True to the Music
ProD8 Rackmount DI
Owner’s Manual
Radial Engineering Ltd.
1638 Kebet Way, Port Coquitlam BC V3C 5W9
tel: 604-942-1001 • fax: 604-942-1010
email: info@radialeng.com web: www.radialeng.com
www.radialeng.com
Radial ProD8 Owner's Manual V1.0 - Part #: R870 1190 00
Subject to change without notice
Radial ProD8 Owner’s Manual
TABLE OF CONTENTS PAGE
Introduction .................................................................... Inside Cover
ProD8 Overview ............................................................................... 1
Feature Functions ............................................................................ 2
Rackmounting .................................................................................. 3
Using the ProD8 ............................................................................... 4
Adding Effects .................................................................................. 5
Typical Stage Set-up ........................................................................ 6
Redundant Inputs for Backup Instruments ....................................... 7
Redundant Inputs for Backup Playback ........................................... 8
FAQ .................................................................................................. 9
Warranty Information .........................................................Back Cover
Congratulations on your purchase of the Radial ProD8.
The Radial ProD8 is a simple yet remarkably clever direct box in that it provides all of the standard features
one would find in a typical rackmount DI plus several refinements: First off, it jams eight (8) direct boxes into
a single rack space making it the highest density DI on the market. Secondly, it is equipped with redundant
inputs on each channel that are pre-merged mono to reduce mixer and snake channel requirements or can
be used as redundant inputs for system backup. Thirdly, an effects-loop on each channel lets you share
your effect with two devices saving money and space. And finally, reversible rack rails let you position the
inputs and the outputs on the front or back of the rack to best accommodate your live or studio set-up.
As with all Radial products, we highly recommend that you read this short manual before using the ProD8
so that you become familiar with all of the features and functions to get the most out of this device. Should
you have any questions, please visit the FAQ section on our Radial web site as this is where we post the
latest applications. You can also email us at info@radialeng.com should you have a question that is not
answered.
We are confident that you will enjoy years of trouble free performance with your new Radial ProD8 and we
look forward to hearing back from you about new an innovative ways you have found to use it. Now start
reading and plugging away!
Radial Engineering
1638 Kebet Way, Port Coquitlam BC V3C 5W9
tel: 604-942-1001 • fax: 604-942-1010
email: info@radialeng.com web: www.radialeng.com
Specifications and appearance subject to change without notice.
OVERVIEW
The Radial ProD8 is an 8 channel passive direct box
and does not require any powering whatsoever to make
it work. The high performance Radial transformers are
extremely efficient and will both balance the signal and
convert the high source impedance of your keyboards to
a balanced, mic level low impedance output.
All channels are identical and completely isolated. Each
channel features two inputs that are merged to mono
using a resistive mixer. This means you can use either
input for a mono source. If you have a stereo source
such as a synthesizer or digital piano, connecting the
instrument to the two inputs will yield a mono mix at the
XLR output. Should you wish to connect a high output
device like a CD player to the ProD8, a -15dB PAD will
reduce the input level going to the transformer to avoid
saturation. The ¼” THRU is a direct feed that would be
used for your personal monitoring system.
True to the Music
To further advantage the user, an effects-loop has been provided that allows the two inputs on each channel to share the same effects processor. Each channel features an internal switch that lets you assign the
THRU output either pre or post the effects-loop depending on how you intend to use the system.
BLOCK DIAGRAM
IN-A
IN-B
*One of eight channels.
PASSIVE
SUMMING
SECTION
THRU
PRE/POST
EFX LOOP
EFFECT
LOOP
-15dB
PAD
THRU
OUT
POLARITY
REVERSE
XLR
OUT
GROUND
LIFT
CHASSIS
GROUND
LIFT
As previously mentioned, the ‘engine’ inside the ProD8 is the Radial transformer. This ‘hi-Z to lo-Z’ device
is designed to convert the impedance and balance the signal so that it matches the level of a typical microphone. This way, the keyboards connected to the ProD8 can be ‘managed’ just like microphones and used
with mic splitters as well as the mic inputs on the mixing console. A polarity reverse switch toggles pins 2
and 3 to allow older pre-AES standard gear to be connected in phase.
