Evolution 403e

3 Channel Amplifier

The Evolution 403e is the most powerful three channel amplifier available today. Housed in the same chassis as the Evolution 900e, the Evolution 403e is the perfect choice for Left, Center, and Right channel amplification in a high performance home theater. For reference caliber performance, coupling the Evolution 403e to Evolution 900e, Evolution 600e, or an Evolution 402e elevates an already potent system to new heights. At a staggering 1,400 watts into 2 Ohm loads, the Evolution 403e is a virtually limitless source of power for any speaker. Power is critical for the explosive dynamics that is essential to the home theater experience. This power capability is coupled to a new green operating mode that reduces standby electrical draw to a mere 2 Watts. However, power alone is not the goal as film soundtracks are the emotional vehicles in movies. It is music, not on-screen action, that communicates loss, fear, victory, and determination in movies - think of Rocky, Darth Vader, and Jaws without their theme music. Conveying emotion through music is the true strength of the Evolution 403e and an essential element for stereo and home theater listening.


The Evolution 403e is equipped with two 3,000 VA transformers and 188,000μF. This power source is the backbone for the output of the Evolution 403e. With this foundation, the Evolution 403e delivers 400 watts into 8 Ohms and 800 watts into 4 Ohms with three 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 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 usable bandwidth of an Evolution 403e 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.

Evolution 3250e

3 Channel Amplifier

Precision and power characterize the Evolution 3250e amplifier. Identical in sound quality and power output as the Evolution 2250e, the foundation of the Evolution 3250e is circuitry and engineering found in the larger Evolution e Series amplifiers. Utilizing the same advanced high speed output devices, massive power supplies, and unique Krell Current Mode circuitry, the Evolution 3250e amplifier elevates movie listening to an audiophile experience.


The latest manufacturing technologies are used throughout the design including surface mount circuit pathways. Surface mount circuitry increases the usable real estate on a circuit board and allows for a more sophisticated circuit in the same area. Surface mount circuitry shortens circuit path lengths, eliminates parasitic capacitance and improves bandwidth.


Blessed with a power supply outfitted with a 2,500 VA power transformer and 163,200μF of capacitance, the Evolution 3250e 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 substantially reduces heat output. 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 3250e is the smallest amplifier in the Evolution e Series. Featuring a 4U (7" High) profile, the Evolution 3250e includes mounts for rack installations bringing elegance not typically found in rack mountable amplifiers. The stylish Aluminum faceplate features the blue power ring and low draw standby mode shared by all Evolution e Series amplifiers.


Multi Channel Amplifier

This new amplifier features legendary Krell amplifier performance in a multi-channel, upgradeable new design. The S-1500 has a flexible design that delivers five, six, or seven channels of amplification. All three configurations include input and output connections for all seven channels. The S-1500/5 and S-1500/6 may be easily upgraded with additional channels, up to seven. Available in silver or black.


Rock solid, linear power supply design renders the S-1500 impervious to speaker demand or AC line fluctuations. A 1,500 VA toroidal transformer is designed for massive current delivery while maintaining an ultra-low noise profile.


A robust, 80,000-microfarad array of quick-charging filter capacitance offers enormous energy storage that is available in an instant. Surface Mount Technology is utilized in the amplifier channels to achieve the high circuit density required for wide bandwidth performance.


Krell Current Mode, fully balanced topologies, are utilized for all amplifier channels for the lowest noise and greatest detail retrieval.


Class-A circuitry is utilized in the input, pre-driver, and driver stages to provide the most accurate signal path.


Eight high-speed power devices per channel deliver 150 W into 8 Ohms and 300 W into 4 Ohms. The amplifier is stable at any load impedance.


All channels support balanced inputs and outputs. High quality, 5-way binding posts allow speaker connections via bare wires, spade lugs, or banana plugs.