recstar has it about right - I've been so busy listening that I can't say I've been able to detail my impressions with a wide-enough range of experience to give you the kind of detail I think you expect. Also, I am still waiting for several 6SN7s to arrive so I can do a decent comparison. Have been running the Electro-Harmonix with gold pins, which Craig says is made in the same factory as the Tung-Sol, and a couple NOS Russian T-plate 6SN7s, which have been very nice. There's a Brimar, a couple Tung-Sols, and an RCA round-plate or two on the way, but who knows when.
So far, I have just been running subjective comparisons between the BA and the Zana Deux. These are not completely fair because I am feeding the BA with the balanced outputs from a NAD M5 and the ZD from the non-balanced analog outs. I have been using exclusively a set of balanced HD650s on the balanced outs from the BA, and a rock-stock set of HD800s with the ZD and on the SE port from the BA.
The ZD is running stock 6C33C-B power triodes, Svetlana recitifiers, and a 50s 6SL7GT driver. The BA is a 307A version, with NOS Ken-Rads, and the above-mentioned NOS Russian military 6H8C driver. Say 500+ hours on the ZD, <25 on the BA, so everything comes with many grains of salt. Also, only digital sources so far. No vinyl to the BA yet, so I'm not sure what good my comments will do you.
The BA is the best-sounding balanced amp I've heard. Great, black background, very precise control of both ends of notes, excellent space between instruments, outstanding damping (maybe a tad tight, as I don't have many hours in on it), and truly outstanding on complex material. I don't think Brubeck's ever sounded as good to me (on CD) as through the BA. The ZD through the HD800s does not achieve the same dead quiet background as the balanced side of the BA through HD650s. It does though seem to have a less-damped sense of immediacy. For example, the opening of Blue Rondo a la Turk on the BA/HD650 is precise, delicious, and will make you sit down, but the same phrases through the ZD/HD800 will smack you into your seat and ruffle your hair.
I am enjoying the hell out of both of them. I hesitate to say much more because: 1) I haven't enough time in on the BA yet; 2) I do not have both amps wired with comparable inputs, the BA taking balanced inputs, the ZD analog; and 3) my 800s are wired SE whilst the 650s are balanced, making direct comparisons with the same cans difficult. As a general comment, I can say that the BA is magical at making sense of even the most complex, over-produced, too-hot stuff, while also making big space with stuff like Herbie-the-K's Mahler pieces (though I'm mostly running jazz through it at the moment). I think though, that with something like a direct-to-disk, chamber trio, or the special one-sided 45 RPM RCA pressing of Fiedler's 1958 Gaite Parisienne (which I've actually heard performed at Symphony Hall), I might choose the upside-de-haid smack of the ZD. Of course, now that I've said that, I'm listening to Voodoo Cadillac by Southern Culture on the Skids through the HD650s off the BA, and it was so. damn. good. it made me stop typing and listen. So, take this all with a grain of salt. My ZD's continued to improve over hundreds of hours and I suspect the BA will do the same. Enjoy, apologies for the bandwidth, and drive it like ya' stole it!
-Tim
