I don't know if it's just my awareness of them or what, but it seems like there are more active direct boxes available now than there ever were. I first stumbled across the Avalon U5 last year while recording The Walkabouts in Seattle. When I asked Floyd Reitsma (my trusty assistant at Studio Litho) about a DI for the bass he pointed at the U5 and said a lot of the engineers liked it. We ran the bass through it (on its own track), along with a Royer R-121 on an Ampeg B-15 (on another), and I was impressed with the depth of the bass sound and the availability of tone controls too. Since then I've owned one and find myself using it frequently.
This class A, solid state unit has the usual 1/4" input and through jacks, a mic level and line level output, gain and tone knobs, and headphone output. It also has a direct speaker level input (that must be used with a speaker still hooked up though) and a high cut switch along with a switch to route the active processed signal out of the thru jack. I find that I generally use the line output right to tape or to a compressor. It has plenty of output through the variable gain control which provides a clean sound. The tone selector is the one feature that really sets it apart from other powered DI boxes. A rotary knob scrolls through 6 EQ curves that all provide handy adjustments for different sounds. Midrange can be scooped, highs can be trimmed, and lows can be pulled out, all helping to tailor your bass, synth, drum machine or guitar. A great trick I learned at Litho is to photocopy the EQ curves and their suggested uses from the manual and tape them to the top of the DI box.
In use, I find that this box works on bass and synth very well, but the tone controls can make interesting electric guitar DI sounds - something that other boxes generally fail at. Roughly compared to other DIs in my collection, the Little Labs PCP has a slightly fuller overall bass guitar tone (a bit more low mids to my ear) and the new Summit TD-100 has a great tube saturation, but neither of these other DIs offer the tone control flexibility or amount of options, and the PCP has no gain control (though the DI in the PCP is just one of its many features). If the U5 was the only DI box that a studio owned they would be set, as its options are many and its sound is amazing - yet among a collection of active DIs it still shines with its tone controls and versatility. ($595, www.avalondesigns.com)