All tube operating points below are by no means definitive good sound recipe for your particulate tube project. Lowest THD point is not necessary best sounding one and there is always some variance even in a NOS tube batch from the same manufacturer! Below information is only useful as a general starting point and is ment to get you in a ballpark when no measurement equipment is available.
Another EL lineup output pentode, but less known and used. In my opinion unfairly so, because this is in fact miniaturized 6V6 – tube with probably longest life cycle of them all, found in numerous instrumental amps and other equipment.