Up to 25 dB additional level for passive microphones. Provides 2 different levels of ultra clean reinforcement. Patented, discreet JFET class A circuit. Recommended for use with all passive dynamic microphones. Recommended uses for product:Singing, Podcasting, braodcasting.Sometimes, it will delay as the custom of clearance. We offer an extended 30 day cancellation period on all goods. It means a repair service or a replacement is offered for any faulty goods during the 1month period, beginning on the day on which the 14 day cancellation period ends. We value feedback as important inspiration in our development of business.