Type 6BS7 is essentially a type 6BR7 with the signal grid taken out to a top cap in order to overcome the external 'hum problem'. However, hum was not a problem to professional hi-fi designers who preferred the single-ended 6BR7 for other good reasons and (on the whole) ignored the 6BS7.

Moreover, ham-fisted DIY enthusiasts who could not handle the 6BR7 often could not the 6BS7 either (since hum is not the only problem in high-gain audio amplifiers). Above all, it makes no sense to design and market a valve specifically for incompetent customers! As a result the 6BS7 was much less widely used.

The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 50 mm tall.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9	tc
	ic	ic	k	h	h	s	a	g2	g3	g1

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	gm
	6.3	0.15	250	100	-3	2.1	1.25

Thanks to Frank Philipse for supplying the above datasheet

This exhibit was last updated on 04 July 2007 {find valves by name}