The Usher P-307 is a modern, reference-level preamplifier. It is the control center of today's high-end sound systems. Its two main functions are source selection and volume control — and Usher has made every effort to keep that input as accurate as possible. To avoid unwanted interactions with adjacent source components, the P-307 uses high-quality relays and switching designs to ensure that every source is intact. Thus all sources remain separate from one another and from the power amplifier and cables. The P-307 completes any high-end sound system by allowing you to control and appreciate the subtle nuances of your music.