Operation: Chapter 3

Amplifier input clipping

On the other hand, the maximum level at the amplifier’s input terminals is +26 dBu, regardless of the setting of the channel input level controls. It is possible that the output signal from the source may be too high and, thus, distorted before it reaches the amplifier gain control, either because the source device is clipping or the amplifier input stage is overloaded. In either case, no amount of level control adjustment at the amplifier can remove this distortion, and you should lower the output level of the device feeding the amplifier until the distortion stops.

OUTPUT RELAYS/THERMAL CYCLING

Reference Series amplifiers have high-current output protection relays which disconnect the output in the event of overheating, DC offset, audio signals below 5 Hz on the output terminals or excessively low line voltage. When this happens in the RA300/500, the PROTECT indicators of both channels will glow. Additional protection circuitry keeps RFI out of the audio circuits, assuring clean, stable operation in difficult environmental conditions.

If the unit shuts off, turn off the power and check for problems with the wiring, input level, or ventilation of the amplifier.

Continued high-temperature operation may also trigger an internal thermal fuse, which will shut the unit off entirely until it has cooled off. In this case, the PROTECT indicators and POWER indicators will turn off as well.

Overheating is the most common cause of amplifier shutdown. You must ensure that the heat sinks of the amplifier are not blocked and can receive a supply of cooler air.

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RA150/300/500 Reference Manual

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Alesis RA300, RA150, RA500 manual Amplifier input clipping, Output RELAYS/THERMAL Cycling
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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.
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