Power Amplifier Reviews

I used these amplifiers extensively over several weeks and tried them in several configurations. Since I received the two-channel amp first, I hooked it up in my high-end music system. The speakers I use most frequently are a pair of Quad Electrostatics. On paper, using these with the Krell looks a bit like a marriage between Kate Moss and Arnold Schwarzenegger. The Quads are famous for their purity and transparency, yet they lack punch at the bottom end and can only go moderately loud before they self-destruct. On the other hand, the Krell's traditional strengths are power, dynamics, and true disdain for anything wimpy. Yet the combination worked surprisingly well—the amp was remarkably transparent, and it was able to coax a more-powerful bottom end and better dynamics from the delicate Quads without causing distress.

I also used the KAV-250a with the Snell Type As that form the left and right main speakers of my home theater, and this is where things really came to life. The Snell is a refrigerator-sized speaker capable of prodigious output and extended bass, and the Krell was able to really get a grip on it to generate waves of rock-solid bass with window-shattering dynamics. Authoritative was the word that kept coming to mind. I was amazed at how clean and pure the amp sounded—no trace of transistor hash here, and images were very well focused and positioned in space. I've heard some tube amps that have a touch more spaciousness and a richer sense of harmonics, but I'm sure Krell would argue that phase errors were responsible for the false sense of space and that excessive even-order harmonic distortion was responsible for the richness. They would argue that their amp is the more-accurate device.

Using both amps in combination for home theater really displayed the superiority of these products. Because they're so smooth, clean, and powerful, they're able to sail through extraordinarily difficult material without becoming raucous or difficult to listen to. Try chapter 32 of The Matrix, where the helicopter crashes into the building. The surround effects are breathtaking when using the Krells, and the music manages to remain clear and full in the face of severe competition from the sound effects. I also found that I was able to get tighter and faster LFE sounds by turning off the subwoofer and folding the bass into the main speakers.

At $7,500 for both amps, this package is undeniably expensive, yet it's one of Krell's most affordable setups. You expect excellence from Krell, but I was impressed that it can be found even in their more-affordable products. If you can swing the entry fee, this system will give you some of the best home theater performance available without compromising your two-channel stereo listening, which is truly a blessing for those dedicated to the so-called marriage of audio and video.

Highlights
• Wonderful flexibility between two-channel and multichannel uses
• Powerful, transparent sound
• Amazing build quality

HT Labs Measures: Krell KAV-250a/3 Amplifier

The above measurement shows that the Krell KAV-250a/3's left amplifier channel, with two channels driving 8-ohm loads, began clipping at 0.038% distortion and 207.4 watts. The amp reaches 0.1% distortion at 233.2 watts and 1% distortion at 294.8 watts, as shown above. Into 4 ohms, the amp begins clipping at 407.9 watts and reaches 0.1% distortion at 427.3 watts and 1% distortion at 498.7 watts. The amplifier's frequency response was +/-0.16 decibels from 20 hertz to 20 kilohertz. The response only dropped to -0.04 dB at 10 Hz and to -0.88 dB at 50 kHz. Crosstalk was -102.5 dB from left to right at 1 kHz and -97.2 dB from right to left at 1 kHz. THD+N from the amplifier was less than 0.023% at 1 kHz.—AJ