®
Firefly
Tube Direct Box
True to the Music
™
User Guide
®
www.radialeng.com
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam
British Columbia, Canada, V3C 5M5
tel: 604-942-1001 • fax: 604-942-1010
email: info@radialeng.com
True to the Music
www.radialeng.com
True to the Music
®
®
™
Radial Firefl y
Tube Direct Box
Table of Contents Page
Feature set ...................................................................................................................1
Overview.......................................................................................................................3
Making connections ......................................................................................................4
Setting Up the Firefl y for Various Instruments ..............................................................8
Setting the output controls ............................................................................................9
Remote switching and mute with JR•2 .........................................................................10
Rackmounting kit ..........................................................................................................11
Specifi cations ...............................................................................................................11
Block diagram ...............................................................................................................12
Radial Limited Warranty ................................................................................Back Cover
Congratulations and thank you for purchasing the Radial Firefl y! You are now the proud
owner of what is arguably the most exacting direct box ever made. The Firefl y combines state
of the art electronics with a tube drive and transformer coupled output to produce a clean
warm tone. And hidden inside are a ton of very cool features designed to enable the Firefl y
to be used in all types of applications for all types of instruments.
Although you will fi nd the Firefl y to be super easy to use, we recommend you to take a few
minutes to read the manual to ensure you understand the various features and get the most
out of this amazing device. If after reading the manual you need further clarifi cation, please
visit the Firefl y F AQ page on the Radial web site. This is where we post questions and answers
from users along with the latest updates. Then, if you still do not fi nd what you are looking
for, we invite you to send an email to info@radialeng.com and we will do our very best to get
back to you promptly.
Now get ready to plug into one of the most enjoyable pieces of audio equipment ever!
Radial Engineering Ltd.
Fire y™ Tube Direct Box
®
FRONT PANEL FEATURE SET
True to the Music
1 2 43
65
7
1. TRIM-A & B: Input level controls used to match the gain between the two instruments.
2. SELECT: Selects the active input for fast instrument changes. The illuminated LED
indicates the active input.
3. MUTE LED: Indicates when the mute function is active. Remote controlled via the
optional JR•2 footswitch.
4. DRAG: Used to retain the natural feel of the instrument by adjusting the load for
passive pickups.
5. LOW CUT: Variable high-pass fi lter rolls off low frequency resonance that can cause
feedback or muddy up the sound.
6. LEVEL: Level control for the balanced XLR output. Variable from mic to line-level.
7. PROTECTIVE FRONT LIP: The enclosure design create a protected zone around the
switches and knobs to prevent damage.
8. POWER: Locking 5-pin XLR power supply connection. The external supply helps
reduce noise and delivers +/-16 volts (1600mA) that is internally stepped up to 48V for
the tube.
9. OUTPUT: Balanced XLR output connects to the PA or recording system. Transformer
isolated to eliminate hum & buzz caused by ground loops.
Radial Engineering Ltd.
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Fire y™ Tube Direct Box
True to the Music
REAR PANEL FEATURE SET
10
98
10. 180º POLARITY: Inverts the signal polarity by fl ipping pins-2 and pin-3 on the XLR
output. Used to reduce resonant peaks that cause feedback.
11. GROUND LIFT: Disconnects pin-1 at the XLR out. Helps reduce noise caused by
ground loops.
12. AUX PRE/POST: Changes the signal path of the ¼” AUX OUT. When set to the
inward position (pre) the AUX OUT provides a direct clean buffered feed from your
instruments. When set to the outward position the AUX OUT is like the main XLR
output, post tube stage, fi lter section and insert loop.
13. TUNER OUT: Always-on, high-Z output used to connect an electronic tuner.
14. REMOTE: Used to connect the optional JR2 remote footswitch. When connected, this
lets you select the active input channel or mute the Firefl y for tuning.
15. AUX OUT: High-Z thru-put for stage amp. Confi gurable ‘pre or post’ tube and insert.
16. INSERT: Buffered effects loop uses standard ¼” TRS send & receive cable to interface
guitar pedals and studio rack effects.
17. INPUTS A & B: High-Z inputs lets you switch between two instruments for quick onstage changes. The input level is set using the TRIM-A & B controls.
18. AUX THRU (side panel): Recessed switch engages transformer
isolation for ¼” AUX OUT to eliminate hum and buzz caused by
ground loops.
11 12 13 14 15 1716 18
®
Radial Engineering Ltd.
