6550

The 6550 is a beam power tetrode developed by Tung-Sol in 1955 specifically for high-power audio amplifier use, with a plate dissipation of 35W. It shares the KT88's octal base and general operating envelope but has a distinctly different sonic character: tighter, more controlled, and more linear than the KT88, with slightly less midrange bloom but superior bass definition. The 6550 is the original output tube of the McIntosh MC275 and many Ampeg bass amplifiers, where its clean headroom and damping characteristics are valued. Tung-Sol 6550 (original and reissue), GE 6550A, and Svetlana/SED 6550C are the notable variants.