The THAT5171 from THAT Corp., Milford, MA, is a digital gain controller IC for low-noise analog, differential, and current-feedback audio preamplifiers. Used with an appropriate analog gain block, the IC can set gain in 1 dB steps, while preserving low noise and distortion. The device operates from ±5 V to ±17 V supplies and supports input signal levels as high as 22 dBu at 5.6 dB gain and ±17 V supplies, with guaranteed gain error of ±0.5 dB max. at all gain settings. The 5171 is controlled via SPI; 4 general-purpose digital outputs—connected to input pads, analog switches, mute circuits, or LEDs—can be controlled via this interface.