closing. At this pint the amplifier’s outputs are not connected to the speakers. After the protection circuits detect that the unit has completely stabilized, the speaker relays will engage. Another click will be heard at this point. The amplifier is now ready to use. The amplifier will be at temperature and sound its best after approximately 15 minutes.

Operation of the amplifier is simple. It is important to note that care must be taken in the operation of the whole system in relation to the significant power output of either amplifier. Mistakes, such as switching between active sources without muting the preamplifier output or bumping/miscuing a phonograph cartridge, can generate large transients at low frequencies. When this type of transient activity occurs, the amplifiers can generate enough power-surge to damage most loudspeakers. All switching of sources should be done with the preamplifier level either muted or fully attenuated (turned down). Inputs to the amplifier should never be changed while the amplifier is on.

Care must be taken when setting high playback levels. Because of their tremendous reserve of clean power, Krell amplifiers safely drive speakers to higher sound pressure levels than other amplifiers. This often results in driving the speakers to their limit. Always turn the volume level down at the first sign of distortion.

When turning off the system, the amplifier should always be first. This avoids the possibility of a turn-off transient occurrence from some other component to the speakers.

F.PROTECTION CIRCUITRY

The KSA-150 and KSA-250 have a sophisticated series of circuits that protect them from dangerous input signals or loads on the output. These circuits also analyze various amplifier functions to prevent speaker damage that may be caused if the amplifier fails to function properly.

There are two protection modes: Input and Output. When the Input Protection is engaged the amplifier will remain on, with the front panel LED illuminated, but it will not pass a signal. This indicates a problem with the input signal caused by the preamplifier or source component. This is most often a DC condition. The amplifier will resume passing signal when the problem is resolved.

When the Output Protection is engaged the amplifier will turn off, with the front panel LED turning off as well. This usually indicates a problem with the speaker wires, their connection, or the speakers themselves. Once the problem is located and resolved the amplifier will turn on normally with activation of the front panel switch. The Output Protection will also engage if the amplifier fails. If the amplifier will not turn on with all inputs and outputs disconnected, please contact your dealer or Krell Service.

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Krell Industries KSA 150 / 250 owner manual Protection Circuitry
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KSA 150 / 250 specifications

Krell Industries has long been a leader in high-end audio equipment, and their KSA 150 and KSA 250 amplifiers exemplify this commitment to excellence. Both models are celebrated for their exceptional performance, build quality, and innovative technologies, aimed at delivering pure, accurate sound reproduction.

The KSA 150 and KSA 250 feature a unique class A design, which is fundamental to their sonic performance. Class A amplification is known for its low distortion and high linearity, allowing these amplifiers to deliver a clear and dynamic audio experience. The KSA 150 provides an output power of 150 watts per channel into 8 ohms, while the KSA 250 ups the ante with 250 watts per channel into 8 ohms, making them suitable for even the most demanding speakers.

One of the standout characteristics of these amplifiers is the robust power supply and large transformer design. The dedicated power supply ensures ample current delivery, which is crucial for maintaining control over the speaker drivers and providing the energetic dynamic range that listeners appreciate. Krell's proprietary circuitry design further enhances performance by minimizing feedback and ensuring that the amplifier maintains its integrity even at high output levels.

Both models incorporate advanced thermal management technology. With their large heat sinks and efficient cooling systems, the KSA 150 and KSA 250 can dissipate heat effectively, allowing for continuous operation without risk of overheating. This engineering not only prolongs the life of the components but also ensures consistent performance during extended listening sessions.

Another feature of the KSA series is the balanced and unbalanced input options, providing flexibility for various audio setups and ensuring compatibility with a wide range of source components. This adaptability is crucial for audiophiles who often shuffle equipment to achieve the best sound.

In terms of aesthetics, the Krell KSA amplifiers are designed with a modern yet classic appearance that complements high-end audio systems. The sturdy chassis and premium finishes reflect the attention to detail and craftsmanship synonymous with the Krell brand.

Overall, the Krell KSA 150 and KSA 250 amplifiers represent the pinnacle of audio engineering, making them a perfect choice for enthusiasts seeking top-tier sound quality and performance. Whether for home theater or high-fidelity listening, these amplifiers deliver an unparalleled audio experience that continues to impress both critics and consumers alike.
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