I never was a basshead but everything changed when I connected my Abyss 1266 Phi TC directly to the speaker taps of my First Watt F7.
Oh boy, thats what I call a visceral experience of sheer power!
But it`s still hard to find an E88CC or variant that delivers a tight, full and accurate subbass in the deepest registers without having other issues.
Actually I really love my RTC E188CC (Mullard) in every way - except the subbass that is portrayed more like white noise ... ;) In the meanwhile I tried Siemens E188CC, some Amperex bugle boys and Sylvanias. Finally I came back for the stock tubes of my dac (Lab 12 Dac 1 Reference), some 6922 from Electro Harmonix.
From my small experience these are the only tubes (by far) bringing out a real proper subbass. But as they lack in other regions now I`m still on the run for the perfect tube.
Soundwise I really love the Mullards (E188CC) for theier voloptous, wide open and very well textured presentation but I could live with something less warm as long as the tubes have a delicate and slightly fuller charakter (also liked the bugle boys for theier medium warm tonality, except for the mids that were way too upfront in my eyes).
So, what could I do? Happy for every constructive feedback!