Krell Illusion II

The Illusion II is a high-end preamplifier from Krell, designed to sit at the heart of a hi-fi installation combining analogue and digital sources. It complements a classic selection of balanced and unbalanced inputs with five dedicated digital inputs, allowing it to integrate as readily into a traditional system as into a modern streaming setup.

Its design adopts a dual-mono architecture: the left and right channels each have their own power supply regulation and their own circuit boards, an approach that limits interference between channels and preserves stereo separation. Signal amplification relies on surface-mount technology using multiple-output current mirrors, claimed to offer linearity far superior to conventional open-loop designs. The circuit operates in balanced Krell current mode, with a bandwidth of 700 kHz and no feedback, for open-loop distortion generally below 0.003%. Volume control is handled via a balanced resistance ladder, intended to preserve bandwidth and transient response regardless of the level selected. The headphone circuit shares the main stage, offering the same performance for private listening as for speaker output.

The built-in digital module supports streams up to 24-bit / 192 kHz in LPCM, via AES/EBU, coaxial and optical inputs. Digital signals are processed by an ESS Sabre converter before being fed into the balanced analogue circuit operating in Krell current mode.

The power supply, oversized for this type of unit, is built around a 95 VA transformer paired with 40,000 pF of capacitance, intended to respond quickly to dynamic musical demands and to improve noise rejection against mains fluctuations. A so-called eco standby mode reduces power consumption to 2 W.

This preamplifier is aimed at users who already own a high-end system combining analogue and digital sources, and who are looking for a preamplifier stage capable of handling both worlds without compromise, including for demanding headphone listening.