The VR56 is a pre-WWII military receiving pentode valve. The VR prefix in the type designation stands for Valve Receiving.

The valve in civilian name is an EF36. This valve was obsolete by the 1960s, and our data sheets show that the EF36 had identical characteristics and pin connections to the EF37 and EF37A. These were all high gain low current intermediate frequency amplifiers in superhet receivers and all featured external metalisation. With their low capacitances they would be useful at radio frequencies as well as IF.

It is interesting that as the series progressed, and eventually only the EF37A was produced, the valve had acquired the characteristics of low noise and low michrophany and the EF37A became a standard audio pre-amplifier for professional use before the advent of the EF86.

The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 81 mm tall.

References: Datasheet & ¹⁰⁴⁰.

 
Pin Connections

IO	1	2	3	4	5	6	7	8	tc
	m	h	a	g2	g3	nc	h	k	g1

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	0.2	250	100	-2	3	0.8	2.5M	1.8

Thanks to Frank Philipse for supplying the above PDF datasheet