Transformers are particularly advantageous with keyboards and other devices that are electrically powered
through the common AC electrical system as they isolate the input from the output to help eliminate hum
and buzz caused by ground loops. A ground-lift switch further helps reduce noise by disconnecting pin-1 on
the XLR thus allowing the system tech to derive the channel ground from either the input or the output.
Radial Engineering Ltd. ProD8 Owner’s Manual
1
¼" PHONE PANEL
REVERSABLE RACK EARS
1
allow you to setup the ProD8
with either the ¼" jacks or XLR
connectors facing front.
IN-A/B dual inputs on each
2
channel auto-merge to mono.
3
THRU parallel thru-put connects
to on-stage amp or mixer for
personal monitoring.
4
LOOP each channel features
an effects-loop on a TRS jack.
Works like an insert on a mixing
console.
5
-15dB PAD reduces the input
level by -15dB to prevent
overload from high output
devices.
XLR PANEL
XLR OUTPUTS are balanced
6
600 ohm, mic-level and 100%
transformer-isolated to prevent
ground loops.
7
LIFT disconnects pin-1 on the
XLR output to isolate ground via
the transformer.
8
180° reverses pins 2 & 3 on the
XLR inverting the signal polarity
to correct out-of-phase signals.
True to the Music
1
6
2
7
3
4
8
5
INTERNAL
9
WELDED 14-GUAGE STEEL
9
10
11
12
13
rackmount enclosure is finished
in durable baked enamel.
10
RADIAL TRANSFORMER
with linear frequency response
from 20Hz to 18KHz for natural
sound. Mu-metal shield blocks
electromagnetic interference.
11
PRE/POST EFX internal switch
allows the THRU output to be
pre or post the effects-loop.
Factory set to post effects-loop.
12
CHASSIS GROUND internal
switch allows individual ground
paths for each channel.
Factory set in the lifted position.
13
MIILITARY-GRADE doublesided PCB is bolted to steel
standoffs for toughness.
14
ISOLATED CONNECTORS
extremely tough glass-filled
nylon for true channel isolation
from chassis ground.
Radial Engineering Ltd. ProD8 Owner’s Manual
2
14
True to the Music
RACKMOUNT OPTIONS
Reversible rack rails allow you to decide which connector panel faces the front of your rack.
Depending on your system setup, you may want to have the XLRs facing ‘out’ of your rack and the ¼” inputs
and thru-puts on the inside. This would be the most common approach especially if you are using a number
of rack-mounted sound modules.
Some system techs prefer to have access to the ¼" inputs. They will then have an XLR or multi-pin breakout
panel made to connect the snake systems. This approach is useful when using the ProD8 with non-rackmounted instruments.
The ProD8 can accommodates both setups. Simply unscrew the two large Phillips screws on the rack ear,
loosen the center screw and rotate the rack ear to the side that works best for you. Re-insert the screws so
that they are nice and tight and you are ready to go!
CHASSIS GROUNDING
The Radial ProD8 is equipped with a threaded ground lug on the chassis to allow star grounding. The
ground lug connection, along with the internal chassis ground switch, would likely only be used in complex
stage set-ups where extreme noise problems may occur. We suggest you speak with a qualified technician
should you plan to use alternate grounding schemes.
Threaded ground lug connections
(one obscured by rack ear).
Radial Engineering Ltd. ProD8 Owner’s Manual
3
True to the Music
USING THE RADIAL ProD8
For live touring, the most common approach to using a direct box is to connect the instrument to the A/B inputs, your personal monitoring amp system from the THRU and the balanced XLR output to the PA system.
The Radial ProD8 of course does this and then multiplies this by eight. Since the ProD8 is so fl exible, the
following diagrams show some of the system set-ups that you could apply.
8 MONO KEYBOARDS
As described above, the ProD8 is plug & play
easy to use as any standard passive DI. Connect an instrument to either input, the THRU to a
monitor system and the XLR out to a mixer.
