MATCHED PAIR 12AT7WA - E81CC ZaeriX Aero Services London by Brimar Rochester at Thorn-AEI factory 60's year NOS-NIB, Codes 2I1 / 3980 and 1I1 / 3980 , COPPER Grids Posts, Balanced Triodes for Ip & Gm, Semibox square 2 ribbed Black Plates, Large Ring O Getter halo, in Original Box (v142 - v152) Sweet Sounding, Great Midrange
Warning: Last items in stock!
These are NOS Tubes (New from Old Stock no longer in production)almost certainly already tested in the factory at the time but before the sale they are tested by us one by one, to do this we use our TTA (the warmer) that allows us to heat up to 20 valves simultaneously and then perform the measurements with the "Characteristic Meter Avo VCM 163 "so the heating time will be the same for the whole lot in order to obtain precise and reliable relative numbers for the subsequent selection made with a software developed by us that compares all the values of Ip and Gm of the whole lot (80 total measurements for 20 tubes lot) and extrapolates the singles, the pairs, the triplett, the quartets to various tolerances.
consider that for each Tube (double triode) there are four measurements to be agreed (Ip and Gm for each triode)
For traceability the Tubes are individually numbered on bulb/base and inside the box, other numbers that you read inside the box are NOT the values but are our references for recording the measurements on our archive.
For information we specify that the measurements are performed at constant Va, therefore having Ip and Gm within certain tolerances, also the Ra and the μ will be similar.
|note||Burned, Tested by Audiokit with TTA+ AVO VCM 163 + Matching Software developed by us|
|dati||Update at 9 August 2019 MZ|