The ECC40 design from dates back to the early days of all glass construction in the UK. The CV3884 is the ECC40 produced to a UK government specification. The groove around the hard glass foot where it joins to the soft glass envelope looks typical Philips Eindhoven. The type face is spartan plate gothic as used on Mullard valves.
The CV3884 has two independent triodes within the single envelope and with a gain of 30 would be useful for most purposes including instrumentation. Mullard describe the ECC40 as a low-microphony double triode with separate cathodes, primarily intended for use as an AF voltage amplifier or phase splitter. The 6SN7GT was the valve it was designed to replace and three years later it was superseded by the ECC82 on the B9A base.
The grid is wound on copper supports with a large heat-sink plate at the top.
The two triodes side by side with no internal electrostatic screen. The locating pip is moulded into the skirt portion of the envelope.
The anode is stitched together and the extra width is for heat dissipation.
The thin glass tube envelope is 20 mm in diameter and, excluding the B8A base pins, is 60 mm tall.
