The 50CD6 is the 300mA heater version of the 6CD6G beam tetrode. The parameters given are for single ended audio use with an anode load of 1,500 Ohms.
The valve is also specified for push pull service, where it will deliver 13.5 Watts at 1.7% distortion in class A.
Unusually the valve was primarily designed for use as a line output stage in television receivers.
The 50CD6, which is a 'greedy' valve and by no means cheap, would not be a cost-conscious designer's obvious first choice for something as mundane as audio output. The 50CD6 was quite widely used in TVs during the late 1950s. If memory serves correctly, it was often the first valve in the set to fail and very costly to replace.
The anode supply can be 700 Volts, with a positive surge of up to 6,000 Volts. The anode dissipation is 15 Watts and the screen dissipation 3.0 Watts. The anode current can be 170 mA. Other parameters would be a screen voltage of 170 Volts and a negative grid surge of -150 Volts.
The classic envelope is 48 mm in diameter and, excluding the IO base pins, is 48 mm tall.
References: Datasheet & 1040. Type 50CD6G was first introduced in 1951.
Absolute Maximum Operating Conditions¶
Updated February 24, 2016.