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For 25 years, Sound By Singer has been the leading exponent of Krell sound in the world. The reasons for this are simple. First, Krell produces the most musical and technically advanced solid state hi fi components manufactured in the USA. Second, Krell, like Sound By Singer, is dedicated to propagating the best two channel and multi channel music sound possible.
That dedication has been renewed with a vengeance with the introduction of Krell’s Evolution series of preamplifiers, integrated amplifiers, power amplifiers, and digital sources. You could call Evolution a Renaissance, but that doesn’t convey just how far Krell has once again advanced the art of music reproduction.
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EVOLUTION ARCHETYPE
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The lead components of the new Krell sound and their best preamp and amplifiers ever are the Krell Evolution One mono power amps and the Krell Evolution Two line stage |
All signal gain in the Evolution Two is realized in the current domain using proprietary multiple-output current mirrors with nearly 500 times the open loop linearity of other designs. Negative feedback is not used anywhere in the Evolution Two preamplifier, nor is it necessary. Open-loop distortion is typically less than 50 parts per million, and the open loop bandwidth extends to two megahertz. The result is an extraordinarily wide and deep image, with an open and effortless sound.
The Evolution Two volume control is realized with a digitally controlled analog circuit with 216 step resolution, which uses low resistance, high-linearity solid-state switches and discrete precision resistors. Control signals for the switches are optically coupled for low noise and maximum signal integrity. The bandwidth and transient response of the Evolution Two circuitry are virtually unaffected by the volume setting. Typical volume controls, working in the voltage domain, introduce frequency response and phase anomalies that change in accordance with the degree of attenuation. The current domain attenuator in the Evolution Two avoids these anomalies, revealing high frequencies that sound especially smooth and extended. Music seems to emerge from “jet black” silence. The analog and digital signal paths are not interconnected in the Evolution Two. Where necessary, digital control signals are optically coupled to analog circuits. The Evolution Two has two buffered tape outputs: one linked to the main signal selection bus, and another with its own independent signal-selection bus. This allows the option of listening to one source while recording another, or the option of connecting two tape decks having different input signals. Both tape outputs have single ended and voltage outputs. Either the fourth single-ended input or the third balanced input can be user-configured as a tape monitor input, allowing the opportunity to use home or professional recording equipment.
Housed in a separate chassis, the Evolution Two power supply makes use of extensive electrical and magnetic shielding to keep radiated interference out of critical preamplifier circuits. Internal line conditioning circuitry filters RF noise on the AC power, and compensates for asymmetric power waveforms and DC on the mains. Power for the analog stages comes from a large 170 VA toroidal transformer. This transformer drives four 8-amp bridge rectifiers and 39,600 microfarads of filter capacitance. Each Evolution Two preamplifier channel has as much power supply capability as many stereo power amplifiers. Most stereo preamplifiers use 10 VA transformers. The Evolution Two power supply utilizes 30 times the current capability of typical designs, thus guaranteeing itsÂ’ ability to deliver enormous transients without hesitation. The Evolution Two main regulators for the analog stages are scaled-down versions of those used to power the output stages of the Evolution One amplifier. Operating in current mode, with fully complementary gain stages and output drivers, wide bandwidth, low output impedance, and high current capability, the main regulators easily exceed the requirements of the analog stages. The driver and output stages in the main analog regulators use five pairs of 150 Volt, 8 Amp, 40 megahertz power transistors.
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A dedicated 90 VA toroidal transformer with three independent secondary windings powers the Evolution Two digital control circuitry. The regulators for the control circuitry team ultra-stable voltage reference chips with the same discrete high-current driver and output transistors used in the main analog regulators.
These ample power reserves are brought to the Evolution Two via high reliability 12-pin connectors with machined, gold plated, three-amp contacts. Secondary voltage regulators for each analog stage in the Evolution Two provide ultra-quiet, rock-solid supply rails, as well as complete isolation between all the analog stages.
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In the 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.
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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.
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The Evolution 505 SACD/CD player continues Krell’s longtime investment in creating state of the art digital sources. In an inspired stroke, Krell has eliminated a cause of distortion that has plagued digital disc playback since its inception. By taking the nascent analog signal from the DACs and leaving it in its native language, current, all the musical subtleties and textural shadings are preserved.
