Radial OX8 8 Ch Rackmount Mic Splitter User Guide
- October 30, 2023
- Radial
Table of Contents
- Radial OX8 8 Ch Rackmount Mic Splitter
- Introduction
- INTRODUCTION
- BASICS
- Isolation Transformer
- FEATURES
- Connecting Two Mixing Consoles
- INTERNAL GROUNDING OPTIONS
- FAQ
- SPECIFICATIONS
- RADIAL ENGINEERING LTD. 3-YEAR TRANSFERABLE WARRANTY
- References
- Read User Manual Online (PDF format)
- Download This Manual (PDF format)
Radial OX8 8 Ch Rackmount Mic Splitter
Radial OX8 Microphone Splitter – User Manual
Introduction
The Radial OX8 is an eight-channel, balanced microphone splitter that divides the mic signals in three ways direct output, direct output with ground lift, and an isolated output. This user guide covers the installation and operation of the Radial OX8 microphone splitter. We recommend that you take a few minutes to read through this manual to familiarize yourself with the many innovative features that are built in. If you have questions or applications not covered in this manual, visit the Radial website at www.radialeng.com to check the FAQ section for the latest updates. You can also send an email to support@radialeng.com.
Design Concept
The Radial OX8 is a compact 1RU package. A high-performance bridging
transformer is used on the isolated output to eliminate hum and buzz caused by
ground loops. The OX8 is an off-the-shelf splitter that allows anyone to
design and assemble a splitter-snake with plug-and-play simplicity and
professional audio quality without the need for custom metalwork or complex
soldering.
Basics
Splitting microphone signals is not as simple as just wiring the
microphones to all the consoles. Issues such as impedance loading, ground
loops, and phantom power can degrade the signal and introduce noise. The OX8
uses high-performance audio isolation transformers to decouple the signal
passing through it and eliminate ground loops that cause hum and buzz in audio
systems.
What is a Mic Splitter?
A mic splitter divides a microphone signal into multiple outputs. It’s most
common in sound reinforcement and live recording when the onstage microphones
must be split to feed two mixing consoles.
What is a Ground Loop?
A ground loop is created when an audio system has multiple paths to ground,
often called earth. This situation can occur when two AC-powered audio
devices, such as two mixing consoles, are plugged into different power
circuits and connected together via a signal cable. Both audio devices have a
path to ground through the third prong on the AC mains cable. The signal cable
completes the loop by connecting the devices together through the signal
cable’s shield.
Signal Flow
The OX8 has eight inputs and three outputs. Inputs 1-8 are DB-25 connectors
and there are eight XLR connectors on the front panel. Inputs 1-8 also include
Euroblock connectors, a -36dB PAD, and a front panel ground lift. The internal
ground lift and isolation transformer are connected via a DB-25 connector.
Product Usage Instructions
- Connect your microphones to inputs 1-8 using XLR or Euroblock connectors.
- Choose the output type for each input: direct, direct with ground lift, or isolated.
- Connect the outputs to your mixing consoles or other audio devices using standard cables.
- Adjust the -36dB PAD as needed to prevent distortion or clipping.
- If you experience ground loop hum or buzz, use the front panel ground lift or internal ground lift to eliminate it.
INTRODUCTION
This user guide covers the installation and operation of the Radial OX8 microphone splitter. We recommend that you take a few minutes to read through this manual in order to familiarize yourself with the many innovative features that are built in. Should you have questions or applications not covered in this manual, we invite you to visit the Radial website at www.radialeng.com to check the FAQ section for the latest updates. Of course, you can also send us an email at support@radialeng.com.
OX8 DESIGN CONCEPT
The Radial OX8 is an eight-channel, balanced microphone splitter in a compact
1RU package that divides the mic signals three ways; to a direct output; a
direct output with ground lift; and an isolated output. A high-performance
bridging transformer is used on the isolated output to eliminate hum and buzz
caused by ground loops. Splitting microphone signals is a straightforward
concept. It’s most common in sound reinforcement and live recording when the
on-stage microphones must be split to feed two mixing consoles. When done
improperly, splitting a signal can dull frequency response, lower the output
and worst of all, cause ground loops that produce buzz and hum. To avoid these
pitfalls, sound reinforcement companies have been building custom “splitter-
snakes” for many years. The OX8 is an off-the-shelf splitter for the rest of
us allowing virtually anyone to design and assemble a splitter-snake with
plug-n-play simplicity and professional audio quality without the need for
custom metal work or complex soldering.
