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 Evolution 400e


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Frequency response 20 Hz to 20 kHz +0, -0.18 dB <0.5 Hz to 125 kHz +0, -3 dB   Signal-to-noise ratio >108 dB, wideband, unweighted, referred to full power output >118 dB, "A"-weighted   Gain 25.4 dB  

Total harmonic distortion <0.02% at 1 kHz, at 400 W, 8 ©   <0.15% at 20 kHz, at 400 W, 8 ©    

Input impedance Single-ended: 100 k ©   Balanced: 200 k ©   CAST: 70 ©

Input sensitivity Single-ended or balanced: 3.04 V RMS CAST: 3.04 mA RMS  

Output power 400 W RMS at 8 ©   800 W RMS at 4 ©    

Output voltage 160 V peak-to-peak 57 V RMS  

Output current 37 A peak Slew rate 100 V/Œºs               




The Evolution 400e amplifier is the smallest monaural amplifier in the Evolution Series. With a robust 400 watt output into 8 Ohms, this baby brother delivers plenty of punch. Potent enough for almost any application, the Evolution 400e shares the same sophisticated circuit topologies as its larger siblings but packs it into a smaller chassis. The Evolution 400e is perfect for when high performance is critical but space is at a premium. Power Supply The Evolution 400e is equipped with a massive with a 4,000 VA transformer. This power source is the backbone for the output of the Evolution 400e.


With this foundation, the Evolution 400e delivers 400 watts into 8 Ohms, 800 watts into 4 Ohms, and 1,600 watts into 2 Ohms. The FTC mandates that power ratings are quoted using a 1000 Hz sine wave into a fixed 8 Ohm resistor with final power specification stated at 1% distortion. Krell engineering considers this specification too lenient and not indicative of what an amplifier is required to provide. Krell designs to a much stricter standard. Our power tests use a 20-20,000Hz signal into 8, 4, and 2 Ohm loads with our final specifications stated for .1% distortion. Internal high-current line conditioning circuitry effectively blocks RF noise entering via the AC line and compensates for any asymmetry or DC offset in the power waveforms.

The amplifiers' low level and gain stages are powered via multi regulated rails that provide total immunity from supply fluctuations and assure noise-free circuit operation. Primary rail voltages are quasi-regulated, enabling an "on-demand" supply of power that is highly responsive to dynamic load.   Circuitry Highlights Krell's new Active Cascode Topology™ is a significant departure from traditional amplifier circuitswhere the positive and negative rail voltages are each applied entirely across a single row of transistors. High voltage swing and gain requirements dictate that the transistors be "pushed" into non-linear operating regions and, in some cases, dangerously close to breakdown.

Krell topology divides the full voltage swing across multiple rows of transistors, and all devices are active-biased (i.e., they all carry the audio signal). Because individual transistors in the cascode array "see" only a proportional fraction of the rail voltage, they operate in a region that provides optimum linearity, gain, and safety. And because the devices are not being pushed to their limits, the amplifier runs cooler and more reliably. The improved linearity and stability greatly reduces the need for negative feedback, which is known to cause sonic degradation. Krell Evolution power Amplifiers use only 8 dB of feedback throughout the topology-a small fraction of the amount implemented in typical designs.