2
Fire y™ Tube Direct Box
®
True to the Music
OVERVIEW
The Firefl y is a direct box. What this means from a ‘technical’ standpoint is that the Firefl y is
designed to deliver the sound of the instrument to the recording system or PA without introducing artefact. But the sheer fact that the Firefl y employs a tube as part of the circuit means
that the tube will add warmth and natural even order harmonics to the signal. Technically,
DI boxes like the Radial JDV™ are much more accurate while the Firefl y is designed to add
character. That being said, the Firefl y remains a direct box and therefore, it must perform the
task... and do it well.
The primary task of a direct box is to convert the unbalanced high impedance signal from
an instrument to a balanced low impedance signal suitable for a PA system or for recording.
The output from a direct box is usually equivalent to a mic level signal. This enables the DI to
‘comfortably live’ along side microphones, using the same mic splitters, mixing console inputs
and microphone preamps. Standardizing the signal makes it easy to switch around cables
on hectic stages when trouble shooting. And although the Firefl y is able to produce a much
hotter output than a typical DI box, turning down the master volume is all that is required to
match things up.
Several extra features have been added to the Firefl y to increase functionality on stage and
better adapt to the various instruments that may be connected. For instance; two inputs make
it easy to swap instruments. Drag Control lets you adjust the load on the pickup for optimum
signal transfer. The 4 meg-ohm input impedance lets you properly load piezo pickups so that
they sound right. You can also add options such as a remote control for input switching and
quiet tuning on stage. And of course you can rack mount the Firefl y in a single space using
the optional 19” rack adaptors.
Radial Engineering Ltd.
TYPICAL SETUP
3
Fire y™ Tube Direct Box
True to the Music
MAKING CONNECTIONS
Before making connections, always ensure all levels are turned down or equipment is turned
off. This will help you avoid turn-on transients that could harm more sensitive components
such as tweeters from being damaged.
Connect the power supply to the Firefl y. This mid-cable supply is equipped with a 4-pin XLR
connector at one end and a universal IEC connector at the other end. The power supply will
accept input voltages from 100V to 240V thus enabling the Firefl y to be used in countries around
the world. It comes with the appropriate power cable to comply with local electrical systems.
Start by setting theTRIM A & B controls and the LOW -CUT fi lter fully counter-clockwise to the
7 o’clock position (minimum setting). Set the DRAG control about halfway to the 12 o’clock
position and ensure the ON button is set to the inward position. Set the master LEVEL control
to the 2 o’clock position.
TRIM-A
TRIM-B
DRAG
LOW CUT
LEVEL
®
MIN
MAX
MIN
MAX
MIN
MAX
MIN
MAX
Cable connections are made at the rear panel. Connect the instrument to INPUT-A using a
standard ¼” guitar cable. Connect the XLR output to your mixing desk or preamp using a
standard XLR cable. Make sure the three rear panel recessed switches are in the outward
position by checking with a tweaker or small screwdriver.
Test at low volume
Y ou are now set to start testing audio. Always test at a low volume fi rst before turning up. This
will help you avoid loud transients from damaging more sensitive components. Turn up the gain
on your mixing desk or preamp to a low level. Set the input SELECT button to input-A. The LED
will illuminate to show you which input is active. Slowly increase the input TRIM-A until you
reach a comfortable listening volume. If you like, plug in your second instrument and adjust
the TRIM-B to match. Simply depress the AB selector switch to toggle between instruments.
Radial Engineering Ltd.
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Fire y™ Tube Direct Box
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True to the Music
Connect an amplifi er
Y ou can now connect to your stage amplifi er if you are using one. A stan-
dard ¼” guitar cable connects from the AUX OUT to the input of your amp.
This output may be transformer isolated by depressing the side-mounted
recessed switch. This helps prevent ground loops that can cause hum
and buzz in your system. Using the isolated setting is recommended
when connecting to guitar or bass amplifi ers and effects pedals. Taking the transformer out
of the circuit will deliver a slightly different sound. Try toggling the switch in and out to see
how it works with your setup.
Pre/post aux switch setting
The buffered AUX OUT output can be toggled between
PRE or POST settings by depressing the set & forget
recessed AUX OUT PRE/POST switch on the rear panel.
When set to PRE (inward position) the instrument signal is
sent directly to the stage amp before it is processed by the
tube, effect loop and low cut fi lter.