BASICS
What is a Mic Splitter
In modern concert production, there are often two separate sound sys-tems. The
main PA covers the audience or “house” while a monitor sys-tem covers the
stage so the performers can hear. A third system may be added if the concert
is to be recorded. Each system requires it’s own mix-ing console because the
mix that sounds good in the house simply won’t work for the monitors or be
suitable for a recording. A mic splitter provides the means to split the
original signal from the on-stage microphones and send it to the various
systems, main PA, monitors and recording so that each can get a clean,
unaffected signal directly from the mic. However, splitting microphone signals
is not as simple as just wiring the microphones to all the consoles. Issues
such as impedance loading, ground loops and phantom power can degrade the
signal and introduce noise. To solve these issues the OX8 uses high-
performance audio isolation transformers to decouple the signal passing
through it and eliminate ground loops that cause hum and buzz in audio
systems.
Inside a Transformer
A transformer consists of two coils of wire in close proximity to one another
wound around a metal core. One coil is the input of the transformer (primary),
the other coil is the output (secondary). A transformer is said to
electrically isolate, or decouple, the input from the output because there is
no physical connection between the primary and secondary windings. When the
primary winding is energized by the mic signal, a magnetic field is produced
and the lines of force cut across the turns of the secondary winding.
Alternating current (AC) which makes up the audio program is transduced from
one winding to another through induction. Direct current (DC) which is
responsible for buzz and hum in sound systems, is blocked by the transformer
eliminating noise caused by ground loops.
What is a Ground Loop
A ground loop is created when an audio system has multiple paths to ground,
often called earth. This situation can occur when two AC-powered audio
devices, such as two mixing consoles, are plugged into different power
circuits and connected together via a signal cable. Both audio devices have a
path to ground through the third prong on the AC-mains cable. The signal cable
completes the loop by connecting the devices together through the signal
cable’s shield.Once the loop is complete there is the electrical potential for
DC voltage to flow through it. This potential is caused by the interaction
between devices with different ground voltage references and allows unwanted
spurious current to flow through the shields of the signal cables. This flow
of DC voltage creates noise in the signal wires through induction and
capacitance at the base frequency of 50 or 60 Hz (hum) and the upper harmonics
of 120 Hz, 240 Hz, etc. (buzz). Isolating or decoupling the audio signal with
a transformer at a point between the two devices is the best way to block the
unwanted flow of ground-potential currents and eliminate hum and buzz in audio
systems.
Sound Quality
Besides isolation to prevent hum and buzz, audio transformers must sound
brilliant and sound quality is what sets Eclipse® and Jensen® transformers
apart. Designed for pro-audio applications, they include a host of features
not found in general-purpose audio transformers. A core material of nickel-
iron allows ultra high input levels before saturation, linear frequency
response, excellent bandwidth and near-zero phase distortion. Consistent unit-
to-unit performance is achieved through precision computer controlled winding.
The core is sealed inside a mu-metal can which provides enhanced shielding
from electromagnetic interference. The built-in Bessel low pass filter removes
ultrasonic distortion that can mask natural sound and cause ear fatigue.
SIGNAL FLOW
Take a moment to follow the signal path through the block diagram below.
-
Parallel Inputs
For flexibility, the OX8 has three paralleled inputs.- Female XLR connectors on the front panel
- 25 pin D-SUB (DB-25) on the rear panel
- Euroblocks screw terminals on the rear panel (Set of eight Euroblock terminals sold separately, Order # R800 8050).
-
Direct Output
The DIRECT output is the primary “straight through” output and provides a return path for 48V phantom power for condenser microphones and active direct boxes. In the diagrams we refer to the main FOH console as connected to the DI-RECT output. In fact it doesn’t matter which console, main or monitor is connected to DIRECT as long as it is the only console that will supply phantom power. The DIRECT output is paralleled to DB-25 and Euroblocks terminals for flexibility. -
Auxiliary Direct Output with Ground Lift
The DIRECT OUT WITH GROUND LIFT is an auxiliary output that uses eight front panel switches to lift the ground. This output may be patched to another audio system that may or may not be transformer isolated itself. The DIRECT WITH GROUND LIFT output is paralleled to DB-25 and Euroblock terminals. -
Isolated Output
The ISOLATED outputs use eight precision audio isolation transformers to decouple the mic signals from the DIRECT outputs. This output may be patched to a separate audio sys-tem without creating ground loops. The ISOLATED output is paralleled to DB-25 and Euroblock terminals.
