AUSTRALIAN MONITOR KA800 Operation Manual

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AUSTRALIAN MONITOR KA800 Operation Manual | Manualzz

O p e r a t i o n M a n u a l

IMPORTANT!

Please read carefully.

This operation manual contains important information regarding safety precautions, installation, performance, operation and maintenance of your KASeries power amplifier. You should familiarize yourself with the contents of this manual before operating your amplifier.

Safety Precautions and Labelling

The rear panel of the unit has a number of markings and internationally recognized symbols related to the hazards and precautions that should be taken when operating MAINS connected equipment.

REFER SERVICING TO

QUALIFIED PERSONNEL.

NO USER SERVICEABLE

PARTS INSIDE.

The presence of a LIGHTNING FLASH with an arrowhead contained within the boundaries of an equilateral triangle is intended to alert the user that dangerous uninsulated voltages may exist within the unit's enclosure. These voltages may be of a sufficient magnitude as to constitute the risk of an 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 user can service or re-use in this or any other product.

This symbol is reinforced with the text:

!CAUTION!

RISK OF ELECTRICAL SHOCK

DO NOT OPEN

If you are in need of special assistance and the information you require is outside the scope of this manual, please contact your nearest service agent or

Australian Monitor direct:

The presence of an EXCLAMATION MARK contained within the boundaries of an equilateral triangle is intended to alert the user that there is important operating and maintenance literature that accompanies the unit.

!WARNING!

DO NOT EXPOSE TO EITHER

RAIN OR MOISTURE

The unit should not be operated in a situation where it may encounter the entry of water, rain, or any fluids.

To expose the unit to the above conditions may make the operation of the unit hazardous and increase the risk of electrical shock.

THE TECHNICAL OFFICER

AUSTRALIAN MONITOR

C/- AUDIO TELEX COMMUNICATIONS PTY LTD

PRIVATE BAG 149,

SILVERWATER. N.S.W. 1811

AUSTRALIA.

Local

Phone

(02) 9647-1411

Fax

(02) 9748-2537

International 61-2-9647-1411 61-2-9748-2537

Email

Internet [email protected]

www.australianmonitor.com.au

Features:

- Custom designed, 2RU heavy duty alloy chassis.

- Open modular construction for ease of servicing.

- Symmetrical layout - even weight distribution.

- Well-regulating, high current power supply.

- High efficiency toroidal mains transformer.

- Binding post and Neutrik "Speakon" output connection.

- Stereo or bridged / mono operation.

- Input signal strapping (loop through) connectors.

- 21 Position detented attenuators.

- Balanced inputs and buffered attenuators.

- 1 Watt output indication (2.828 volts).

- 1 dB below output clip indication.

- Massive heat-sink / heat-exchangers.

- Efficient front to back cooling.

- Dual, twin speed axial fans.

- Multi-role output fault indication.

- Front carry handles. Rear rack mount ears.

- Plug in signal modifiers (optional).

- Signal ground lift switch.

- High-quality, close-tolerance components

throughout.

Protection Features

- Suppression of inrush current at mains turn-on.

- Input muting at turn-on.

- Input overvoltage protection.

- Radio-frequency interference suppression.

- Short-circuit protection and indication.

- High overload mains fuse.

- Internal, independent DC supply rail fuses.

- Layout, grounding, decoupling and componentry have been optimized to provide the user with

stability, reliability and longevity.

Contents

1. Introduction

2. Controls, Connectors and Indicators

2.1 Front Panel

2.2 Rear Panel

3. Installation

4. Operation

5. Bridge Mode

6. Two Ohm or Not Two Ohm

7. Maintenance

8. Warranty

9. Specification

Page

11

13

15

16

7

9

5

6

17

18

19

List of Illustrations

Figure 1. Block Diagram

Figure 2. Front Panel Layout

Figure 3. Rear Panel Layout

Figure 4. Case Dimensions

Figure 5. "Speakon" Connector Wiring

Figure 6. Bridge Mode Speaker Wiring

Page

8

10

5

6

12

15

Introduction 5

1. Introduction

Congratulations on choosing Australian Monitor for your professional amplification requirements.

The design of your KA -Series Audio Power Amplifiers embrace all the aspects of a well designed unit. The visual design, mechanical, electrical and sonic parameters, along with our dedicated manufacturing process, have all been optimized to provide a professional tool that exhibits quality, reliability and longevity.

