The Russian audiophile tube 6S33S-V (6С33С-В) is a high-durability power triode with a directly heated oxide cathode, designed for use as a control element in voltage regulators for military equipment. Manufactured by the Svetlana plant, it is the premium "V" (enhanced reliability) variant of the 6S33S and is electrically identical to the legendary 6C33C-B, a tube that has become a cornerstone of Hi-End audio. It is a New Old Stock (NOS) item, never used, and is prized by audiophiles for its exceptionally low internal resistance, high current capability, and robust construction.

Key Features & Specifications

• Name: 6S33S-V / 6С33С-В
• Type: triode, high-durability
• Application: voltage regulator (control element), power amplification
• Cathode type: oxide, direct heating
• Envelope: glass
• Mass: 200 g
• Filament voltage: 6.3 V / 12.6 V
• Filament current: 6.6 A / 3.3 A
• Anode voltage: 120 V (nominal)
• Anode current: 0.45–0.63 A
• Anode power: 60 W
• Steepness (transconductance): 30.0–50.0 mA/V
• Reverse grid current: 5 µA
• Microphonic noise: 300 mV
• Socket type: rsh3 (Septar 7-pin)

Maximum Ratings

• Max anode voltage: 250 V (when plate dissipation exceeds 30 W; derates to 450 V at ≤30 W)
• Max anode dissipation: 60 W
• Max cathode-heater voltage: 300 V
• Amplification factor (μ): ≈ 2.8

Applications & Compatibility

• Primary use: regulating valve (control element) in electronic voltage stabilizers for military and industrial equipment.
• Audio use: output stage in single-ended and push-pull Hi-End amplifiers, as well as OTL (output transformerless) designs, thanks to its low internal resistance and high current swing.
• Equivalents: 6C33C-B (the standard export designation); 6S18S (an older, lower-reliability equivalent with identical electrical characteristics).
• Note: the 6S33S-V is the enhanced-reliability version; the suffix «В» denotes increased quality and durability for military applications.

Condition

• Status: NOS (New Old Stock). Never used.
• Origin: Made in the USSR by the Svetlana plant.

Why Choose This Tube?

The 6S33S-V is a rare power triode that combines the ruggedness demanded by military voltage regulation with the electrical virtues that audiophiles treasure. Its directly heated cathode and very low internal resistance allow it to deliver substantial current into low-impedance loads, making it a natural choice for OTL headphone amplifiers and single-ended designs that require uncompromising drive. As the "V" variant, it offers enhanced reliability over the standard 6S33S and the earlier 6S18S, ensuring stable performance and extended service life. For DIY builders and restorers alike, this NOS Svetlana tube represents an opportunity to own a component that has earned a permanent place in the Hi-End audio canon, whether as a regulator in a military power supply or as the heart of a modern amplifier.