The 6C33C-B is a power triode designed for use as a series
  voltage regulator. The 6C33C-B has very high perveance and
  very high transconductance. It has high current capabilities,
  making it suitable for Output Transformerless audio power
  amplifiers.

                                  General Data

                              Heater Characteristics

    Heater voltage....................6.3 or 12.6 ac or dc
    Heater current....................6.4 or  3.3 amps

                        Direct Interelectrode Capacitances

    Input...................................30.0 pf
    Output..................................10.5 pf
    Transfer................................31.0 pf

                                Mechanical Data

    Mounting position.......................Vertical
    Overall length..........................5.25" (max)
    Seated height...........................4.75" (max)
    Diameter................................2.5" (avg)
    Base....................................Septar

                                Pin Arrangment



                            Pin 1...Heater
                            Pin 2...Heater
                            Pin 3...Cathode
                            Pin 4...Anode  (thick)
                            Pin 5...Grid 1
                            Pin 6...Heater
                            Pin 7...Heater

                              Absolute Maximum Ratings
                      (according to manufacturer datasheet)

    Anode voltage...........................600 V (if tube isn't heated)
                                            400 V (if Pa < 30 Watts)
                                            250 V (if Pa > 30 Watts)   
    Anode dissipation.......................60 watts
    Cathode current.........................630 milliamps
    Heater to cathode.......................+300 volts
    Maximum grid 1 resistance...............200,000 ohms


  Typical Characteristics for using in voltage series regulators



    Anode voltage...........................120
    Cathode resistor........................35 ohms
    Anode current...........................550 milliamps
    Transconductance(Gm)....................40000 micromhos
    Anode resistance........................65-80 ohms