Krell DUO 125 XD

Description

The Krell Duo 125 is a 2-channel power amplifier delivering 125 watts at only 0.03% THD and incorporating Krell’s iBias technology. Krell’s “XD” (Xtended Dynamics, Xtended Dimensionality, Xtended Detail) upgrade for the iBias amplifiers takes an already great sounding amplifier and raises its performance to the next level. “XD” is a classic example of Krell’s continuous R&D efforts reaping benefits across multiple product lines. During the development of the K-300i Integrated Amplifier Krell’s engineers discovered substantial sonic improvements by lowering the output impedance below traditional norms. So they applied this technique to their existing line of amplifiers and the improvement was so substantial that it required a unique designation, hence, “XD.”

It was no simple matter to just lower the output impedance. This affects the amplifier’s stability and transient response so each stage prior to the output stage had to be re-tuned to work optimally with the lower output impedance. This lower output impedance exerts more control over the speaker drivers and damps out unwanted vibrational modes, allowing a more accurate reproduction of the original signal.

Krell’s iBias Class A technology allows their latest amplifiers to run in full Class A mode to full power while minimizing heat generation. Previous efforts at using a “tracking” bias, while effective, only measured the incoming signal and set bias levels from this information. Our new patent pending iBias technology significantly elevates the effectiveness of previous designs by calculating bias from the output stage. This seemingly small change in topology results in a dramatic improvement in sound quality, especially midrange richness and purity.

Power supply technology has always been an important contributor to the Krell sound. The power supplies of our Krell iBias Class A amplifiers have been optimized for use with the iBias circuit. Depending on the model, up to four 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 even better and more accurately.
Unlike traditional Class A amplifiers, iBias Class A amps have a compact design that allows rack-mounting, making them ideal for custom installation as well as traditional audiophile systems. This convenient form factor is made possible through thermostatically controlled ventilation fans. The fans used are specifically chosen for quiet operation, and operate at the speed required to maintain the ideal internal temperature. They run only during periods of peak energy demand – when the music is at its loudest – so they are inaudible in normal use.

The new amplifiers include RJ 45 Ethernet connectivity and an internal web page that is accessible from any smartphone, tablet, or laptop. Network connectivity brings convenience, monitoring, and reporting to end users. 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.
Once the amplifier is connected to a network router with Internet access, the amplifier’s advanced protection systems are now viewable on an Internet-connected device. Excessive current, output DC, fan speeds, short circuit, and overheating are all monitored in real time. If an issue occurs, the fault is displayed on the front panel and reported on the web server interface. Emails will automatically be sent to as many as three email addresses to notify the end user and/or the dealer of the condition.

Everything Audiophiles and Home Theater Fans Could Want in an Amplifier.
Krell iBias Class A amplifiers are the first to deliver the rich musicality of Class A amplifiers, the uncompromised dynamics of classic Krell amplifiers, and the efficiency and low power consumption of Class G and H amplifiers.

Because the iBias circuit eliminates crossover distortion, the amplifier is able to resolve more of the detail and microdynamics in even the best analog recordings. Simply put, the music breathes. Whether an iBias amplifier is called on to reproduce the extreme dynamic range of high-resolution digital files, the minute intricacies of a 45-rpm, 180-gram vinyl record, or the complexity of today’s latest blockbuster action film, it does so without altering or abating the music in any way.

The iBias amplifiers’ unprecedented ability to retrieve the subtlest details gives their sound an incredible dimensionality, with an ambient, broad and extraordinarily deep soundstage. As spacious as the sound is, though, the amplifiers are still able to produce pinpoint stereo imaging if the recording calls for it.

It’s all the power and control for which Krell has always been famous, with a level of resolution and musicality in the midrange and treble that has simply never been heard before.

In short, the new patent pending iBias Class A Krell amplifers give today’s audiophiles and home theater fans everything they could possibly want in an amplifier.