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EVOLUTION AMPLIFIERS
The new Krell Evolution amplifiers enjoy the hereditary advantage, from faceplate to binding posts, first born in the Evolution One amplifier. Realized in monaural, stereo, and three channel configurations, the Evolution amplifiers bring the engaging reproduction of music and movie soundtracks debuted in the flagship Evolution One to a potent new platform. With virtually unlimited power available, delivered through the most refined circuitry yet conceived, the Evolution amplifiers strike the fine balance between pure visceral response and delicate articulation. Elegant, graceful, powerful – new from Krell, classic from Krell. The Krell Evolution amplifiers range in power from a 300W stereo amplifier, the Evolution 302 to the extraordinary 900W monaural Evolution 900 amplifier. Intriguingly, as their power goes up, the sound gets better and better. Atypical of a solid state amplifier, but then, Krell never ran with the herd.
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EVOLUTION PREAMPLIFIERS
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Evolution 202
Often overlooked, the preamplifier is a critical component in the signal chain. A small signal must be care-
fully amplified without damaging the ephemeral staging and dimensional components of the music. The Evolution 202, using a combination of advanced technologies and inspired design, elevates this task to an art form. Music emanates from an expanse that outlines the recording venue, transporting you to the moment of creation. With the Evolution 202 Preamplifier, musicians appear, silhouetted by the air about them, filling the room with a mesmerizing depiction of the recording. Engaging, captivating, entrancing -- new from Krell, classic from Krell.
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FEATURES
1.5 MHz open loop bandwidth in a zero feedback, balanced, Krell Current Mode design terminating in Krell CAST.
All signal gain is realized in a surface mount topology using proprietary multiple-output current mirrors with nearly 500 times the open loop linearity of other designs.
Zero negative feedback is used anywhere in the preamp, nor is it necessary. Open-loop distortion is typically less than 0.005% (50 parts per million).
A complete Evolution (source, preamplifier, amplifier) system, connected in CAST, reduces the number of voltage gain stages to the minimum, one. The resulting noise floor is approaching the theoretical limit of technology.
The volume control is realized with a 16-bit balanced resistor ladder --bandwidth and transient response of the preamp circuitry are virtually unaffected by the volume setting.
Housed in a separate chassis, the power supply makes use of extensive electrical and magnetic shielding to keep radiated interference out of critical preamplifier circuits.
A 170 VA toroidal transformer drives four 8-amp bridge rectifiers and 39,600 microfarads of filter capacitance.
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| A new Krell designed digital control circuit monitors and optimizes the preamplifier's operating parameters. |
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The Evolution 222 brings the advanced technologies and inspired design of the Evolution 202 to single chassis format. Often overlooked, the preamplifier is a critical component in the signal chain. A small signal must be carefully amplified without damaging the ephemeral staging and dimensional components of the music. Heard through the Evolution 202, music emanates from an expanse that outlines the recording venue, transporting you to the moment of creation. The Evolution 222 is the perfect companion for the Evolution 402 Amplifier and Evolution 505 Source. Engaging, captivating, entrancing -– new from Krell, classic from Krell.
FEATURES
1.5 MHz open loop bandwidth in a zero feedback, balanced, Krell Current Mode design terminating in Krell CAST.
All signal gain is realized in a surface mount topology using proprietary multiple-output current mirrors with nearly 500 times the open loop linearity of other designs.
Zero negative feedback is used anywhere in the preamp, nor is it necessary. Open-loop distortion is typically less than 50 parts per million.
A complete Evolution (source, preamp, amplifier) system, connected in CAST, reduces the number of voltage gain stages to the minimum, one. The resulting noise floor is approaching the theoretical limit of technology.
The volume control is realized with a 16-bit balanced resistor ladder -- bandwidth and transient response of the preamp circuitry are virtually unaffected by the volume setting.
150 VA toroidal transformer drives four 6-amp bridge rectifiers and 19,800 microfarads of filter capacitance.
Krell designed digital control circuit monitors and optimizes the preamplifier's operating parameters.
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HOME THEATER
S–1000
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Krell’s new surround preamp/processor, the S-1000, combines robust, high-end audio performance with HDMI video switching in one easy to use, feature-rich package. A unique software-based eight-channel digital room equalizer maximizes system performance in any room.
Picture state-of-the-art digital audio chipsets, operating with upsampled 24-bit precision are utilized.
