TELEFUNKEN Elektroakustik Black Diamond Series Vacuum Tubes are manufactured in partnership with JJ Electronic of Slovakia. The new production tubes are designed to be harmonically rich and tonally balanced. Each tube is rigorously tested, cryogenically treated and extensively burned-in. The Black Diamond Series 6V6-TK is newly manufactured rendition of the legendary 6V6. The 6V6 is a beam-power tetrode vacuum tube ideal for use in hi-fi audio equipment and music instrument amplifiers. Preceded by the 6L6, the 6V6-TK is a lower-powered tube that gained much wider popularity and use. The Black Diamond Series 6V6-TK offers a robust tone and great overhead. The rigorous quality control and durable construction yields a dependable tube ready for the most demanding applications. TELEFUNKEN Elektroakustik will not be held responsible (financially or otherwise) for equipment that is damaged from the use of tubes purchased from us. Each tube has been fully tested to ensure reliability and is guaranteed to perform as described. It is the responsibility of the customer to consult with the equipment manufacturer (or qualified technician) for the selection of proper tubes and proper installation and biasing procedures.