At least as far as high-end power amplifiers go.
Based on a design the company calls: Analog Switching Amplifier, a power oscillator is modulated by an audio signal to produce an amplified signal using a reconstruction filter without the bandwidth limitation of a conventional, fixed-frequency, carrier-based PWM (pulse-width modulation) control.The result is a nearly ruler-flat frequency response.
At $3800 each, the Reference 18 is not cheap by any means, but it's far less expensive than many other flagship monoblocks on the market.