Grace REX User manual

Microphone Preamplifier Pedal / EQ / Boost
Owner’s Manual Rev. A
Grace Design, PO BOX 1812, Lyons, CO 80540
303.823.8100 / [e-mail]
www.gracedesign.com
REX

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1 Welcome
Thanks for purchasing the REX! Like its bigger sibling ROXi, it
is designed to provide performing and recording musicians
with the highest quality mic preamplication available. REX is
compact, rugged and great sounding, so no matter where and
how you play - whether you toss it in your case, or mount it to
your pedalboard, you can rely on it to sound great and work
awlessly for many years.
While setup and operation is pretty simple, please take a little
time to read through this manual and familiarize yourself with
its features and functions. It will make a big dierence that
you know exactly what to do to adapt quickly to whatever
conditions may come your way on stage. Most of all, have fun
and go play!
2 Safety and Symbols
Caution: Read Accompanying Documents
This symbol, located on the equipment and in
this manual, refers to important instructions.
Read this manual thoroughly before operating
this equipment.
Service Information
The Grace Design REX contains no user serviceable
components. Contact Grace Design for repair and upgrade
information. In the event that your Grace Design REX needs to
be returned to the factory, contact us for a return authorization
number.
3 Features
• Studio-quality mic preamplier
• 48V phantom power
• Separate FX send and return
• 1/4” unbalanced line output
• Balanced XLR DI transformer iso output
• 10dB variable boost control
• Mute and Boost footswitches
• High and Low shelving EQ
• 9VDC operation
• Over 30V internal operating voltage
• Pedalboard friendly design
• 5 year transferable warranty
• Made in the USA
Contents
1 Welcome 2
2 Safety and Symbols 2
3 Features 2
4 Top Panel Controls 3
5 Rear Panel Connectors 3
6 Unpacking and Installing 3
6.1 Installing 3
6.2 XLR Microphone Input 4
6.3 Insert Send And Return (Fx Loop) 4
6.4 AMP Out 4
6.5 DI Output 4
6.6 9VDC Power Input 4
7 Operation 4
7.1 Setting The Gain 4
7.2 HPF 4
7.3 Low EQ 4
7.4 HIGH EQ 5
7.5 Boost 5
7.6 Boost Switch 5
7.7 Mute Switch 5
8 Block diagram 5
9 Specications 6
10 Cleaning and Care 7
11 Warranty Info 7
12 Manual Revisions 7

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4 Top Panel Controls
+48V
ISO
GND
GAIN LOW HIGH BOOST
HPF
MIC IN SEND RETURN LINE OUT DI OUT
+10
0
+10
-10
+10
-10
0
0
I
0
BOOST MUTE
REX
MICROPHONE PREAMP
2 73 4 5 6
9 10
1 8
11 12 13
1. 48V phantom power switch
2. GAIN control
3. LED signal level indicator
4. LOW EQ control
5. HIGH EQ control
6. BOOST level control
7. LED power indicator
8. OUTPUT ground / ISO switch
9. HPF switch
10. BOOST footswitch
11. BOOST active LED
12. MUTE active LED
13. MUTE footswitch
5 Rear Panel Connectors
PUSH
1
2
3
1 2 3 4 5 6
1. 9VDC power input – 2.1mm center negative
2. DI out, balanced XLR transformer isolated
3. Unbalanced AMP line output 1/4” TS
4. Insert return 1/4” TS
5. Insert send 1/4” TS
6. MICROPHONE input XLR
6 Unpacking and Installing
This REX has arrived to you in a box that features Korvu®
internal packaging, which was carefully designed to protect
its contents from the uncertain world of freight handling. We
recommend you hang on to this box in the event that you
want to ship it somewhere, it will beat having to rummage
around for a box and bubble wrap or worse, Styrofoam
peanuts. This box contains:
• Your new preamp, REX
• 9VDC power supply
• A USB stick with this Owner’s manual
In the event that your are missing any of these items, please
contact your retailer or us directly at 303-823-8100 and we will
get you squared away.
6.1 INSTALLING
REX is designed to operate like any normal footpedal - at your
feet. You can carry it in your guitar case, shoulder bag, upon a
magic oating pillow, or strapped to your pedalboard. If you
choose the latter, you can remove the 4 threaded rubber feet
to allow mounting with Velcro. Hang on to those rubber feet
though, you may want them down the road. Also, remember
that when mounting it to your pedalboard, do so in a way

