As with cables, tubes are a completely subjective matter with many variable parameters ultimately determining their performance in any given application. Some people like the Philips E88CC SQ, others don't. Personally, I think they are on par with some of the finest E88CC variants around. Philips tubes literally are Amperex tubes (or in the very least they were manufactured at the same facilities). The earlier large print variety of the Philips is better, IMHO, than the later small type versions. Good listening.
-Richard
-Richard