The L63 is an octal based amplifier triode. It is a low impedance device and although designed as a general purpose valve it is often used at audio frequencies.
The triode is set high in the envelope.
With a single grid the front-to-back dimension is small.
The heater is a coiled wire with heavy insulation. The heater is inserted into the cathode as a single inverted V without being twisted to minimise the external magnetic field.
The classic envelope is 37 mm in diameter and, excluding the IO base pins, is 90 mm tall.
References: Data-sheet & 1040. Type L63 was first introduced in 1938. See also1938 adverts.
