I have finished building the thing, and while it sounds amazing with a boost of some kind after, without the boost there is a very significant volume drop as compared to bypass, such that it is only really usable on its own with the volume cranked, and even then, it seems to be about half as loud as unity. I have tested it with different 12AX7s, all of which work fine in other circuits, and no change. The next thing I was going to check are the cathode bypass caps, but I was wondering if anyone else had that issue / has a better idea as to what the issue might be.