The Digisound‐16 is a two‐channel, 16‐bit DAC‐ADC system with a 32K word buffer. Because of its high performance and low cost it is an attractive signal source for psychoacoustic experiments. The device can be modified to serve as a precision digital oscillator by using the technique of fractional addressing [W. M. Hartmann, J. Acoust. Soc. Am. 82, 1883‐1891 (1987)]. The frequency resolution is 0.003 Hz over the audible range and the total distortion approaches the theoretical limit of − 85 dB for single‐channel operation. The modification requires that the 15‐bit address register be replaced by a 24‐bit increment‐and‐add circuit. Two‐way communication between the modified device and the host computer allows the address increment to be changed continuously so that the oscillator can be manually tuned, as in the method of adjustment. The portion of the buffer that is recycled can be reduced by factors of 2, under program control, to as little as 2K words. The reduced buffer length promotes efficiency while compromising frequency resolution and distortion figures. [Work supported by the National Institutes of Health.]