Altec Lansing 4200A User Manual

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6125A

 

4200A

 

MULTI-CHANNELPOWER AMPLIFIERS

Altec Lansing Professional

 

1000 W. Wilshire Blvd. Suite 362

 

Oklahoma City, OK 73116 USA

 

A division of Altec Lansing Technologies Inc, Milford PA 18337-0277

Made In USA

Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

TABLE OF CONTENTS

1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 UNPACKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 AC POWER REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

3.1

Voltage Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

3.2

Current Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

3.3

AC Grounding & Earth Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

4 CABLE REQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 Input Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.2 Output Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5 RACK-MOUNTINGREQUIREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5.1 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5.2 Cooling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

5.3 Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

6 FRONT PANEL FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

7 REAR PANEL FEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

7.1

Input Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

7.2

Input Ground Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

7.3

Multi-ChannelOperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

7.4

50Hz Low Cut Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

7.5

Input Level Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

7.6

Stereo/Mono Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8

7.7

Dual Channel Mode/Bridge Mode Switches . . . . . . . . . . . . . . . . . . . . . .

8

7.8

Loudspeaker Output Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

7.9

AC Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

8 SELF-PROTECTIONFEATURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1 Power Supply Undervoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.2 Power Supply Overvoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.3 Output Overcurrent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.4 Heat Sink Overtemperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.5 Unacceptable DC or High Frequency Output Content . . . . . . . . . . . . 10 8.6 AC Power Interruption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

9 TYPICAL APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

9.1 Six Channel Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

9.2 Dual Mono Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

9.3 Bridged Mono Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

9.4 Typical PA Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

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Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

10 DESIGN THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

11 TROUBLESHOOTING TIPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1 No Audio Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.2 Distorted Sound . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 11.3 Hum or Buzz Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

12 DIMENSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

13 SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

14 WARRANTY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Caution:

This power amplifier can produce dangerous output voltage levels, high power levels, and high sound pressure levels in loudspeakers. In order to minimize the risk of injury, damage, or hearing loss, please read the entire owner’s manual before connecting to a sound system.

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

The lightning flash with arrowhead symbol, within an equalateral triangle, is intended to alert the user to the presence of uninsulated "dangerous voltage" within the product's enclosure that may be of sufficient magnitude to constitute a risk of electric shock to persons.

The exclamation point within an equalateral triangle is intended to alert the user to the presence of important operating and maintenance instructions in the literature accompanying the device.

TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT REMOVE COVER. NO USER SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.

TO REDUCE THE RISK OF FIRE OR ELECTRICAL SHOCK, DO NOT EXPOSE THIS

APPLIANCE TO RAIN OR MOISTURE.

TO REDUCE THE RISK OF FIRE, REPLACE ONLY WITH SAME TYPE FUSE. REFER REPLACEMENT TO QUALIFIED SERVICE PERSONNEL.

WARNING: THIS APPARATUS MUST BE EARTHED THROUGH THE SUPPLIED

POWER LINE CORD

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Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

1.INTRODUCTION

The 6125A and 4200A power amplifiers combine the efficiency of a MOSFET high-speedswitching output stage with the sophistication of modern microprocessor and DSP technology to produce amulti-channelamplifier with unprecedented versatility and power in a single 3RU package.

Although similar to other amplifiers with class D output stages, the 6125A and 4200A amplifiers employ internal microprocessor and DSP algorithms to optimize output switching characteristics and eliminate the usual harshness associated with high-frequencyaudio in standard class D amplifiers. This optimization results in aspread-spectrum switched output that varies with input amplitude and frequency, and minimizes radiated emissions by eliminating thesingle-frequencyhigh-energyradiated interference normally associated with switching outputs. The use of a simple linear power supply removes another potential source ofradio-frequencyinterference, an important consideration as racks become more and more heavily populated with digital signal processing equipment. A small switching supply using flyback topology provides an efficient power source for logic, protection,pre-ampli-fier and indicator circuits.

To assure reliable operation, the usual protection from excessive high-frequency,DC offset, and thermal overload is supplemented by power supply undervoltage, power supply overvoltage, and output overcurrent detection, all monitored and controlled by the latest in miniaturized microprocessor technology.

In sum, 6125A and 4200A amplifiers combine the best of the new digital technologies with the best of the traditional analog technologies to provide a product that will supply clean sound at full output from every channel while generating minimal heat, thus increasing the reliability of every other piece of equipment in a rack as well as preserving its own.

