Radial Engineering JPC MK3 User manual

USERGUIDE
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: [phone] • fax: [phone]
email: [email protected] • www.radialeng.com
JPC
www.radialeng.com
STEREOPCDIBOX
ISOLATEDIN· ACTIVEOUT
MK3

JPC USER GUIDE
Stereo PC Direct Box
TABLE OF CONTENTS PAGE
Introduction..............................................................................1
Input & output panel features ..................................................2
Inside view & features .............................................................3
Connecting the JPC.................................................................4
JPC features............................................................................7
Frequently asked questions.....................................................8
Block diagram and specifications............................................11
Warranty....................................................................Back cover
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: [phone] • fax: [phone]
email: [email protected] • web: www.radialeng.com
Features and specifications are subject to change without notice.

TruetotheMusic
Radial Engineering JPC User Guide
1
INTRODUCTION
Congratulations on your purchase of the Radial JPC direct box.
The Radial JPC is a stereo direct box that has been specifically designed to interface computer sound
cards and other consumer electronic products with professional sound systems. It is unique in
that it combines the advantages of transformer-isolated inputs with an active drive circuit,
giving you the ‘best of both worlds’ in a compact and extremely flexible package.
Transformer coupled inputs have the unique advantage of isolating the
‘source’ from the ‘destination’. This proven approach eliminates 60-cycle hum
and buzz caused by ground loops when two electrically powered devices are
connected together. Because the active circuit does all of the impedance
conversion and balancing, a dedicated 1:1 transformer can be used. This
results in a hybrid design that is at once great sounding, compact and
more affordable.
As with all great designs, simplicity is a fundamental trait, and the
Radial JPC certainly fits the bill.Achoice of ¼”, 3.5mm and RCA input /
thru-put connectors make interfacing a snap with all types of equipment.
Asingle switch inserts a –15dB pad into both channels, two power LEDs
(one for each channel) confirm 48V phantom is turned on, and a pair of
XLR output connectors round out the feature set.
Of course like all Radial products, the JPC is built to handle the most
abusive environments. Our unique bookend design protects switches and
connectors from damage while the 14-gauge steel I-beam construction
eliminates outside stress that could torque the PC board and cause solder
jointfailure.Afull-bottomno-slippadprovideselectricalinsulationandmechanical
isolation while also helping the JPC ‘stay-put’ on hectic stages.
Although the JPC is really easy to use, we highly suggest you read through this
manual and familiarize yourself with the JPC’s features. This will help you make the most
outof this marvellousdevice.Wealsosuggestvisiting our websiteatwww.radialeng.comformore
information and updates. Should you have any questions or concerns that are not covered in this manual
we invite you to contact us by email at [email protected].
Now plug in your JPC and let the show begin!
®

FEATURES AND FUNCTIONS
®TruetotheMusic
Radial Engineering JPC User Guide
2
OUTPUT PANEL
6. Groundliftswitch breaks the groundconnectionbetween
the input and the output. The default position is lifted to
prevent hum from ground loops.
7. Stereo left and right XLR male output connectors are
isolated from the chassis and follow AES standard with
pin-2 hot.
8. No-slip full rubber bottom provides mechanical isolation,
electrical insulation and ‘stay-put-ability!’
9. 14-gaugesteelbookend design creates a protective zone
around buttons and connectors. Tough baked enamel
finish for years of ‘great looking’ performance.
INPUT PANEL
1. –15dB Pad is used to prevent loud sources from
overloading the JPCs audio circuit.
2. 48VPower LEDs letyou know thatphantomhas been
turned on and is powering the two channels.
3. Dual 1/4” jacks can be use for a stereo device or two
mono signals.
4. 3.5mm TRS stereo mini connector designed for direct
connectionofPCs,laptops,andportableaudiodevices
without adaptors.
5. Stereo RCA connectors are great for connecting
consumer electronics like CD players, VCRs and DJ
mixers. RCA thru-puts provide a duplicate output for
splitting and routing flexibility.




