Features

The Evolution 900e is the most powerful member of the Evolution Series. At a
staggering 3,600 watts into a 2 Ohm load, the Evolution 900e is a virtually
limitless source of power for any speaker. This power capability is coupled to a
new green operating mode that reduces standby electrical draw to a mere 2 Watts.
While power is essential for lifelike volume levels and realistic dynamics, the
true benefit of this engine is its ability to dominate a speaker and extract the
ultimate performance from any speaker design. Dedicating one amplifier per
speaker is the recognized best path to ultimate performance. As such, the
Evolution 900e is a monaural design requiring two for stereo reproduction or
left and right power amplifiers in a home theater system.

FEATURES

Power Supply
The Evolution 900e is equipped with two
3,000 VA transformers and 108,000 μF. This power source is the backbone for the
output of the Evolution 900e. With this foundation, the Evolution 900e delivers
900 watts into 8 Ohms, 1,800 watts into 4 Ohms, and 3,600 watts into 2 Ohms. The
FTC mandates that power ratings are quoted using a 1,000 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 circuits where 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 14 dB of feedback throughout the topology-a small
fraction of the amount implemented in typical designs.

Krell Active Cascode Topology offers several performance advantages. It
breaks through bandwidth limitations of conventional designs and delivers very
high current. The power bandwidth of an Evolution 900e is 120 kHz; far greater
than the bandwidth of a typical high performance amplifier. The result is near
perfect performance in the audible range with no phase anomalies typical of
lower bandwidth designs. Because the "work" is spread across multiple devices,
the amplifier is more load tolerant. Open-loop output impedance is extremely
low-about one hundred times lower than with most power amplifiers-ensuring
exceptional speaker control. All of these performance gains are achieved while
maintaining a high rail voltage, which provides a beneficial "flywheel" effect-a
de facto regulation that enables the amplifier to better deal with sudden
changes in power requirement, such as those caused by large signal transients.

Evolution amplifiers feature Krell CAST technology. CAST is a unique circuit
and connection breakthrough that eliminates distortions inherent in voltage
based amplification. A complete Evolution (source, preamplifier, and amplifier)
system, connected with CAST interconnects reduces the number of voltage gain
stages to the minimum, one. The resulting noise floor is approaching the
theoretical limit of technology. Emanating from a completely black background,
music explodes from absolute silence moving the listener closer to the goal of
recreating the live musical event in the listening room.

Specfication

Frequency response
20 Hz to 20
kHz +0, -0.18 dB
<0.5 Hz to 120 kHz +0, -3 dB
Signal-to-noise
ratio
>113 dB, unweighted, referred to full power
output
>122 dB, "A"-weighted
Gain
25.4 dB

Total harmonic distortion
<0.02% at 1 kHz, at 900 W,
8 Ohms
<0.15% at 20 kHz, at 900 W, 8 Ohms
Input
impedance
Single Ended: 100 kOhms
Balanced: 200 kOhms
CAST:
70 Ohms
Input sensitivity
Single Ended or Balanced:
4.55 V rms
CAST: 4.55 mA rms
Output power
900 W RMS
at 8 Ohms
1800 W RMS at 4 Ohms
Output voltage
240 V
peak-to-peak
85 V RMS
Output current
60 A peak

Slew rate
90 V/μs
Output
Impedance
<0.023 Ohms, 20 Hz to 20 kHz

Damping Factor (referred to 8 ohms)
>350, 20 Hz to 20
kHz
Transformer
Two 3000 VA (6000 VA total) for audio
circuitry
One 10 VA for digital control circuitry
Power Supply
Capacitance
108,000 μF
Power consumption

Standby: 2 W
(High-current standby: 440W) Idle: 650 W

Maximum: 5000 W
Heat Output
Stand-by: 7 BTU/hr.
(High-current standby: 1500 BTU/hr.
Idle: 2200 BTU/hr.
Maximum: 7700
BTU/hr.
Inputs
1 single-ended via RCA connector
1
balanced via XLR connector
1 CAST via 4-pin bayonet
connector
Outputs
1 pairs Krell binding posts

Dimensions
17.3 in. W x 9.8 in. H x 26.1 in. D
438
mm W x 248 mm H x 662 mm D
Weight
Shipped: 190 lb., 86
kg
Unit Only: 175 lb., 79.2 kg