[turretslug]

In the case of the EBC41, perhaps the 6AT6/EBC90/DH77 had already achieved popularity in the UK market- a valve pitched as having a triode primarily intended as AF amp would not need anything more than the by-then well established 7-pin base and the double-diode-sharing-cathode-with-triode-AF-amp technique had been an established and successful part of AM receiver design since the mid-'30s. Thus, a Rimlock/Noval DDT was probably seen as low in the priority list. Maybe Pye could get a good deal on EBC41s and their existing radio and TV production meant economic bulk purchasing/holding of Rimlock/B8a sockets anyway. The EBC41 does have an internal screen and an inherently skirted socket adds to the screening integrity- maybe Pye felt that this was worthwhile with what was pitched as a high-quality, high-fidelity set, though there's probably not much in it.