Power Amplifier-20 W 70 & 100 V Outputs

The RDL FP-PA20A is a compact 20 W RMS constant-voltage power amplifier designed for 70 V or 100 V audio outputs. It combines balanced or unbalanced line-level input handling with an integral audio compressor that controls clipping while supporting a high overall operating level. Its published 50 Hz to 20 kHz frequency response, low distortion figures, detachable terminal-block connection, compact enclosure, and UL 2043 plenum rating provide a clearly defined foundation for system design.

Ideal Use Cases

This model is suited to constant-voltage audio systems requiring 20 W RMS output at either 70 V or 100 V. It can accept a balanced +4 dBu or unbalanced -10 dBV line-level source, making it appropriate when either input format is part of the signal path. The UL 2043 plenum rating also supports projects where plenum-rated equipment is required. Its 2.3-inch height, 3.25-inch width, and 6-inch length help accommodate installations with limited equipment space.

Why Choose This Model

The integral compressor is central to the FP-PA20A design. Its threshold is set 6 dB below rated output, with automatically adjusting attack and release. This arrangement controls clipping while helping maximize audio level for the available output power. A red PEAK LED indicates compressor activity, while a separate green LED confirms power. The amplifier also includes a single-turn audio-taper gain adjustment for direct level control.

Installation and Integration

Audio input and output connections use a detachable terminal block. The input impedance is 20 kΩ balanced bridging or 10 kΩ unbalanced. Maximum input levels are +23 dBu balanced and +15 dBV unbalanced. Minimum levels required to cross the compressor threshold are -26 dBu balanced and -28 dBV unbalanced.

The amplifier requires ground-referenced 24 Vdc power. Current requirement is 1650 mA for continuous RMS power output or 1000 mA for normal uncompressed audio. The recommended power supply is not included. Listed supply options are the PS-24V3A for the USA and PS-24V3 for international use, or the PS-24KS for the USA and PS-24KX for international use. The specified ambient operating environment is 0°C to 30°C maximum, with 20°C recommended.

Performance Highlights

The FP-PA20A delivers 20 W RMS at 70 V or 100 V. Frequency response is specified at 50 Hz to 20 kHz within ±3 dB. Published THD+N is less than 0.1% at 1 kHz and less than 0.5% from 50 Hz to 20 kHz, measured at the compressor threshold level corresponding to 4 W RMS output power. Noise is specified below -80 dB relative to 20 W RMS.

Common-mode rejection is greater than 55 dB from 50 Hz to 120 Hz. Combined with balanced bridging input support, this provides concrete performance information for integrating the amplifier into a balanced signal chain. The compressor, gain adjustment, and separate status indicators provide immediate control and monitoring without adding unspecified processing functions.

What Makes It Different

The defining combination is its 70 V and 100 V constant-voltage output capability, integral clipping-control compressor, compact dimensions, and UL 2043 plenum rating. The design is intended to maintain a high overall audio operating level and maximize level for the available output power. RDL also specifies audio quality superior to standard amplifiers. Unlike specifications that list only output wattage, the FP-PA20A provides detailed compressor behavior, input thresholds, impedance, distortion, noise, and power requirements for informed system planning.

Final Assessment

The RDL FP-PA20A is a focused choice for a 20 W RMS, 70 V or 100 V constant-voltage audio requirement. Its balanced and unbalanced input compatibility, automatic compressor behavior, low published distortion, detachable terminal-block connection, and plenum rating address both signal performance and installation needs. Before deployment, confirm the required output voltage, available 24 Vdc current, ambient conditions, and the appropriate separately purchased power supply.