TruetotheMusic
Radial Engineering JPC User Guide
3
INSIDE VIEW
13. Militarygrade PC board withfullsurfaceground plane
to reduce RF noise susceptibility.
14. High duty-cycle switches for a maintenance free long
life.
15. Welded I-beam construction makes it impossible to
torque the PC board.
®
10. IsolatedXLRconnectors to eliminate chassisground
potential.
11. Active drive circuit electronically balances stereo
signals for long cable runs without loss.
12. Transformers on both inputs provide 100% isolation
to eliminate hum and noise from ground loops.
10 11 12 13 14 15

CONNECTING THE JPC
Caution! Make sure all levels are down before connecting!
The JPC is powered by 48V phantom thru the XLR outputs, and automatically turns on when phantom
power is activated. Activating phantom power at the console can cause a loud transient signal spike
which could cause a big “bang” in your sound system or even cause a speaker to blow. Make sure your
system levels are turned off before connecting the JPC and activating phantom power.
The JPC is designed to make connecting all types of audio signals easy. The JPC features a combination of standard stereo
connectorsfoundon PCs and consumerelectronicdevices.These areconnectedjustlikea home stereo system.Cablesthat
shipwithmany devices will workwiththe3.5mmand RCAinputs.TheJPCcaneven interface electronic musicalinstruments,
like keyboards and drum machines with 1/4” cables. Or, in a pinch, the JPC can be used as a standard instrument DI.
Finally, the JPC’s ‘thru-put’ feature gives you the option to split the signal and adapt from one connector type to another.
The Inputs and thru-puts
The JPC is outfitted with a wide array of connectors to make life easy during hectic set-ups. It is important to note that the
3.5mm mini jack is a stereo TRS (tip-ring-sleeve) connector. The ring connects to channel-1 (left), the tip to channel-2 (right)
and the sleeve is a common ground. The RCA jacks follow standard left and right configuration and also feature parallel
thru-put jacks for convenience. One of the wonderful features of the JPC is that all inputs on the front panel are wired in
parallel and may also be used as thru-puts.
TruetotheMusic
Radial Engineering JPC User Guide
4
®

3.5mm TRS stereo input
This is a standard connector used on notebook
computers and personal music players. It uses a mini
Tip, Ring, Sleeve (TRS) jack in a stereo configuration.
When used with the -15dB PAD, this input can be used
withheadphone level outputs. Whenusinga headphone
output as a source, be sure to turn down the headphone
leveltominimum.Evenwiththe-15dBPADa headphone
amplifier can overload the JPC when it's level is not set
to minimum.
RCA stereo inputs
Thesejacksacceptunbalanced,consumeraudiosignals.
Virtually any audio output that appears on an RCA
connectorcanbe connected to thisinput.This includesa
longlistofelectronicslikeCDplayers, cassette recorders,
AM/FM tuners, video cassette recorders, etc.
RCA thru-puts
A duplicate of the input signal is available at the RCA
thru-put connectors. This feature can come in handy to
split the signal to a second mixer or tape recorder.
Un-used connectors as thru-puts
Allofthe JPC’sinputconnectors are parallelled together.
This means that any unused inputs can also be a thru-
put to split the stereo signal and/or adapt one format
connector to another. For example, one can connect a
CD player using the RCAstereo input jacks and use the
3.5mmjack as athru-putto split thesignalto a notebook
computer. It also works the other way. When the 3.5mm
jack is used as an input, the RCAthru-puts can be used
to connect a recorder or second mixer. Clever!
TruetotheMusic
Radial Engineering JPC User Guide
5
Cass, CD, or VCR connected with stereo RCA cable
Notebook PC with single stereo 3.5mm cable
3.5mm input used as thru-put to connect laptop
®

TruetotheMusic
Radial Engineering JPC User Guide
6
Dual mono 1/4” TRS input
These two unbalanced 1/4” input jacks are used with
stereo devices like electronic musical instruments and
PC audio recording interfaces that output left and right
signals on separate jacks.
A 1/4" headphone output from a stereo device may also
be connected to the JPC 1/4" inputs with a stereo-to-dual
monoadaptorcable as show totheright.EngagethePAD
when using a headphone outputs as a source.
Using the JPC as an instrument DI
Although the Radial JPC is designed to work with
computer sound cards and other consumer level hi-
impedance devices, it can also be used with instruments
thatfeatureactiveelectronicssuchasacousticguitarsthat
havea built-in pick-up andpre-amplifier, bass guitarswith
active pickups and electonic keyboards.
We do not, however, recommend using the JPC with
instruments that have passive pickups, like a standard
bass guitar or contact pezio pickups. The JPCs input
transformerswillintroduce impedance loading whenused
with passive pickups due to the impedance mismatch.
Impedance loading will cause high frequency loss that
may be unacceptable. The Radial JDI, ProD1, J48 and
Pro48are DIs bettersuited because theinputimpedance
is designed to match instrument with passive pickups.
Stereo 1/4” TRS connector wired to dual mono connectors
®
An instrument with active pickups connects to the 1/4"
input. If a thru-put to an amp is required an adaptor must
be applied to the like RCA output.

