Key Facts of the 6C33C Tube

Here are some key facts and information regarding this tube. The information below is gleamed from tube datasheets, websites, forums and playing with the tube itself (but not in an electrical circuit yet).

• In Cryllic, it is 6C33C. In transliterated English it is 6S33S.
• Comes in two flavours, the vanilla (6C33C/6S33S) and the rugged version (6C33C-B/6S33S-V).
• The main difference between the B and the normal version are the 'B' has lower Internal resistance and can withstand much more g forces in impacts and loads.
• Rate life is around 1,000 hours, but in a non-military/extreme environment and operated well below maximums, this could extend out to 10,000 hours as suggested by some.
• The tube is actually two triodes in one envelope. The cathode, plates and grid are internally connected in parallel. The heater is left separate, which can then be used singularly or both in a parallel or series connection.
• The tube is designed to run with lower voltage (150-250V range) and higher currents (150-250mA range).
• Very low internal resistance and a good candidate for OTL.
• The heater takes a lot of heater power; either 12.6V @ 3.3A or 6.3V @ 6.6A. That is 41.58W.
• The heater needs to turn on at least 2 minutes prior to B+ voltage. The longer the better.
• The tube itself feels very rugged, sturdy and well built.
• It was made in a number of different factories; Ullyanov, Svetlana and Poljaron.
• It was first discovered in the West via a MiG-25 from a defector's plane.
• Uses a special socket and has been suggested that it needs to be ceramic because of the high heat in the operation of the tube.
• The pins of the socket generally need to be well ventilated and clean to ensure good cooling and electrical contact.
• The tube runs hot and cooling and placement are critical to reliability and long life. Consider forced cooling, and considered passive cooling.
• A link from Good Sound Club with lots of advice on the tube. Rather biased opinions, but nonetheless valid observations from someone who has used this tube extensively.