The KA -Series amplifiers are 2 unit (3.5") tall, 19" wide rack mountable units.

Each channel of the amplifier comprises a balanced active input with a buffered attenuator driving a differential class A drive stage which in turn drives a fan-cooled, class AB, MOSFET output stage configured as a source follower. The unit operates from a high current-capable linear power supply.

These units have been specifically designed to deliver their high power output with minimal distortion, and provide the critical degree of control required by your speakers, at high duty cycles for extended periods.

Figure 1 Amplifier Block Diagram

6 Controls & Connectors

2. Controls,

Connectors

& Indicators

Figure 2 Front Panel Layout

Controls & Connectors 7

Front Panel

The KA Series models have identical front panel layouts.

Figure 1 shows the panel layout of the KA Series. The functions of the controls and indicators are as follows:

1 Attenuator

Level control for your amplifier is provided by a 21 position detented potentiometer and indicates gain reduction in decibels from the 0 dB position

(maximum gain, no attenuation).

2 Status Indicator

This is a dual color LED which displays the status of the output stage and displays three levels of operation.

These levels are:

Below 1 watt

1 watt and above

(unlit)

(green)

1dB below actual clipping (red)

The LED will turn green once the output voltage exceeds 2.828 volts (1 watt re 8 ohms or 2 watts re 4 ohms). This is equivalent to:

24.5dB below rated power for a KA800 or

26.0dB below rated power for a KA1200.

The LED will change to red once the output exceeds the -1dB point before actual clipping of the amplifier’s output stage. The threshold of the

-1dB point is referred to the amplifier supply rails and alters with changes in the mains supply, changes in the load and duty cycle fluctuations.

The attack and decay time (ballistics), of the status circuit are those of a Peak Programme

Meter (P.P.M.)

If using this indicator to line up sensitivities, apply a steady state tone (e.g. slate on a mixing console).

The 1 watt level is the mid-point between the indicator illuminating and extinguishing green.

3 Fault Indicator

This amber LED will flash when a fault condition exists.

The fault detection circuit monitors the difference between drive and output in your amplifier.

If you have a short on the speaker output (or a blown negative rail fuse) the LED will flash brightly in sync with the programme. This LED will also flash with programme peaks for gross overloads or if the load is 2 ohms or less.

The circuit has two stages of operation:

1. It will provide indication (e.g. gross overload) 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

Press the switch to the right for power on ( I )and to the left for power off ( 0 ). At start-up (turn-on) the input to the amplifier is muted by 30dB for approximately two seconds.

5 On/Thermal Indicator

This is a dual colored LED which will normally be

green and indicates that the amplifier is on and receiving mains power.

In the advent of a thermal overload this LED will turn red indicating that the internal operating temperature of one or both amplifier channels has exceeded a safe level of operation and the channels will be automatically muted. The fans will continue to run and once the effected channel/ s have had a cool-down period, they will un-mute and return to normal operation.

NOTE: The amplifier is not damaged by running into clipping, but speakers may be. To maximise the life of your speakers, try to keep clipping infrequent.

NOTE: You should always ensure that the fan grille is kept clean and free from the build up of dust and lint. This will ensure longer operation of your amplifier and reduce the possibility of it prematurely going into thermal shutdown mode.

8 Controls & Connectors

Figure 3 Rear Panel Layout

Controls & Connectors 9

Rear Panel

6 Balanced Input

A female 3-pin XL type connector is provided on each input:

Pin 1 = Signal Ground;

Pin 2 = Hot (non-inverting or in phase);

Pin 3 = Cold (inverting or reverse phase).

6a Signal Strapping

A male 3-pin XL type connector is provided and wired in parallel with the female input XLR for strapping / looping signal between amplifiers.

7 Signal Ground Lift Switch

When this switch is engaged it disconnects signal ground from the input connectors on both channels. It is intended to be used when “hum” is caused by earth loops (due to different ground potentials between source equipment and the amplifier) or stray magnetic field pick up on the input ground/shield wiring. (It does not interrupt signal ground continuity on the strapping connector). The amplifier should be turned off before engaging this switch!

8 Binding Post Outputs

Touch proof binding posts (banana jacks) are provided for speaker output termination with banana plugs or bare wire. The red post is used as

positive and the black post is used as negative.

8a SPEAKON Output Connector

The NEUTRIK (NL4MP) 4way SPEAKON connector is provided as an additional speaker output.