TruetotheMusic
Radial Engineering JPC User Guide
7
The -15dB pad
This push-button switch reduces the input level going to the JPC circuit. Some audio devices with overly powerful outputs
can overload the JPC inputs. Simply depress the pad switch if the sound is distorted.
Phantom power LED indicators
The JPC is powered by 48V phantom thru the XLR outputs, and automatically turns on when phantom power is activated.
Activating phantom power can cause a loud transient signal spike. Make sure your system levels are turned off before
activating phantom power. The two power-on LEDs on the front panel will illuminate when phantom power is present. If the
LED’s do not light, check to see if the phantom power for each channel is active at the console. The JPC is not equipped
to run off a battery or a separate power supply.
Transformer isolation
Probablythe most challenging aspectwhensettingup a soundsystemisreducing system noise.The most commonproblem
is buzz and hum due to ground loops. This is generally caused by two pieces of equipment, each with its own separate
ground path, and differing voltage potentials, interacting together. The JPC eliminates this problem by providing 100%
transformer isolation on both inputs.
Using the ground lift
To ensure the widest possible compatibility with a variety of audio devices, a ground lift switch is provided on the JPC. The
default position is lifted (pushed in) as the JPC’s transformers are designed to isolate the input ground from the output.
However, there may be times when a ground path thru the JPC is desired. In these circumstances, the switch by-passes
the input transformers to provide the input source with a path to ground (pin-1).
Using the XLR output
The JPC XLR outputs follow theAES standard with pin-2 hot. This is generally connected to a microphone snake or directly
into a mixing console. As a phantom powered device, this is also where the JPC derives it’s working power. The output is
mic level and as such, should be connected to a mic pre-amp such as is common in professional mixers.
Plug and play easy
Ultimately, a good direct box should be plug and play easy to use. The JPC is a sophisticated device on the inside that is
designed to be easy to use on the outside. By understanding the design, we feel that you can now make better use of the
features that are built into this marvelous direct box.
®

FREQUENTLY ASKED QUESTIONS
What is a direct box anyway?
The name ‘direct box’ comes from direct insert box. This is why these marvelous contraptions are also called DI’s. ‘Direct
Insertion’ means exactly that: To insert a signal directly or take an audio signal from the source and send it directly to a
mix point or recorder.
Direct boxes perform several important functions: They are designed as impedance matching and signal balancing devices.
This means that they take the high impedance source and ‘transform’ it to the low impedance used in balanced sound
systems. Balanced signals inherently cancel noise and due to their lower impedance, can travel much further. Balanced
signals are the norm in professional recording, broadcast and live sound. By properly matching the impedance you will
enjoy better sound, less noise and an extended frequency response.
What kinds of audio devices will the JPC work with?
Virtually any electronic audio device that outputs an unbalanced, hi-z signal. See the chart below for more details.
TruetotheMusic
Radial Engineering JPC User Guide
8
JPC Input Compatible Device
3.5mm Notebook computers
Personal music & MP3 players
Solid state voice recorders
Micro-cassette recorders
Any device with a 3.5mm output
RCA CD players
Cassette players/recorders
Video cassette recorders
Any device with RCA outputs
1/4” Stereo electronic musical instruments
Stereo headphone outputs
®

