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Illusion Preamplifier

The Illusion preamplifier extends the Krell tradition of separating the power supply from the audio circuitry in our flagship preamplifiers. Sharing the new Class A iBias power amplifier aesthetic and featuring Krell CAST technology, the Illusion preamplifier is the ideal match for the new Solo 375 and Solo 575 power amplifiers.

The optional crossover functionality offers the ability to use a subwoofer/satellite speaker arrangement and still maintain the highest quality sonic performance. Previous to the Illusion preamplifier, this system configuration would require signals to pass through a subwoofer’s lower quality crossover circuitry. The Illusion preamplifier is the centerpiece of a world class audio system where space is at a premium.


Krell Industries, LLC designs and manufactures high-performance audio and video equipment for serious music enthusiasts and home theater aficionados. Every Krell component is a unique synthesis of science and art. Recorded performances are, by their very nature, works born of passion. Our goal is to bring that passion to life in your home. From source to loudspeakers, Krell components reproduce the definitive music and home theater experience based on the principles of innovative engineering, impeccable build quality, and unerring accuracy in sonic reproduction.

Crossover Highlights
Owing to Krell’s work in the Modulari Duo Reference loudspeaker, the unique crossover feature is a highly sophisticated option. When the optional board is present, additional crossover menu items become available. Definable parameters include independently assignable crossover frequencies and filter types for the high and low pass sections. Choices include 40Hz, 55Hz, 75Hz, and 100Hz crossover points with 12dB, 24dB, and 48dB Butterworth or 24dB Linkwitz-Riley style filters. The high pass section of the crossover uses the full Illusion preamplifier circuitry for its output stage.

Circuitry Highlights
The Illusion preamplifier is a dual monaural circuit design with the left and right channels afforded their own power supply regulation and individual full chassis sized boards. All signal gain is realized in surface mount topology using proprietary multiple-output current mirrors with nearly 500 times the open loop linearity of other designs 1.5 MHz open loop bandwidth in a zero feedback, balanced, Krell Current Mode design terminating in Krell CAST. A complete Krell system (source, preamp, and amplifier) system, connected using CAST interconnects reduces the number of voltage gain stages to the minimum, one. The resulting noise floor approaches the theoretical limit of technology. Negative feedback is not used anywhere in the preamp, nor is it necessary. Open-loop distortion is typically less than 0.003%. The volume control is realized with a balanced resistor ladder — bandwidth and transient response of the preamp circuitry are virtually unaffected by the volume setting.

Power Supply Highlights
The Illusion audio circuits receive power from a Krell Current Mode analog power supply housed in its own dedicated chassis. The power supply avoids the common integrated circuit topology used in many preamplifiers and instead mimics the design topology of Krell Evolution e Series amplifiers. The circuitry is completely discrete giving it the ability to respond quickly to current demands and also be unaffected by all but the most severe AC voltage power fluctuations. Oversized for a preamplifier, the power supply features a 290 VA transformer and 41,600µF of capacitance. Locating the power supply in its own chassis presents the ideal configuration for isolating stray electrical and magnetic interference from the critical preamplifier signal path. Capable of delivering current and voltage swing for any musical event, the Illusion power supply is gentle on AC requirements when not in use. A new eco-friendly design reduces standby power draw to 2W.



2 pr. CAST via 4-pin bayonet connectors

2 pr. balanced via XLR connectors

3 pr. single-ended via RCA connectors


Tape input

1 pr. single-ended via RCA connector


Main outputs

2 pr. CAST via 4-pin bayonet connectors

1 pr. balanced via XLR connector

1 pr. single-ended via RCA connector



Subwoofer outputs

1 pr. balanced via XLR connector

1 pr. single-ended via RCA connector


Tape outputs

1 pr. single-ended via RCA connector,buffered


Control inputs

1 RS-232 input via a 9-pin D-subminiature connector

1 remote IR detector input via a 3-conductor 3.5 mm connector

1 12 VDC trigger input via 3.5 mm connector

1 preamplifier link via an RJ-45 connector


Control outputs

2 individually programmable 12 VDC trigger outputs via 3.5 mm connectors

1 preamplifier link via an RJ-45 connector

Power output

1 phone power output (±20 VDC) for KPE via a 9-pin D-subminiature connector

Input impedance

CAST: 25 Ohms

Balanced: 40 k Ohms

Single-ended: 20 k Ohms

Output impedance

CAST: >1 M?

Balanced: 250?

Single-ended: 125?


12 dB (CAST or balanced output)

6 dB (single-ended output)

Volume control

Balanced, current-mode, 16-bit, discrete R-2R ladder

Input overload

Balanced, current-mode, 16-bit, discrete R-2R ladder

Output overload

CAST: 16 rnA RMS

Balanced: 16 V RMS

Single-ended: 8 V RMS


Frequency response

20 Hz to 20 kHz ± 0.02 dB

0.35 Hz to 720 KHz +0, -3 dB

Single-ended: 8 V RMS


Total harmonic distortion plus noise

Balanced Output: <0.003%, 20 Hz to 20 kHz, 4 V RMS or 4mARMS


Signal-to-noise ratio

4 V RMS balanced or 4 mA RMS CAST output

Wideband, unweighted: >100 dB

"N' weighted: >109 dB


Power consumption

Standby: 60 W

Power on: 65 W

Power on, with KPE: 75 W



Preamplifier only:

17.3 in.W x 3.8 in. H x 18.3 in. D

43.8 cm W x 9.7 cm H x 46.4 cm D

Power supply only:

17.3 in. W x 3.8 in. H x 17.7 in. D

43.8 cm W x 9.7 cm H x 44.8 cm D

Preamplifier and power supply:

17.3 in. W x 7.6 in. H x 18.3 in. D

43.8 cm W x 19.2 cm H x 46.4 cm D



Shipped: 61 lbs., 27.6 kg

Preamplifier only: 18 lbs., 8.1 kg

Power supply only: 28 lbs., 12.7 kg

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