This emerging standard of loudspeaker to amplifier connection allows access to both channels of the amplifier via the one connector for bi-amp applications. Channel-A is considered the dominant channel and has both channels wired to the

Speakon connector. See the installation section of this manual for detailed information on Speakon wiring.

9 Mains Connection

Your amplifier is fitted with an internationally recognised IEC mains inlet connector.

Please ensure that the connecting mains lead for use with this connector is of an approved type and is of sufficient current carrying ability.

Your KA800 and KA1200 require a minimum mains lead rating of 10 amps when operated from a 220 to 240 volt mains supply.

NOTE: Your unit must always be earthed!

10 Mains Fuse

A 20mm x 5mm fuse drawer is provided within the housing of the IEC mains connector. When you recieve your amplifier it will have a working fuse and a spare fuse inside the fuse drawer. The drawer can only be opened once the mains lead is removed from the connector. The fuse is provided to protect both the mains and your amplifier as well as reducing the degree of damage if an internal fault exists.

When replacing the fuse, replace with an antisurge (slow blow) type of the current rating indicated on the back panel above the fuse holder.

Warranty does not cover a blown fuse or any resulting damage due to an incorrect fuse rating or type.

The KA800 requires a 8 Amp Anti-Surge fuse.

The KA1200 requires a 10 Amp Anti-Surge fuse.

11 Bridge Switch

Pushing this switch in engages the BRIDGED/

MONO mode of operation. In this mode your amplifier will only accept signal applied to channel

A’s input XLRs and the level of both channels will be controlled by channel A’s attenuator. The output from channel B will automatically be of the opposite polarity (reversed phase) and speaker termination should be sourced from the red binding-post outputs.

D.C. Rail Fuses

(Internally fitted)

Removing the bottom lid will show PCB mounted fuse holders holding the rail fuse for each supply to each channel. These 3AG “fast blow” type fuses are in series with the positive and negative supply rails for each channel of your amplifier’s output stage. These fuses provide overall protection of the output stage and can also be used to isolate individual channels in case a fault condition exists.

If you need to replace the rail fuses they must be replaced with the same type and current rating:

KA800 = 8 Amp.

KA1200 = 10 Amp.

NOTE: Replacement of the fuses should only be carried out by a competent and experienced person.

10 Installation

Figure 4 Dimensions

Installation 11

3. Installation

Power Requirements

heat to build up within the unit and possibly force the unit into its thermal shutdown mode.

Model:

Mains Voltage

240, 220-230

KA800

Fuse Rating

8 Amps

Power consumption at idle = 120 Watts.

Power consumption at rated power = 1450 Watts.

Model:

Mains Voltage

240, 220-230

KA1200

Fuse Rating

10 Amps

Power consumption at idle = 160 Watts.

Power consumption at rated power = 2200 Watts.

Ensure that your mains voltage is the same as the rear panel mains voltage marker (+/- 10%).

Mounting

Your amplifier is designed for standard 19" rack mounting and occupies 2 EIA rack units (3.5"). The mounting centers are:

Vertical: 3.0" (76.2mm)

Horizontal: 18.2" (461.2mm) to 18.7" (473.8mm).

The slots in the mounting flange will accept bolt diameters up to 1/4" (6.35mm).

We recommend that you provide additional support for the amplifier, especially if road use is planned, as the weight can bend some racks otherwise. This support can be provided by secure shelving, support rails or a rear rack mounting strip to match up with the rear rack mount ears provided on your KA Series amplifier.

Cooling

Each channel of your KA800/KA1200 amplifier is cooled by an axial fan which draws cool air from the front of the unit and expels the heated air from the rear of the unit. These units offer two speed fans which run at half speed, switching to full speed when the internal heatsink temperature exceeds 60 0 C (128 0 F).

An unrestricted airflow into and out from the unit must be provided. Any restriction of the air flow will cause

If the units are to be operated in an environment where the airflow is restricted such as sealed racks or 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).

The input to your amplifier is a balanced 3-pin system and requires all three pins to be connected. Only high quality twin-core shielded cable should be used.

When wiring for a balanced source the connector going to the input of your amplifier should be wired as follows:

Pin 2 = HOT (In Phase - non inverting).

Pin 3 = COLD (Reverse Phase - inverting).

Pin 1 = GROUND / SHIELD.