2.UNPACKING

As a part of our system of quality control, every Altec Lansing product is carefully inspected before leaving the factory to ensure flawless appearance. After unpacking, please inspect for any physical damage. Save the shipping carton and all packing materials, as they were carefully designed to reduce to minimum the possibility of transportation damage should the unit again require packing and shipping. In the event that damage has occurred, immediately notify your dealer so that a written claim to cover the damages can be initiated.

The right to any claim against a public carrier can be forfeited if the carrier is not notified promptly and if the shipping carton and packing materials are not available for inspection by the carrier. Save all packing materials until the claim has been settled.

3.AC POWER REQUIREMENTS

3.1Voltage Requirements

The 6125A and 4200A amplifiers can be operated from nominal 120VAC or 240VAC, 50/60Hz mains. This is user-configurableby changing the insert in the AC Inlet (See section 7.9). The power connector on the amplifier accepts a standardIEC-320receptacle.

For nominal 120VAC operation, the power cord should be three-conductor,rated for at least 13A (16AWG). The line fuse should be type MDA, 12A.

For nominal 240VAC operation, the power cord should be three-conductor,rated for at least 10A (18AWG). The line fuse should be type MDA, 10A.

3.2Current Requirements

1.)

Idle (no audio):

 

 

6125A

4200A

 

120V: 0.81A

120V: 0.9A

 

240V: 0.42A

240V: 0.5A

2.)

With typical audio inputs:

 

8loads on all channels

 

 

120V: 4A

120V: 4.6A

 

240V: 2A

240V: 2.3A

4loads on all channels

 

 

120V: 6.5A

120V: 7.0A

 

240V: 3.3A

240V: 3.5A

6125A and 4200A amplifiers consume less than 12 amps when all channels operate at 1/8 power into rated (4 ohm) loads. This condition satisfies the UL, CSA and building electrical code requirements for a piece of audio equipment not to consume more than 80% of the current available when plugged into a grounded 15 amp outlet and operated at 1/8 of maximum power.

3.3 AC Grounding and Earth Grounding

To reduce the risk of ground loop hum, all system ground references should originate at the same point in your AC power distribution. Do not remove the amplifier’s ground pin, as it creates a potential shock hazard.

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Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

4.CABLE REQUIREMENTS

4.1Input Cables

Be sure to use shielded cable whether balanced or unbalanced. Shielding which is properly grounded will protect the signal from outside electrical interference such as RF, fluorescent lighting, and computer/display emissions. As a general rule, unbalanced or single-ended(tipsleeve) lines of less than 10 feet are satisfactory, but greater distances or noisy field environments require a balanced signal. Avoid running input lines in close proximity or parallel to long speaker lines, AC power cables, or power transformers, as this may generate hum or oscillation.

4.2Output Cables

These amplifiers are capable of delivering high levels of output current, therefore the wire gauge used for speaker cables is particularly important. Inadequate wire gauge can add significant resistance to the speaker’s own impedance, especially over long distances, reducing the power which is actually delivered to the speaker. It could also result in a decreased damping factor and possible fire hazard. Since power at the speaker load is of primary concern in system design, we have included a table to best determine appropriate wire gauge for your application. The following table lists the resistance per 100 feet of common copper wire gauges, and also gives the percentage of the speaker load power which would be lost in an arbitrary 100 ft run of different gauges of2-conductorcopper speaker wire.

Wire Gauge

/100ft

8load

4load

#8

.0605

0.8%

1.5%

#10

.1018

1.3%

2.5%

#12

.1619

2.0%

4.0%

#14

.2575

3.2%

6.4%

#16

.4094

5.1%

10.2%

#18

.6510

8.1%

16.3%

Table 4.1: Wire gauge resistance/power loss

This table expresses the power loss as a percentage of the load’s power rather than the total amplifier output power in order to accurately determine power loss at other cable lengths. For example, if you plan to deliver 150 watts to an 8load through50 ft of 14 ga. cable, the power loss in the cable would behalf that of a 100 ft run of #14 wire as shown in the table, or 1.6% of 150W, which is an insignificant 2.4 watts. However, if you were to run200 ft of18 ga. cable to a4load, the loss would be twice that of the 100 ft run shown in the table, or 32.6% of 250W, which is 81.5 watts lost as heat. Always be sure to use adequate gauge speaker wire.

