ECC81, MATCHED PAIR OF MULLARD , SAME FACTORY CODE, Tk3 B7G2, BLACKBURN JULY 1957 MANUFACTURE

ECC81, MATCHED PAIR OF MULLARD , SAME FACTORY CODE, Tk3 B7G2, BLACKBURN  JULY 1957 MANUFACTURE

On offer today is a lovely matched pair of Mullard  ECC81 Blackburn manufactured in July 1957      Carrying good white print, they tests as excellent using my AVO Valve Characteristic Meter VCM163 with the following results: At Va = 250V Vg = -2.0V 

V1: Section 1: Ia = 9.0 mA; gm = 4.5 mA/V

V1: Section 2: Ia = 9.0 mA; gm = 4.5 mA/V

V2: Section 1: Ia = 12.0 mA; gm = 4.6 mA/V

V2: Section 2: Ia =11.0  mA; gm = 4.7 mA/V

The specification for a new/100% emission valve is:

Ia = 10 mA; gm = 5.5 mA/V

As you can see, this result show a strong pair of valves, well matched both inter valve and also showing excellent matching of each triode section within each envelope.