When wiring from an unbalanced source you must ensure that pin 3 is connected to pin 1 (input ground), 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 (in phase with the amplifier’s output),

Pin 3 = Ground/Shield (joins to pin 1).

Pin 1 = Ground/Shield

NOTE:

In-line XLR connectors often have a termination lug that connects directly to the chassis of the connector.

Do not link this lug to pin 1 at the amplifier’s input as it will defeat the amplifier’s input grounding scheme.

This lug is often referred to as a "drain” and is used to provide a termination to the chassis for shielding purposes when a floating signal ground is required between the source and destination, or when disconnecting the signal ground is required to reduce earth loop noise, or noise induced into signal grounds from stray magnetic fields.

12 Installation

Output Wiring

When wiring to your speakers always use the largest gauge wire your connector will accept. The longer the speaker lead the greater the losses will be, resulting in reduced power and less damping at the load. We recommend using a heavy duty two core flex (four core flex if bi-amping) 10 to 12 gauge (2mm 2 to

2.5mm

2 or 50/0.25 or equivalent) as a minimum.

Binding Post Outputs

When terminating to the 4 mm binding post (banana jack) output connectors, banana plugs or bare wires can be used. The red terminal is positive and the black 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 negative output to the load.

SPEAKON Outputs

When using the NEUTRIK SPEAKON (NL4MP) connector for speaker output, use only the mating

NEUTRIK NL4FC in-line connector. This connector is designed so that both channels can be fed from a single connector.

Two SPEAKON connectors are provided on the amplifier.

SINGLE CONNECTION

The "Channel A" SPEAKON actually carries both channel A & channel B outputs (see Figure 5: Speakon

Connector Wiring Diagrams).

The "Channel B" SPEAKON carries the Channel B output only.

This arrangement allows you the option of connecting 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 B output twice!

Channel A is used as the “dominant” channel and when sourcing a dual output from Channel A the following standard should be used:

Channel A = Left or Low Frequencies.

Channel B = Right or High Frequencies.

When in bridge mode:

Pin 1+ = Bridge Output Positive

Pin 2+ = Bridge Output Negative.

BRIDGED CONNECTION

DUAL CONNECTION BI-AMP CONNECTION

Figure 5. "Speakon" Connector Wiring Diagram

Operation 13

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 instances the fault in a “floating” (ungrounded) piece of equipment will look for the shortest path to ground which could possibly be your amplifier's input. If the fault current is large enough it will destroy the input to your amplifier and look for the next available path, which may be you!

Before making any connections to your

KA1200 amplifier observe the following:

1.

2.

3.

4.

5.

Ensure the mains voltage supply matches the label on the rear panel of your amplifier (+/- 10%).

Ensure that the power switch is OFF (to the left -

0)

Ensure that all system grounds (earth) are connected from a common point. Avoid powering equipment within a system from multiple power sources that may be separated by large distances.

Check the continuity of all interconnecting leads to 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 output of the amplifier.

Before operating your that:

KA800/KA1200 amplifier, ensure

- The attenuators are at the “OFF” position (fully anticlockwise).

- The GROUND LIFT Switch is not engaged (should be in the “out” position).

- The BRIDGE Switch is not engaged if you are not running the amp in bridged mode.

Powering Up

REMEMBER

The amplifier should be the last piece of equipment that you turn on and the first piece of equipment that you turn off.

We recommend turning the attenuators on your amplifier down when turning the unit on.

When you power up your KA800/KA1200 , your amplifier goes through an establishment period before it will accept signal. The Inrush Current Supression (ICS) circuit is in operation for the first 0.5 seconds. This limits the mains current to prevent "nuisance-tripping" of circuit breakers.

During this period the THERMAL/ON LED will flash

red whilst the mains voltage gradually charges up the power supply. You will then hear a relay “click”, indicating mains is now directly applied to the amplifier and the THERMAL/ON LED will be green.

While the ICS circuit operates there is also a 30dB mute on the signal input. After two seconds this mute will release, allowing any applied signal to pass unattenuated.

When switching the amplifier off, wait a couple of seconds before switching the unit on again. This allows the ICS circuit to reset.

Level Matching

The normal operating position for the attenuator is the "0 dB" position (fully clockwise, no attenuation).

In this position the amplifier operates at full gain.

Turning the attenuator back (anticlockwise) reduces the input sensitivity by the amount marked on the attenuator scale (dial).

