Designed for commercial and industrial use, the CSMA 280 Commercial Series Mixer/Amplifier from JBL is a mixer/amplifier with four mixer-channel inputs and one output channel. It's capable of reaching 80W of peak power with 10W per channel. The unit's front panel sports volume controls for each channel, as well as two master volume adjustment knob, bass and treble controls, and a power switch. The volume controls are illuminated so they can be seen and operated in darkened environments.
The amplifier, capable of driving both eight and four Ohm loads, can be used with 70V and 100V distributed audio systems without the need for a separate transformer. On its back panel you'll find the mic/line inputs, unbalanced RCA inputs, speaker connections, Hi-Z and phantom power switches, and more. The unit is also equipped with a RJ45 connector for use with JBL CSR-V in-wall volume controls (available separately).
This Commercial Series mixer/amplifier boasts such features as voice activating ducking (useful for paging over background music), priority muting for channel one's input, and a sleep mode which automatically powers down the unit when no audible signal has been received for longer than 30 minutes. Also, with an auxiliary output, you may connect to an additional amplifier, though the master volume and tone controls will have no bearing on the resulting signal.
8 inputs into 2 output channel with 80W of power.
Independent Bass and Treble controls for each output channel.
Input level and output volume controls.
The Hi-Z switch will switch in the built-in output transformer allowing the unit to drive 70V or 100V speaker systems directly when connected to the appropriate output terminals.
Phantom power (27 V) can be applied to all mic inputs by turning on the phantom power switch.
Voice activated ducking is available on input channel one. The audio input level required to activate ducking is set using the trim pot on the rear panel. Adjusting in the counter-clockwise direction will reduce that level, while the full clockwise setting will disable the VOX function
Input Channel one may be used as a priority channel, muting all other channels when pins four and five are shorted using a switch closure. If the amplifier has entered sleep mode due to inactivity, invoking priority will also bring the unit out of sleep and ready for transmitting an announcement.
Remote Volume Control
Remote volume control can be implemented using a CSR-V controller connected via an Ethernet cable to the RJ45 connector on the back panel.
This unit is designed to go into sleep mode after approximately 30 minutes operating with no signal at any of the inputs. Return of signal (-40 dBu or 7.75mVRMS) to any input will wake the unit. Also, a switch closure across the priority input pins will return the unit to normal operating mode.
An auxiliary output that you may connect to additional amplifiers is available. The audio signal is the mix of the input channels. Note that the master volume control and tone controls will have no effect on the aux output signal.