AUSTRALIAN MONITOR AM1200 User manual

Operation Manual
AM1200

REFERSERVICINGTO
QUALIFIED PERSONNEL.
NO USER SERVICEABLE
PARTS INSIDE.
!WARNING!
DO NOT EXPOSE TO EITHER
RAIN OR MOISTURE
!CAUTION!
RISKOFELECTRICALSHOCK
DO NOT OPEN
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.
IMPORTANT!
Please read carefully.
Thisoperationmanualcontainsimportantinformationregarding
safetyprecautions,installation,performance,operationand
maintenance of your AM1200 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's enclosure. 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
operationofthe unit hazardousandincrease the risk
of electrical shock.
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

Features:
- 4, 3 or 2 channel operation.
- Custom designed, 3RU heavy duty alloy chassis.
-Modularconstruction.
-Symmetrical layout- evenweight distribution.
-Linear,well-regulating,highcurrentpowersupply.
-Dualisolatedhighcurrentsecondaries.
-Highefficiencytoroidalmainstransformer.
-Continuoushighpowercapability.
- Lateral Mosfet Class AB output stage.
- Binding post and Neutrik "Speakon" output
connection.
Protection Features
-Suppressionof inrushcurrentat mains turn-on.
-Inputmuting at turn-on.
-Inputovervoltageprotection.
-Radio-frequencyinterferencesuppression.
-Thermalprotectionandindication.
-Short-circuitprotection and indication.
-Inputsignalstrapping(loopthrough)connectors.
-Activebalancedinputs.
-21 Positiondetented attenuators.
-Massiveheat-sink/heat-exchangers.
- Efficient front to back cooling.
- Dual, twin speed axial fans.
-Frontand rearcarryhandles.
-Frontand rear mountingpoints.
-High-quality,close-tolerancecomponentsused
throughout.
- Mains Circuit Breaker.
-IndependentDCsupplyrailfusesperchannel.
-Layout,grounding,decouplingandcomponentry
havebeenoptimizedtoprovidetheuserwith
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 AM1200 Audio Power Amplifier
embracesalltheaspectsofawelldesignedunit.The
visual design, mechanical, electrical and sonic
parameters,alongwithour dedicatedmanufacturing
process, have all been optimized to provide a
professional tool that exhibits quality, reliability and
longevity.
TheAM1200 amplifiersare3unit(5.25")tall,19"wide
Figure 1 Amplifier Block Diagram
Introduction 5
rack mountable units.
Each channel of the amplifier comprises a balanced
active input with an attenuator driving a differential
classA drivestage whichin 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.

6 Controls & Connectors
Figure 2 Front Panel Layout
2. Controls,
Connectors
& Indicators

Front Panel
Figure 1 shows the panel layout of the AM1200. The
functionsofthecontrolsandindicatorsareasfollows:
1.Attenuator
Levelcontrol foryouramplifierisprovidedbya21
positiondetentedpotentiometerandindicatesgain
reduction in decibels from the 0 dB position
(maximumgain,noattenuation).
2. Status Indicator
ThisisadualcolourLEDwhichdisplaysthestatus
of the output stage and displays three levels of
operation.
Theselevelsare:
Below-20dB (unlit)
-20dBandabove (green)
1dBbelowactualclipping (red)
The LED will turn green once the output voltage
exceedsthe -20dBpoint (3.5volts).
The LED will change to red once the output ex-
ceeds the -1dB point before actual clipping of the
amplifier’soutputstage.Thethresholdofthe-1dB
point is referred to the amplifier supply rails and
alterswith changes in the mainssupply, changes
in the load and duty cycle fluctuations.
Theattackanddecaytime(ballistics),ofthestatus
circuit are those of a Peak Programme Meter
(P.P.M.)
NOTE:Theamplifierisnotdamagedbyrunninginto
clipping,butspeakersmaybe.Tomaximisethelife
of your speakers, try to keep clipping infrequent.
3. 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).
4. Power Switch
PresstheswitchDOWNfor powerON and UP for
power OFF. At start-up (turn-on) the input to the
amplifier is muted by 30dB for approximately two
seconds.
5. On / Thermal Indicator
Whenswitching theamplifier on, thisred LEDwill
momentarilyflashRed,indicatingcorrectoperation
oftheMainsIn-RushCurrentSuppressioncircuit.
After establishment of the Inrush Current
SuppressioncircuittheLEDwill change to Green
indicatingtheunitisonandreceivingmainspower.
In the advent of a thermal overload this LED will
illuminateredindicatingthattheinternaloperating
temperature of one or all amplifier channels has
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.
6. Bridge Mode Indicator
This LED will illuminate yellow when the relative
pairsofchannelsoftheamplifierhavebeenselected
tooperateina "BRIDGE"modeofoperation.
Selection of the bridge mode is accomplished by
engagingtherearpanel"PUSHTOBRIDGE"Switch.
See section 5 (page 15) for more information on
Bridgemodeoperation.
Controls & Connectors 7

8 Controls & Connectors
Figure 3 Rear Panel Layout

Rear Panel
7. Balanced Input
A female 3-pin XL type connector is provided on
eachinput:
Pin 1 = Signal Ground;
Pin2= Hot (non-invertingorinphase);
Pin3=Cold(invertingorreversephase).
7a.SignalStrapping
A male 3-pin XL type connector is provided on
channels A and D and is wired in parallel with the
female input XLR for strapping / looping signal
betweenamplifiers.
8. Bridge Switch
Pushing this switch in engages the BRIDGED/
MONO mode of operation for the relative pair of
channels. In this mode, your amplifier will only
acceptsignal applied tothe Channel-AinputXLR
(for channels A and B) or signal applied to the
Channel-DinputXLR(forchannelsDandC).
Channel-A will now control the level of the A/B
bridged pair and Channel-D will now control the
leveloftheD/Cbridgedpair.
Speaker termination should be sourced from the
redbinding-postoutputs.
9. 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-A (or D) is considered the
dominantchannelandhasbothchannelswiredto
theSpeakonconnector.Seetheinstallationsection
ofthismanualfordetailedinformationonSpeakon
wiring.
9a.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.
10.MainsLead
Youramplifierissuppliedwithaheavydutymains
Controls & Connectors 9
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.
! CAUTION !
Your amplifier must always be earthed!
11.MainsCircuitBreaker
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.
12.D.C. Rail Fuses
YourAM1200amplifierisfittedwith8Ampfusesper
rail - per channel, as overload protection for the
outputstageof your amplifier.
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.
Note:ThefrontpanelFaultIndicatorwillilluminate
and pulse in sync. with the program source if the
negativesupplyRailfuseblows.
DistortionwillresultandthefrontpanelStatusLED
will illuminate RED if the Positive Rail fuse blows.
Replace only with 8 Amp, 3AG fast acting type
fuses.

Figure 4 Dimensions
10 Installation