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that preserves access to the microphone input and the XLR DI
output, as they may need to be plugged and re-plugged on a
nightly basis.
REX is powered by a 9VDC input. This jack is a standard 2.1mm
BOSS™ style, with center negative. The current requirement
is 340mA, so you’ll need to make sure you have this available
from your pedalboard power supply. Or, simply use use the
included 9VDC wall wart. We tested many supplies, and
this is the lowest noise, lowest prole one we could nd.
Plugging in
By holding the REX in your hand, you probably already have
a pretty good idea what to do from here. Plug a mic in, turn it
up and go. But keep reading, because there’s some details that
will help you get the most out of your new preamp.
6.2 XLR MICROPHONE INPUT
This is where you connect your microphone to the REX. The
connector is wired pin 2 positive, pin 3 negative and pin 1
ground. Phantom power is supplied on pins 2 and 3.
Before plugging in, rst make sure the gain knob is turned all
the way down and the 48V phantom power switch is set to o.
Then connect your microphone and if 48V is needed, simply
activate it with the 48V switch. Always remember to turn 48V
power on after connecting your microphone and o before
disconnecting your microphone.
6.3 INSERT SEND AND RETURN (FX LOOP)
This is a buered, unbalanced insert point (pre boost) for
connecting outboard eects or a tuner to REX. This allows
mono outboard signal processing to be placed in series with
the signal, while still utilizing all of REX’s output capabilities.
They are 1/4” TS jacks each wired tip signal, sleeve ground.
If you wish to connect just a tuner to the REX, you may
connect the SEND to your tuner’s input and leave the RETURN
disconnected. Doing so will allow your tuner to always be
active even when the REX is MUTED.
6.4 AMP OUT
This output is for sending a non-transformer isolated output
to your tuner, a stage amp or anywhere else you may need an
additional unbalanced signal sent. It is a 1/4” TS jack, wired tip
signal, sleeve ground.
6.5 DI OUTPUT
This XLR output is balanced and transformer isolated, for
sending signal to a front of house, monitor console, or any
mixer or interface where a balanced, isolated signal needs to
be sent. XLR pinout is: pin 2 positive, pin 3 negative and pin 1
ground.
Flipping the top panel GND/ISO toggle switch to ISO will
disconnect the REX ground from the XLR output. Do this if the
PA system is picking up hum or buzz from the REX.
6.6 9VDC POWER INPUT
This is where you provide life giving power to REX. The jack is a
standard 2.1mm BOSS™ style, with the center negative. Either
use the included Grace Design power supply unit, or make
sure that the supply you are using conforms with the power
input requirements - 500mA output is recommended.
7 Operation
7.1 SETTING THE GAIN
With your microphone connected to the XLR input and sound
going into the microphone, turn the GAIN knob clockwise
until the signal / peak LED indicator is on and lit solid green.
This will represent a good operating level. The indicator will
start to ash red when your signal is 10dB before clipping, so
an occasional red ash is ok, but mostly red means you should
turn the gain control down / counterclockwise.
7.2 HPF
The High Pass Filter (HPF) allows signal information only above
75Hz to pass to the output. You can also think of this as a low-
cut. This lter employs 12dB per octave roll o and is designed
to be very musical sounding. Simply ip this switch to the UP
(on) position to tame unwanted low end rumble or stage noise
that may nd its way into your microphone.
GAIN
Hz
40 75 20k1k
0dB
-12dB
HIGH PASS FILTER
7.3 LOW EQ
The Low control of the REX is xed at 250Hz corner frequency
with a gain range of -10 to +10dB. This is a xed shelving type
control, which means frequencies below the selected corner
frequency are boosted or cut. Use this control for cutting or
boosting bass frequencies. It’s all about the bass.