INPUTS
& DRAG
CONTROL
DRAG
CONTROL
CLASS-A
BUFFER
Simplifi ed Block Diagram of PRE signal path
AUX OUT
¼” OUTPUT
(PRE)
However, when set to POST (outward position) the AUX OUT output is identical to the main
XLR output. Most musicians will likely opt for the POST setting to send the tube processed
sound to their amp in order to gain the added warmth of the tube. Simply leave the PRE/POST
switch in the outward position if this is your preference.
INPUTS
& DRAG
CONTROL
CLASS-A
BUFFER
Radial Engineering Ltd.
TUBE
AMPLIFICATION
STAGE
Simplifi ed Block Diagram of POST signal path
INSERT
SEND &
RETURN
5
HIGH
PASS
FILTER
Fire y™ Tube Direct Box
AUX OUT
¼” OUTPUT
(POST)
True to the Music
Connect an electronic tuner
The Firefl y is equipped with an ‘always-on’ TUNER output that is designed to hook up an
electronic tuner to provide constant visual feedback while performing. The TUNER output is
buffered and electronically isolated to prevent noisy digital tuners from bleeding clock noise
into your instrument sound. The TUNER output is tapped before the tube gain stage providing a clean instrument output that can be used to split the signal to another preamp when a
tuner is not connected.
JR•2 remote footswitch
For even more control over the Firefl y , you can add the optional
JR2 footswitch. This two button footswitch can activate the
MUTE function for silent on-stage tuning via the always-on
TUNER output and toggle between instrument inputs A & B.
®
For convenience the JR•2 can be connected with either a ¼”
TRS cable or a locking Female XLR ~to~ ¼” TRS cable. Both
connections are offered on the rear panel but only one should
be used at a time.
¼” TRS to TRS XLR to TRS
Radial Engineering Ltd.
6
Fire y™ Tube Direct Box
®
True to the Music
Adding effects
As with any preamp or direct box, you can connect effects in line between your instrument
and the Firefl y the same way you would when connecting pedals in front of your amp. With
this set up, each instrument can have its own set of effects.
The Firefl y is also equipped with a ¼” TRS INSERT jack that enables you to share effects
between both instruments. This rear mounted jack requires a standard studio insert cable
whereby one end is equipped with a ¼” TRS and the other equipped with two ¼” plugs designated as send and receive. Simply connect the send to the input of the fi rst pedal in the
chain and the output to the receive plug. With this setup, when you change instruments the
signal will automatically be routed to the pedals.
Radial Engineering Ltd.
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Fire y™ Tube Direct Box
True to the Music
SETTING UP THE FIREFLY FOR VARIOUS INSTRUMENTS
The Firefl y is designed to adapt to just about any instrument whether it employs a magnetic
pickup, piezo or combination with an active buffer.
Magnetic pickups and Drag control
One of the more subtle yet indispensable functions is Drag Control™. Drag is designed to be
used with magnetic pickups such as the ones found on most electric guitars, basses and the
type that can be placed in the sound hole of an
acoustic guitar. Magnetic pickups are very similar to transformers in that they react differently
depending on the load that is presented. So
when connected to a tube amp, they become
part of the circuit and sound a particular way.
When presented with a high impedance buffer,
the sound changes. Guitarists often complain
that they hate wireless systems or pedals,
preferring true bypass devices. Drag Control
lets you reintroduce the load on the pickup
to replicate the tone and feel as if connected
directly to a tube amplifi er.
Start with Drag Control set to the 12 o’clock position. Turning the Drag Control clockwise will
brighten the tone (less Drag) while turning the dial counter-clockwise with darken it (more
Drag). Turn the Drag Control on by pushing in the switch and use a small screwdriver or guitar
pick to adjust. Listen to fi nd the tone that best suits your preference. 12 o’clock simulates the
tone of a Stratocaster connected to a Fender Twin.
Magnetic pickup in acoustic guitar sound hole.
®
Active instruments
For active instruments such as a keyboard, active bass or an active acoustic guitar with built-in
preamp, the Drag control will have very little or
no effect as the signal is already buffered. The
advantage to using the Firefl y is to warm up the
tone by passing the signal through the tube and
audio transformer. This will produce a ‘vintage’
effect that is pleasing to the ear.
Piezo transducers
The Firefl y is equipped with a special high
input impedance that is ideally suited for piezo
equipped instruments. Piezos are finicky
devices that tend to squawk or sound peaky
unless treated properly. When the Drag Control
is turned off, (switch in out position), the input
impedance jumps to 4 meg-ohms. This provides
the piezo with the right type of impedance to
properly load the pickup and smooth out the
sound.
Radial Engineering Ltd.