5.RACK-MOUNTINGREQUIREMENTS

5.1Mechanical

The 6125A and 4200A amplifiers are designed to fit in standard 19-inchequipment racks. The front panelrack-mountears are sufficiently strong for most applications, however if you desire further integrity for mobile racks, we recommend using the four additional holes in the back of the chassis for supplementalrear-mounting(see dimensional drawing for details).

5.2Cooling

Be certain that both the front and back of the rack have unhindered access to free air flow. Fan direction is from front to back. It is not necessary to leave empty space above or below.

5.3Grounding

In some installations where the sound system is sensitive to RF noise or system-inducedoscillation, it may be necessary to ground the amplifier’s chassis to the rack enclosure . This is accomplished using star type lockwashers on the four rack mounting screws. These star washers will penetrate through the amplifier’s paint to adequately ground the chassis to the rack.

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Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

6.FRONT PANEL FEATURES

6.1Power Switch

When the unit is switched on there is a five second delay, during which time the PROTECT circuit will activate, disconnecting the speakers from the amplifier output. When turning off the amplifier, the load is removed instantly, and the protect LED will briefly turn on as the power supply discharges.

6.2Signal Indicator

The signal present LEDs illuminate at an input level of about 13mVrms (-35.5dBu).

6.3Clip Indicator

The clipping LEDs illuminate at an input level of about 870mVrms (+1.0dBu), with all channels driven by 1KHz into 8. This indicates that the signal processing circuitry has determined output levels to be approaching the available power supply rails and has begun to “soften” signal peaks. Actual onset of “hard” clipping depends on audio program and total load impedance and does not occur until the signal processing circuitry can no longer compensate, which means that signal integrity can be maintained even if the clipping indicators illuminate for short periods of time.

6.4Thermal Status Indicator

The thermal LEDs illuminate when the temperature of any one of the heat sink extrusions reaches 85 to 90°C. Both channels of the affected amplifier module will shut off until the measured temperature drops below about 70°C. The amplifier should be able to maintain proper

operation at an ambient room temperature of 50°C (122°F) or less with typical audio program and all channels driven into 4.

6.5Protect Indicator

The protect LEDs illuminate when the fault monitoring microprocessor has determined that one of the following conditions exists:

-Power supply undervoltage

-Power supply overvoltage

-Output overcurrent

-Heat sink overtemperature

-Unacceptable DC output content

-Unacceptable high frequency output content

-AC power interruption

Because the signal processing module used in the 6125A and 4200A amplifiers processes two channels simultaneously, a fault in one channel will result in a protect condition for both channels processed by the same module, ex. channels 1-2,3-4,and5-6(6125A only). Thus there will never be a case where only one of the amplifier channels is shown in protect mode. When a pair of protect LED's are illuminated, internal relays have removed the channel pair's speaker loads from the amplifier output and connected the speakers to ground. If the fault is isolated to one module (channel pair), the other channels will remain unaffected.

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Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

* Model 6125A shown - Model 4200A only has channels 1-4.

7.REAR PANEL FEATURES

7.1Input Connectors

The 6125A and 4200A inputs use balanced two piece "Euroblock" style connectors. It is recommended that balanced input connections be used whenever possible to take full advantage of the amplifier's common mode rejection properties, and to reduce ground-loopproblems. If a hum problem persists even though balanced inputs are used, try connecting a balanced signal to the Euroblock input with the input cable's shield lifted at the amplifier end of the cable (ie. no ground connection),but connected to ground at the signal source. This eliminates potential ground currents through the input cable yet preserves the benefits of shielding. If connecting an unbalanced signal to the Euroblock input, connect the signal wire to (+) and the cable shield to both(-)and ground.

7.2Input Ground Switch

This switch separates the input signal ground from the chassis ground on all inputs. Ground connections from an incoming signal float from the chassis ground when the switch is out. Unless there are special circumstances which require the input signal ground and chassis ground to be disconnected, it is best to leave this switch in.

7.3Multi-ChannelOperation

The 6125A is essentially three stereo amplifiers in one chassis, for a total of up to six separate channels. The 4200A is essentially two stereo amplifiers in one chassis, for a total of up to four separate channels. Thus, the following references to Stereo, Mono, or Bridged operation is with regard to each of three or twopairs of channels in the amplifier. For example, Channel 1 and Channel 2 together can provide stereo, mono, or bridged operation, completely independent of Channels3-4or Channels5-6settings.

