The PD220 is a double triode audio output valve from the 1930s. It was designed to work in class b2 push pull. These double valves were a way to achieve greater audio power at reasonable cost from a dry battery radio receiver.

With a grid to grid peak to peak input voltage of 58 Volts, the rated 2.85 Watts output would be developed across an anode load of 11,500 Ohms. The input resistance of the push pull pair is 3,300 Ohms.

The top view shows the makers name and the type designation. The holes in the top mica mark the positions of each of the cathode assemblies.

The classic envelope is 40 mm in diameter and, excluding the B7 base pins, is 89 mm tall.

References: Datasheet & ¹⁰⁴³. Type PD220 was first introduced^¶ in 1933.

 
Pin Connections

B7	1	2	3	4	5	6	7
	g1(2)	g1(1)	a(1)	f	f	-	a(2)

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	gm	Pout	D
	2.0	0.2	150	-1.15	0.4	0.9	2.85W	5%

Thanks to Frank Philipse for supplying the above PDF datasheet

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