Single owner since new and other than a minor heat sink blemish it is in perfect condition, thus rated 8/10.
Krell's new KSA-200S is a large stereo chassis, conservatively rated at 200Wpc into 8 ohms (23dBW). The rating continues to double down to a 1 ohm loading, where a 1600Wpc output is specified. Krell's proprietary output-stage bias system delivers dynamic class-A operation up to the maximum 8 ohm power rating, with an increasing proportion of class-AB operation with the higher current associated with lower load impedances. This "Sustained Plateau" biasing scheme is said to offer the sonic benefits of pure class-A without the massive energy inefficiency and correspondingly huge, hot heatsinks. The energy-conscious KSA-200S idles at 120W. If it ran in pure class-A, it would have to idle at around 1kW—over eight times as much wasted energy drawn from the wall.
The KSA-200S accepts unbalanced (RCA socket) and balanced (XLR) inputs. Optimum operation in unbalanced mode is obtained with shorting links tying the unused "cold" XLR terminals to ground. This achieves the lowest hum and noise performances.