An ultrasound system for investigating a subject comprises a probe, a signal processing module, and an interconnecting cable. The probe includes an annular phased array transducer defining multiple signal processing channels. The signal processing module includes a controller, a transmitter, a receiver, delay circuitry, and a video section. Within the delay circuitry, each signal processing channel includes an inphase branch and a quadrature branch. Each branch includes an analog-to digital converter (ADC) and a delay first-in-first-out (FIFO) memory. Dynamically variable delays are implemented by varying the sampling and FIFO input rates relative to constant FIFO output rates. The variable clock rates are derived by switching between phase-staggered replicas of a master clock MCLK, which has a rate at the nominal center frequency of the ultrasound signal prior to sampling. The timing circuit used to derive the variable clock rate signal uses a focus FIFO to serve as a timing buffer between the variable clock rate signal and the master clock signal. Inphase data streams from each channel are combined in a pipelined adder; quadrature data streams are similarly combined. An interpolator permits accurate combinations of the summed inphase and quadrature data streams. The resulting combination is directed to the video section for output. Advantages of the disclosed system include low signal processing, memory and data rate requirements, resulting in a more reliable and economical high-performance ultrasound system.