The N147 is the M-OV equivalent of the Mullard EL33 audio output valve.
The design is as a high sensitivity output pentode for use in AC mains equipment. The normal use was in domestic radio receivers as a single ended stage.
The top micas showing the copper rods of the control grid. The KT61 offers similar performance but is a beam tetrode that avoided the Mullard patents. The KT61 is not a direct replacement for the El33/N147.
The IO base pins.
Thanks to Mark Mallison for sending the images.
The classic envelope is mm in diameter and, excluding the IO base pins, is mm tall.
References: Data-sheet, 1040 & 1043. Type N147 was first introduced in 1938. See also1938 adverts.