 

 

 

 

 

 

7.4

50Hz Low Cut Switch

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Each pair of channels has a 50Hz second order

+ - G

 

 

 

 

 

 

 

 

 

 

 

(12 dB per octave) low-cutfilter option which is applied

 

 

 

 

 

 

to both channels within the pair. When the switch is

Euroblock

 

 

 

pressed, the audio signal is -3dBat 50Hz,-15dBat 25 Hz,

+ - G

-27dBat 12.5Hz, etc.

Connector

 

 

 

 

 

System

7

Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

Model 6125A shown.

Model 4200A has only four channels.

7.5Input Level Controls

Input Level Controls attenuate input signal from 0dB down to -.For best performance, Altec recommends that the level controls be operated at full level (0 dB attenuation).

In STEREO mode, each level control corresponds directly to the input signal on its respective channel.

In MONO Mode, the input signal connected to channels 1, 3, or 5 are used to drive channels 2, 4, or 6 respectively, and the level controls for channels 1, 3, and 5 likewise control channels 2, 4, and 6. When switched to Mono mode, channels 2, 4, or 6 level controls become inactive.

In BRIDGED mode, the level controls function the same as in mono mode.

7.6Stereo/Mono Switch

The 6125A is comprised of three stereo amplifiers (two on the 4200A), each operating independently of the others, with Stereo/Mono switching available for each channel pair. If this switch is set to Stereo mode, the channel pair operates as two discrete amplifiers, each with its own input connection and level control.

Switching to Mono mode allows one input (channel 1, 3, or 5) to drive both channels of a stereo channel pair. Pressing the Mono switch disables the channel pair's

other input connection, as well as its level control. The first channel's input and level control now determines the signal to both channels.

7.7 Dual Channel/Bridge Mode Switch

Bridging a power amplifier is the process whereby two channels are supplied the same signal, with the second channel's phase inverted 180°. The speaker is then connected across the (+) output connections of each channel, resulting in twice the power to the speaker that either channel could deliver by itself. Since in Bridge Mode both connections have voltage present, never connect or touch either speaker wire to ground.

The 6125A is capable of three channels of bridged output (two channels on the 4200A). To use bridged mode, first press MONO from the Stereo/Mono switch on the channel pair to be bridged. This sends the same audio signal to both channels. Then press BRIDGE from the Dual/Bridge switch on the channel pair to be bridged. This inverts the phase of the input signal to the second channel. These two channels are now operating together in Bridged Mono mode, and the output must be taken from the two

(+) terminals of the corresponding bridged channel pair

7.8 Loudspeaker Output Connectors

Three terminal blocks (two on the 4200A) provide connections for the speaker outputs. In BRIDGE mode, the channel 1, 3, or 5 (+) connection is the Bridged

(+) speaker output terminal, and the channel 2, 4, or 6 (+) connection is the Bridged (-)speaker output.

CAUTION! NEVER CONNECT THE TWO BRIDGED OUTPUTS TOGETHER OR CONNECT EITHER BRIDGED OUTPUT TO GROUND.

8

Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

Model 6125A shown.

Model 4200A has only four channels.

7.9AC Inlet

The 6125A and 4200A amplifiers can be configured by the customer for operation at either 115VAC or 230VAC mains. Switching from one to the other simply requires the following steps:

1.) Unplug the amplifier from the wall and remove the power cord from the rear of the amplifier.

2.) Using a small screwdriver as a lever, unlatch the fuse holder in the AC inlet and remove it.

3.) Remove the voltage selection insert and rotate until the new nominal mains voltage level indication (115 or 230) is on top and properly oriented for reading.

4.) Replace the voltage selection insert in the AC inlet, making sure that it is plugged in all the way.

5.) Replace the fuse with the appropriate size (see #6 below), and press the fuseholder back into the AC inlet until it latches.

6.) Using a power cord of the appropriate size and with the appropriate terminations, plug the cord into the rear of the amplifier and then into the wall. The amplifier is now ready for use at the new mains voltage.

If the mains voltage is 110-125VAC, the required fuse is MDA 12, 250V, and the required power cord is 3- wire grounded, 13 Amp (16AWG) minimum.

