JBL Libra 300 Power Amplifier

JBL Libra 300 Power Amplifier

The JBL Libra 300 is a single-channel PA mixer amplifier from JBL’s Libra series, built for public address and background music in schools, places of worship, offices, retail spaces, community halls and factories. It delivers 250 watts of rated output power and combines the amplifier, mic mixer and media player in one unit, so a complete announcement and music system needs only this amplifier and a set of PA speakers.

Six balanced microphone inputs (TRS, 1.7 mV) allow multiple announcement points, lecterns or wireless receiver outputs to stay connected permanently. Two auxiliary RCA inputs (100 mV) take music sources, and a separate balanced line input accepts a feed from another mixer or processor. A built-in USB media player with Bluetooth covers everyday background music from a pen drive or a phone without extra hardware. Preamp and line outputs (balanced TRS) allow the Libra 300 to feed additional power amplifiers in larger installations.

Key Features

• 250 W rated output power, single channel (mono)
• 6 balanced microphone inputs on TRS connectors
• 2 auxiliary RCA inputs and 1 balanced line input
• Built-in USB media player with Bluetooth streaming
• Speaker outputs for 4 ohm / 8 ohm and 70 V / 100 V lines
• Preamp and line outputs for expansion with additional amplifiers
• Bass tone control (plus/minus 10 dB at 100 Hz)
• 24 V DC backup operation at 50 percent or more of rated power
• Fan-less, high-efficiency design for quiet, reliable running

Low-Impedance and Line Outputs, Explained

The barrier-strip output offers both worlds of PA wiring. The 4-ohm and 8-ohm terminals suit short runs to a few nearby speakers. The 70 V and 100 V terminals are for distributed lines: many ceiling or wall speakers spread across a building, each with its own transformer, wired in parallel over long distances without the losses of low-impedance cabling. The touch-proof cover on the strip keeps the high-voltage line terminals safe once wired.

Reliability for Daily Duty

Announcements cannot wait for a reboot, so the Libra range is designed to be efficient and fan-less: no fan noise in quiet rooms, and no fan to fail. If mains power drops, the amplifier runs from a 24 V DC supply (such as a battery bank or UPS-backed DC source) at half or more of its rated power, keeping paging and evacuation announcements alive. Frequency response of 50 Hz to 15 kHz (plus/minus 3 dB) covers speech and background music with clarity.

The complete specification, including inputs, outputs and power supplies, follows below.