Abstract: An electrical property sensor is presented that includes a printed circuit board with a first face separated from a second face by a thickness, the first face having a length and a width. The sensor also includes an aperture extending from a first face of the printed circuit board to a second face of the printed circuit board. The aperture includes a receiving electrode and a transmitting electrode. When a fluid flows through the aperture and a voltage is provided at the transmitting electrode, a cunent flow is measured at the receiving electrode.

Abstract: Sag of a power signal delivered to of an amplifier is controlled. The maximum amount of sag is limited to limit crossover distortion. A measuring circuit monitors an observed signal to generate a measured signal. A sag control circuit receives the measured signal and one or more input control signals, and in response generates a sag control signal. A regulator circuit receives the sag control signal and a raw power supply signal and in response generates a regulated DC power supply signal for the amplifier. The regulator circuit decreases the maximum power available to the amplifier as the sag control signal magnitude increases, so as to increase distortion and compression in the output signal (e.g., and achieve a "warm", "airy" or "forgiving" sound quality resembling or improving the sound of a vacuum tube amplifier).

Abstract: A regulated power supply control system with adjustable operating point and adjustable dynamic behavior for use with electronic power supply circuits, such as musical instrument amplifiers. The control system includes a measurement circuit (20) that generates a measured signal (22) based on an observed signal (18) in an amplifier (10); a sag control circuit (24) that generates a sag signal (32) based on the measured signal (22); a referenced circuit (34) that generates a static reference signal (38); and a regulator (44) that uses the static reference signal (38) and sag signal (32) to generate a regulated power supply output (14) that is used by the amplifier (10). The sag control circuit (24) permits adjustment of the sag signal 32 by a user-operated sag magnitude control (26), sag rate control (28), and sag recovery rate control (30).