Outputs

If the mains voltage is 220-250VAC, the required fuse is MDA 10, 250V, and the required power cord is 3- wire grounded, 10 Amp (18AWG) minimum.

8.SELF-PROTECTIONFEATURES

The 6125A and 4200A amplifiers contain circuitry to self-protectduring extreme fault conditions. These fault conditions are:

1.) Power supply undervoltage

2.) Power supply overvoltage

3.) Output overcurrent

4.) Heat sink overtemperature

5.) Unacceptable DC or high frequency output content

6.) AC power interruption

Except for AC power interruption, the detection of any fault will result in the activation of protection circuitry on a particular module, which consists of two channels. That is, a short circuit on the output of channel 1 will result in both channel 1 and channel 2 entering protect mode. This is because the signal processing module, which processes both channels simultaneously, does not distinguish between the two channels within a channel pair when processing a fault.

An AC power interruption will result in all channels entering protect mode simultaneously, just as if the amplifier is being turned off.

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Operating Manual 6125A and 4200A Multi-ChannelPower Amplifier

In all cases, the amplifier will restart the signal processing module after a short delay and will reconnect the speakers after several seconds if no further fault conditions exist. This allows the servo circuitry to bring any residual DC offsets to zero before speakers are connected.

Specific conditions resulting in a fault are as follows:

8.1Power supply undervoltage - less than about 55 volts on the either supply rail. Possible causes would

be total load on the outputs exceeding recommendations (remove some speakers - 4load min, 8min bridged),

low AC mains voltage (reduce extension cord length or increase wire size, or switch to an AC mains circuit more capable of supporting the amplifier's power requirements), or improper AC inlet mains voltage setting (make sure nominal AC mains voltage matches the number in the viewing window on the AC inlet).

8.2Power supply overvoltage - more than about 92 volts on either supply rail. Possible causes would be high AC mains voltage (change to an AC mains circuit with voltage within the amplifier's stated requirements) or improper AC inlet mains voltage setting (make sure nominal AC mains voltage matches the number in the viewing window on the AC inlet).

8.3Output overcurrent - more than 15 to 20 amps being drawn from any output. Possible causes would be total load on the affected output exceeding recommendations (disconnect some speakers), or a short circuit on one of the outputs driven by the affected module (inspect speaker wiring for proper connection).

The above conditions are checked by the signal processing module on a switching cycle by switching cycle basis and are therefore monitored as often as a million or more times a second, allowing protection well before destructive conditions have time to cause part failure.

8.4Heat sink overtemperature - a measured heat sink extrusion temperature of more than 85 to 90 degrees C. The three-speed fan will switch to medium speed at an extrusion temperature of 45 to 50 degrees C, and to high speed at a temperature of 70 to 75 degrees C. The overtemperature fault will clear itself when the measured temperature is below about 70 degrees C. The fan will operate at low speed below about 50 degrees C.

8.5Unacceptable DC or high frequency output content - a DC offset in the output signal of more than a few hundred millivolts indicates module failure, and will trigger a DC protect fault. High frequency (20kHz to 100kHz) in the output at high amplitudes can cause speaker damage and causes a fault condition more or less rapidly as frequency and amplitude vary.

These two conditions (DC and HF) are tested by the same circuit so the exact cause cannot be isolated. If the fault condition persists after disconnecting all inputs and outputs from the amplifier, there is probably a module failure requiring service. Note: the self-testing circuit may take as long as 30 seconds to recover from this fault, so be sure to give the amplifier enough time to reset itself. If after 30 seconds the module has recovered, begin plugging in one input and output at a time in an effort to isolate a systemhigh-frequencyor oscillation problem.

8.6 AC power interruption - a dropout (or brownout of sufficient magnitude) of more than one half mains line cycle and less than one whole cycle in duration.

9.TYPICAL APPLICATIONS

The 6125A is essentially three stereo amplifiers in one chassis, each with dual stereo, dual mono, and bridged mono capabilities, while the 4200A is two stereo amplifiers (four channels), but with more power per channel than the 6125A. Input connections arehard-wiredwithtwo-pieceEuroblock connectors, while speaker outputs are wired to four position screw terminal blocks.Note: The

6125A is used for the following application details, but the 4200A is used in a similar fashion, to a maximum of four channels.

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