18 W High Ambient Temperature Audio Power Amplifier with Power Supply

Ideal Use Cases

The RDL FP-PA18H is designed for audio systems requiring 18 W RMS into an 8 Ω load in ambient temperatures from 0°C to 70°C. Its ultracompact, all-metal construction measures 1.15 inches high, 3.25 inches wide, and 3 inches long, making it suitable where available installation space is limited. The amplifier accepts either balanced or unbalanced line-level audio, allowing it to work with +4 dBu nominal balanced sources or 10 dBV nominal unbalanced sources. A power supply is included for a complete amplification package.

Why Choose This Model

High-efficiency Class D operation combines with thermal and short-circuit protection to support reliable operation within the specified environment. The integrated compressor/limiter controls clipping and maximizes average output power. Its threshold is set 3 dB below rated output, with automatically adjusting attack and release times. A red COMP LED shows compressor activity, giving a visible indication when the audio reaches the compression threshold. Separate green OUTPUT ACTIVE and blue POWER LEDs provide additional operating-status information.

Installation and Integration

Detachable terminal blocks are provided for input and output connections. The line-level input has an impedance of 10 kΩ balanced bridging or 5 kΩ unbalanced, while a single-turn audio-taper control provides gain adjustment. Minimum input levels required to cross the compressor threshold are specified as 18 dBu balanced and 20 dBV unbalanced. Maximum input levels are +23 dBu balanced and +21 dBV unbalanced.

The included supply accepts 100 to 240 Vac at 50–60 Hz, with a maximum input rating of 1 A, and provides 24 Vdc to the module. Amplifier current requirements are 80 mA at idle and 975 mA maximum, with a ground-referenced supply connection. Recommended supply models are PS-24KS for the USA and PS-24KX for international use.

Performance Highlights

The FP-PA18H delivers 18 W RMS into 8 Ω with a specified frequency response of 20 Hz to 20 kHz, within +/-1 dB. THD+N is specified at less than 0.5% from 20 Hz to 20 kHz. Common-mode rejection is greater than 45 dB from 50 Hz to 3 kHz, and noise is specified at less than 72 dB below 18 W RMS with a +4 dBu input.

An integrated output signal detector monitors amplifier activity across the audio range. Its thresholds are 30 mW at 20 Hz, 20 mW at 30 Hz, 10 mW at 50 Hz, and 5 mW from 65 Hz through 20 kHz. The detector provides an open-collector output rated at 5 mA and controls the green OUTPUT ACTIVE indicator.

What Makes It Different

The defining capability of this model is its specified operation at ambient temperatures as high as 70°C while maintaining an ultracompact footprint. It brings together Class D efficiency, an all-metal enclosure, balanced or unbalanced input compatibility, detachable connections, and protection against thermal conditions and short circuits. The compressor is integrated directly into the signal path, controlling clipping while increasing average output power, and the three dedicated LEDs clearly identify power, output activity, and compression.

Final Assessment

The RDL FP-PA18H is a focused 18 W amplifier for an 8 Ω audio load where compact dimensions, elevated-temperature operation, and line-level input flexibility are required. Its wide-range included power supply, Class D output circuit, compressor/limiter, signal detector, status indicators, detachable terminal blocks, and electrical protection provide the essential functions for integrating a small amplifier into a defined audio system.