NOTE:

If full power output is required you should operate your amplifier with the front panel attenuator above the -15dB position, otherwise clipping of the input circuitry and its resultant distortion will occur before full output power is achieved.

Sensitivity

Your amplifier is a linear device operating with a fixed 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.

The voltage gain factor of your amplifier is:

37 (31.5 dB) for a KA800

45 (33.0 dB) for a KA1200

The input sensitivity for your KA800/KA1200 amplifier when the attenuator is at the “0” dB attenuation position (fully clockwise) is nominally:

+4.0dB (1.23 volts in) for rated power into a 8 ohm load.

+3.0dB (1.10 volts in) for rated power into a 4 ohm load.

14 Operation

Each channel of your KA800/KA1200 amplifier has a nominal balanced input impedance of 30kOhms

(@1kHz) and should not present a difficult load for any signal source.

Your signal source (i.e. the equipment feeding the amplifier) should have an output impedance of

600 Ohms or lower to avoid unwanted high frequency loss in the cabling.

Input overload occurs at +20.5dBu (8.25 volts).

See the specification section for more detailed information.

Hum Problems

Most equipment is designed for minimum hum when used under ideal conditions. When connected to other equipment, and to safety earth in an electrically noisy environment however, problems will often occur.

The three "E"s of hum and hum related noise which can plague your audio system are: a) Electrostatic radiation, b) Electromagnetic radiation, and c) Earth loops

Electrostatic radiation capacitively couples to system elements causing an interference voltage that mainly affects higher impedance paths, such as amplifier inputs. The source is generally a nearby high voltage such as a mains lead or a speaker lead.

The problem can usually be reduced by moving the 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 lower impedance paths. Radio transmitters or stray magnetic fields from mains transformers are 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 various pieces of equipment and their connections to safety earth.

This is by far the most common cause of hum, and it occurs when source equipment and the amplifier 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 produces a voltage drop due to the wire’s resistance. This voltage difference between the amp earth and source equipment earth appears to the amplifier's input as a signal and is amplified as hum.

There are three things you can do to avoid earth loop problems:

1.

Ensure your mains power for the audio system is

“quiet” i.e. without equipment on it such as airconditioning, refrigeration or lighting which may generate noise in the earth circuit.

2.

Ensure all equipment within the system shares a common ground/ safety earth point. This will reduce the possibility of circulating earth currents as the equipment will be referenced to the same ground potential.

3.

Ensure that balanced signal leads going to the amplifier are connected to earth at one end only.

Signal Ground-Lift Switch

When proper system hook-up has been carried out, you may still have some hum or hum related noise.

This may be due to any of the previously mentioned gremlins.

Your KA800/KA1200 amplifier has a “Signal Ground Lift” switch which disconnects the input ground wiring from the amplifier. A substantial drop in hum and or hum related noise can result from judicious use of this switch.

NOTE

If the input ground lift switch is used you must ensure adequate shielding of the input wiring. If the signal source equipment does not provide adequate shielding (i.e. a definitive connection to ground) you must disconnect the shield from the input connector's ground pin (Pin-1) and re-connect it to the "drain" contact on the input connector. This will ensure the shield on your input wiring actually goes to the amplifier chassis and subsequently to earth.

DO NOT CONNECT PIN-1 DIRECTLY TO THE

DRAIN CONNECTION.

You will defeat the amplifiers internal grounding scheme and possibily cause instability to the amplifier.

Always ensure that your amplifier is off and the attenuators are down when you engage this switch.

This switch should only be used when the amplifier is operated from a balanced signal source.

NOTE: Be wary of quasi-balanced outputs, these are often no more than floating unbalanced outputs.

Bridge Mode 15

5. Bridge Mode

The term BRIDGE is used when two independent amplifier channels are used to drive the same load.

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 its phase reversed so it is exactly 180 0 out of

phase with the input signal.

As two amplifiers with a phase difference of 180 0 are now driving the load you will now have double the voltage into the load. This means you will now have four times the power into that load. The output can now be considered as an active balanced output.

A common use of an amplifier in BRIDGE mode is for driving 70 volt & 100 volt distribution lines. In BRIDGE mode, The KA1200 can produce over 100 volts with line impedances over 8 ohms whilst the KA800 can produce over 84 volts with line impedances over 8 ohms.

Equally the units can be used in bridge mode to provide the correct voltage/power requirements for an applicable load.

As shown in Figure 6, there are three steps in setting up your mode.

