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Operation

Controls & Connectors

Level Controls

The front-mounted level controls act differently depending on the mode of operation.
In the stereo mode, each level control determines the volume of the corresponding
amplifier channel as in a typical amplifier. In the 70V Mono and Dual Mono modes, the
controls have a different function and determine the mix of the signal levels from the
different input modules (input modules can be assigned to either the "A" or "B" chan-
nel by the jumpers on the module). The front level controls determine the mix of the
two input module signals. They do not control the volume level of each amplifier in
these modes.  Essentially, the volume level of both amp channels is fixed at maximum and the overall level of
the mixed input module signals determine the output volume level. To increase the overall volume of the amplifier
output, turn up both front panel controls by the same amount. This increases the signal level of each
module's input into the amplifier while keeping the mix the same. Similarly, turn down both controls to the same
knob position to reduce the overall output volume from the amplifier. 

Sleep Mode Defeat

The M-Class amplifier includes a sleep mode feature that
greatly reduces the power consumption of the amplifier
after it has been idle for more than 3 minutes.  Any audio
activity present at the input will wake the amplifier up
instantaneously so that there is no loss of audio. A sleep
mode switch located in the upper right hand corner of the
module bay can be set to activate or deactivate this feature
using a thin, flat-bladed screwdriver. (If a module is inserted
in the right bay, turn off the power and remove the module
before proceeding.) If the sleep feature is desired, make sure
the switch is in the down position. If the sleep feature is not
desired, make sure the switch is in the up position.

Channel Balance

Channel Balance only works in the Dual Mono mode of operation. In Dual Mono
mode, both amplifier channels get the same audio program at the same level. 

To provide some direct control over the amplifier volume levels, a Channel Balance
control is provided. This control allows the adjustment of one amplifier channel
output volume over the other. To reduce the volume level of channel "B" while
leaving the volume of channel "A" unchanged, the Channel Balance control is rotated counterclockwise.
The diminishing arrow with the "B" next to it indicates that rotating the control in that direction diminishes the
"B" channel volume. Likewise for reducing channel "A" volume. Putting the control at the center of rotation
allows equal, and maximum, volume from both channels.

Lo-Cut Switch

The M-Class amplifier is a direct-coupled amplifier, which means that there are no
output transformers used to deliver the 70V audio to the speakers. Because of this, the
M-Class amplifier has a Flat frequency response below 20 Hz. This extended low
frequency operation can be troublesome for some transformer-coupled speakers
typically used in 70V audio systems. The relatively inexpensive transformers used in
these speakers cannot handle frequencies much below 60 Hz. When frequencies lower than this are applied to
these speaker's transformers, they can saturate causing distortion and high instantaneous power consumption. 

The Lo-Cut filter allows a low frequency roll-off to be introduced into the output signal preventing the speakers
from receiving too much low frequency content. The 65 Hz position should be used for all transformer
coupled cone type speakers. The higher frequency roll-off of 

1

25 Hz provides an extra level of safety for horn

speakers. Some horn speakers can be adversely affected by frequencies below 

1

20 Hz since they are designed

to reproduce higher frequency signals.

8

Summary of Contents for M-Class M300

Page 1: ...M Class Amplifier M300 M450 M600 Models Installation and Use Manual 2001 Bogen Communications Inc All rights reserved 54 2037 01D 1205 ...

Page 2: ... for replacement of the obsolete outlet 10 Protect the power cord from being walked on or pinched particularly at plugs convenience receptacles and the point where they exit from the apparatus 11 Only use attachments accessories specified by the manufac turer 12 Unplug this apparatus during lightning storms or when unused for long periods of time 13 Refer all servicing to qualified service personn...

Page 3: ... Speakers 7 Standard Input Module 7 Balanced Input Connections 7 Unbalanced Input Connections 7 OPERATION 8 11 Controls Connectors 8 9 Level Controls 8 Sleep Mode Defeat 8 Channel Balance 8 Lo Cut Switch 8 Effects Loop 9 Output Feeds 9 Modes of Operation 9 10 Stereo Mode 9 70V Mono Mode 10 Dual Mono Mode 10 Audio Buses 10 Modules 11 Standard Input Module 11 Standard Input Module Priority Jumper 11...

Page 4: ......

Page 5: ...ng noise and ground loops The amplifiers require little maintenance and cleaning as internal electron ic components are located outside of the forced air stream flow Front mounted fan filters provide easy removal and cleaning M Class amplifers have a variety of electronic protection circuits including overcurrent DC voltage and ther mal circuits A special Clip Limiting circuit continuously monitor...

Page 6: ...pedance output loads A built in Clip Limiting circuit activates and reduces input signal levels when output distortion exceeds a few per cent or when the output load draws too much current One for each channel 4 Power Switch Circuit Breaker Controls AC power to the amplifier and also works as a circuit breaker If the circuit breaker trips push it to the OFF position O and then to the ON position l...

