alpine car audio


Alpine R-A90S Amplifier Versatile 6 5 4 or 3 Channel Class D Car Amp 900w RMS

Alpine R-A90S Amplifier Versatile 6 5 4 or 3 Channel Class D Car Amp 900w RMS

The most versatile 6-channel amplifier

R-Series 6/5/4/3-channel Power Amplifier with Staggered Power - RMS Power Ratings 4x 75 Watts + 2x 150 Watts or 4x 75 Watts + 1x 500 Watts


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Product Information


Experience your music in Hi-Res with the R-A90S 6-channel R-Series amplifier. This is one of the most versatile Class-D 6-channel amplifiers on the market, featuring a unique staggered power channel layout that has double the power on the last two channels, as well as built-in high-pass and low-pass filters to build any kind of sound system.

The “R” line of speakers and subwoofers have a heritage of sound quality you can hear from a block away, and the newly added R-Series amplifiers are no exception. Aside from their best-in-class performance, these amplifiers are tuned to emphasize the characteristics of the R-Series speakers and subwoofers, giving you that legendary R-Series experience.

The Alpine R-Series Sound Components

The R-Series lineup is “The Loudest Family on the Block”. The products are designed to be played loud, delivering a fun and exciting listening experience, and are known for dependable performance and high-quality sound. All R-Series components are developed to perfectly match each other.

Staggered Power Design

With double the power on the last two channels, the R-A90’s 5th and 6th channels can be bridged to provide up to 500 Watts RMS @ 4 Ohms to your subwoofer system. The R-A90S has a unique staggered power channel layout, that has double the power on the last two channels. This means you can set the amp to deliver 4x 75 Watts + 2x 150 Watts to run 2 separate subs, or configure it 4x 75 Watts + 1x 500 Watts to run one very powerful subwoofer.

The Amp That Grows With You

Thanks to the unique staggered power channel layout, the R-A90S can host different levels of power on each channel, compared to traditional multi-channel amplifiers. The R-A90S can effectively function as both a 3-way active amplifier and a 5-channel amplifier by delivering the power you need to the channels where you need the most.

Next Level System Builds

For the best possible sound experience, use the built-in band-pass, high-pass, or low-pass filter to individually power each component in your system and assign frequency bands for accurate and reliable sound reproduction.

Remote Bass Knob Ready

You can connect the RUX-KNOB2 remote bass knob (optionally available) to the R-A90S to control the subwoofer gain level (channel 5 + 6) straight from your dash.

Small Footprint and Installation Flexibility

Compact and Powerful: the new digital amplification circuit allows high power output while keeping a small footprint. The R-A90S measures just 324mm in width x 273mm in length for easy installation. The logo center-plate can be adjusted to install the amp in landscape or portrait orientation.

Thermal Protection

Along with Alpine’s new intelligent amplifier platform, the new R-Series amplifiers feature an improved heat sink and protection circuit design that eliminates thermal shut-down, for dependable music playback.

Low/High-Power Speaker Signal Inputs

The 6-Channel RCA speaker signal inputs accept low and high-power signals. This makes it easy to connect the R-A90S directly to your original car stereo, regardless of your head unit’s power output. The power cable terminal accepts heavy gauge cables of up to 4 AWG.


  • Terminal Layout: One side
  • Small footprint for easy installation
  • Screw terminals (for speaker and power cables)
  • Amplifier Type: Class-D (Digital)
  • Channel Design: 6/5/4/3 Channel Design with Ch 5 + 6 Power Stagger Feature
  • Thermal Management Control
  • Top Mounted LED Power/Status Indicator
  • Speaker Level Input with remote turn on
  • Crossover: Adjustable Low-pass (LPF), High-Pass Filter (HPF) and Band-Pass Filter
  • Gain Control: Adjustable
  • Remote Bass Control (RUX-KNOB2) Ready
  • Max Power Output Ratings
  • Total Max Power: 1800W
  • RMS Power Ratings
  • Per Channel into 2 Ohms, 14.4V (≤1%THD+N): 4 x 100W + 2 x 250W
  • Per Channel into 4 Ohms, 14.4V (≤1%THD+N): 4 x 75W + 2 x 150W
  • Per Channel into 4 Ohms, 14.4V (≤1%THD+N): 4 x 75W + 1 x 500W (bridged)
  • Per Channel into 4 Ohms, 14.4V (≤1%THD+N): 2 x 150W + 1 x 500W (bridged)
  • Variable HPF/HPF-H: 50Hz - 400Hz / 400Hz - 6kHz
  • LPF: 50Hz - 400Hz
  • BPF-L / BPF-H: 50Hz - 400Hz / 400Hz - 6kHz
  • Power Requirements: 14.4 V.DC (9 - 16 V allowable)
  • Input Sensitivity (RCA Input): Hi: 0.5V - 10V / Low: 0.2V - 4.0V
  • High Level Input with automatic power on
  • Cable size: Power Cable AWG 4, SPK Cable AWG 8
  • Frequency Response (+0/ -3dB: 1W into 4 Ohms): 10Hz - 45kHz
  • THD+N (@ 10W into 4 Ohms): <0.02%
  • THD+N rated power into 4 Ohms): <0.03%
  • Damping Factor: >500 (ref. 10W into 4 Ohms at 100Hz)
  • Signal to Noise (rated power into 4 Ohms): >103dB (Ch 1-4) / >106dB (Ch 5+6)
  • Weight: 4.52kg
  • Heat Sink (WxHxD) mm: 273 x 50.8 x 200
  • With attached brackets (WxHxD) mm: 273 x 50.8 x 324

What's Included

  • Alpine R-A90S Amplifier
  • Three 30-amp ATO fuses (installed)
  • 4 Mounting feet
  • Four 3/4" Screws
  • Eight M2.5x5.5mm Machine screws
  • 2mm Allen wrench
  • 3mm Allen wrench
  • Owner's manual

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