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GAIN
Hz
40 125 20k
0dB
-15dB
+15dB
LOW SHELF EQ
7.4 HIGH EQ
The High control of the REX is xed with a 2kHz corner
frequency, with a gain range of -10 to +10dB. Again, this is a
xed shelving type control, which means everything above the
corner frequency is boosted or cut. Otherwise known as the
treble knob. If you think your banjo may be too bright (which it
probably is), turn this knob counterclockwise. If you think your
electric 2 string gourd needs a little more bite, turn this knob
clockwise. If you’re not sure, start turning it one way or the
other until it sounds better.
GAIN
Hz
20 2.0k 20k
HIGH SHELF EQ
0dB
-15dB
+15dB
EQ BASICS
With such a simple EQ section, it’s easy to make quick, broad
adjustments to your microphone’s signal. You won’t really
be able to chase down and make surgical adjustments to a
particular trouble spot, but you’ll nd with a little practice
you can easily adjust your tone in a useful way. If your sound
really requires a more surgical approach (i.e. a parametric EQ
control), you can easily insert one into the FX loop.
As with all EQ settings, the more you know about what
your instrument needs the better o you will be making
adjustments on the y. We recommend you get to know these
controls and experiment a lot with them to nd what works
best.
7.5 BOOST
Need to rock a wee bit harder? This knob will let that happen.
It sets the amount your signal is boosted when you activate
the ‘BOOST’ footswitch. Fully counter-clockwise is zero boost
added, fully clockwise adds +10dB of boost. The boost is after
the FX loop and aects both the DI and line outputs.
As you know, adding boost can easily send a microphone in
to feedback territory, so start small. If you need to boost your
output, start with a gentle boost amount and work your way
upwards. If you start to hear stage feedback or are overloading
the input at the console, then you’ll need to back it o.
7.6 BOOST SWITCH
Yep. This switch activates the Boost circuit, at whatever level
you set with the boost knob. This circuit is global, so the
boosted signal will be coming out of every output. For those
about to rock, you’ll need to activate this switch rst before we
will salute you. The LED will light up AMBER for awesome.
7.7 MUTE SWITCH
This switch mutes the DI and AMP outputs. This enables you
to quickly and easily cut your signal to the FOH or stage amp
and tune or sneeze without having to have the soundperson
mute your channel. When MUTE is active, the adjacent LED
illuminates RED.
8 Block diagram
ISO OUTPUT
TRANSFORMER
GAIN LOW BAND
BOOST / CUT
HIGH BAND
BOOST / CUT
BOOST GAIN
HPF
SIGNAL / PEAK
INDICATOR
ON/OFF
GROUND LIFT
FRONT PANEL TOGGLE SWITCH
MUTE / TUNE
FRONT PANEL KNOB
FOOTSWITCH
CONTROL TYPES:
-6dB
+48V ON/OFF
75Hz
BOOST
INSERT RETURN
INSERT SEND
AMP OUT
BALANCED XLR MIC INPUT ISO BALANCED OUT
+48V PHANTOM POWER

