The Evolution 402e is the flagship stereo amplifier in the Evolution e Series utilizes the same technological advances as in the larger Evolution monaural amplifiers. The Evolution 402e is an extremely powerful stereo amplifier with the distinct advantage of a smaller footprint. As in its larger siblings, the Evolution 402e combines this power with a modest 2 watt power draw when in standby mode. Perfectly matched with an Evolution 202 preamplifier for stereo application, the Evolution 402e also shines as part of a home theater. In this application, the Evolution 402e gets mated with the Evolution 707 Reference Surround Preamplifier/Processor and an Evolution 403e Three Channel Amplifier for ultimate home theater performance.
The Evolution 402e is equipped with two 2,200 VA transformers and 188,000μF of capacitance. This power source is the backbone for the output of the Evolution 402e. With this foundation, the Evolution 402e delivers 400 watts into 8 Ohms, 800 watts into 4 Ohms, and 1,600 watts into 2 Ohms with all both channels driven simultaneously. 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. 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.
Krell's 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 usable bandwidth of an Evolution 402e is 300 kHz; triple 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.
The Evolution 302e is a powerhouse stereo amplifier in a compact chassis. Packing advanced Evolution circuit technology and prodigious power output, the Evolution 302e delivers superior performance in smaller scale applications. This power is coupled to a modest 2 watt power draw when in standby mode. Perfectly matched with an Evolution 222 preamplifier for stereo application, the Evolution 302e also shines as the Left and Right amplifier when coupled to an S-1200 Surround Preamplifier/Processor in a home theater system.
The Evolution 302e is equipped with a massive with a 3000 VA transformer. This power source is the backbone for the output of the Evolution 302e. With this foundation, the Evolution 302e delivers 300 watts into 8 Ohms, 600 watts into 4 Ohms, and 1,200 watts into 2 Ohms with all both channels driven simultaneously. 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. Our power tests use a 20-20,000Hz signal into 8, 4, and 2 Ohm loads with our final specifications stated for .1% distortion.
Frank Berryman - Ultra High-End Review
"The Krell Evolution 302e is quite simply a killer amplifier."
Refined reproduction and overwhelming power define the Evolution 2250e. Boasting technology sourced from award winning larger siblings, the Evolution 2250e provides the immense power and unmatched sound quality that are the hallmarks of all Krell amplifiers. Sharing the same advanced high speed output devices, massive power supplies, and unique Krell Current Mode circuitry; the Evolution 2250e delivers performance that was previously reserved for products costing far more.
Sophisticated and expensive to execute, surface mount circuitry is featured throughout gracing the design with short circuit path lengths, vanishing parasitic capacitance and improved bandwidth. Alone, the Evolution 2250e is ideal for use in stereo music systems. When coupled to the three channel Evolution 3250e, this duo makes ideal amplification for home theater applications.
Blessed with a power supply outfitted with a 2,500 VA power transformer and 136,000 μF of capacitance, the Evolution 2250e is a powerhouse. Power output of 250 W per channel into 8 ohms and 500 W per channel into 4 ohms will drive any loudspeaker to its full dynamic capability. An additional transformer for control and protection circuitry also provides power for a new energy efficient standby mode. Similar to turning off a 150W light that is always on in your house; standby power draw is only 2W. This 99% reduction in electrical usage also reduces heat output substantially. The high-current and high-voltage analog supplies have additional noise filtration circuitry to reduce high-frequency switching noise.
Housed in elegant silver or black brushed anodized Aluminum, the Evolution 2250e is the smallest amplifiers in the Evolution e Series. Featuring a 4U (7" High) profile, the new amplifiers bring prodigious power to applications requiring smaller amplifiers without sacrificing sonic performance. The stylish Aluminum faceplate features the blue power ring when in operating mode and green in low draw standby mode that is shared by all Evolution e Series amplifiers.
"Extraordinarily controlled in the bass, dynamic to a fare-thee-well, transparently precise into the very tips of its hair and tonally neutral... these were all impressive hard skills"
Jörg Dames - 6 Moons.com