Tung-Sol 6550 Power Vacuum Tube, Platinum Matched Sextet Powerful, balanced and detailed soundstage. More dynamic and 3-dimensional than any other 6550 type Gold-plated and carbonized grids to prevent grid emission and bias runaway. Increased Plate voltage and dissipation further enhances performance and reliability Platinum sextet (6 tubes), computer-matched by manufacturer on proprietary equipment KT88 equivalent