Soviet 6C33C. One of the very few indirectly heated power triodes. These were used in Soviet military applications as a voltage regulator. They require a Septar socket. Heater current is very fierce: 7 Amps. These bottles get hot! Sonically, they are superb and construction is second to none.
Found in high end Hi Fi amplifiers such as: B.A.T, Almarro, Lamm Industries.
Warning: Last items in stock!
AMPLITREX or Factory matched, depending on supply.