Radial Engineering JDI Manuale utente

JDI STEREO USER GUIDE

JENSEN TRANSFORMER EQUIPPED

PASSIVE DIRECT BOX

Radial Engineering Ltd.

1845 Kingsway Ave., Port Coquitlam, BC V3C 1S9, Canada

Tel: 604-942-1001 • Fax: 604-942-1010 • Email: [email protected]

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

RADIAL JDI STEREO PASSIVE DIRECT BOX

USER GUIDE

Introduction....................................................................................... 1

JDI Stereo Features ......................................................................... 2

Making Connections......................................................................... 3

Using the PAD .................................................................................. 4

Using the Ground Lift........................................................................ 4

Passive vs. Active............................................................................. 5

Understanding Loading .................................................................... 6

Optional Mounting Accessories ........................................................ 7

Specications ................................................................................... 8

Block Diagram .................................................................................. 9

Radial Limited Warranty ...................................................Back Cover

Thank you for purchasing the Radial JDI Stereo. This marvelous passive direct box employs two great sounding Jensen

transformers to convert the impedance and balance the signal. Jensen transformers are legendary in their ability to transfer the

minute details of your most cherished instrument and gracefully handle transients without choking. This makes the JDI Stereo

a very effective D.I. box for all types of instruments.

The JDI Stereo is in fact a very easy to use direct box that is purposely made to be compact and quick to deploy. You simply

plug in and it works. No power required. There are however some great features that are built in that should be understood in

order to get the most out of your JDI. So please take a few minutes to go through this user guide to ensure you get the most out

of it. If after you have read it, you nd yourself asking questions; please visit the FAQ section on the web page. This is where

we post updates and questions from users. If you still do not nd the answer or need further clarication, we invite you to send

us an email at [email protected] and we will do our very best to reply in short order.

Now get ready to enjoy what can only be called the best sounding passive direct box ever made!

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

FEATURES

1. -15dB PAD: Reduces the input sensitivity of the left

channel to prevent overload.

2. ¼" INPUTS: Left and right unbalanced, hi-Z inputs used

to connect instruments.

3. ¼" THRU-PUTS: Left and right parallel outputs used to

connect the hi-Z instrument signal to an amplier, tuner

or personal monitoring system.

4. -15dB PAD: Reduces the input sensitivity of the right

channel to prevent overload.

5. I-BEAM REINFORCED: 14-gauge steel enclosure with

rigid I-beam construction makes it impossible to torque

the PC board and cause solder joints to go cold.

6. BOOKEND DESIGN: The bookend design creates a

protective zone around the switches and connectors.

7. XLR OUTPUTS: Left and right balanced, low-Z mic-level

output. Wired to AES standard pin-1 ground, pin-2 hot

(+) and pin-3 cold (-).

8. GROUND LIFT: Disconnects pin-1 at both XLR outputs

to reduce hum and buzz caused by ground loops.

9. FULL BOTTOM PAD: Isolates the D.I. from the amp

chassis and keeps it from sliding around on busy stages.

4 5

6 9

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

OVERVIEW

MAKING CONNECTIONS

The Radial JDI is a passive direct box. This means that it does not require any power to make it work. You simply plug in and it

will quietly go to work. Further, as the JDI Stereo employs transformers, these naturally block stray DC voltage that can cause

system noise. This also means that 48V phantom power as used with condenser microphones will not harm the JDI Stereo.

As with all audio gear, always ensure audio system levels are turned down or equipment turned off before making connections.

This will avoid plug-in or turn-on transients from damaging more sensitive components such as tweeters.

There are two channels on the JDI Stereo. These are identical and feature a ¼" INPUT, a ¼" THRU-put and a balanced XLR

out. Connect your source instrument to the input and the balanced XLR out to the PA system or recorder. The THRU connector

provides the means for connecting the instrument to a stage amp or personal monitor system. Simply connect the THRU to your

amp or monitor. Unbalanced cables are much more susceptible to noise than their balanced counterparts. Keeping unbalanced

cables under 8 meters (25') in length is good practice while balanced cables can easily extend 100 meters (300'). The balanced

output of the JDI Stereo is mic level, meaning that it should be connected to the mic input of a mixing console or mic preamp.

Amp

Thru Thru

MonitorsSub-Mixer

Input

Using the JDI Stereo with a bass and stage amp JDI Stereo with a keyboard, mixer and powered speaker

Inputs

Balanced Outs Balanced Outs

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

USING THE -15dB PAD

USING THE GROUND LIFT

Inside the JDI Stereo are two high performance Jensen transformers. These can be hit hard with plenty of level without worry.

In fact, many artists and engineers enjoy the sound of the JDI when pushed hard as it will exhibit a natural compression when

the transformer is pushed towards saturation.

There are however instances when the output from an instrument can be extreme. To prevent from excessive saturation, the

JDI Stereo has a -15dB input pad that reduces the input sensitivity. Examples could be a very high output digital piano or maybe

the overly aggressive output from a DJ mixer.

Passive direct boxes like the JDI Stereo are particularly effective at reducing hum and buzz by so called ground loops. But

ground loops manifest themselves in many different ways including induced DC noise into the cable from nearby power supplies

or transformers, DC offset currents from less than ideal electronic designs, or simply a bad electrical supply that is causing

havoc. The Jensen transformers will block DC current while passing audio.

To further assist, the JDI Stereo is equipped with a ground lift switch that lifts pin-1 on both XLR connectors at the same time.

When the electrical ground and the audio ground conict, you can encounter noise and simply lifting the audio ground will

usually solve the problem.

