You need a figure 8 pattern mic. The beyerdynamic set me back about $650 (but it's a ribbon, and I bought it for that reason -- just happened to work for M/S) but there are less expensive variable-pattern condensers that also have the figure 8 pattern.
The source mic (the one aimed at the singer or player) can be either directional or omni. I haven't tried it with omni, since I have an Audio-Technica and a RODE that sound pretty good.
It works like the old "Hafler Effect" to get surround sound for two-track stereo: you wire up two speakers in front, just like always, and then wire a third speaker behind the listening position that's hooked up to hot leads from L and R. The third speaker extracts phase information that is lost with ordinary two speaker reproduction, and gives you surround sound -- the only expense being the third speaker and its wires. I have an ancient Dynaco Stereo integrated hi-fi amp (designed by David Hafler) that has built-in speaker connections for the third speaker.
By reversing the polarity of one track, you're canceling out the "shared" portions of the tracks, so you then hear the differences (L-R and R-L) in the sound field.
It sounds like voodoo, but that's all there is to it.
I think I said that I've been through a Red Rover (Syntrillium's own device); when that died, I got a Tascam US428. When THAT died, I splurged on the Mackie Universal Control, which worked fine until I dropped it on its head and broke a motorized fader. It's repaired now, so it's back in the studio. There's a lot to be said for being able to push hardware faders and turn knobs, but the mouse click process can give you really precise editing.
There are several devices that are less costly than the Mackie that work more like the Red Rover (Tascam makes one) which is fine if you're doing one track at a time. The Mackie is actually overkill for what I doing now, but I like having it anyway.
I'm really glad I got the D888. At first, it seemed TOO simple -- not much editing capability, not many dedicated knobs, so you end up scrolling through menus some -- but on the other hand, once you learn how to run it, it's extremely easy to set up and record stuff off the cuff. I recorded about 5 hours of my late CW band and got around 35 usable songs to burn to CD. The only flaw (other than the usual missed notes, lyrics, and downright mistakes) is that the singer insisted on using his new Beta 58 mic, and it didn't have much top end, so the vocals sound muffled.
It only records at 44.1/16, which is fine for what I'm doing with it. I'll take it tonight to a lecture at the local Unitarian Church -- I'm recording and burning CDs for them -- and it'll do everything I need it to. Two tracks for the lecture: a lavalier wireless for the lecturer and a room mic to pick up questions from the audience, which have proven to be unintelligible against the room noise.
Plus, since I got
the D888 at the local store, I was able to trade in a bunch of stuff I wasn't using, so I wasn't out that much cash. There's a D888 discussion group:
http://www.korgstudios.com/forums/forumdisplay.php?f=160
You might check it out before you commit.