Radio Design Labs RU-PA40D
40W Amplifier with VCA, Power Supply, 20W RMS/Channel @ 8 Ohms


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Radio Design Labs' RUPA40D is the perfect choice in many applications where a high quality, high-efficiency utility amplifier is needed to drive a pair of 4 Ohm or 8 Ohm speakers. It is best 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 RUPA40D is ideal for foreground sound amplification in small to medium rooms or in a specific zone within a retail space.

The RUPA40D 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 RUPA40D outputs will drive a 4 Ohm or 8 Ohm speaker or multiple speakers connected to present a 4 O or 8 O load to the amplifier. The output impedance is switch-selectable on the front panel of the module.

The RUPA40D 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 KO 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 RUPA40D 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 RUPA40D 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 RUPA40D, 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 RUPA40D 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
  • Unbalanced RCA Jack Inputs; Balanced Detachable Terminal Block Inputs
  • 20 Watts RMS per Channel into 8 Ohms – 40 Watts Total
  • 15 Watts RMS per Channel into 4 Ohms – 30 Watts Total
  • VCA Control on Detachable Terminal Block
  • External Control Using 10 KO Potentiometer or 0 to 10Vdc
  • Compatible with RDL Remote Level Controls
  • Switch-Selectable Stereo or Mono Operation
  • Studio Quality, Aurally TransparentCompressor/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
  • RUPA40D includes North American Cord; RUPA40DE excludes Power Cord
24 VDC 500mA Switching Power SupplyRadio Design Labs PS-24AS 24 VDC 500mA Switching Power Supply

Radio Design Labs' PS-24AS is a 24 Vdc switching power supply with a North American AC plug.  500 mA, dc plug.Specifications: Input: 100 to 240 VACOutput: 24 Vdc, 500 mA (UL, CSA)Dimensions: 1.65" x 2.75" x 1.45" (4.2 x 7 x 3.7 ...

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