Can I use any input as an output?
Yes, any unused input can also be used as an output. The input side of the JPC is wired in parallel. The signal from one
stereo input will be available on the other connectors as a stereo output. RCAjacks are a very common connector found on
most consumer electronics. This is why the JPC has a dual stereo set of RCAjacks labelled ‘input’and ‘thru-put’. However,
on some occasions it may be necessary to patch a stereo signal from a device with RCAjacks, like a CD player, to a device
with 3.5mm jacks, like a notebook computer. The JPC can perform as a connector adapter while at the same time output
a balanced signal on XLR connectors.
Can I use the Radial JPC like a regular DI box for instruments?
Althoughthe Radial JPCwasdesigned to workwithcomputer sound cardsandother consumer levelhi-impedancedevices,
it can also be used with active instruments such as acoustic guitars that have built-in pick-up pre-amplifiers with internal
batteries.Wedo not, however,recommendusingtheJPCwithpassiveinstrumentslikeabass guitar,astheinputtransformers
low impedance may introduce some loading due to the impedance mismatch.
Will it then harm the JPC if I connect a bass to it?
No, of course not. We only state this advisory as we make DIs for instruments such as the J48 and JDI that are simply
better for instruments. The JPC will certainly work in a pinch.
Can I use the JPC on keyboards?
Yes. Just make sure you do not overload the JPC by driving too much signal through it. The JPC’s smaller transformers
are designed for consumer type levels. Keyboards, samplers and drum machines usually output a much more dynamic and
uncompressed level. The JDI, the Duplex, ProD1 and ProD2 are better suited for electronic musical instruments.
What is the advantage of transformer isolating the inputs?
Whenanytwo pieces of electricallypowered equipmentareconnectedtogether, theyformacircuit. Mostoften,the reference
voltages from each device differs, causing stray voltage to appear at the connections, which in turn can cause system noise
commonly known as ground loops. By isolating the inputs through a transformer, we are physically de-coupling the signal
path, and thus, eliminating any opportunity for ground loops in the system.
I am not getting any sound.
Check to see if you have the 48V phantom power turned on at your mixer. The two LEDs on the JPC will illuminate when
phantom power is present.
TruetotheMusic
Radial Engineering JPC User Guide
9
®

TruetotheMusic
Radial Engineering JPC User Guide
10
Radial J-Rack
The sound is distorted.
Tryturningdown the level from thesourceordepressingthe–15dB pad to reducetheinputsignalfromthe source. Excessive
levels can saturate the input transformers, which could cause distortion. Make sure you are supplying the JPC with a full
48V phantom supply. Some inexpensive mixers will supply lower voltages, which could starve the JPC’s circuit.
I am hearing buzz / hum.
Check the ground lift switch on the side of the JPC. Select the lifted position for the JPC to isolate the input ground from the
output. This will eliminate buzz & hum caused by voltage potential between the input source device and the main console
at the other end of the XLR outputs.
Can the JPC be rack mounted?
Yes. With the Radial J-Rak, as many as 8 JPCs may be mounted in two standard 19” rack spaces. The J-Rak allows the
JPC inputs to face either to the front or the rear of the rack as needed.
®

TruetotheMusic
Radial Engineering JPC User Guide
11
BLOCK DIAGRAM AND SPECIFICATIONS
JPC Specifications
Type of DI: Stereo active 48V phantom powered
Input impedance: Unbalanced 10K-Ohms
Output impedance: Balance 600-Ohms
Frequency response: 20Hz to 20kHz
Linear performance: +/- 2dB from 20Hz to 20kHz
Total harmonic distortion: 0.06% @ 20Hz, 0.005% @ 1kHz
Phase distortion: 0.02º at 1kHz
Maximum input voltage: 3.12 Volts RMS ( 9V peak )
Output level -30dBu w/o pad (0dBu/ref: 1V RMS input)
-45dBu w/ pad (0dBu/ref: 1V RMS input)
Input connections: 1/4” TS, 3.5mm TRS, stereo RCA x 2
Output connections: XLR balanced, AES pin-2 HOT
Size: 3.5” wide, 2” high, 5.5” deep
Weight: 1kg or 2lbs
Construction: Welded 14-gauge steel
Finish: Baked enamel coating
®

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 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.Acopy 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.
THEREARE NO EXPRESSED WARRANTIES OTHER THAN THOSE ON THE FACE HEREOFAND DESCRIBED
ABOVE. NO WARRANTIES WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO, ANY
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FORA PARTICULAR PURPOSE SHALLEXTEND
BEYONDTHERESPECTIVE WARRANTYPERIODDESCRIBEDABOVEOFTHREEYEARS.RADIALSHALLNOT
BE RESPONSIBLE OR LIABLE FOR ANY SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES OR LOSS
ARISING FROM THE USE OF THIS PRODUCT. THIS WARRANTY GIVESYOU SPECIFIC LEGALRIGHTS,AND
YOU MAY ALSO HAVE OTHER RIGHTS, WHICH MAY VARY DEPENDING ON WHERE YOU LIVEAND WHERE
THE PRODUCT WAS PURCHASED.
www.radialeng.com
Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam BC V3C 5M5
tel: [phone] • fax: [phone]
email: [email protected] • web: www.radialeng.com
JPC MK3- Manual v2.1 part#: R800-9631-00