Those familiar with Krell’s penchant for pushing the limits of hi-fi audio technology will not be disappointed with the new Krell Industries Illusion ($15,000) and Illusion II ($7,000) preamplifiers. Consistent with past preamplifier models by Krell, the Illusion preamp separates the power supply from the audio circuitry to ensure playback that is uninhibited by the interference associated with noisy, vibration-inducing power transformers. The Illusion also employs a high-end crossover circuit, allowing the us…