The RU‑PA40D is the ideal choice in many applications where a high quality, high‑efficiency utility amplifier is needed to drive a pair of 4 Ω or 8 Ω speakers. It is specifically suited to amplification applications where users need to adjust the gain. Examples include projectors or monitors with fixed audio outputs used in classrooms, boardrooms or video conferencing. The RU‑PA40D is ideal for foreground sound amplification in small to medium rooms or in a specific zone within a retail space.

The RU‑PA40D features two balanced line‑level inputs on a detachable terminal block. Two unbalanced line level inputs are available on high‑reliability gold plated phono (RCA) jacks. A front‑panel gain control trimmer permits setting the maximum gain for each channel. The gain range accommodates the range of typical balanced and unbalanced audio signal levels. Each of the two RU‑PA40D outputs will drive a 4 Ω or 8 Ω speaker or multiple speakers connected to present a 4 Ω or 8 Ω load to the amplifier. The output impedance is switch‑selectable on the front panel of the module.

The RU‑PA40D is equipped with an internal stereo VCA for setting the output level on both amplifier channels. A detachable terminal block provides for the connection of an external 10 KΩ potentiometer or a 0 to 10 Vdc control voltage. RDL remote controls are available to provide single‑turn, multi‑turn (rotary encoder) or pushbutton (ramp or fixed level selection) user level control. VCA control insures long term noise‑free level adjustment. Remote control is possible using audio, control or common computer network wire.

A front‑panel switch is provided to sum the audio inputs to mono. In the STEREO mode, the RU‑PA40D independently amplifies each audio channel, left (L) and right (R). If speaker placement in the specified installation is incompatible with stereo amplification, the INPUT MODE switch may be set to SUMMED MONO.

The RU‑PA40D includes a stereo analog compressor/limiter for audio fidelity noticeably superior to conventional class D amplifiers with digital limiting. The input GAIN settings determine whether the limiter alone is used for clipping suppression, or if the full compressor/limiter will be used to substantially increase the average output power beyond that of a standard 40 W amplifier. A red front‑panel LED flashes when the limiter is preventing output clipping. The RU‑PA40D, with compression, is capable of producing average audio output levels and clarity normally expected from stereo amplifiers with a much higher output power rating.

A blue POWER LED illuminates when the RU‑PA40D is powered from its external 24 Vdc power supply (included). The module is equipped with both thermal and output short‑circuit protection. The high‑efficiency Class D output stages produce minimal heat for all levels of expected voice or music modulation.

• VCA Controlled Stereo Audio Power Amplifier
• 20 Watts RMS per Channel into 8 ohms - 40 Watts Total
• 15 Watts RMS per Channel into 4 ohms - 30 Watts Total
• Unbalanced RCA Jack Inputs; Balanced Detachable Terminal Block Inputs
• VCA Control on Detachable Terminal Block
• External Control Using 10 K ohms Potentiometer or 0 to 10 Vdc
• Compatible with RDL Remote Level Controls
• Switch-Selectable Stereo or Mono Operation
• Studio Quality, Aurally Transparent Compressor/Limiter
• Compressor/Limiter Controls Clipping
• Compressor Produces Maximized Average Output Power
• Compression Enabled Using Input Level Adjustments
• LED to Indicate Audio Compression Threshold
• High-Efficiency Class D Operation
• Thermal and Short-Circuit Protection
• RU-PA40D includes North American Cord; RU-PA40DE excludes Power Cord

• Inputs (4): Line level: Balanced (+4 dBu) Left and Right, Unbalanced (-10 dBV) Left and Right
• Input Impedance: 50 k ohms balanced, 20 k ohms unbalanced
• Gain Adjustments (2): Single turn, one per channel
• Minimum Input Levels: -11 dBu balanced, -18 dBV unbalanced (to cross compressor threshold)
• Maximum Input Levels: +22 dBu balanced, +12 dBV unbalanced
• VCA Control: External 0 to 10 Vdc (linear), 10 k ohms linear taper potentiometer, RDL remote controls10 Vdc VCA reference voltage output provided
• Frequency Response: 20 Hz to 20 kHz (+/- 1 dB, 4 or 8 Ohms)*
• THD+N: < 0.1% (1 kHz, 1 W, 4 or 8 Ohms); < 1% (50 Hz to 20 kHz,)* *measured at compressor threshold level equaling 12 W RMS (8 Ohms) output power
• Compressor: Threshold nominally 2 dB below rated output, automatically adjusting attack and release times
• Crosstalk: Better than 60 dB (1 kHz, no compression)
• Noise (below 20 W RMS): < -80 dB (VCA control 6.25V; output level 6 dB below max.) < -70 dB (VCA control max.)
  Selectors (2): Slide switches: Output Impedance 4 Ohms or 8 Ohms; Input Mode SUMMED MONO or STEREO
• Output Power: 20 W RMS into 8 ohms per channel, 40 W RMS total; 15 W RMS into 4 ohms per channel, 30 W RMS total
• Output Circuit: Class D
• Ambient Operating Environment: 0° C to 40° C Maximum; 20° C Recommended
• Indicators (2): Red LED: THRESHOLD LED indicates compressor activity; Blue LED: POWER on
  
• Power Supply (included): 100 to 240 Vac, 50-60 Hz, 1.5A; 24 Vdc output to module