THE FIREFLY TUBE DIRECT BOX INCORporates
Radial’s time-tested Class A FET circuit
and zero negative feedback design, prized for its
natural tone and stable output. This signal is fed
into a single Ruby Tube 12AX7 for warmth and
character, then routed through their transformercoupled
output, which eliminates buzz and hum
from ground loops. The Firefly has two ¼" inputs
that can be switched manually via the front panel,
or remotely with the optional JR2 footswitch (the
JR2 also gives you access to the mute function).
Each input has a dedicated trim control to match
the output levels of different instruments. The
drag control lets you lower the input impedance
to match up better with passive magnetic pickups,
or bypass it completely for a 4MΩ impedance best
suited to piezo pickups. A variable low cut filter
lets you dial out the sub low frequencies that can
make your bass muddy in the mix, and a master
volume controls the overall output to your amp
or to the board.
Around back, the Firefly has an xlr output
with ground lift, and a phase-polarity switch. The
pre/post switch lets you route the aux-out signal
straight to your amp from the buff er, or through
the tube, effect loop, and low-cut filter—mirroring
the output of the xlr. A locking 5-pin xlr
connector attaches the mid-line external power
supply, which can accept voltages between 100
and 240 volts. The ¼" tuner out is post-Class A
input, but pre-tube, so it can be used to send a
clean signal to another source. It is always on for
silent tuning while muted. A trs jack gives you
an insert point for an effect loop. On the side of
the unit, a dedicated ground lift for the aux out is
a welcome addition. The unit itself is housed in a
heavy-duty steel case, with a convenient carrying
handle that can be removed for rack installation.
Many of the controls are recessed switches or
dials that require a small screwdriver to access,
and all the front panel knobs are well protected
from the casing’s overhang.
First, I plugged my passive Mike Lull P5 into
input A, and connected the aux out to a Genz Benz
GBE1200/Uber 212 rig. I set the gain at 12:00 and
engaged the drag control, adjusting the sweep
with a guitar pick. The drag control is said to simulate
the sound of being plugged into a tube amp.
The tone definitely darkens as you lower the control,
with a decrease in volume that can easily be
replaced with the gain knob. The lowest low cut
settings are hard to hear unless you’re cranking
big watts and moving some air, but rotating the
control clockwise noticeably raises the low cut frequency.
The key is learning to hear the sweet spot
for each instrument, in each situation.
Next, I plugged the Firefly into Pro Tools via
the xlr out and recorded some samples. I was
able to hear the subtle changes from the drag
control much clearer while monitoring through
headphones. My P5 fattened up nice and round
with lower settings and a little gain bump. The
master volume lets you “play the tube” a bit as
well. I bypassed the drag control and connected
my David Gage Realist-equipped Juzek acoustic
bass to the now 4MΩ input. I recorded samples
with the phase switch in both positions and
found one to be darker with less definition, while
the other was more open and detailed. The overall
tone was very natural and full—I could easily
use this sound alone without adding a microphone
to the mix.
The Firefly is a top-notch DI that imparts
sweet tube warmth to all that passes through it,
and the feature set gives you many advantages
onstage as well as in the studio.
Bottom Line Radial Engineering’s new
Firefly Tube Direct Box has cool basscentric
features, and it shines live and
in the studio.
FIREFLY TUBE DIRECT BOX
Audio circuit Discrete Class A FET with
Signal to noise ratio 85dB @ +4dB
Dynamic range >100dB
Noise floor –98dB at unity
Inputs Two ¼" Hi-Z, selectable A or B,
Outputs 3-pin AES standard XLR, ¼"
Output impedance 150Ω nominal
Switches Phase, XLR ground lift, aux
ground lift, aux pre/post, input select,
Controls Input gain (20dB max), low
cut (–3dB @ 5Hz–500Hz), drag load
adjust (22k–500K, 4MΩ in bypass),
Power 5-pin XLR ±16V & 48V, 1600mA
Construction 14-gauge steel, baked
Size 5.75" x 8.25" x 1.75"
Weight 4 lbs
Warranty 3 years transferable