Krell KSA-100 (1980)
A high-power stereo amplifier designed by Dan D'Agnostino, built for dynamic performance and low-impedance drive capability.
Overview
The Krell KSA-100 is a stereo power amplifier released in 1980 by American manufacturer Krell. Designed by Dan D'Agnostino, it was described as a "super booster" — a high-current amplifier capable of driving difficult speaker loads with authority. It delivers 100 watts per channel into 8 ohms, 200 watts into 4 ohms, and 400 watts into 2 ohms, with the ability to output up to 800 watts per channel at 1 ohm. The unit uses pure complementary circuitry with pure Class A operation and features an oversized power supply for enhanced performance.
Specifications
| Rated output | 100W + 100W (8 Ω, 20 Hz to 20 kHz, both channels driven) |
| Rated output | 200W + 200W (4 Ω) |
| Rated output | 400W + 400W (2 Ω) |
| Input Sensitivity / Impedance | 1V/22k Ω |
| Total harmonic distortion factor | 0.05% or Less (20 Hz to 20 kHz, 1W to Rated Output) |
| Frequency characteristic | 0.5 Hz ~ 100 kHz -3dB; 20 Hz ~ 20 kHz -0.5 dB (1W ~ Rated Output) |
| Signal-to-noise ratio (IHF-A) | 110dB |
| Rated load impedance | 2 Ω or more |
| Damping factor | 120(1kHz) |
| Slew rate | 80 v / μ sec |
| Power | 100 VAC, 50Hz/60Hz |
| Power consumption | 610W (maximum idling) |
| External dimensions | Width 483x Height 226x Depth 612 mm |
| Weight | Approximately 35 kg |
Design
The KSA-100 uses a pure complementary circuit with pure Class A operation. Negative feedback is limited to 15 dB to prioritize dynamic performance. The power block includes a heat sink and an extremely quiet cooling fan, maintaining the power block temperature between 75 and 80 degrees Celsius. It is equipped with a 160,000 μF capacitor and two 1.1 kW-class toroidal transformers, providing a power supply equivalent to that of a 400W-class amplifier operating in Class B.
Context
Designed by Dan D'Agnostino and introduced in 1980, the KSA-100 was positioned as a high-current, high-power amplifier capable of driving low-impedance speakers with control and stability. Its robust power supply and thermal management reflect Krell’s engineering focus on performance under demand.
Market
Originally priced at ¥930,000, the KSA-100 remains a sought-after amplifier among vintage audio collectors for its build quality and drive capability.
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