6CS7 RCA USA NOS-NIB 50-60's Year Two Pair same internal structure for Leben CS600 - CS660P (v2 - v5 + v3 - v4)
TWO SELECTED PAIRS 6CS7 RCA USA NOS-NIB years 50-60, SAME INTERNAL STRUCTURE !! 4 Sections Balanced for Ip & Gm for each pair on 8 measurements, (they are double triodes but with different sections) Copper grid rods, 3 rib Gray Plates, O Ring Getter, in original box (v2 - v5 + v3 - v4) are used on Leben CS600 and CS660P
ATTENTION !! At the time, these Tubes were produced by a few factories in 3-4 structural types and were rebranded with at least fifty logos of different manufacturers and retailers and from different countries, therefore they may have different boxes, serigraphs, brands, marketing countries, find four identical in all is really difficult but we have brought them together by structural typology, geometry and color of the internal parts therefore identical and coming from the same factory, the sound timbre will be the same (listen with the ears not with the eyes...)
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) so for the pair of Tubes the measurements are well EIGHT "
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.
- Burned, Tested & Selected by Audiokit with TTA+ AVO VCM 163 + Matching Software developed by us
- ins 12/01/2023 MZ