Lightning Boy Audio’s Opti-Mu Prime compressor uses a unique circuit design with a pair of 12AU7 tubes. One drives the optically controlled vari-mu circuit, which constantly re-adjusts the plate voltage of the preamp tube, based on how loud the instrument is being played. The second serves as a preamp, and is the only tube in the audio path. All Lightning Boy gear is built with paper-in-oil caps and low noise Vishay/Dale metalized film resistors, and the Opti-Mu Prime is hand-wired with silver-plated Teflon insulated wire. Learn more at www.lighntingboyaudio.com.