Valvo Aa quad, same year 1942, German army property, NEW

Description

Here is a Quad of Aa tubes made by Valvo, Germany. 

Detailed description

These tubes were Wehrmacht property of the German army in the second world war. The stamps on the base of the tubes are most likely performance checks,

The Aa vacuum tube was developed in 1928 by Siemens & Halske. The Aa tubes are direct heated triodes. They were used for telephony (Poströhre). They are long life tubes with life time of 100.000 hours. 

These tubes can be the basis for superior sonics in a preamplifier. The quad has NOS values and good looks. On the pictures they look dusty; this is because they have not been cleaned in order to preserve the print.

Note: my tubes are often not the cheapest. But is very hard to find better tubes !

Test results 

Valve  V1

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

4,6  mA 1,0  mA/V OK

>  NOS =  NOS

Valve  V

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

4,1 mA 1,0  mA/V OK

> NOS > NOS

Valve  V

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

4,6  mA 1,1  mA/V OK

> NOS > NOS

Valve  V

Ia (plate current): Transconductance (Gm): Gas test, Shorts test:

4,8 mA 1,1  mA/V OK

> NOS > NOS

Values for new unused tubes:

• The rated emission value for a new Aa is:  4 mA. 
• The rated transconductance value for a new Aa is:  1,0 mA/V . 

Test conditions & equipment:

Mutual transconductance, plate current, gas and shorts test equipment: AVO Mk IV (Dutch army tester) , AVO Valve Data Manual 23rd edition 1981, RFT stabilised mains, Utracer3+, Philips PE 4832, 2x Korad KA3005P programmable power supply, 2x Keithley 2700 and 2x Fluke 145. 

Test conditions: Ua (plate voltage) = 220 Volts, Ug = -4,5 Volts and Uf = 4 V ± 3% (factory conditions).

Please read our test page.

 

Summarized description