Krell FPB 600 Stereo Power Amplifier 
Home Theater Power Amplifiers Stereo Amplifiers
Written by Greg Petan   
Tuesday, 01 April 1997

Introduction
Unlike many manufacturers' claims of improved performance from one generation to the next, the Krell Full Power Balanced 600 is not only a HUGE improvement over its predecessor the KSA 300S, it is a kick in the head and a punch in the gut to just about everything I have heard before, tube or solid state. In the areas of transparency, mid range and treble purity, and bass control and bass extension; the FPB 600 has that non fatiguing utter ease that sucks me into a recording much the way a live performance can, and reproduced music almost never does.

"In this corner, weighing in at..."
At 185 pounds, don't even try to lift this thing yourself. Much of the FPB 600s weight comes from its massive pair of toroidal transformers which are wired in parallel and act as the heart of this heaving beast. Rated at 600 watts into 8 ohms, the power output doubles as the load is halved. We are talking nearly 2400 fully regulated watts into 2 ohms. This amp also features the latest evolution of the plateau biasing circuit introduced in the KSA series of amps. This circuit anticipates the power demands of the output by monitoring the incoming signal, as the demand for power increases, the amp supplies the necessary power. After a grace period of fifteen seconds and no additional high current signal demands, the amp returns to its appropriate power setting. This feature allows for Class A bias output without all the wasted electricity and heat.

Along with these design features comes a build quality and reliability that can only be described as awe inspiring. From the moment I plugged this amp in it has never given me pause, strange sounds or quirky operation hassles.

Hold on to your hat.
The great fun of this amp is experiencing its speed and delicate grace. One minute and then, wham! Its ability to deliver huge unrestrained dynamics and thunderous bass control and extension the next. Check out Stanley Clarks' East Riverside Drive Track 1 "Justice's Groove." The cut starts out with some synthesized vocal effects along with some electronic drum strikes. Thanks to the Krell's superb treble transparency these sounds are richly textured and surrounded by a synthetic, yet believable acoustic. Then almost from another planet, the bass line drops the hammer down and you begin to understand what real bass is all about. This amp is absolutely unrelenting in its grip on the speakers, no matter what I threw at it, the FPB remained unfazed.

Still, as much fun as bass impact is, it is midrange performance that defines a truly great amp, and the Krell fills the bill. The female vocals on "Sunrise" from The Grateful Dead's Terrapin Station is supremely grainless and breathy without any hint of electronic edge or artificial highlighting. Dynamics flow through the mids giving greater artistic intent, subtle inflections once lost in the haze are now just plain there. I have heard this cut through at least two dozen amps both solid state and tube and it has never sounded this right.

As far as sound staging and imaging goes, the Krell strikes a balance that is neither overly forward or laid back. Its center image is very stable, rounded yet not at all vague. As the sound stage unfolds, the images are presented with the elusive combination of airiness and solidity that real instruments convey. Fine spatial resolution give the impression of great depth and width and while this aspect of it's performance is the best I have heard in my system; it leads me to my one area of criticism.

The Downside
If there is one area the 600 could be improved, I feel it is in the amp's ability to define the air that exists between and around the performers. There is a very slight grey-ness or opacity that homogenizes the soundstage just a bit. This is a very minor problem which is only noticeable when compared to some of the low-powered, single-ended and push-pull tube designs. It is also a trade-off I am willing to accept based on the list of virtues the Krell 600 possesses.

Conclusion
The Krell FPB 600 is the type of audio component that fuels great audio obsessions. Insanely powerful and poetically graceful, the amp handles all types of music and controls any speaker with aplomb. Designed and built to uncompromising standards, the FPB 600's cost of $12,500--though thoroughly justified by it's virtues--is not for the uninitiated. Start saving today.
Manufacturer Krell
Model FPB 600 Stereo Power Amplifier
Reviewer Greg Petan





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