The EL84 output pentode was classically used in the Mullard 10W high quality audio amplifiers of the 1950s and 1960s. Other makers copied the design and this is one from Mazda. It is marked as of Foreign origin and this suggests late production when the UK industry was in decline.

The performance figures given here refer to class A operation.

See EL84 for full details.

Looking inside the anode cavity the three grids can be seen, showing that this is a true pentode. The suppressor grid is of a very open pitch such that it appears as a single thick line in each of the anode gaps.

The thin glass tube envelope is 21 mm in diameter and, excluding the B9A base pins, is 70 mm tall.

References: Datasheet, ³⁰⁰² & ¹⁰⁴⁰. Type EL84 was first introduced^¶ in 1953.

 
Pin Connections

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

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	gm	Pout	Pdiss
	6.3	0.76	250	250	-7.3	48	5.5	6.7	2.2	12W

Thanks to Frank Philipse for supplying the above PDF datasheet

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