Page 7: ...processing The Post EQ Output Feed provides a signal that has been affect ed by the external signal processing equipment and the lo cut filter 7 Operational Mode Selector The M Class amplifier has 3 distinct modes of operation Stereo 70V Mono Dual Mono that are designed to provide a wide range of application coverage For a description of the different modes see the Operation sec tion of this manua...

Page 8: ...them Caution The fan blades are accessible when the grille cover and filter are removed Be careful not to place your finger or other objects into the fan 3 Fan Grille To insert or replace the grilles first insert the tabs on the wider end of the grille in to the notches in the front center casting Snap the other end of the grille in to the snap slots Check that the grille is securely in place To r...

Page 9: ...ier to allow mounting in 19 racks Attach the rack ears as shown in the Installation Components section If any feet have been attached to the bottom of the amplifier remove them Load the amplifier into the rack and secure it to the rack with appropriate hardware not included Rear Rack Mounting For greater rear support when rack mounting an M Class amplifier the RPK86 Rack Mounting Kit not included ...

Page 10: ...ation of the right module since it will be covered by the module see Operation Sleep Mode Defeat The input modules are installed by simply sliding them along the card guides inside the module bays until the faceplate firmly sits against the M Class chassis then use the two screws supplied with the module to secure it to the chassis Note The input module included with the amplifier is pre installed...

Page 11: ...both channels are bridged into a single mono channel Use only speakers that are designed to work with 70V audio systems when connecting to these terminals The speaker terminals can accept up to a 10 ring lug and have integral clamping plates which make wiring easier The 70V output terminals are indicated by a yellow field above them The polarity of the output terminals is indicated for speaker pha...

Page 12: ...osition If the sleep feature is not desired make sure the switch is in the up position Channel Balance Channel Balance only works in the Dual Mono mode of operation In Dual Mono mode both amplifier channels get the same audio program at the same level To provide some direct control over the amplifier volume levels a Channel Balance control is provided This control allows the adjustment of one ampl...

Page 13: ...nal equipment The outputs are also quasi balanced for better noise immunity but connection lengths for these outputs should still be kept as short as possible The Pre EQ Output Feed provides the signal before any external signal processing affects it The Post EQ Output Feed provides a signal that has been affected by the external signal processing equipment and lo cut filter Depending on the appli...

Page 14: ...no mode except that the amplifier supplies two channels of low impedance amplification in this mode see Dual Mono Mode Block Diagram This mode still mixes the input signal from the different modules but a Channel Balance control is provided to adjust the output levels of one channel against the other see the section on Channel Balance It is important in this mode to set the assignment jumpers on t...

Page 15: ...luded in the module that comes pre installed with the ampli fier The module is factory set for 0 dB gain Set each switch for the channel s desired gain either 0 dB X1 or 18 dB X8 Other Input Modules Various input modules can be installed in the M Class amplifier Refer to the instructions that come with each module for specific connection and setup information The module jumpers must be set prior t...

Page 16: ...l Adjust Gate controls of TEL1S for optimum paging control Application 2 Stereo low impedance music system with microphone override Stereo program material plays into low impedance speakers When the microphone becomes active the stereo music is muted to a predetermined level and the microphone is easily heard When the microphone signal stops the music fades back to its previous level Mode of Opera...

Page 17: ...optimum paging oper ation Application 4 2 mono zones low impedance speakers telephone paging and background music Zones have significantly different volume levels Background music plays through the system when no page is being made One zone is low volume while the other is high volume During a telephone page the background music mutes to a predetermined level and the telephone page is heard at cor...

Page 18: ...atus LED is off INTERMITTENT OPERATION Status LED is green Signal LED is off Level controls turned down No signal from source Input module jumpers in wrong bus configuration if available Status LED is green Signal LED is green Clip Limit LED is off Status LED is green Signal LED is green Clip Limit LED is off Input signal level too high Poor speaker connections Lo cut switch set to Flat 70V mono s...

Page 19: ...ncluded RCA Mono 70V mode unbalanced 5 pin touch proof Barrier Strip RCA Pre Post EQ Output Power Bandwidth 20 Hz to 40 kHz 5 THD THD 1 kHz rated power less than 02 Load Impedance 4 8 ohms 70V Minimum Load Impedance Stereo 3 2 ohms Frequency Response 1 watt 20 Hz to 20 kHz 0 25 dB Output Regulation 1 kHz direct 1 kHz bridged 0 5 dB 8 ohms 1 5 dB 70V Inputs Plug in modules Electronically balanced h...

Page 20: ... FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED AND EXCLUDED TO THE MAXIMUM EXTENT ALLOWABLE BY LAW Bogen s liability arising out of the manufacture sale or supplying of products or their use or disposition whether based upon warranty contract tort or otherwise shall be limited to the price of the product IN NO EVENT SHALL BOGEN BE LIABLE FOR SPECIAL INCIDENTAL OR CONSEQUENTIAL DAMAGES INCLUDING B...

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