KA800/KA1200 amplifier for running it in BRIDGE

Whilst the amplifier is off,

1. Connect the signal source to the Channel-A female input XLR. The Channel-A attenuator becomes the level control for both channels.

2. Engage the “push to bridge” switch.

3. Connect your load between the red binding post output terminals, where the positive side of the load is connected to the channel A output (marked

BRIDGE+) and the negative side of the load goes to the channel B output (marked BRIDGE

-

). There are no further connections required.

You can also source the output from the Channel-A

SPEAKON output connector where Channel-A will be on the pin marked 1+ and Channel-B will be on the pin marked 2+.

NOTE: You should check after market manufactured

Speakon interconnecting speaker leads before connecting them to your amplifier. Some leads are manufactured for specific purposes, or specific use, and may have pins shorted inside the connector. Any speakon lead with shorted pins will obviously short the output of your amplifier (either to ground, or output to output - be careful).

Figure 6 Bridge Mode Speaker Connection

16 Two Ohm or Not Two Ohm

6. Two Ohm or

Not Two Ohm

NOTE:

Ensure adequate ventilation and monitor the FAULT indicators to guard against thermal shutdown when driving two ohm loads.

A Preamble.

The load that a loudspeaker presents to an amplifier is very complex and at different frequencies can be inductive, capacitive, resistive, or a combination of these (reactive). With the complex interaction of these attributes, which alter from loudspeaker to loudspeaker, a definitive load for an amplifier does not really exist.

Loudspeakers operating within an enclosure are specified with a nominal impedance. This nominal impedance is only a rough guide to the load it presents to an amplifier.

As an example, a loudspeaker with a nominal impedance of say 8 ohms, may have an impedance of over

50 ohms at resonance (bass frequencies), drop to less than 6 ohms after the resonance peak (through its mid band area) and then increase to over 16 ohms for higher frequencies.

A 4 ohm load makes an amplifier work "harder" than an 8 ohm load at the same voltage, as double the current is required.

Though various loudspeakers may be marked with the same nominal impedance, some loads are more difficult than others.

Bass frequencies usually exhibit higher impedances and require higher voltages to achieve the desired result. They also reflect higher energy back to the amplifier simply due to the amount of cone excursion involved at lower frequencies.

The Mid frequency band usually offers the lowest impedances and the highest duty cycles requiring both high voltage and high current.

The High frequency region usually offers a moderate impedance and usually does not need much voltage but the instantaneous current demand can be much greater than you think.

As well as this burden on the amplifier, the transient waveforms found in actual use can demand a lot more current than the "steady-state" sinewaves used in most amplifier bench tests.

The power output of your KA800/KA1200 quoted on the specification sheet is derived from a voltage excursion into a resistive load for a sine wave at a given frequency. Though this method is in line with the various standards that exist, it only gives an indication to the maximum voltage swing (before clipping) for a given load. This method of rating power does not give an indication of the current (Ampere) capability of the amplifier, nor does it show the amplifier’s ability to sustain high energy waveforms.

Your KA800/KA1200 amplifier is designed to be able to deliver more than twice the current than that shown on the specification sheet to cope with difficult loads and/or high energy waveforms.

This extra current reserve is the result of over engineering and is the headroom the amplifier utilizes to control the loudspeaker and deal with the “reactive energy” from the loudspeaker load that has to be dissipated within the amplifier.

Your KA800/KA1200 amplifier is able to drive 2 ohm loads or operate in BRIDGE mode into 4 ohms. The operator must be aware that when driving 2 ohm loads or bridged 4 ohm loads that the currents running in the output stage are very large and will cause greater heat build up within the amplifier than higher impedance loads.

The Front Panel FAULT Indicators can be used to provide an indication of the "difficulty" of the load and will give the operator an indication of the heat build up in the output stage.

If the fault indicators flash with the "clip" LED or do not illuminate until well into clipping then the load can be considered as normal or easy.

If the fault indicator starts to flash before the "clip"

LED then the load should be considered complex and/or difficult.

For the more complex and/or difficult loads, the illumination of the "fault" LED on programme peaks should be interpreted as the output level limit.

Driving the output continuously past this point could result in muting of the output stage, fuse's blowing or premature thermal shutdown.

The fault detection circuit is also thermally compensated, and fault indication will occur earlier when the unit is hot. If the "fault" LED continually lights earlier than normal, then the unit is heating up. If the signal level is not reduced to compensate for the heating of the unit then thermal shutdown may occur.

