/12AU7 Grey Pair Brimar long plates, NOS specs (V257/258)

Description

Pair: 12AU7 made by Brimar, in 1955 & 1956

This is a pair CV491 (= ECC82) produced by Brimar in the UK. They are the Special Quality Military version of the regular 12AU7, with military coding KB/AD.  The tubes have halo getters and long ribbed plates (Version 3987), see pictures. Very healthy tubes with NOS specs! Tubes with matching systems; see test results.

The although the print is slightly rubbed of, tubes show no signs of use and measure new; so most likely these are unused new tubes (pulls from military equipment)!

Sonics

This early long plate CV491 is highly regarded for its sound; warm and realistic with a solid bas. I refer to the many threads on the web for more information. Excellent preamp valve, low noise, very good in preamps. Note: if your system is too bright this tube is serious option. Long plate ECC tubes in general tend do be more microphonic than the shorter cousins. Because of the superior sound it is worth to give it a try. Till now I have not come across with long plates with excessive microphonics. 

Test results*

Valve 1 V257	Ia (plate current): Transconductance (Gm): Gas test, Shorts test:	9,6/ 9,9 mA       2,4/ 2,4  mA/V OK	=  NOS =  NOS
Valve 2 V258	Ia (plate current): Transconductance (Gm): Gas test, Shorts test:	9,1/ 9,1 mA 2,1/ 2,1  mA/V OK	= NOS = NOS

  *  For test methods and factory specification read the tube testing page.

 

Short description