Description
Krell Class A iBias Technology
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.
Plainly stated, Class A designs are the most musically
accurate circuit topology available. Class A amplifiers do not suffer from the
inherent distortions that all Class AB amplifiers experience. In a traditional
Class A design, the output transistors conduct full current at all times
regardless of the actual demand from the speakers. Often, only a fraction of
this power is needed to reproduce an audio signal at normal listening levels.
The rest of the power is dissipated through the amplifier’s heat sinks,
producing large amounts of wasted heat. With Krell’s iBias™ technology, bias is
dynamically adjusted, so the output transistors receive exactly as much power –
but only as much power – as they need.
Krell’s iBias Class A technology allows our 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.
The core of the technology is an innovative, patent pending
design for a dynamic intelligent bias circuit. Our iBias Class A circuit
directly measures the output current of the amplifier and adjusts the bias to
the optimum level. Because iBias Class A measures the output current, the real
time demands of the specific speaker connected to the amp are directly
incorporated into the circuit function. In addition, iBias Class A even reduces
the bias when the signal is at very low levels, making its operation undetectable
by ear and even by standard amplifier measurements.
In sliding bias schemes, the circuit merely estimates how
much bias is needed based on the input signal and an “assumed speaker
load.” Compared with iBias Class A, these sliding bias technologies are much
less effective – and much less accurate.
Power Supply Highlights
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.
Network Connectivity
The new amplifiers include RJ 45 Ethernet connectivity and Once the amplifier is connected to a network router with Circuitry Highlights Audio signal voltages are converted to current at the Current mirrors in the final gain stages use a new output |
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With this combination, the iBias amplifiers may now deliver
substantially more power while using a smaller footprint. Normally used in
demanding, high-bandwidth video circuits, these transistors allow the design of
gain stages with superb accuracy and very low distortion. The signal path is
fully complementary and fully balanced from input to output. Independent
complementary pre driver and driver stages for the positive and negative output
transistors make the output stages extremely fast and linear. This unique
circuit is impervious to low-impedance or reactive loads; it simply drives any
loudspeaker with absolute confidence, achieving the very best possible sonic
results.
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