In 1975 Mark attended a concert that was put on by the Jesus music band Amplified Version, Mark began to talk with them, and they convinced Mark that for The Lighthouse Boys to continue successfully they needed to get a sound system to take with them on the road. That same year a sound system was purchased. In 1976 The Lighthouse Boys became a full quartet when Frank McNinch joined on bass vocals to fill out the sound. They also added Garry Miller on bass guitar and Kenny Knight on drums to fill out the rest of the band.