PRS‑xBxxx Basic Amplifiers

PRS-xBxxx Basic Amplifiers

The PRS-xBxxx is the basic power amplifier series of the Bosch Praesideo system, designed to provide stable and reliable audio amplification for PA/VA and EVAC systems conforming to IEC 60849 standards.

The amplifiers utilize high-efficiency Class-D technology combined with SMPS switching power supplies, reducing energy loss, limiting heat generation, and allowing the device to operate stably in high-temperature environments. All models in the series support both main AC power and a 48VDC backup battery, with automatic switching in case of power failure, ensuring continuous system operation in emergency situations.

The PRS-xBxxx does not connect directly to the Praesideo network but is integrated via the PRS-16MCI Multi-Channel Interface, which provides network audio signals, control, and monitoring functions. Through the PRS-16MCI, the amplifier is capable of monitoring operating status, power supply, and system errors, as well as monitoring speaker lines and speakers as required by the EVAC system.

Each amplification channel is equipped with an integrated output transformer for 70V and 100V speaker systems, along with two independent speaker outputs, Group A and Group B, supporting class-A loop wiring. This design allows for speaker line redundancy or channel redundancy, where one channel of the amplifier can be used as a backup amplifier for another, increasing system safety and availability.

In addition to network audio, the amplifier also provides local analog audio inputs for low-priority signal sources, with the ability to adjust the volume level individually for each channel. In the absence of a network connection, the device can still operate in stand-alone mode.

Furthermore, the amplifier is equipped with comprehensive protection circuits such as overload, short-circuit, and over-temperature protection. When the internal temperature reaches a dangerous threshold, the power stage will automatically shut off and the front panel fault indicator light will activate, allowing operators to quickly detect and resolve the problem.

The device is designed for installation in a 19-inch rack, 2U high, suitable for professional PA/EVAC control panels. With a wide range of power levels from 60 W to 500 W, the PRS-xBxxx series flexibly meets the needs of various system scales, from small areas to large projects such as factories, shopping malls, hospitals, airports, and office buildings...

Key Features

• High-efficiency Class-D power amplifier, stable operation, low heat generation.
• SMPS switching power supply, low starting current, suitable for EVAC systems.
• Supports AC power and 48 VDC backup battery, automatically switching on/off in case of power failure.
• Integrated 70 V / 100 V output transformer for distributed speaker systems.
• Independent A/B speaker outputs for each channel, supporting class-A loop wiring and redundancy.
• Complete channel isolation, allowing for redundant amplifier configuration.
• Connectivity and monitoring via PRS-16MCI Multi-Channel Interface.
• Monitoring of power supply, amplifier, and speaker output (when using PRS-16MCI) - compliant with IEC 60849.
• Overload, short-circuit, and over-temperature protection; automatic shutdown in case of malfunction.
• 19” (2U) rack mountable, suitable for professional PA/EVAC control panels.

Technical Specifications

Overview

• Amplification Technology: Class-D.
• EVAC Standard: IEC 60849 / BS 5839-8.
• Applications: PA/VA, EVAC, Praesideo systems.

Power Supply

• AC Voltage: 115 / 230 VAC ±10%, 50/60 Hz.
• Battery Backup Power: 48 VDC (-10% to +20%).
• Power Switching: Automatic AC ↔ Battery.

Configuration & Power

• PRS-1B500: 1 × 500 W.
• PRS-2B250: 2 × 250 W.
• PRS-4B125: 4 × 125 W.
• PRS-8B060: 8 × 60 W.

Speaker Output

• Speaker voltage: 70 V / 100 V (selectable individually per channel).
• Output: Group A & Group B (per channel).
• Support: Class-A loudspeaker loop wiring.

Load Impedance (per channel)

• PRS-1B500: 20 Ω (100 V) / 10 Ω (70 V).
• PRS-2B250: 40 Ω (100 V) / 20 Ω (70 V).
• PRS-4B125: 80 Ω (100 V) / 40 Ω (70 V).
• PRS-8B060: 160 Ω (100 V) / 80 Ω (70 V).

Audio Performance

• Frequency Range:
  • 60 Hz - 19 kHz (-3 dB).
  • PRS-8B060: 80 Hz - 19 kHz.
• Total Harmonic Distortion (THD): < 0.3% @ 1 kHz (50% power).
• S/N Ratio: > 85 dB (pilot tone off).
• Crossovereignment: -70 dB @ 1 kHz.

Connectivity & Control

• Local audio input: 0 dBV (balanced).
• Local audio volume control: per channel.
• PRS-16MCI connection: RJ45 (per channel).
• Terminals: speaker, local audio, spare amplifier input.

Protection & Monitoring

• Overload protection.
• Short-circuit protection.
• Overheating protection (power stage shutdown).
• AC power, battery, and amplifier status monitoring.

Dimensions & Environment

• Dimensions (HxWxD): 88 × 483 × 400 mm (19” rack). 2U)
• Weight:
  • PRS-1B500: 12 kg.
  • PRS-2B250: 14 kg.
  • PRS-4B125: 15 kg.
  • PRS-8B060: 13.7 kg.
• Operating temperature: -5 °C to +55 °C.
• Humidity: 15% - 90% (non-condensing).