L
LOOP
IN-A
THRU
IN-B
MONO
Personal Mixing
Console
OUT
1
PAD
MONO
House Mixing
Console
4 STEREO KEYBOARDS
You can set up 4 stereo keyboards and have
them all play in stereo. Connect the keyboard
stereo out two ProD8 channels.
8 MERGED MONO KEYBOARDS
Stereo keyboards can easily be merged to mono
to save snake and mixer channels. Connect the
stereo keyboard to the A/B inputs on one ProD8
channel. The signal is merged to mono.
L R
LOOP
IN-A
THRU
IN-B
MONO
Personal Mixing
Console
OUT
1
PAD
MONO
House Mixing
Console
8 MERGED STEREO KEYBOARDS
You can set up 8 stereo keyboards and have them
all play in stereo by using the dual A/B inputs on
two ProD8 channels.
L R
LOOP
IN-A
THRU
IN-B
STEREO
Personal Mixing
Console
OUT
1
PAD
Radial Engineering Ltd. ProD8 Owner’s Manual
STEREO
House Mixing
Console
LOOP
THRU
IN-A
IN-B
OUT
2
PAD
4
L R
LOOP
IN-A
THRU
IN-B
STEREO
Personal Mixing
Console
OUT
1
PAD
STEREO
House Mixing
Console
L R
LOOP
THRU
IN-A
IN-B
OUT
2
PAD
True to the Music
THRU
OUT
ADDING EFFECTS
The LOOP jack on each channel works like an "insert" connection on a mixing console. The LOOP jack is
a TRS type that can send the signal out to a processor and return it to the ProD8 signal path. Connect the
input and output of an effects processor to the LOOP jack using an "insert cable" which may be purchased
at a music retailer.
Each channel is fi tted with an internal EFX PRE/POST switch. The position of this switch determines if the
THRU output will be PRE or POST the effects-loop. When the switch is set to PRE, the THRU output will
be unaffected by the effects-loop. When the switch is set to POST, the effect processor will be heard at the
THRU output. The XLR output is always POST effects-loop. The ProD8 ships factory set to post effects-
loop so a processor in the loop will be heard on all outputs.
MONO EFFECTS
When one ProD8 channel is confi gured
for a mono keyboard connect the LOOP
jack to the input and output of the effects
processor with one insert cable. If the
dual A/B inputs on a ProD8 channel are
used to connect two mono keyboards
the effects processor is shared between
them. This can save mixer channels and
money. This also lets you share effects
when running redundant modules for
backup.
Insert Cable
MONO
Digital Multi Effect
LOOP
STEREO EFFECTS
When two of the ProD8 channels are
confi gured for a stereo keyboard, connect the LOOP jacks on both channels
to the left and right inputs/outputs of a
LOOPLOOP
stereo effect processor with two insert
cables. If the dual A/B inputs on a ProD8
channel are used to connect two stereo
Insert Cable
keyboards the effects processor is
shared between them.
Radial Engineering Ltd. ProD8 Owner’s Manual
STEREO
Digital Multi Effect
5
Insert Cable
Insert Cable
R
L
True to the Music
FLEXIBLE FOR LARGE KEYBOARD SETUPS
It is important to note that channels may be confi gured in different ways. For in-
stance, in the example below channels 1 and 2 are used for a stereo master key-
board and a pre-patched backup that is ready to go. Channels 3 through 6 are used
for mono sound modules. Channels 7 and 8 are set up in stereo for a drum machine
with a stereo effect processor. All the instruments are connected to a personal mon-
itor mixer via the THRU outputs and to a main mixer through the XLR outs.
Console
House Mixing
M M M
Console
Personal Monitor
M
L R
Backup MIDI Controller
L R
Master MIDI Controller
Radial Engineering Ltd. ProD8 Owner’s Manual
6
True to the Music
REDUNDANT MODULAR KEYBOARDS
Major concert tours cost millions to setup. Today, keyboard players often travel with
back-ups to minimize downtime should a module fail. The merged inputs allow a
second set of modules or keyboards to be connected in standby should a back-up
be needed.
