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Krell Solo 575 XD Mono Amplifiers Pair - As Traded
Condition: Used. Good, some dents (see photos)
Includes: Power Cables
SN: 30318020215 / 30319120261
Made in USA
Includes 3 month (90 day) warranty
Overview
Krell's XD (Xtended Dynamics, Dimensionality & Detail) upgrade for the iBias amplifiers elevates an already outstanding amplifier to new heights of performance. XD exemplifies Krell's commitment to continuous research and development, yielding improvements across various product lines. Through the development of the K-300i Integrated Amplifier, we discovered significant sonic enhancements by reducing the output impedance below traditional standards. When this technique was applied to our existing amplifier lineup, the resulting improvement was so remarkable that it warranted its own unique designation—XD.
However, lowering the output impedance was not a straightforward task. It significantly impacts the amplifier's stability and transient response, requiring each stage prior to the output stage to be meticulously retuned to synergize optimally with the lower output impedance. This reduction in output impedance grants greater control over the speaker drivers and effectively suppresses unwanted vibrational modes, resulting in a more faithful reproduction of the original signal.
Krell Class A iBias™ Technology represents a leap forward in amplifier design, combining the hallmark qualities of Krell's legendary Class A amplifiers with innovative efficiency. Featuring a patent-pending circuitry, these amplifiers deliver true Class A operation without the heat and energy inefficiencies associated with conventional designs.
The power supply of Krell iBias Class A amplifiers is meticulously optimized for use with the iBias circuit. Multiple toroidal transformers, depending on the model, supply power to amplifier modules mounted on individual heat sinks, minimizing electrical path length and impedance. This design enhances speed and speaker control, resulting in superior audio reproduction.
Unlike traditional Class A amplifiers, iBias amps boast a compact design suitable for rack-mounting, facilitated by thermostatically controlled ventilation fans. These fans operate quietly and activate only during peak energy demand, ensuring an unobtrusive user experience.
The amplifiers feature RJ 45 Ethernet connectivity, enabling convenient monitoring and control via smartphones, tablets, or laptops. Configuration options include display settings and energy-saving presets. Advanced protection systems monitor various parameters in real time, with automatic email notifications in case of faults.
The iBias circuitry employs proprietary Krell technologies for signal gain, maintaining signal integrity in the current domain throughout the amplifier. The use of specialized transistors in the final gain stages enhances power handling and minimizes distortion, ensuring accurate and detailed sound reproduction.
Notably, Krell amplifiers are fully direct-coupled, eliminating coupling capacitors in the audio path for improved speaker control and extended low-frequency response. The inclusion of Krell CAST™ inputs and circuitry further enhances sonic performance by unifying interconnected components and preserving the original signal integrity.
These amplifiers offer the musicality of Class A operation, dynamic range of classic Krell designs, and efficiency of Class G and H amplifiers. By eliminating crossover distortion, they reveal intricate details and microdynamics in audio recordings, delivering an expansive soundstage with pinpoint imaging.
In essence, Krell iBias Class A amplifiers provide audiophiles and home theater enthusiasts with unparalleled performance, combining power, control, and musicality in a groundbreaking amplifier design.
Specification
Frequency response 20 Hz to 20 kHz +0, –0.15 dB
108 dB, wideband, unweighted, referred to full power output
>115 dB, “A”-weighted
Gain 27 dB
Total harmonic distortion
Generating expert take…
Krell Industries, founded in 1980 in the United States by Dan D'Agostino and his wife Rondi, emerged from a passion for pushing audio engineering boundaries. Based initially in Bridgeport, Connecticut, and later settling in nearby Orange, the brand drew its name from the advanced alien race in the 1956 film Forbidden Planet, symbolizing limitless technological power. The company's debut at the 1981 Consumer Electronics Show with the KSA-100, a high-power Class A amplifier, sparked immediate demand and established Krell as a force in American hi-fi innovation.
Krell specializes in high-end amplification, with its power amplifiers—epitomized by flagships like the Master Reference Amplifier—earning legendary status for their raw dynamics and precision. The lineup extends to preamplifiers, surround sound processors, digital-to-analog converters, CD and Super Audio CD players, loudspeakers, and subwoofers, all engineered for uncompromised performance in music and home theater systems.
Positioned firmly at the pinnacle of the high-end audio market, Krell commands respect among discerning audiophiles for its cutting-edge circuitry, massive power supplies, and relentless pursuit of sonic excellence. A top-tier brand alongside legends like Levinson and Threshold, it appeals to buyers seeking reference-level gear that defines the genre, even amid recent ownership transitions following Rondi's passing in 2024.
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