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9 Specifications
GAIN RANGE
Mic In, Line Out, Boost 0dB +7dB to +57dB
Mic In, Line Out, Boost 12.47dB +20.0dB to +69dB
Mic IN, DI Out, Boost 0dB -21dB to +28dB
Mic IN, DI Out, Boost 12.47dB -9dB to +41dB
Boost 0-10dB
THD+N 1kHz, 22Hz-22kHz BW (MIC Input to Line Output)
@ 20dB Gain Line out +10dBu < -95dB
DI out -18.8dB < -80dB
@ 40dB Gain Line out +10dBu < -90dB
DI out -18.8dB < -80dB
@ 57dB Gain Line out +10dBu < -81dB
DI out -18.8dB < -77dB
@ 69dB Gain Line out +10dBu out (boost at max) < -69dB
DI out -18.8dB < -69dB
INTERMODULATION DISTORTION - SMPTE/DIN 4:1 7kHz/50Hz
@ 40dB Gain Line out +10dBu < 0.009%
DI out -18.8dB < 0.030%
FREQUENCY RESPONSE (Input to DI Output)
Mic input @ 0.5dB Gain -3dB 11Hz – 63kHz
FREQUENCY RESPONSE (Input to Line Output)
Mic input @ 0.5dB Gain -3dB 9Hz – 180kHz
I/O IMPEDANCE
Mic Input 8.1kΩ
Insert Input 200kΩ
Insert Output 375Ω
DI Outputs 150Ω
Line Output 500Ω
SIGNAL / PEAK LED METER
Green threshold -13dBu
Red threshold +12dBu
MAXIMUM INPUT LEVEL
Instrument Input +10dBu
Insert Return (0dB Boost) +22dBu
MAXIMUM OUTPUT LEVEL - 100k Ohm load, 0.1% THD
DI Outputs -7.9dBu
Line Out +20.9dBu
Insert Send +15.6dBu
EQ
Gain +/- 10dB
Low Frequency 250Hz Shelving
High Frequency 2kHz Shelving
DYNAMIC RANGE 22Hz-22kHz BW
Minimum Gain, Line Out 129dB
Minimum Gain, DI Out 129dB
OUTPUT NOISE 22Hz-22kHz BW
DI Out -117.5dBu (-102dBu A weighting)
Line Out -98dBu (-100dBu A weighting)
OUTPUT MUTE ATTENUATION
DI Output -98.2dB
Line Out -95.5dB
POWER
Connector 2.1mm Center Negative
Nominal Input Voltage 9VDC
Nominal Input Current 3.06W (340mA)
WEIGHT and DIMENSIONS
0.8lbs (0.4kg) H2.5” x W5.1”x D4.5” (H6.35cm x W13.0cm x D11.4cm)

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10 Cleaning and Care
Your REX chassis is constructed out of high quality
aluminum and steel. Under normal circumstances, very little
maintenance is required to keep it looking good. However,
if you nd it getting more dirty or dusty than you like, here
are some cleaning tips: We recommend using a little shot of
Windex™ applied to a clean, dry, lint free cloth. Gently wipe all
surfaces, taking care not to allow the cleaning product to build
up around or under the knobs.
11 Warranty Info
• Grace Design warrants this product to be free of defective
parts and workmanship for a period of ve years. This
warranty period begins at the original date of purchase
and is transferable to any person who may subsequently
purchase the product during this time.
• This warranty excludes the following conditions: normal
wear and tear, misuse, customer negligence, accidental
damage, unauthorized repair or modication, cosmetic
damage and damage incurred during shipment.
• During the time of this warranty, Grace Design will repair
or replace, at its option, any defective parts or repair
defective workmanship without charge, provided the
customer has appropriate proof of purchase and that the
product has its original factory serial number.
• In order for Grace Design to provide ecient and timely
warranty service, it is important that you mail the
completed warranty registration card enclosed with all
of our products within 10 days of the original date of
purchase. You may also register your product directly with
Grace Design by telephone [phone] Monday-Friday
9:00am to 5:00pm MST), or you can register your product
online at www.gracedesign.com.
• This warranty is in lieu of all other warranties whether
written, expressed, or implied, INCLUDING ANY
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
• In no event will Grace Design be liable for lost prots
or any other incidental, consequential or Exemplary
damages, even if Grace Design is aware of the possibility
of such damages. In no event will Grace Design’s liability
exceed the purchase price of the product.
• This warranty gives the customer specic legal rights. The
customer may also have other rights, which vary from
state to state. Some states do not allow limitations on
implied warranties or consequential damages, so some of
the limitations of the above may not apply to a particular
customer.
12 Manual Revisions
Revision Page Change Date Initials
A all Initial release 01/12/2023 edg