I have the mhdt in a second system and find the 6n3 comes across with a nice cleaner sound thank the GE or WE. The strange thing is and I may try it is to get tube adapters ($25 very nice quality) from Garage 1217 web site and run 6922 or 6sn7's. I have a huge stash of very nice NOS 6922, 6sn7 tubes. Check out Head-Fi web sight on preferred tubes for the mhdt. Many run the 6sn7 and 6922 which I would think is a much better tube than the funky 5670 but it does sound good so going with adapter may be a waste of time. I've not heard of mhdt going up in flames using adapters.
Tube imperfections
This is my first foray into tube rolling and I have a question about tube construction/consistency. First, I'm rolling tubes in an MHDT Orchid DAC. It came with the upgrade to a WE396. While the unit sounds very nice, I'm suspecting I may like other tubes based mainly on discussions here and other blogs. I've gotten a couple to roll through now but wanted to start with one similar to the original (I didn't get it with the unit), and ordered up a JAN GE5670. Upon inspecting it, there is a very clear warp in the bottle, a tilt, and this is also affecting the internals. Essentially, the tube exhibits about an 8 to 10 deg tilt. It does have the JAN etching along with the triangle. The vendor assures me that it passed the JAN screenings and also their own tests for low noise and proper operation. Is this more common than not in smaller tubes, should I not be surprised at such variations and ultimately, is this detrimental to sound quality? The vendor has offered to take it back but said that the others in stock won't be "perfect" either. Should I shop for another until I land on one that appears better? Are military grade better sounding? As a side question, is the JAN/2C51 marked WE396 potentially different sounding to one just marked WE396 which I have. Should I try one? I realize that audible variations may be hard to hear at the DAC level so there's that. Hoping to learn from the AG community. Thanks for reading.