Why DACs Produce Ultrasonic Output

The 2026 notes on ultrasonic DAC output have outgrown their home inside the valve-stages article, so they are now an article of their own: This Is Why DACs Produce Ultrasonic Output.

It covers why every DAC puts out images and fast edges above the audio band, why oversampling and noise shaping move the problem rather than remove it, clock feedthrough in multibit DACs, and what all this does to the analogue stage that follows. The original Thermionic Valve Analogue Stages for Digital Audio now links to it.