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LISTENING
I have listened to several of Mr. Zeff鈥檚 Class G/H amplifiers before, and I always came away impressed with the sonics and the overall efficiency, especially at fractional power levels where we do most of our listening. I鈥檓 happy to report the KS 300.2 offered more of the same, as well as gobs of power when needed. Connected to my reference listening system in my very quiet listening room,
I began my auditions with the amp set to full range output. The amp may be on the small side and rather ordinary looking, but the sonic performance was anything but ordinary. I always make notes as I listen to several dozen of my favorite tracks for sound quality evaluations.
During this session, I found myself writing the same two words several times鈥� 鈥淪mooth鈥� and 鈥淣atural鈥� were my most frequent observations, as the amplifier simply sounded natural and didn鈥檛 add any character or coloration of its own to the music. I also noted it was quite good at re-creating a sense of space in my recordings that were done in large venues, and none of the detail or ambience was missing. The amp sounded very much like a good Class AB design, but with far greater efficiency. Dynamics were excellent, and there was absolutely no trace of distortion caused when the amplifier would modulate its rail voltage. I usually have some concern about the added noise of a fan cooled amplifier, but throughout my session, I never heard the fan at all, and in fact I forgot it was even there.
Changing things around and connecting the amp to my subwoofer system, I set the crossover to 100Hz low-pass, and summed the output signal. The first note I made in this mode was 鈥淎uthority鈥�. The KS 300.2 showed an abundance of power and retained the ability to control the woofer well. The sound was tight and articulate, and when I increased the level, my ears cried uncle well before the KS 300.2 ran out of steam. This is one of those amplifiers that you can use with equal success on your components or your subs, and never get tired of listening to it.
PERFORMANCE/BENCH MEASUREMENTS
On the bench the KS 300.2 measured very respectably in all areas. It exceeded its rated power levels, and all of the features and controls worked very well. Signal to noise was excellent as well, as was stereo separation, and THD vs frequency measurements. The single gain pot provided excellent tracking of the gain of each channel, with never more than 0.2dB of difference between them. This is much better than average, and speaks to Arc Audio鈥檚 choice of very good quality components. Thermal testing showed excellent performance as well, the inherent efficiency of the design coupled with a well designed cooling system means this amp should very seldom have a thermal problem.
CONCLUSION
Combining the latest technology and the true artistry of a world class designer, the Arc Audio KS 300.2 represents one of the best examples of real world efficiency and sonic performance. Very few amplifiers pack this much power into a chassis this small, and sound this good while doing it. And at a suggested retail price of only $399 (US) the KS 300.2 is also one of the best watt per dollar values in the high efficiency amp market.
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