Specifications

Architect's and Engineer's Specifications

The power amplifier shall be a two-channel unit capable of being switched to single-channel bridged mode operation. All components shall be of high quality and mechanical construction and optimized for high reliability under adverse physical and electrical conditions. Cooling shall be convection-type only, with no fan mounted inside the amplifier.

The inputs shall be differentially balanced with active current sources for rejection of electro- magnetic interference. The input connectors shall be 3-conductor 1/4" TRS jacks mounted on the back panel. Additional unbalanced RCA/ phono inputs shall also be mounted on the back panel. [RA300 and RA500: There shall also be provision for female XLR input jacks on each channel.]

The output stages of the amplifier shall be a high current, triple darlington type biased for class AB operation, fully rated for continuous 4 ohm operation with 2 ohm dynamic stability (stereo mode only). An active DC servo circuit is to be employed to automatically null DC output voltage offsets. The amplifier shall feature active circuitry that continuously monitors the output stage for excessive DC offset, short circuits and thermal overload. In the event of an output fault, the protection circuitry will activate the output relay and disconnect the loudspeaker load. This circuitry will also mute the amplifier during power on/off transitions.

The power supplies of the amplifier shall utilize heavy-duty stacked steel EI laminated transformers for maximum performance and reliability, with high current bridge rectifiers, massive secondary capacitors and current in-rush limiters. An external voltage selection switch on the back panel shall allow the user to switch between 120-volt and 230- volt AC power input. A power switch shall be provided on the front panel with an on/off indicator lamp.

The front panel of the amplifier shall feature two detented volume controls capable of delivering full rated power at full clockwise rotation with a +4 dBu input, and turning the amplifier down at least 70 dB or to silence at full counterclockwise rotation.

The chassis shall be rack mountable in a standard 19" EIA equipment rack. Output connectors shall be two-way binding posts capable of accepting heavy gauge wire or banana-type connectors.

The power output of the amplifier shall be 75 watts per channel (RA150), 150 watts per channel (RA300) or 250 watts per channel (RA500) into a 4-ohm load, with no more than .02% total harmonic distortion. The units shall be capable of 150 watts (RA150), 300 watts (RA300), or 500 watts (RA500) into an 8-ohm load when operated in bridged mono mode with no more than .05% total harmonic distortion.

The amplifier shall be an Alesis RA150/300/500 Reference Series power amplifier.

RA150/300/500 Reference Manual

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Alesis RA500, RA150, RA300 manual Architects and Engineers Specifications

RA150, RA500, RA300 specifications

The Alesis RA series of amplifiers—comprising the RA300, RA500, and RA150—have earned a respected spot in the audio equipment landscape, catering to both musicians and audio professionals. With a blend of innovative technology, robust performance, and user-friendly features, these amplifiers offer solutions for various sound requirements.

Starting with the RA300, this amplifier delivers a solid output of 150 watts per channel at 4 ohms, making it ideal for smaller studio setups or personal listening environments. It is built with a lightweight yet durable design, employing a modern Class AB architecture that ensures low distortion and high audio fidelity. The RA300 features comprehensive input options, including balanced XLR and quarter-inch TRS inputs, allowing seamless integration into diverse setups. Additionally, the built-in protection circuitry prevents overheating and damage during prolonged use, ensuring longevity and reliability.

The RA500 steps up the power and performance, presenting a robust 250 watts per channel at 4 ohms, making it suitable for larger venues and demanding applications. It utilizes advanced thermal management technology, which aids in efficient heat dissipation, ensuring the amplifier operates smoothly even under heavy load. The RA500 also boasts significant dynamic range and headroom, making it a preferred choice for professional environments where audio clarity and volume are paramount. The addition of a frequency response that spans from 20Hz to 20kHz means it can faithfully reproduce a wide range of audio frequencies.

Meanwhile, the RA150 serves as a versatile option for various applications, delivering 75 watts per channel at 4 ohms. Despite its compact size, the RA150 does not compromise on sound quality or functionality. Its Class AB amplifier technology results in enhanced audio accuracy, making it popular among beginner studios and educational settings. The straightforward controls and indicators ensure that users can quickly adjust settings for optimal performance.

All three amplifiers in the Alesis RA series share a common goal: to provide high-quality sound amplification without unnecessary complexity. Their combination of solid construction, advanced technologies, and thoughtful features make them suitable for a multitude of audio environments—from home studios to professional gigs. Whether you opt for the RA300, RA500, or RA150, you are investing in a reliable tool designed to deliver exceptional audio performance, catering to the needs of discerning audiophiles and professionals alike.