SED Winged C is a Russian vacuum tube brand produced at the former Svetlana plant in St. Petersburg, a factory whose tube-making lineage traces back to a 1937 RCA license. Following a 2003 trademark agreement, the St. Petersburg manufacturer (JSC Svetlana) retained exclusive rights to the distinctive "Winged C" logo — a stylized Cyrillic S resembling a winged letter C — while the Svetlana name itself passed to New Sensor in the United States. Tubes from the St. Petersburg plant were subsequently sold under the SED St. Petersburg, Russia branding, and the Winged C mark became the visual identifier collectors and amp builders look for.

The brand is best known for its power tubes, including the 6L6GC, EL34, 6550, and KT88, along with preamp types such as the 12AX7. Built on the original Soviet-era tooling and materials, SED Winged C tubes earned a reputation in guitar, bass, and hi-fi circles for warm, full-bodied tone and mechanical robustness, and they have been used as factory or replacement tubes by amplifier makers including Mesa/Boogie. With production at the St. Petersburg receiving-tube line having ended, remaining stock has taken on a sought-after, near-collector status among players chasing the so-called "holy grail" Russian tube tone.

SED Winged has 2 products cataloged on Equipboard, including Guitar Amplifier Tubes.