Digital audio formats include Dolby Digital Surround EX, Dolby Digital 5.1, DTS 6.1 ES, DTS 5.1, DTS NEO:6, and Dolby Pro Logic II, in addition to 9 proprietary Krell Music Surround modes.
Krell software provides digitally controlled bass management with user-selectable crossover points, optimizing the systems speaker/subwoofer interface.
Audio decoding is accomplished with 24-bit/192 kHz DACs, for the most accurate analog signal possible.
Krell Current Mode analog circuitry is utilized in the critical preamplifier section, and a fully balanced de-sign delivers the extremely wide bandwidth required for accurate audio reproduction.
An analog preamp mode bypasses all digital circuits, providing the most direct signal path for multi-channel and stereo recordings.
The S–1000 has 7 single-ended, 1 balanced, and 1 single-ended multi-channel analog audio inputs, as well as 6 coaxial and 2 optical digital inputs. Both single-ended and balanced analog audio outputs are utilized for all 7.1 channels.
A unique software-based eight-channel digital room equalizer maximizes system performance in any room. For each of four memory settings, the user can program filter type (high-pass, low-pass, notch, peaking, and high/low shelf), frequency, shape, and level for every channel. Each of the four memory settings is assignable to a device.
VIDEO FEATURES
Video circuitry is fully discrete with a bandwidth of up to 350 MHz, ensuring the integrity of all progressive, high definition component, and HDMI signals.
Inputs and outputs for composite, S-Video, component, and HDMI are supported.
An on-screen display indicates status and facilitates system set-up.
FLASH memory enables easy software upgrades.
Evolution 707
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The Krell Evolution 707 is an audio/video tour de force which delivers unparalleled music and cinema soundtrack reproduction through the use of a fully complement of advanced Krell technologies, including: Krell Current Mode, Evolution CAST, Class A, Evolution CAST and balanced outputs, user-configurable input assignment and system macros, main and remote zone control capability and broadcast-quality video circuitry.
Krell Evolution 707 features include:
8.4 channels of audio output features two center channel outputs and four subwoofer outputs for maximum flexibility in system design.
Two digital signal processors (DSPs), the Crystal CS49623 and CS49302 are employed to perform all surround mode processing.
Supports Dolby Digital Surround EX, Dolby Digital 5.1, DTS6.1 ES, DTS5.1, DTS NEO:6, Dolby Pro Logic II processing as well as Dolby TrueHD and DTS HD Master Audio lossless surround formats, plus nine proprietary Krell Music Surround modes.
Digital processing circuitry runs in double precision mode at a word length of 48-bits for the most precise division of frequencies and optimization of the system’s speaker/subwoofer combination.
12 output stages are fully balanced and feature Krell Current Mode topology with 1.5 MHz of bandwidth for accurate reproduction of today’s demanding movie soundtracks. Current audio signal transfer (CAST) outputs are supported for all 12 channels.
Evolution CAST, which stands for current audio signal transmission, is a proprietary method of sending the audio signal between components in the current domain, from a high impedance transmitter to a low impedance receiver. Krell components connected in Evolution CAST act together as an electrically unified whole, free from the deleterious effects normally imposed by the connecting cables.
Preamp mode bypasses all digital circuitry and routes the analog input, stereo or 7.1 multi-channel directly to the volume control for the purest path possible.
Separate power supplies for digital and analog circuit paths are linear design and feature custom made low-noise transformers and robust regulation.
All-discrete video circuitry bandwidth is greater than 350 MHz and provides pristine pass-through of all progressive and wideband high definition signals, including HDMI.
Faroudja DCDi Cinema (Directional Correlational Deinterlacing):
- A per-pixel video format converter – a unique algorithm identifies all the moving edges in a scene and adjusts the angle of interpolation at each pixel
- Eliminates staircasing or jagged edge artifacts
- Film mode detection features bad edit correction
- Emmy award winning
Faroudja Truelife Video Enhancer:
Identifies transitions considered to be the details in an image such as skin texture, freckles or hair for artifact free image enhancement.
 S-1500
The logical companion to the new S-1000 processor, the Krell S-1500 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.
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.
CONNECTIONS
All channels support balanced inputs and outputs. High quality, 5-way binding posts allow speaker connections via bare wires, spade lugs, or banana plugs.
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