Предусилители — Krell Illusion

The Illusion is a two-chassis stereo line preamplifier from Krell, its supply housed in a second case, and it dates from 2014. Krell calls it the bigger brother of the later single-chassis Illusion II. Krell intended it for its Solo 375 and Solo 575 mono power amplifiers, and it supports Krell's CAST current-mode interconnect technology.

Key specs that matter

The input panel offers two pairs of CAST connections, two XLR pairs, three RCA pairs and an RCA tape input. Main outputs are two pairs of CAST, one XLR and one RCA, and there are XLR and RCA subwoofer outputs that work with the optional crossover board, plus a buffered tape output. Frequency response is 20 Hz to 20 kHz ±0.02 dB and 0.35 Hz to 720 kHz at -3 dB. THD+N is below 0.003% from 20 Hz to 20 kHz at 4 V RMS. Gain is 12 dB on CAST and balanced inputs and 6 dB on single-ended inputs. Input impedance is 40 kOhm balanced and 20 kOhm single-ended, and output impedance 250 ohm balanced and 125 ohm single-ended. Maximum output is 16 V RMS balanced. Signal to noise ratio exceeds 109 dB A-weighted. The preamplifier chassis measures 438 x 97 x 464 mm and weighs 8.1 kg, and the power supply 438 x 97 x 448 mm and 12.7 kg.

Engineering and use context

Krell laid the Illusion out as dual mono, placing each channel on its own full-size board with separate regulation, and it is a zero-feedback balanced Krell Current Mode design with an open-loop bandwidth of 1.5 MHz. Surface-mount current mirrors with multiple outputs give high open-loop linearity. Volume is controlled by a balanced current-mode 16-bit discrete R-2R ladder. In a full Krell system linked with CAST cables, the signal travels as current between components, reducing the number of voltage gain stages to one. The separate supply, modelled on Krell's Evolution e amplifiers, uses a 290 VA transformer and 41,600 µF of capacitance. The optional crossover offers points at 40, 55, 75 or 100 Hz with Butterworth slopes of 12, 24 or 48 dB or a 24 dB Linkwitz-Riley slope. Control connections include RS-232, IR input, a 12 V trigger input, two programmable trigger outputs and an RJ-45 link, and the supply provides ±20 V DC for Krell's KPE phono stage.

Pairing

The Illusion is intended for Krell Solo 375 and Solo 575 mono amplifiers and other CAST-equipped Krell amplifiers, and it powers the KPE phono stage from its own supply.

Alternatives

The Krell Illusion II is the single-chassis version with an ESS Sabre DAC, five digital inputs and a headphone jack.