Power amplifiers stereo — Krell KSA I400

The KSA I400 is a stereo power amplifier from Krell, an American high-end audio manufacturer with decades of reputation for powerful, exceptionally low-distortion solid-state amplification. The KSA I400 represents a considerable statement within Krell's current amplifier catalogue, combining substantial output with remarkably tight measured specifications.

Key specs that matter

Input impedance is 100k ohms balanced or 50k ohms single-ended, with output impedance held to an exceptionally low under 0.05 ohms on both connection types. Output power is 400W into 8 ohms, doubling cleanly to 800W into 4 ohms - a textbook power doubling reflecting a robust, well-regulated power supply. Gain is 26.5dB. Frequency response spans an extraordinarily wide 10Hz to 100,000Hz within plus-or-minus 3dB. Signal-to-noise ratio exceeds 105dB, with total harmonic distortion plus noise under 0.05% with full global feedback, and damping factor exceeding 400 - a high figure indicating outstanding control over connected loudspeaker driver movement. Maximum power consumption is 2,000W. At 483 x 190 x 533mm and 45.4kg, the KSA I400 represents a substantial stereo amplifier commitment.

Sound and use context

Expect exceptional control and grip over connected loudspeakers reflecting the damping factor exceeding 400 - Krell's characteristic combination of substantial current delivery and exceptionally low output impedance is specifically engineered to deliver tight, authoritative bass and precise transient response regardless of a loudspeaker's demands.

Pairing

The clean power doubling into 4 ohms and exceptionally low output impedance suit demanding, low-impedance loudspeakers directly, and the wide 100k ohm balanced input impedance eases compatibility with virtually any preamplifier.

Alternatives

Krell's broader amplifier catalogue, including the compact DUO series and other stereo and monoblock configurations, offers alternatives for buyers wanting a different balance of power output and chassis size within the same core Krell engineering philosophy. Krell's decades of continuous solid-state amplifier refinement are fully reflected in the KSA I400's considerable specification sheet, extending a design philosophy the brand has consistently applied across successive generations of its power amplifier catalogue. Recommended overall for buyers seeking genuine Krell-level control and authority.