-36dB PAD
The front panel PAD switch allows you to connect line-level output devices to
the OX8. Engaging the PAD reduces the level by -36dB for that particular
channel at the ISOLATED output.
Isolation Transformer
After the PAD the signal is fed to the isolation transformer where the mic signal is decoupled to eliminate noise from ground loops. For the most flexibility when designing technical ground systems, each transformer features an internal switch allowing the signal ground to connect around the transformer.
RF Filter (not shown in the diagram)
The three paralleled inputs employ a RF network filter on their ground paths
to prevent unused inputs from acting like anten-nas when the ground is lifted.
Any radio frequencies picked up by an open pin will be shunted to ground.
FEATURES
- Locking XLR Inputs – Front panel female XLR jacks allow easy connection of individual signals. Rugged, glass-reinforced nylon construction for reliable connections.
- PAD -36dB – Reduces level-level input signals to microphone level, allowing them to be run alongside mic signals without crosstalk. Only the ISOLATED output is affected by the PAD.
- Front Panel Lift Switch – Disconnects the ground path at the DIRECT WITH GROUND LIFT auxiliary output. Using the front panel ground lift can eliminate ground loop noise between equipment connected to the OX8 direct outputs.
- Easy ID label zones – For dry-erase markers or wax pencil identification. Handy when using several OX8 at a time.
- Internal Chassis Ground Lift – Input connectors are 100% isolated from the chassis, but an internal switch is provided to connect signal ground (pin-1) to the chassis without modifying the OX8. By default, this switch is factory set to “lifted” allowing the chassis to “float” ungrounded and should remain this way unless a specific grounding scheme requires the signal ground to be tied to the chassis.
- Military Grade PCB – The dual layer circuit board is manufactured with plated through holes and secured with 8 standoffs.
- Transformers – Each transformer is mounted directly on the PCB in close proximity to the input for the shortest possible signal path. Choice of standard Eclipse or optional Jensen transformers.
- Heavy-duty Switches – Front panel switches are metal encased and rated at 20,000 operations.
- Internal Ground Lift – Each channel features an internal switch that, by default, is set to “lifted” so the transformer can isolate ground potential voltages. It may be used by system designers to accommodate specific grounding schemes when desired.
- 14-Gauge Chassis – Made extra tough with heavy gauge steel and welded corners to provide excellent shielding and durability. Finished in baked enamel.
- Isolated Output – This output is transformer isolated to block noise caused by ground loops and is wired in parallel to DB-25 and Euroblock terminals.
- Direct With Ground Lift – This is an auxiliary output wired in parallel with the DIRECT output. The signal grounds may be disconnected using the front panel LIFT switch. This output is wired parallel to the DB-25 and Euroblocks terminals.
- DB-25 Pin-out Diagram – The pin-out for the female DB-25 connector is diagramed on the rear panel. All DB-25 connectors follow the Tascam standard for eight channel analog signal interface.
- Euroblock Sockets – These panel sockets receive 12-pin Euroblock screw terminals. Each Euroblock connects four channels with bare wire termination and facilitate custom options like interfacing a connector panel or multi-pin disconnect. Euroblocks screw terminals are optional and must be ordered separately. (Radial order # R800 8050)
- Direct Output – This output passes signal through the OX8 and provides the return path for phantom power. This output is wired parallel to the DB-25 and Euroblock terminals.
- Rear Inputs – The rear panel DB-25 and Euroblock inputs connect all eight channels and are wired parallel to the front XLR connectors.
- Chassis Ground – Ground screw connection point used in conjunction with the internal chassis lift switch to bond the OX8 to earth.
CONNECTING THE OX8
OX8 Inputs
You can connect mics and direct boxes to the OX8 using the front panel XLR
inputs, or the rear panel DB-25 and Euroblocks terminals. Which input you
choose to use will depend where the OX8 is located and what you are connecting
to it. For instance, individual microphones may be connected directly via the
front panel XLRs , or a multi-channel snake may be used to connect to the
DB-25 inputs . Finally, a wall-mounted panel of XLRs may be connected to the
Euroblock inputs with a multi-channel snake cable .
