12AU7 / ECC82 pair Radiotechnique France, NIB, labeled Belvu, same date code V20/174 (emissie checken)

Description

This pair 12AU7 tubes is made in 1958 by La Radiotechniques (RT) in France. 

La Radiotechniques was at first (1919 – 1931) a subsidiary of the French Compagnie générale de la télégraphie sans fil (CSF). Later (1947) it became a subsidiary of Philips of the Netherlands, who also owned Amperex and Mullard. The Radiotechnique Suresnes factory in 1951 produced half of France’s reception tubes and 30–40% of the wireless telephony receivers.

The tube has a typical design; see pictures. The tube has a halo getter and grey plates.  The tube date codes are 5818 & 5813 are manufactured in the 18th & 13th week of 1958  (same manufacturing year). The tubes are delivered in generic vintage BelVu boxes.

The sonic properties of the La Radiotechniques / Belvu 12AU7 are described as: “These tubes give wonderful imaging, sparkle, dynamic, organic and open sound with a holographic 3D soundstag”.

The tubes are thoroughly tested. Both tubes match the factory specifications very well. The pair consists of two strong tubes with balanced systems. See test results in the section below.

Test results

Test methods and test conditions are outline on the tube testing page.

The measurement data below illustrate that the tubes are in good till excellent condition. 

Valve 1 V278	Ia (plate current): Transconductance (Gm): Gas test, Shorts test:	9,2 /9,4 mA     1,9 /1,9 mA/V OK	=  NOS / NOS =  NOS / NOS
Valve 2 V174	Ia (plate current): Transconductance (Gm): Gas test, Shorts test:	9,1 /8.3 mA  1,7 /1,7 mA/V OK	=  NOS / strong =  strong / strong

(Telefunken factory specification see test page)

Summarized description