Maintenance 17

7. Maintenance

Your KA800/KA1200 amplifier will need minimal maintenance. No internal adjustments need to be made to the unit to maintain optimum performance.

To provide years of unhindered operation we suggest a maintenance inspection be carried out on a regular basis, say every 12 months or so.

Fans

Due to the openness of the air path through your

KA800/KA1200 amplifier, very little dust should settle within the amplifier. The unit has been designed so that any dust and/or foreign particles that do settle within the amplifier will not unduly hinder the cooling of the unit.

The mesh grille in front of the fans will act to limit the amount of dust and lint entering the unit. You will find in time that there will be a build up of dust and lint on the grille which may start to hinder the airflow through the unit. You should periodically remove the dust and keep the grille clean. Removal of dust from the rear grille will also aid cooling.

Over time, dust may build up on the leading edge of the fan blades and reduce their cooling efficiency.

The time taken for this to happen will depend on the environment and the amount of use.

The fan blades are accessible once the lids are removed and can be easily cleaned. You need only hold the fan rotor still and wipe the dust off the blades.

Many users stall the fan and use compressed air to blow the dust off the fan blades. It is important to note that the fan blades must be held still whilst blowing air over the blades otherwise you may burn out the bearings in the fan.

Fuses

Along with rear panel mains fuse, there is four (4) rail fuses provided internally in the unit. These rail fuses are in series with the positive and negative output supply to each amplifier channel and provide overall protection for the output stage. If the amplifier is subjected to heavy use such as short circuits, 2 ohm or bridged 4 ohm loads, these fuses will eventually fatigue and may require replacing to ensure they do not fail at an inconvenient time.

NOTE

Make sure the unit is off and is unplugged from the mains. Give the main filter capacitors time to discharge before removing lids and inspecting the fuses.

You should replace the fuse if the element is sagging

or discoloured. Only ever replace with the same type fuse and current rating.

When checking for a failed fuse, do not rely on visual inspection alone. You should use an ohmmeter to check continuity.

Only competent or qualified persons should attempt any service or maintenance of your amplifier.

18 Warranty

8. Warranty

Australian Monitor warrants the original purchaser of each KA-Series 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 original date of purchase.

Australian Monitor 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 blown fuses, faulty fuse contacts, thermal problems due to obstructed airflow, or defects or malfunctions resulting from accidents, misuse, abuse, operation with the incorrect AC mains voltage, connection to faulty equipment, modification or alteration without prior factory approval or service by unauthorised personnel.

It is the owner's responsibility to ensure that normal maintenance inspections are carried out at regular intervals as recommended in the maintenance section of this manual. Australian Monitor reserves the right to refuse warranty service where the owner fails to take reasonable care in use and maintenance of the amplifier.

To validate this warranty, the original purchaser must complete and mail the warranty registration card directly to Australian Monitor within fourteen (14) days of purchase.

To obtain warranty service, the equipment should be shipped to an authorised Australian Monitor dealer or direct to Australian Monitor. Freight to Australian

Monitor is at the owner's expense.

Units with a defaced serial number will not be accepted 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 designs and specifications at any time without notice or obligation to previous purchasers.

KA -SERIES 2 YEAR WARRANTY REGISTRATION

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

ADDRESS

CITY

STATE CODE

MODEL

SERIAL N

o

DATE PURCHASED

DEALER

COUNTRY

Ensure that you fill out and send your warranty registration card.

Use this copy to record a duplicate of the details.

Specification 19

Model:

KA1200

Output Power

E.I.A. 1 kHz, <0.1 % THD+N.

8ohm

Single channel driven.

440W

Both channels driven.

400W

Pulsed @ 1 kHz, at onset of clipping,

10% duty cycle, re 4 ohms.

Single channel driven.

Both channels driven.

Bridge mode

16 ohm load

8 ohm load

4ohm

680W

600W

800W

750W

800W

1200W

Output Impedance

@ 1 kHz <0.025 ohms

Damping Factor

@ 1 kHz re 8 ohms >320:1

Output Rise Time

(80%, leading edge of 20kHz square wave)

<2.8

µ S

Slew Rate

60V per µ S

(leading edge, 20kHz square wave @ clipping)

Weight

Net 37.5 lb (17kg), Shipping 43lb (19.5kg)

Model:

KA800

Output Power

E.I.A. 1 kHz, <0.1 % THD+N.