Connecting the DB-25 I/O
The DB-25 connectors on the rear panel use the TASCAM pin-out standard for
analog audio. Connecting the OX8 to devices equipped with DB-25 connectors
like digital multi-track recorders and mic preamps is simply a matter of using
compatible DB-25 audio cables. Radial-balanced DB-25 cables are a perfect
match for the OX8 and can be ordered in standard or custom lengths. The pin-
out diagram is silk-screened on the rear panel for reference and represents
the panel-mount female pin-out. To make your own interface DB-25 cables follow
the pin-outs below for male and female connectors.
Connecting the Euroblock Terminals
Euroblock, or European-style terminal blocks, also called Phoenix blocks, are
removable screw terminal connectors. The Euroblock connector requires no
soldering to terminate. Instead, the wire is stripped, inserted into slots in
the connector and locked into place with a standard screwdriver. The connector
then mates with the socket. Pin termination for the Euroblock terminals are
clearly marked on the rear panel.
Referring to the pins on an XLR connector:
- Connect pin-1 (GROUND) to the G terminal.
- Connect pin-2 (HOT) to the + terminal.
- Connect pin-3 (COLD) to the – terminal.
Connecting Two Mixing Consoles
This is the most basic OX8 setup and allows the MAIN PA and MONITOR consoles to have access to the stage microphone signals. The MAIN PA console connects to the DIRECT output and supplies 48V phantom power to the mics and active direct boxes. The MONITOR console uses the ISOLATED out-put and is therefore electrically decoupled from the first console. The MONITOR console may be powered from a separate AC-mains circuit with-out creating ground loops.
Connecting Three Mixing Consoles
This advanced setup connects three consoles to an OX8. The MAIN PA console
connects to the DIRECT output and the MONITOR console to the auxil-iary DIRECT
with LIFT output. In order to avoid hum and buzz from ground loops these
consoles should be powered from the same AC main cir-cuit or a power
distribution system designed to prevent ground loops from forming. A third
RECORDING console connects to the iso-lated output and is therefore
electrically decou-pled from the MAIN PA and MONITOR consoles. The RECORDING
console may be powered from a separate AC mains circuit without creating
ground loops.
INTERNAL GROUNDING OPTIONS
The Radial OX8 features two internal grounding options that will be of interest to system engineers when integrating the OX8 into complex audio- visual systems. Most users will not need these options and can accept the factory default settings.
Internal Ground Lift – Each Channel
Each channel’s transformer features an internal ground switch that re-connects
the ground around the transformer. It may be used on a per-channel basis to
accommodate specific grounding needs. For example, it may be neces-sary to set
this switch to closed for devices that have a floating ground, like battery-
powered laptop computers or devices powered with an AC to DC adaptor. By
default this switch is set to open, or lifted (out position) so the
transformer can decouple equipment connected to the ISOLATED outputs. Pushing
the switch in (closed) will connect the input ground to the output ground at
the ISO-LATED output for that channel.
Internal Chassis Ground Lift – All Channels
All connectors are 100% isolated from the steel chassis allowing chassis and
signal ground to be kept separate. However, a single internal switch is
provided to connect the pin-1 cable shields to the chassis without modifying
the OX8. By default, this switch is factory set to open or “lifted” allowing
the chassis to “float” ungrounded. Should a specific grounding scheme require
the cable shields to be bonded to the chassis simply set this switch to closed
(pushed in position). The switch may be accessed through a small hole in the
side of the steel chassis or by removing the top cover. The chassis ground
switch does not effect the isolation provided by the transformer at the
ISOLATED output. On the rear panel a ground screw provides a convenient point
to bond the chassis. Use a heavy gauge solid copper wire to bond the OX8
chassis to your technical ground.
FAQ
Can I use the Radial OX8 to split line-level signals?
You can use the Radial OX8 to accept line-level signals by depressing the
-36dB input PAD. The output will however be mic level as this is the norm with
mic splitters. If you want to split line levels, the LX8 may be a better
choice.
What is the difference between the various Eclipse and Jensen transformer
options?