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Acoustic guitar with active preamp.
Passive piezo transducer on acoustic guitar.
Fire y™ Tube Direct Box
®
True to the Music
Adjusting the high pass fi lter
One of the most effective features built into the Firefl y is the high-pass fi lter. This variable
control lets you eliminate low frequency resonance from the instrument and produce a cleaner
more defi ned sound. This is benefi cial for both studio recording and on a live stage.
0dBu
20 20k50 100 200 500 1k 2k 5k 10k
Freq Response Graph For High Pass Filter
Hz
In the studio, low frequencies can often blend together causing modulation and beating as
they compete in the same frequency bands. By rolling off unneeded bottom end, you can
more easily combine instruments and create a less congested recording. This ‘Nashville’
trick is often used to size various acoustic instruments such as contra bass, acoustic guitar,
banjo and fi ddle to create a more uniform and pleasing mix. Start with the high-pass fi lter set
completely counter-clockwise. This essentially dials the fi lter out of the circuit. Slowly increase
the cut-off frequency by rotating the control clockwise. You will hear it as it takes effect. Try
experimenting with various cut-off points to get a feel as to what sound best to you.
In live situations, the high –pass fi lter is particularly effective at eliminating low frequency
resonant feedback. By cutting out excessive lows, you will also gain more control over the
mix. Cutting lows reduces the demands on the PA system which in turn reduces distortion.
And if you have ever played electric guitar you know that feedback occurs much more readily
with a distorted sound... so yes, the same applies with acoustic instruments: less distortion
equals less feedback.
SETTING THE OUTPUT CONTROLS
The Firefl y XLR output is equipped with two switches: a
180° polarity reverse and a ground lift. Start by setting both
of these to the outward position.
180° polarity reverse
The 180° polarity reverse can perform various functions. When pushed in, this toggles the
electrical phase at the balanced XLR output by swapping pin-2 and pin-3. If you so happen
to be using some older equipment that does not follow the AES standard (pin-2 hot), this can
be used to reverse the polarity and bring the Firefl y into proper electrical phase.
More often than not, the polarity reverse will be used for other uses. For instance, in the
studio, you may be combining the direct feed from the Firefl y with a microphone. Depending
on where the microphone is positioned in the room, you may fi nd that reversing the polarity
can help fatten the tone.
Radial Engineering Ltd.
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Fire y™ Tube Direct Box
True to the Music
On stage, reversing the polarity is sometimes used by the front of house engineer to better
phase-align the bass amp with the PA system. This can be very ef fective in smaller clubs where
today’s high powered bass rigs can compete with the PA. With acoustic guitars, sometimes
the sound from the PA can cause huge peaks on stage known as hot spots or room modes.
These cause the instrument to prematurely resonate which in turn causes feedback. Reversing
the polarity will electronically ‘move’ the peak and often solve the problem.
Lifting the ground
Pushing in the ground lift switch lifts the ground connection on pin-1 at the XLR output. When
you do so, this assumes that the instrument and Firefl y are being grounded by another de-
vice such as a stage amplifi er. Lifting the ground lifts the audio ground which in turn will often
eliminate hum and buzz caused by ground loops. After you have connected the system, if you
hear hum or buzz, try pushing in the switch to lift the ground.
REMOTE SWITCHING AND MUTING
The Firefl y is equipped with a remote control jack for the optional
Radial JR2 remote control footswitch. This compact switcher
features two footswitches and three LEDs. Power is supplied by
the Firefl y thus eliminating the need for batteries or secondary
power supply. Connection between the two devices is done
with a balanced cable with ¼” TRS connector at one end and
choice between a ¼” TRS or XLR at the other. The XLR has
the added benefi t of being able to be locked.
With the JR2 connected, you can remotely select between inputs A and B to select the desired
instrument. The second switch is used to mute the Firefl y for quiet on stage tuning via the
always-on TUNER output. Depressing the footswitch illuminates the LED indicators to let you
know which function is active.
®
JR•2 Connected with a ¼” TRS cable JR•2 Connected with locking XLR ~ TRS cable
SLEEVE
12
3
TIP
RING
SHIELD SHIELD
SHIELD
SHIELD
RING
RING
TIP
SLEEVE
TIP
SLEEVE
Wiring diagram for JR•2 connection cable.
Radial Engineering Ltd.
10
Fire y™ Tube Direct Box
®
True to the Music
RACK MOUNTING THE FIREFLY
For touring the Firefl y may be mounted into a standard 19” rack using the optional rack mount
kit. This three piece kit (part number: R800 2020 02) enables one or two Firefl ies to be rack
mounted in a 1RU rack space.
