The Eclair Engineering Evil Twin is a tube direct input box that is best suited for use in the recording studio. DI boxes are useful in general for live shows as well, but I would recommend just using this one in the studio since it's tube based and a lot more expensive than your average DI box. The box stands on it's own and isn't rack mountable, and contains 1/4" input and output connections as well as an XLR output.
The make up of the Eclair Engineering Evil Twin isn't difficult to follow, although it definitely has more features that your standard DI box will. This is a beautiful thing as it gives you a whole lot of control to work with. It's got switches for a -20 db pad, bypass/loop, a ground lift, a simple EQ that you can switch to boost at either 3 kHz or 9 kHz, and also a polarity switch. Lastly, it has a large gain knob for setting your level. I haven't seen a manual nor do I think one would be necessary.
The sound of the Eclair Engineering Evil Twin makes it one of the best DI boxes that I've ever heard, if not the best. I love the flexibility here, but the raw tone is really what makes it what it is. It's awesome for recording anything where you'd want a direct signal, including of course bass guitar which it is probably best suited for. It isn't your typical flat direct sound either; it's got it's own, full bodied tone that is anything but your typical stale DI sound. Not much more that can be said other than it must be heard to get full appreciation.
Although very rare, the Eclair Engineering Evil Twin is one of the best direct input boxes available. I believe it's the only product that Eclair Engineering has to offer, and for whatever reason they didn't make many of them at all, nor am I sure if they are still even making them. The price is certainly a lot for a DI box, as it's about as expensive as you'll see one, but it's designed for professionals looking for top tier tone regardless of price. Engineers have made this a highly sought after DI box, so if you ever get the chance to try or buy one, definitely do not pass up the opportunity if you can afford it.