The 25A6G is an audio output pentode that was designed for single ended use in universal sets. The heater is designed for series connection across the mains supply, and the anode ratings reflect the low HT available when no mains transformer is available.

The view looking up into the valve from the base. The heater passes through the cathode tube eight times. The control grid is wound on substantial Copper supports.

The classic envelope is 45 mm in diameter and, excluding the IO base pins, is 104 mm tall.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	m	h	a	g2	g1	-	h	k

 
Absolute Maximum Operating Conditions

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm	Pout	D
	25	0.3	160	120	-18	36	12	42,000	2.4	2.2	10%

Thanks to Frank Philipse for supplying the above datasheet

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This exhibit was last updated on 10 May 2009