Single unit mounting:
Double unit mounting:
SPECIFICATIONS
Frequency response .................................................................20Hz ~ 20kHz
Maximum Gain - 1/4” input to XLR out .....................................+22dB
Noise ........................................................................................-98dBu
Dynamic range .........................................................................100dB
Equivalent input noise ..............................................................-100 dBu
Input impedance (drag control off) ............................................ 4Meg-Ohms
Input impedance (drag control on) ............................................ Variable from 22k ~ 500k Ohms
Output impedance at XLR ........................................................200 Ohms (nominal)
Low-cut fi lter: ............................................................................ Variable from 25Hz ~ 500Hz (-3dB point)
Size (W, D, H) & weight ............................................................5.75” x 8.25” x 1.75” (2.75” with handle)
146mm x 210mm x 45mm (70mm with handle)
Weight ......................................................................................3.95lbs. (1.80kg)
Power supply ............................................................................+/-16v (1600mA) 5-pin XLR power supply
All specifi cations average – depending on tube or termination. Please see web page for further details.
Radial Engineering Ltd.
11
Fire y™ Tube Direct Box
True to the Music
BLOCK DIAGRAM
®
LIFT
OUTPUT
PHASE
INVERT
MUTE
AUX OUT
Direct
Isolate
SELECT
FET
HIGH
BUFFER
CLASS A
VOLTAGE
PASS
HIGH
FILTER
CLASS A
VARIABLE
CW
LEVEL
C
NO
NC
RELAY
INSERT
FET
HIGH
BUFFER
CLASS A
VOLTAGE
INSERT
BUFFER
TUNER
CATHODE
GAIN
UNITY
BUFFER
COMMON
CATHODE
NC
A/B SELECT
RETURN
FOLLOWER
INSERT
DRIVER
CLASS A
VOLTAGE
AMPLIFIER
C
NO
CW CW
TRIM A TRIM B
MUTE
Pre-Tube
INSERT
LOGIC
CONTROL
Post
A/B SELECT
Radial Engineering Ltd.
FET
BUFFER
CLASS A
DRAG
CONTROL
C
NO
NC
INPUT A
INPUT B
12
Fire y™ Tube Direct Box
THREE YEAR TRANSFERABLE LIMITED WARRANTY
RADIAL ENGINEERING LTD. (“Radial”) warrants this product to be free
from defects in material and workmanship and will remedy any such defects free of charge according to the terms of this warranty. Radial will
repair or replace (at its option) any defective component(s) of this product
(excluding fi nish and wear and tear on components under normal use) for
a period of three (3) years from the original date of purchase. In the event
that a particular product is no longer available, Radial reserves the right
to replace the product with a similar product of equal or greater value. In
the unlikely event that a defect is uncovered, please call 604-942-1001
or email service@radialeng.com to obtain an RA number (Return Authorization number) before the 3 year warranty period expires. The product
must be returned prepaid in the original shipping container (or equivalent)
to Radial or to an authorized Radial repair center and you must assume
the risk of loss or damage. A copy of the original invoice showing date of
purchase and the dealer name must accompany any request for work to
be performed under this limited and transferable warranty. This warranty
shall not apply if the product has been damaged due to abuse, misuse,
misapplication, accident or as a result of service or modifi cation by any
other than an authorized Radial repair center.
THERE ARE NO EXPRESSED WARRANTIES OTHER THAN THOSE
ON THE FACE HEREOF AND DESCRIBED ABOVE. NO WARRANTIES
WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE SHALL EXTEND BEYOND THE
RESPECTIVE WARRANTY PERIOD DESCRIBED ABOVE OF THREE
YEARS. RADIAL SHALL NOT BE RESPONSIBLE OR LIABLE FOR ANY
SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS
ARISING FROM THE USE OF THIS PRODUCT. THIS WARRANTY
GIVES YOU SPECIFIC LEGAL RIGHTS, AND YOU MAY ALSO HAVE
OTHER RIGHTS, WHICH MAY VARY DEPENDING ON WHERE YOU
LIVE AND WHERE THE PRODUCT WAS PURCHASED.
www.radialeng.com
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: 604-942-1001 • fax: 604-942-1010
info@radialeng.com • www.radialeng.com
Radial® Firefl y™ User Guide - Part #R870-1175-00 • rev.2
Specifi cations and appearance are subject to change without notice.
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