The C-valve is a tube-based microphone and instrument preamplifier using discrete transistor and tube gain cells. It provides adjustable input gain, variable tube saturation for harmonic content, and an onboard limiter. Front-panel meters (large analog VU, six-segment input) aid gain setting. It supports 48V phantom power, phase and Enhance switching, insert points, and two analog inputs (XLR mic and 1/4" line). A rear RCA S/PDIF output handles 24-bit, 48/96 kHz digital audio.