The Mullard ECC81 was designed for RF use and is of medium impedance.

It was used as a frequency changer in five station television sets. In this application the oscillator triode would be the first to cease working.

The ECC81 also makes an excellent phase splitter in modern audio applications.

The thin glass tube envelope is 20 mm in diameter and excluding B9A base pins the length is 47 mm.

References: Datasheet & ¹⁰⁴⁰.

 
Pin Connections

B9A	1	2	3	4	5	6	7	8	9
	a(2)	g1(2)	k(2)	h	h	a(1)	g1(1)	k(1)	hct

 
Absolute Maximum Operating Conditions^¶

Triode	Vh	Ah	Va	Vg	mAa	ra	gm
	6.3	0.6	250	2.0	10.0	10,000	5.5

Thanks to Frank Philipse for supplying the above PDF datasheet

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