The Bosch PLENA Mixer Amplifier, 4-zone, 240W (model PLE-4MA240-CN) is a high-performance audio device designed for public address solutions in various commercial settings. Built with energy-efficient Class-D technology, it offers a comprehensive set of features for background music, paging, and emergency announcements.
Function Description:
The PLENA Mixer Amplifier serves as a central component in a public address system, integrating multiple audio inputs and routing them to four independent output zones. Its core function is to mix and amplify audio signals, providing flexible control over volume, tone, and priority.
Key functionalities include:
- Audio Mixing and Amplification: It combines signals from various sources (microphones, music players, emergency inputs) and amplifies them for distribution to loudspeakers.
- 4-Zone Output: The amplifier can independently route mixed audio to four distinct loudspeaker zones, allowing for localized sound control.
- Priority Management: It features a sophisticated priority system to ensure critical announcements are heard. The telephone/100V emergency input has the highest priority, overriding all other inputs, including the priority microphone. Microphone/line input 1 can be configured with PTT (push-to-talk) functionality to take priority over other microphones and music sources.
- Ducking Functionality: When a priority input (like a PTT microphone) is active, the background music level can be automatically reduced (ducked) to ensure clear announcements. The ducking level is adjustable.
- Tone Control: Separate high (treble) and low (bass) tone controls are provided for the mixed output, allowing for sound optimization. These controls are designed to enhance voice warmth and deep bass while reducing rumble and harshness.
- Music Source Selection: The amplifier supports three selectable music sources, offering flexibility for background music.
- Emergency Override: A 24V DC output is provided to override remote loudspeaker volume controls during telephone or emergency input signals, ensuring emergency messages are always heard at the required level.
- System Expansion: A line output allows for connecting additional amplifiers for larger systems requiring more output power.
- Visual Feedback: An LED VU meter monitors the master output, providing visual indication of signal levels.
Important Technical Specifications:
- Power Output: 240W (rated output at 0 dB), 180W at -3dB. Idle power consumption is 20W.
- Mains Power Supply: 220-230 VAC, ±10%, 50/60 Hz.
- Frequency Response: 70Hz to 18kHz (+1/-3dB @-10dB ref. rated output).
- Distortion: <1% @ rated output power, 1kHz.
- Tone Control Range: +/-12dB for both bass and treble (setting dependent).
- Microphone/Line Inputs:
- Input 1 (Priority): 1x, 5-pin Euro style pluggable screw terminal, balanced, phantom power capable. Features PTT contact with ducking functionality. Sensitivity: 1mV +1/-3dB (mic), 300mV +1/-3 dB (line). Impedance: >1 kOhm (mic); >1.5 kOhm (line). S/N: >60dB (mic), >70dB (line).
- Inputs 2-3 (Additional): 2x, Combo (XLR or TRS) balanced signal input, phantom power capable. Sensitivity: 1mV +1/-3dB (mic), 300mV +1/-3 dB (line). Impedance: >1 kOhm (mic); >1.5 kOhm (line). S/N: >60dB (mic), >70dB (line).
- Phantom Power Supply: 18VDC for inputs 1, 2, and 3.
- Music Inputs: 3x.
- Aux 1-2: Cinch connectors, stereo converted to mono.
- Aux 3 (Front Panel): 3.5mm mini-TRS connector, stereo converted to mono.
- Sensitivity (Music): 200mV +1/-3dB.
- Impedance (Music): 30 kOhm.
- Emergency/Telephone Input: 5-pin Euro style pluggable screw terminal. Sensitivity: 10mV ~100mV (telephone), 10V-100V (emergency). Impedance: >10 kOhm. S/N: >80dB.
- Line Output: 1x, 3-pin Euro style pluggable screw terminal. Nominal level: 1V. Impedance: <100 Ohm.
- Loudspeaker Output: Screw, floating terminals. Max/rated power: 240W. Zones: 4. Priority output: 24VDC for loudspeaker volume control override.
- Mechanical:
- Dimensions (HxWxD): 100 x 430 x 270 mm (19" wide, 2U high, with feet).
- Mounting: Stand-alone or 19" rack.
- Color: Charcoal.
- Weight (net): Approx. 5 kg.
- Environmental:
- Operating Temperature: -10 °C to +45 °C.
- Storage Temperature: -40 °C to +70 °C.
- Relative Humidity: <95%.
Usage Features:
- User-Friendly Front Panel: The front panel provides intuitive controls for power, input level adjustments for microphones, music source selection, music volume, tone control (bass and treble), zone selection, and master volume.
- Customizable Labels: Label holders are available on the front panel for user-defined descriptions of microphone/line inputs, music sources, and output zones. This allows for clear identification in specific applications.
- Favorite Settings Indicators: Colored pins can be inserted around control knobs to mark preferred settings, aiding in consistent operation. Silver pins indicate preferred settings, while red pins can mark maximum settings.
- Front Panel Aux Input: A convenient 3.5mm mini-TRS input on the front panel (Aux 3) allows for easy connection of portable music devices like mobile phones or laptops.
- DIP Switch Configuration: Rear panel DIP switches allow for quick setup of microphone/line 1 settings, including line/mic level, chime tone on/off, phantom power, and PTT functionality.
- Rotary Knob Adjustments: Rear panel rotary knobs control ducking level for microphone/line 1 and the volume of the telephone/100V emergency input.
- Headphone Socket: A headphone socket is provided below the VU meter for monitoring the mixer output.
- Chime Functionality: A 2-tone chime can be configured to precede announcements from the priority microphone, attracting listener attention.
- Rack Mountable: The unit can be installed in a standard 19" equipment rack using the included mounting brackets, or used as a tabletop unit.
Maintenance Features:
The PLENA Mixer Amplifier requires minimal maintenance to ensure optimal performance and longevity.
- Cleaning:
- Unit Exterior: Periodically clean the unit with a damp, lint-free cloth.
- Air Inlets: Clean the air inlets at least once a year to prevent dust accumulation, which can impede ventilation and lead to overheating.
- Connection Checks:
- Cable Connections: Periodically check all cable connections for corrosion and ensure screw terminals are tightened to prevent loosening.
- Grounding: Verify the ground (Protective Earth) connection of the unit.
- Pin Removal (for setting changes): If the colored pins indicating favorite settings need to be changed, use soft-tipped pliers to carefully remove them. If soft-tipped pliers are unavailable, ordinary pliers can be used with plastic tape on the tips to prevent damage to the front panel.
- Label Cover Removal/Reattachment: Clear plastic covers in front of the labels can be removed by gently inserting a small screwdriver into the cut-out and bending the cover slightly. Reattachment involves inserting the paper label, bending the cover, and fitting it into the slot.
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