithasbeendesignedso
thatanydustand/or foreign particles thatdosettle
withintheamplifierwillnotundulyhinderthecooling
of the unit.
Themeshgrilleinfrontofthefanswillacttolimitthe
amount of dust and lint entering the unit. You will
find in time that there will be a build up of dust and
lintonthegrillewhichmaystarttohindertheairflow
throughtheunit.Youshouldperiodicallyremovethe
dust and keep the grille clean.
Overtime,dustmaybuildupontheleadingedgeof
thefanbladesand reducetheircooling efficiency.
Thetimetakenforthistohappenwilldependonthe
environmentandthe amountofuse.
The fan blades are accessible once the lids are
removedandcanbeeasilycleaned.Youneedonly
hold the fan rotor still and wipe the dust off the
blades. Many users stall the fan and use
Maintenance 17
compressedairtoblowthe dust off thefanblades.
It is important to note that the fan blades must be
heldstillwhilstblowingairoverthebladesotherwise
you may burn out the bearings in the fan.
NOTE:
Makesuretheunitisoffandisunpluggedfromthe
mains. Give the main filter capacitors time to
dischargebeforeremovinglids.
Fuses
Therearefour(4)railfusesprovidedonthebackpanel
of the unit. These rail fuses are in series with the
positiveandnegativeoutputsupplyto each amplifier
channel and provide overall protection for the output
stage. If the amplifier is subjected to heavy use such
asshortcircuits,2ohmorbridged4ohmloads,these
fuseswilleventuallyfatigueandmayrequirereplacing
to ensure they do not fail at an inconvenient time.
Youshouldreplacethefuseiftheelementissagging
ordiscoloured.Onlyeverreplacewiththesametype
fuseandcurrentrating.
Whenchecking for afailedfuse, do notrely on visual
inspection alone. You should use an ohmmeter to
check continuity.
NOTE:
Makesuretheunitisoffandisunpluggedfromthe
mains and give the main filter capacitors time to
dischargebeforereplacingfuses.
Only competent or qualified persons should
attemptanyserviceormaintenanceofyouramplifier!

8.Warranty
AustralianMonitorwarrantsthe original purchaserof
each AM1600 amplifier (purchased at an authorised
Australian Monitor dealer) that it will be free from
defects in materials and workmanship for a period of
two(2)years from the originaldateof purchase.
AustralianMonitor will, at its option,repair or replace
any unit or component covered by this warranty
which becomes defective or malfunctions under
normal use and service during the period of this
warranty, at no charge for parts or labour to the
original owner.
This warranty does not cover thermal problems
due to obstructed airflow, or defects or malfunc-
tions resulting from accidents, misuse, abuse,
operation with the incorrect AC mains voltage,
connection to faulty equipment, modification or
alterationwithoutpriorfactoryapprovalorservice
by unauthorised personnel.
It is the owner's responsibility to ensure that normal
maintenance inspections are carried out at regular
intervalsasrecommendedinthemaintenancesection
of this manual. Australian Monitor reserves the right
to refuse warranty service where the owner fails to
18 Warranty
AM-SERIES2YEARWARRANTYREGISTRATION
IMPORTANT
Please complete this card and return it immediately after unpacking the product.
This card is to be sent DIRECTLY to Australian Monitor.
NOTE! Warranty is effective ONLY upon receipt of this card.
COMPANY
NAME MODEL
ADDRESS SERIAL No
DATE PURCHASED
CITY DEALER
STATE CODE COUNTRY
Ensure that you fill out and send your warranty registration card.
Use this copy to record a duplicate of the details.
take reasonable care in use and maintenance of the
amplifier.
Tovalidatethiswarranty,theoriginalpurchasermust
complete and mail the warranty registration card
directly to Australian Monitor within fourteen (14)
days of purchase.
Toobtainwarrantyservice,theequipmentshouldbe
shippedtoanauthorisedAustralianMonitordealeror
direct to Australian Monitor. Freight to Australian
Monitor is at the owner's expense.
Unitswithadefacedserialnumberwillnotbeaccepted
for warranty service. Any evidence of alteration,
erasure or forgery of the purchase receipt will also
void this warranty.
Australian Monitor accepts no liability for any
consequential damages, whether direct or
indirect, arising from the use or misuse of its
products.
Australian Monitor reserves the right to alter its
designsandspecificationsatanytime without notice
or obligation to previous purchasers.

Specification 19
Test conditions
Inputsource = 600 ohm,Balanced and groundreferenced (CMRR testhadfloating ground &50 ohm
source). Mains regulated to 240 volts / 50hz. All measurements taken at binding post output terminals.
Standardproductionunitsmeasured.Nocompensationapplied.
AM1600Specifications
Output Condition Output Power
E.I.A. Power @ 1 kHz, <0.05 % THD+N. 8 ohm 4 ohm 2 ohm
Singlechanneldriven. 520W 900W 1200W
Bothchannelsdriven. 470W 810W 1050W
Bridge mode @ 1 kHz, <0.05 % THD+N. 16 ohm 8 ohm 4 ohm
940W 1620W 2100W
Dynamic Power @ 1 kHz, at onset of clipping,
20 cycles @ 0dB, 480 cycles @ -20 dB. re 4 ohm. 950 Watts
Distortion (0.5 dB below clipping re 4 ohms)
THD+N (@ 1 kHz) <0.005%
IMDSMPTE (60 Hz & 7 kHz 4:1) <0.015%
IMDDIM30 (3.15kHz square & 15 kHz) <0.007%
Output Impedance @ 1 kHz <0.013ohms
Damping Factor @ 1 kHz re 8 ohms >650:1
Output Rise Time <2.2µS
(80%,leadingedgeof20kHzsquarewave)
Slew Rate >65V per µS
(leadingedge,20kHzsquarewave@clipping)
Frequency Response
20 Hz - 20 kHz < -0.5, -0.15 dB
-3dBpoints 5 Hz - 90 kHz
Input Impedance
Lineto Line(Balanced) 18k ohms
InputSensitivity(nominally)
Forratedpowerre8ohm 1.0 Vrms (+2.2 dBu)
Forratedpowerre4ohm 0.92 Vrms (+1.5 dBu)
VoltageGain 62 times (35.8 dB)
Input CMRR
@ 1 kHz (re 8 ohm rating) >90 dB
Signal / Noise ratio
"A"weighted (re 8ohm rating) >105dB
Crosstalk
@ 1 kHz (re 8 ohm rating) >90 dB
Weight Net 66.0 lb (30kg), Shipping 72.6lb (33kg)
Dimensions HxWxD
excludinghandles 133 x 483 x 375 (mm)
includinghandles 133 x 483 x 460 (mm)
(19 inch EIA rack mounting, 3 units high)

2000
www.australianmonitor.com.au
Distributed by:
Audio Telex Communications Pty Ltd
ACN001345482
www.audiotelex.com.au
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