Eclipse offers a wider range of transformers in order to meet several price
and performance points. The Eclipse MS10™ is our most popular mic splitter
transformer. It provides exceptional performance from 20Hz to 20kHz while the
Jensen has an extend frequency response from 10Hz to 40kHz.
Why did Radial use D-Sub connectors on the OX8?
Back in the 90’s, Tascam began using D-Subs on their DA88 digital recorders
and they quickly became one of the most popular connectors for digital
recording formats on the planet. Since they are very high density, you can
really pack in a lot of channels in a small place. This makes them a good
choice for the OX8.
Can I order a Radial OX8 with two isolated outputs?
No. To get two isolated outputs, you would need to assemble eight JS3™ and
mount them into a J-Rack™. This would give you eight isolated outs in two rack
spaces.
How does the Radial OX8 compare to the Radial LX8?
The OX8 is designed for mic signals (-40dB typical) while the LX8™ is designed
for line levels (+4dB typical). These employ different types of transformers
to handle the different levels.
Does the OX8 need power to make it work?
No. The OX8 is completely passive. Simply plug in and play.
What is the difference between Radial mic splitters and others?
Top professionals specify Radial because they depend on a product that is
durable and will not fail. Radial uses the very best components to ensure
fail-safe use. Others can save you money by being cheaper, but will likely not
deliver the same level of quality or performance. Check the specs. If they are
not complete, then you will likely end up being surprised.
Can I have an XLR panel made to go along with some OX8s?
Yes. Contact the Radial Custom Shop and they can put a quote together for you.
What is the difference between an active splitter and a passive one?
An active splitter is a multi-channel preamplifier or buffer that
electronically amplifies the signal while a passive splitter does not amplify
the signal at all; it uses special transformers to do the task. Most pros
prefer a passive splitter as it taps the signal directly from the mic allowing
each mix position to set the gain stage most appropriate to the individual’s
need.
Will phantom power hurt the OX8?
No. The OX8 is designed to work with phantom power by allowing it to flow
through the OX8’s direct output back to the microphone inputs. The isolated
outputs will simply block phantom power if present.
Why can’t I simply split a signal without a transformer?
You can. But you will be subject to noise caused by stray DC voltage.
Transformer isolation really helps to eliminate hum and buzz which can turn a
great performance into an unusable recording.
SPECIFICATIONS
Specifications OX8-Jensen OX8-Radial
- Audio Circuit Type: Passive transformer-based mic level splitter
- Number of Channels: 8 channel 3-way splitter (1-in/3-out)
- Frequency Response: 20Hz ~ 20KHz (+0dB/-0.2dB) 20Hz ~ 18KHz (+0dB/-3dB)
- Dynamic Range: 140dB 140dB
- Maximum Input: +2dBu @ 20Hz +2dBu @ 20Hz
- THD +Noise: 0.003% @ 1kHz 0.005% @ 1kHz
- Phase Deviation: 0.7° @ 100Hz; 2.8° @ 20Hz 1° @ 100Hz; 5° @ 20Hz
- CMRR: -115dB @ 60Hz 114dB @ 60Hz
- Input Impedance: Source dependent, 10kΩ with Pad on, balanced
- Output Impedance: Source dependent, 10kΩ with Pad on, balanced
Features
- Transformer: JT-MB-CPC, 1:1 ratio Eclipse MS10, 1:1 ratio
- Shield: Dual Faraday, MuMETAL® can
- Input Pad: -36dB (allows line-level sources)
- Ground Lift: Disconnects XLR pin-1 at direct-2 and isolated output
- XLR Configuration: AES standard (pin-2 hot)
- DB-25 Configuration: Tascam analog audio standard
General
- Construction: 14 gauge steel
- Finish: Durable powder coat
- Size (L x W x H): 19” x 6” x 1.75” (48.25cm x 15.25cm x 4.45cm)
- Weight: 7.5lb (3.4 kg)
- Shipping Size (L x W x H): 22” x 10.375” x 4.5” (55.9cm x 26.4cm x 11.4cm)
- Shipping Weight: 8lb (3.63kg)
- Power: Passive, no power required
- Conditions: For use in dry locations only between 5°C and 40°C
- Warranty: Radial 3-year, transferable
RADIAL ENGINEERING LTD. 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 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 containers (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.
References
Read User Manual Online (PDF format)
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