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 TELEFUNKEN EL84-TK is a perfect replacement for any EL84 / 6BQ5 tube offering a reliable and great sound. It is a thermionic valve of the power pentode type. Originally designed for the output stages of audio frequency amplifiers, the EL84 can deliver up to 17 watts. Although it is physically smaller than most common output tubes, this pentode tube can really deliver. In many ways it is similar to the EL34 but without the output “horse power." 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.