8ohm

Single channel driven.

285W

Both channels driven.

255W

Pulsed @ 1 kHz, at onset of clipping,

10% duty cycle, re 4 ohms.

Single channel driven.

Both channels driven.

Bridge mode

16 ohm load

8 ohm load

4ohm

460W

400W

550W

500W

510W

800W

Output Impedance

@ 1 kHz <0.030 ohms

Damping Factor

@ 1 kHz re 8 ohms >260:1

Output Rise Time

(80%, leading edge of 20kHz square wave)

<2.8 µ S

Slew Rate

50V per µ S

(leading edge, 20kHz square wave @ clipping)

Weight

Net 33 lb (15kg), Shipping 38.5 lb (17.5kg)

Common Specifications

Distortion

(0.5 dB below clipping re 4 ohms)

THD+N (@ 1 kHz)

IMD SMPTE (60 Hz & 7 kHz 4:1)

<0.01%

<0.05%

IMD DIM 30 (3.15kHz square & 15 kHz) <0.02%

Input CMRR

@ 1 kHz (re 8 ohm rating)

Signal / Noise ratio

"A" weighted (re 8 ohm rating)

Frequency Response

20 Hz - 20 kHz

-3dB points

< ± 0.15 dB

<10 Hz - 90 kHz

Crosstalk

@ 1 kHz (re 8 ohm rating)

Input Impedance

Line to Line (Balanced) 30k ohms

Input Sensitivity

(nominally)

For rated power re 8 ohm

For rated power re 4 ohm

1.26 Vrms (+4 dBu)

1.10 Vrms (+3 dBu)

>80 dB

>100 dB

>90 dB

Dimensions

excluding handles including handles

H x W x D

3.5 x 19 x 14.8 (inch)

88 x 482 x 375 (mm)

3.5 x 19 x 17.7 (inch)

88 x 482 x 450 (mm)

(19 inch EIA rack mounting, 2 units high)

Test conditions

Input source = 600 ohm, Balanced and ground referenced (CMRR test had floating ground & 50 ohm source). Mains regulated to 240 volts / 50hz. All measurements taken at binding post output terminals.

Standard production units measured. No compensation applied.

www.australianmonitor.com.au

Distributed by:

Audio Telex Communications Pty Ltd

ACN 001345482

www.audiotelex.com.au

International Enquiries

Ph: 612 9647 1411, Fax: 612 9748 2537, E-mail: [email protected]

Sydney

Ph: (02) 9647 1411, Fax: (02) 9648 3698, E-mail: [email protected]

Melbourne

Ph: (03) 9890 7477, Fax: (03) 9890 7977, E-mail: [email protected]

Brisbane

Ph: (07) 3852 1312, Fax: (07) 3252 1237, E-mail: [email protected]

Adelaide

Ph: (08) 8352 4444, Fax: (08) 8352 4488, E-mail: [email protected]

Perth

Ph: (08) 9228 4222, Fax: (08) 9228 4233, E-mail: [email protected]

Auckland

Ph: (09) 415 9426, Fax: (09) 415 9864, E-mail: [email protected]

2000

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Questions and Answers

What is the purpose of the Status Indicator?
The Status Indicator is a dual-color LED that displays the status of the output stage. It indicates three levels of operation: below 1 watt (unlit), 1 watt and above (green), and 1dB below actual clipping (red).
What does the Fault Indicator do?
The Fault Indicator is an amber LED that flashes when a fault condition exists. It monitors the difference between drive and output in the amplifier and provides indication for various fault conditions, such as short on the speaker output and gross overloads.
What is the function of the Attenuator?
The Attenuator is a 21-position detented potentiometer that controls the level of the amplifier. It indicates gain reduction in decibels from the 0 dB position (maximum gain, no attenuation).
What is the purpose of the Signal Ground Lift Switch?
The Signal Ground Lift Switch is used to disconnect signal ground from the input connectors on both channels. It is intended to be used when hum is caused by earth loops or stray magnetic field pick up on the input ground/shield wiring.
What is the difference between the Binding Post Outputs and the Speakon Output Connector?
The Binding Post Outputs are touch-proof binding posts (banana jacks) used for speaker output termination with banana plugs or bare wire. The Speakon Output Connector is a NEUTRIK (NL4MP) 4way SPEAKON connector that allows access to both channels of the amplifier via one connector for bi-amp applications.

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