L R L R
Backup
Synth Module 1
Master MIDI Controller Backup MIDI Controller
MIDI
Radial Engineering Ltd. ProD8 Owner’s Manual
7
Backup
Synth Module 2
Backup
Synth Module 3
Synth Module 4
Backup
True to the Music
REDUNDANT BACK-UP TRACKS
The use of backing tracks has become common in today’s concerts as fans expect to hear the full orchestration and backing vocals of their favorite songs. The ProD8 provides an effective means to connect two
tape recorders via the dual A/B merged inputs on each channel. Simply place the back-up recorder on mute
and sync both machines together. Should a problem occur, mute the main playback recorder and un-mute
the backup system. The show will go on!
Primary Playback Machine
Backup Playback Machine
House Mixing Console
Radial Engineering Ltd. ProD8 Owner’s Manual
8
True to the Music
FAQ
Can I use the ProD8 with guitars or basses?
Yes of course you can, but keep in mind that the resistive mixer may apply a bit of a load on the instrument.
This will not be noticeable with active (battery equipped) instruments like acoustic guitars, but you may
notice a slight drop in level with low output instruments with passive pickups.
Can I use high output +4dB balanced sources with the ProD8?
Not really. The +4dB outputs could overload the transformers which could cause saturation. However,
you can connect -10dB outputs to the ProD8 inputs with the -15dB PAD engaged without overloading the
transformer.
I heard transformer saturation can sound good?
True, especially with very dynamic keyboards like a digital piano. All transformers will saturate at some
point causing distortion. Some transformers will sound good when they begin to saturate and this is often
cited as the type of analogue character that vintage gear can add to the sound. Radial transformers exhibit
the warm Bessel curve with naturally cascading even harmonics that produces a musical distortion which
is pleasant to the ear. If this is not what you want, engage the -15dB PAD to prevent saturation with high
output sources.
Will the Radial ProD8 get rid of the buzz and hum I get in certain clubs?
Most buzz and hum problems are caused by stray AC current running through one piece of gear into another through the signal ground. This is exacerbated by less than ideal AC systems and varying ground
reference voltages that are floating around. Transformer isolation can often eliminate these problems and
eliminate noise.
Can I use the ProD8 backwards like a re-amper?
You could but the resistive mixer may cause a level to shift making it difficult to get the best tone. You would
be further ahead to purchase a product like the Radial X-Amp for re-amping which this is specifically designed for this task.
Can I use the ProD8 as a splitter by sending the thru-put of channel-1 into channel-2?
Yes. Although this is an uncommon way to do things, it will work. Keep in mind that when you split the signal,
you may have to adjust your levels to suit.
Can I use the ProD8 to isolate one mixer from another to help eliminate noise?
Yes, but be careful. Make sure the -15dB Pad is activated and listen for distortion. Your mixer output will
likely be much louder than a keyboard or guitar and therefore you could overload the ProD8 transformer.
Also, you will then have to send the ProD8 outputs to the mic-pre inputs on the second mixer as the proD8
outputs are mic level (not line level). This means that you will be using multiple buffers which could add
some hiss or system noise. Note that Radial produces the Twin-ISO which is specifically designed for linelevel isolation applications.
When driving two channels into one, can the Merge function cause phase cancellation?
Not likely. A simple Y-jack input can cause phase cancellation but seeing as we are employing a passive
resistive mixer, this problem should not occur. If you do hear some phase cancellation, check to make sure
the source is in phase.
Radial Engineering Ltd. ProD8 Owner’s Manual
9
RADIAL ENGINEERING
3 YEAR TRANSFERABLE 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 batteries, finish 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.
To make a request or claim under this limited warranty, 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 warranty. This limited warranty shall not apply if the product has been
damaged due to abuse, misuse, misapplication, accident or as a result of service or modification 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.
1638 Kebet Way, Port Coquitlam BC V3C 5W9
tel: 604-942-1001 fax: 604-942-1010
email: info@radialeng.com web: www.radialeng.com
True to the Music
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