Monaural Power Amplifier (450 watt mono).
Immensely powerful, the Evolution One is a monaural design that features a separate power supply for each channel. Stunning aesthetics hint at the advanced amplifier circuitry housed within its walls. The 450 watt Class A circuitry features the latest advancements in Krell amplifier design including the proprietary Krell Current Mode topology and the latest versions of the Krell Sustained Plateau Bias and CAST circuitries.
Evolution One, the output impedance of the final gain stages is one hundredth that of the final gain stage in most power amplifiers. This provides extremely wide bandwidth and very high current capability. The Evolution One does not employ global negative feedback--the final gain stages use only 8 dB of local, nested negative feedback. This is one-five hundredth of the amount used in most solid-state power amplifiers. The result is an extraordinarily open, liquid, effortless sound.
The rails powering the low level and gain stages in the Evolution One are regulated twice for total immunity from fluctuations in the AC mains and virtually noise-free output. All the regulators use current-mode circuitry for wide bandwidth, low output impedance, and complete immunity to varying load conditions.
The high-current regulators powering the Evolution One output stages use fully complementary gain stages and output drivers. The resulting wide bandwidth and low output impedance of the Evolution One surpasses even the stringent demands of the amplifier output stages. The driver and output stages in the high current regulators use 14 pairs of the same robust, high performance power transistors used in the amplifier output stages. All the regulators are located in the amplifier chassis to provide ultra low impedance supply rails for the audio circuitry. Krell alone employs regulated output stages of this nature, which contribute dramatically to the current capability of the amplifier. Essentially an amplifier within an amplifier, the complexity and cost of the Evolution One regulator virtually insures that no other manufacture dare attempt it.
The new Evolution Bias system features 12 individual bias levels for optimum performance and efficiency. Evolution Bias constantly compares the audio signal at the input stage with impedance at the output stage, and adjusts the bias current accordingly. In addition, a proprietary bias monitor continuously measures and adjusts the output stage bias, eliminating the need for future adjustment or calibration.
Housed in a separate chassis, the Evolution One power supply makes use of extensive electrical and magnetic shielding to keep radiated interference out of critical amplifier circuits. Internal high current line conditioning circuitry filters RF noise on the AC mains, as well as compensating for asymmetric power waveforms and DC on the mains. A dedicated 165 VA toroidal transformer with six independent secondary windings powers the amplifier's low level stages, gain stages, and control circuitry. Power for the high current regulators and amplifier output stages comes from two massive 2500 VA toroidal transformers. These in turn drive eight 35-amp bridge rectifiers and 120,000 microfarads of filter capacitance. High reliability connectors with 56 machined, gold plated, 20-amp contacts transmit these tremendous power reserves to the regulators.
