KRELL KSA-100S

Pre owned. In fair condition. Shows visible signs of wear, as shown in the photos. Original packaging not included.

The Krell KSA-100S is a 100-watt per channel class A power amplifier that exemplifies the engineering excellence of the American manufacturer. Although it is the most “accessible” model in the S series, it retains all the build quality and design features that define Krell products: custom-extruded anodized handles, gold-plated binding posts with laser engravings, and top-tier finishes that give the chassis solidity, elegance, and long-lasting durability.

The KSA-100S is based on Krell’s Sustained Plateau Bias technology, introduced in the Krell Audio Standard, a sophisticated evolution of the “sliding bias” concept. In practice, the amplifier’s bias current increases in four discrete steps, anticipating changes in the signal through an anticipator circuit at the amplifier’s input. This ensures that by the time the signal reaches the output stage, the bias is already set in class A. Once the maximum level is reached, the bias is maintained for 20–30 seconds, dropping to the next lower step only if the signal decreases consistently. This approach delivers the full, linear sound of class A while reducing power consumption and heat compared to “pure” class A operation, a solution Krell calls “Green Class-A.”

The amplifier features four sets of LEDs that indicate the current bias level, useful for monitoring but easily disabled during normal listening without affecting sound quality. Like other S-series models, the KSA-100S offers balanced and unbalanced inputs, two pairs of binding posts for bi-wiring, and a robust power supply capable of driving loads down to 1 ohm, delivering up to 800 watts per channel. Integrated protection handles short circuits, overheating, and other abnormal conditions, ensuring reliability even in cases of connection errors or extreme load situations.

The Krell KSA-100S combines the pure, detailed sound of class A with the flexibility and safety of modern circuitry, offering abundant power, natural dynamics, and uncompromising reliability, making it one of the most refined and high-performing amplifiers in its class.

Technical specifications:

• Power output: 100 W into 8 Ω, doubles with each halving of load impedance down to 1 Ω
• Frequency response: 20 Hz–20 kHz ±0.1 dB; 1 Hz–150 kHz –3 dB
• Distortion: 0.1% at 1 kHz; 0.5% at 20 kHz at full power
• Slew rate: 100 V/µs
• Input sensitivity: 1.4 V RMS
• Gain: 26 dB
• Damping factor: >60
• Input impedance: 47 kΩ
• Power consumption: 100 W idle; 1,400 W full power
• Dimensions: 48.3 W × 21.6 H × 48.8 D cm
• Weight: 36.3 kg net