18 W Audio Power Amplifier with Power Supply

The RDL FP-PA18 is an ultra-compact audio power amplifier that delivers 18 W RMS into an 8 Ω load. Its high-efficiency Class D output, balanced or unbalanced line-level input, compressor/limiter, automatic sleep mode, and included power supply combine the essential signal, protection, and power functions in an all-metal enclosure measuring 1.15 inches high, 3.25 inches wide, and 3 inches long.

Ideal Use Cases

The FP-PA18 is suited to systems in which a line-level source must drive an 8 Ω load with up to 18 W RMS while occupying minimal equipment space. It accommodates +4 dBu nominal balanced signals and -10 dBV nominal unbalanced signals, allowing either input format to be used with the amplifier. Its selectable sleep behavior is useful when audio is intermittent: choose a 5-, 15-, or 25-minute delay, or disable sleep entirely. The compressor/limiter is appropriate for program material that could push the amplifier toward clipping, while the output signal detector supplies an open-collector output for external status monitoring.

Why Choose This Model

This model combines controlled dynamics, visible operating status, and electrical protection with its rated output power. The compressor threshold is set 3 dB below rated output and uses automatically adjusting attack and release times. This controls clipping while maximizing average output power. A red COMP LED indicates compressor activity, a green OUTPUT ACTIVE LED is controlled by the output signal detector, and a blue POWER LED changes from dim during sleep mode to bright while the amplifier is active. Thermal and short-circuit protection are also included.

Installation and Integration

Input and output connections use detachable terminal blocks, allowing the connection interface to be separated from the module during wiring. Input impedance is 10 kΩ balanced bridging or 5 kΩ unbalanced, and gain is adjusted with a single-turn audio-taper control. The minimum levels required to cross the compressor threshold are -18 dBu balanced and -20 dBV unbalanced. Maximum input levels are +23 dBu balanced and +21 dBV unbalanced.

The included power supply accepts 100 to 240 Vac at 50-60 Hz, 1 A maximum, and provides 24 Vdc to the module. The specified 24 Vdc current is 16 mA at idle and 975 mA maximum, with a ground-referenced supply. Recommended supply models are the PS-24KS for the USA and PS-24KX for international use. The permitted ambient operating environment is 0° C to 50° C maximum.

Performance Highlights

The specified frequency response is 20 Hz to 20 kHz at ±1 dB*, with THD+N below 0.5% across the same frequency range*. Noise is specified below -72 dB relative to 18 W RMS with a +4 dBu input, while common-mode rejection is greater than 45 dB from 50 Hz to 3 kHz. The Class D circuit supplies the rated 18 W RMS output into 8 Ω with high-efficiency operation.

Output signal detection is frequency-sensitive, with thresholds of 30 mW at 20 Hz, 20 mW at 30 Hz, 10 mW at 50 Hz, and 5 mW from 65 Hz through 20 kHz. Its detector output is an open collector rated at 5 mA, providing a defined status interface for integration with compatible monitoring equipment.

What Makes It Different

The automatic energy-saving sleep mode reduces combined amplifier and included-power-supply consumption to less than 1 W. Once input audio is detected, the amplifier returns to active operation in less than 150 ms. The selectable delay provides control over when sleep begins, while the disable option supports applications that require the amplifier to remain active. The compressor activity, output activity, and power-state LEDs provide immediate operating feedback without separate test equipment. Ultra-compact all-metal construction, detachable connections, Class D efficiency, and thermal and short-circuit protection complete the practical feature set.

Final Assessment

The FP-PA18 offers a clearly defined combination of 18 W RMS output, balanced or unbalanced line-level compatibility, compression, signal-status indication, and automatic power management. Its compact dimensions and included universal-input power supply simplify integration where an 8 Ω amplifier, controlled clipping, and low sleep-mode consumption are required.