Interesting that your new "hum shields" have no tops at all. I suspected as much from early on. It may simplify the potential improvement needed, if desired. Again, it depends on the headphone. I've reached nirvana with HF-1's and the pupDAC using my Torpedo with no mods at all. It's funny, because my HF-2 seems a bit deficient in the highs by comparison. I also have the SR-225's, but their highs seem exagerrated with somewhat deficient bass. The HD600's with Cardas cables come close to the HF-1's, but are still a bit slow in the highs. My only question is whether a pair of RS-1's are better than the HF-1's or more like the HF-2's. I'm hoping the CanLanta meet will let me find out.
Just MHO, but I find the very old NOS 6J6's the best as opposed to the "Mysterians" Japanese tubes, but that's just a personal preference. My Grados need some mellowing amongst all the detail and maybe that's what I'm attracted to. I like the Sonotone 6J6W's, some of the JAN 6J6's and then the DuMont/RCA 5964's. It's crazy that all these tubes are available in the tens of thousands for $2 and less. Dsavitsk had a stroke of pure genius with creating an amp based on these tubes.
Anyway - also wanted to say that I like the black knob better, too. I think I'll make them all that way unless someone asks. Nice photos!