It seems like there’s a lot of cool DI boxes around these days, often sporting tubes and advanced features. Leave it to British Columbia-based Radial Engineering—makers of some wildly popular direct-injection and inter-connecting boxes—to add its Firefly to the trend. And yes—the Firefly has a tube plus numerous other advanced features, most obviously a sporty, memorable handle that kind of looks like a lightning bug's wing.
 
The Firefly ($599 street) starts with Class A electronics and a “zero negative feedback” design feeding a 12AX7 tube that hits a Jensen transformer at output. Please navigate here for Firefly's full feature list: http://www.radialeng.com/firefly.php. I will point out the following, though: Its two inputs are not only switchable, but mutable; low cut is completely variable; Drag is both defeatable and variable; and Aux Out is not only pre/post, but transformer-isolatable.
 
The Firefly’s external power supply provides ample current for the power-hungry tube circuit and has a locking 5-pin XLR connector and solid build quality—the likes of which many manufacturers neglect.
 
I like to “double DI” bass guitar—typically with one signal very clean and punchy while the other is anywhere from saturated to downright beastly growly, depending on the song. With this in mind, I went into a band-tracking session with a Countryman Type 10 and the Firefly on bass guitar DI for some attitude and dirt. Upon connecting a passive bass, I found that the Firefly didn't allow any real dirty distortion or growl, but it did offer a nicely compressed, slightly textured signal that added some gutsy punch to the mix. I ended up using the Firefly for the clean punch and a SansAmp for the dirt.
 
Active basses brought a little something different to the Firefly table and allowed me to play with the Low Cut filter for some useful results. Both my fretted and fretless active basses provide electronics that allowed me to push the Firefly a little harder for more “tube tone.” Here are passive and active bass web clips: https://soundcloud.com/pro-audio-review-magazine.
 
The Firefly—featuring two inputs with individual trims, quiet switching, an insert point and a shared tuner output—exhibits the ergonomic usefulness that makes Radial products so clever and road-worthy. I enjoyed adjusting the Drag control, finding it subtly useful; it rolls off a little top and extends the bottom end, although it unexpectedly reduced level with only my active basses. I was also eager to use it with my Taylor acoustic’s after-market piezo transducer pickup (which admittedly outputs mostly honky nasal-ness). Unexpectedly (and at least contrary to the manual), I found the tone with Drag added to be more pleasant and rounded, almost likable.
 
The Firefly is a winner based on its well-chosen and flexible features, intelligent design and expected Radial durability. It is not a distortion box, a high gain booster or a signal mangler. In fact, paired with my passive bass and Drag utilized, the Firefly kept up with a Manley Force and an Avalon V5 in exacting comparisons.
 
For a modern bass rig that needs to go anywhere between perfectly pristine and saturated/plump to growling/unruly, I'd put the Firefly up front, hitch it to two basses with footswitch-ability, split out to a tuner and an FX signal path, connect some dirty overdrive and enjoy all the benefits of modern signal routing and schizophrenic bass tone.
 
Radial Engineering
http://www.radialeng.com