KRELL DUO 300 – Winner of Hi-Fi News Editor’s Choice Award

Krell DUO 300

The Krell DUO 300 showed blissful attack with authentic decay, and just the right amount of dryness with the percussion that opens ‘Up On Cripple Creek’. It picked up the snap of the percussion, the kick-drum air movement, with true ‘feel’. Yeah, this is a Krell, alright. Salvation came from Lou Rawls’ At Last [Blue Note], a bit of recording perfection. It was suitably silky, Rawls’ vocals were languorous perfection, while Dianne Reeves sang as clear as a wine glass from Zalto.

Circuitry Highlights

Krell iBias Class A technology allows our latest amplifiers to run in full Class A mode to full power while minimizing heat generation. All signal gain is realized in the current domain using discrete, proprietary, multiple-output current mirrors with extraordinary open loop linearity. There are no generic integrated circuits or op amps used anywhere. Current mirrors in the final gain stages use a new output power device that operates at a 73% higher voltage, delivers almost 10% more current, and offers 120 watts of additional power handling capability as compared to previous devices. The signal path is fully complementary and balanced, Independent complementary pre driver and driver stages for the positive and negative output transistors make the output stages extremely fast and linear. Krell amplifiers are fully direct-coupled, with no capacitors in the audio signal path. This design gives the Krell amplifiers lower internal impedance, which allows firmer, more precise control of your speakers.

Power Supply Highlights

Two 750VA toroidal transformers feed amplifier modules that include the audio circuitry, rectifier, and power supply filtering mounted to an individual heat sink. This design shortens the electrical path from the power supply to the output transistors, reducing the overall impedance and allowing the circuit to respond faster and control the speakers better and more accurately.

Feature Highlights

Network connectivity brings convenience, monitoring, and reporting to end users from any smartphone, tablet, or laptop. Amplifier configuration options include display brightness and timeout. For energy conservation, the amplifiers can be programmed to power off at a preset time of inactivity. Individual channels can be muted and firmware updates can be initiated from the web server. Excessive current, output DC, fan speeds, short circuit, and overheating are all monitored in real time. Messages are displayed on the front panel and reported on the web server interface. Additionally. end users can be sent an email notifying them of any operational anomalies.

Krell Class A iBias Technology

Krell’s new line of iBias amps promise class A performance without the usual pitfalls—high power consumption and lots of heat. The new amps use a fan-cooled chassis to pull off that trick and the result is a series of highly powerful yet compact amplifiers. The new iBias design allows the amp to actively measure the current flow to the speakers and adjusts the amps bias to meet demand—if full power is called for, then full power is what you get. However, if full power is not needed, the amp adjusts the bias so that energy isn’t wasted the way it is in traditional class a designs.

The new amps fit in a standard rack—something that was not possible with old-school Krell amps. This was achieved by using ultra-quiet fans—active ventilation. That makes these new amps a great fit for high-end audio and home theatre installations. The new amps are as transparent and dynamic as we have come to expect from Krell.

Krell’s history is rich with breakthrough Class A amplifiers that have helped build the Krell legacy of offering the best sounding amplifiers available. Audiophiles have always considered Class A technology to be the best sounding operating state for amplifiers. However, despite Class A’s unrivaled sound quality, it has fallen out of fashion because of recent demands to reduce power consumption and heat in home electronics products. Krell engineering took this challenge and redefined the meaning of high performance power amplifier. Our goal – unmatched performance, elegant design, and a compelling array of features. The breakthrough – a patent pending circuit delivering Class A operation without the excessive heat and wasted energy of conventional designs, housed in a striking new form factor, with network connectivity for advanced access and monitoring. The sound is open and unconstrained, in a manner that rivals live performance and the true sound of voices and instruments. Music and dialogue are reproduced with a richness, detail, and startling dynamics that fill a room.

Written by McEvoy

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