The image above shows an audio source and a destination with a common electrical ground. As the audio also has a ground, these

combine to create a ground loop. The transformer and ground lift work together to eliminate the ground loop and potential noise.

60Hz

Hum

GROUND LOOP HUM

TRANSFORMER

BREAKS THE LOOP

ELECTRICAL GROUND PATH

EMI & RADIO NOISE

SOURCE RECEIVE

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

PASSIVE VS. ACTIVE

THE VARIOUS INPUT IMPEDANCE

As a direct box, the JDI Stereo will work with almost any instrument. It is however important to understand a few fundamentals.

The JDI Stereo is passive. This means that it does not require any power to make it work. This also means that it employs the

signal from the source instrument as the ‘drive’ which produces the balanced signal for the PA system or recorder. This also

means that if the input signal is very low, there may not be a strong enough signal to effectively drive the JDI. This is why pas-

sive direct boxes are usually recommended with active sources and active direct boxes like the Radial J48 are recommended

for passive sources.

Examples of relatively low output passive sources include an old Fender bass, piezo pickups and some sound hole acoustic

guitar pickups. Examples of higher output active sources include basses and acoustic guitars with built-in electronics (and a

battery), electronic keyboards and DJ mixers. Active sources are ‘powered’ and are able to produce a more powerful signal

than passive sources.

Radial makes a number of direct boxes to handle just about any situation. These differ by being active or passive and will have

a different input impedance depending on the desired use. As a rule: the higher the input impedance the ‘brighter or glassier’

the tone. The lower the input impedance; the ‘warmer and smoother’ the tone.

You will note that some of this information is conicting. This has to do with personal preference. For instance, sound engineers

tend to prefer to use an active direct box like the J48 with an acoustic guitar as it tends to give the sound more sparkle. Some

bass players prefer the sound of their old P-Bass through a passive direct box like the JDI as it sounds warm and smooth. So

these are merely guidelines.

With piezo transducers, the rules change as these devices tend to sound much warmer and less peaky when presented with

a very high input impedance. The Radial PZ-DI has a load switch that lets you select between 220kΩ like the J48 for magnetic

pickups 1MΩ to follow the original impedance as set by Leo Fender and a 10MΩ input for piezos.

Model Input impedance Application

JDI 130,000Ω (130kΩ) Active/passive bass, acoustic guitar, keyboard, DJ mixer

J48 220,000Ω (220kΩ) Passive bass, acoustic guitar

PZ-DI 10,000,000Ω (10MΩ) Piezo transducer

130kΩ 98%

Amp

Mixing Console

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

UNDERSTANDING LOADING

A problem that was detected early on was the sound or effect that a transformer can impose on an instrument. Back in the early

days of direct boxes, 600Ω broadcast or telephone transformers were used. These had such a low impedance that almost half

of the signal from the instrument would be sent to the mixing desk, leaving very little left for the musician’s amp on stage. Pas-

sive basses would sound listless and have no punch. Active D.I. boxes solved the problem by increasing the input impedance

and buffering (amplifying) the signal to drive it.

The JDI’s input impedance is 130,000Ω – quite different from the old 600Ω days. This means that the JDI will not load down the

pickup, which in turn means that the THRU output going to the stage amp will sound just ne.

600Ω50%

50%

Amp

Mixing Console

600Ω

J-Rak 8 J-Rak 4

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

OPTIONAL RACK MOUNTING KITS

J-CLAMP

The J-Rak 8 and J-Rak 4 are an innovative rack mount chassis. The J-Rak 8 has eight vertical slots for Radial JDI Stereo direct

boxes or the other Radial J-Class products. The J-Rak 4 has four horizontal slots.

Each direct box can be front or rear mounted allowing the system designer to have the XLR’s on the front of the rack or rear,

depending on the application.

The J-Clamp is a mounting adapter that allows any of the

Radial J-Class products to be permanently mounted in loca-

tions such as in podiums, under board room tables and inside

amplifIer and effect racks. Features a heavy-duty steel shell

with built in mounting ange and user-writable tabs.

Radial Engineering Ltd. JDI Stereo™ Direct Box User Guide

SPECIFICATIONS

Audio circuit type: ................................................................................................................... Passive, transformer isolated

Frequency response:..........................................................................................................................20Hz ~ 20KHz (±3db)

Dynamic range: .......................................................................................................................................................... 135dB

Maximum input: ..............................................................................................................................+21dB @ 20Hz ~ 20kHz

Phase deviation:..........................................................................................................................0.3° @ 100Hz; 3° @ 20Hz

Input impedance:....................................................................................................................................130kΩ, unbalanced

Output impedance: ...................................................................................................................................... 150Ω, balanced

Transformer: .............................................................................................................................. Jensen JT-DB-E, 12:1 ratio

Shield:.......................................................................................................................................Dual Faraday, mu-metal can

Input pad:.....................................................................................................................................................................-15dB

XLR conguration:......................................................................................................................... AES standard (pin-2 hot)

Construction: ............................................................................................................... 14 gauge steel chassis & outer shell

Finish:.................................................................................................................................................. Durable powder coat

Size (LxWxD):............................................................................................... 5" x 3.3" x 1.8" (127mm x 84.1mm x 45.5mm)

Weight: .................................................................................................................................................1.55 lbs (703 grams)

Shipping size (LxWxD): ....................................................................................... 6.5" x 4" x 3" (165mm x 102mm x 76mm)

Shipping Weight: ...............................................................................................................................1.92 lbs (870.9 grams)

Power: ....................................................................................................................................... Passive, no power required

Conditions:.......................................................................................... For use in dry locations only between 5°C and 40°C

Warranty: .................................................................................................................................... Radial 3-year, transferable

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