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Radial Engineering   

 

      JDI User Guide

3

Part 3 – The JDI Quick Start

This section is for advanced users — it provides a quick set of instructions for those that are familiar with direct boxes and 

gets right down to action!  We suggest that you read through the entire manual for a better understanding of your JDI. 

Caution! 

When connecting or disconnecting any audio device always ensure the power is off or all levels are set to 

zero.  This practice will reduce the opportunity for any noise such as a capacitor discharge from being sent through the 

amplifier to the speakers, which could cause a big bang in your sound system or even cause a speaker to blow.  This 

is especially true with phantom powered equipment.

The Radial JDI Mk3 is a passive direct box and as such does not require any external power such as phantom or batteries 

to make it work. Just plug-in and play!

To start, make sure all switches are in the ‘out’ position. Plug the instrument into the INPUT. Connect the THRU to the guitar 

amplifier or keyboard mixer and the XLR OUTPUT to the PA or mixing console. Set the PAD to 0dB. Slowly turn up the input 

level at the mixer and listen. See the Part 5 ‘Features and functions’ section about the ‘MERGE’ function. 

The JDI’s Jensen audio transformer should be able to handle most instrument signal levels without distortion. At exceptionally 

high signal levels, the –15dB pad should be used to reduce the input level to the transformer. If you hear distortion, simply 

depress the –15dB pad button. If you intend to use the JDI in parallel with a speaker load, it is important that you read the 

details on this application in the ‘Part 5 - Features and Functions’ section of this manual. 

Since the Radial JDI employs an audio transformer, you are actually isolating the electrical connections between the input and 

output. This will usually eliminate all buzz and hum caused by so called ground loops. The JDI is designed to be grounded 

at either the input or the output side of the transformer. If you encounter 60-cycle hum or noise, lift the ground at the XLR 

output. This will assume the JDI is deriving its ground at the input from the instrument or instrument amplifier. 

The JDI also features a polarity reverse.  This reverses pin-2 and pin-3 at the XLR. As the JDI is set following the AES 

standard with pin-2 hot; reversing the polarity is generally not required unless the instrument is being both DI’d and mic’d. 

The polarity reverse switch would allow both the mic and the JDI to be set ‘in phase’ should these be reversed.

You are ready to go!  Now... close your eyes and listen. The JDI is without a doubt, one of the most musical DI boxes ever 

manufactured.

True to the Music

Summary of Contents for JDI Mk3

Page 1: ...g 1638 Kebet Way Port Coquitlam BC V3C 5W9 tel 604 942 1001 fax 604 942 1010 email info radialeng com web www radialeng com Radial Engineering is a division of C TEC JP CableTek Electronics Ltd JDI and www radialeng com DUPLEX Mk3 ...

Page 2: ... your JDI 11 7 Frequently asked questions 12 8 Block diagram and specifications 15 Warranty Back cover 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 Radial Engineering Ltd is a division of C TEC JP CableTek Electronics Ltd Features and specifications are subject to change without notice ...

Page 3: ...on or crosstalk For simplicity this manual will discuss the JDI All features and functions on the Duplex are identical to those of the JDI Both direct boxes employ the Jensen JT DBE transformer for unmatched audio performance exceptional noise rejection and high signal handling This makes them ideal for acoustic guitar bass and keyboards In fact just about any audio signal is transformed gracefull...

Page 4: ...formance 7 Full bottom no slip pad reduces slipping in use and provides mechanical and electrical isolation 8 Double sided PC board military grade circuit board features a full ground plane for maximum protection against stray magnetic fields and RF noise 9 XLR output connector wired to the AES standard with pin 1 ground and pin 2 hot provides a balanced 150 Ohm mic level signal 10 POLARITY switch ...

Page 5: ...dio transformer should be able to handle most instrument signal levels without distortion At exceptionally high signal levels the 15dB pad should be used to reduce the input level to the transformer If you hear distortion simply depress the 15dB pad button If you intend to use the JDI in parallel with a speaker load it is important that you read the details on this application in the Part 5 Featur...

Page 6: ...eproduce the most accurate picture of the source no matter what the instrument Direct boxes perform the important function of impedance matching and signal balancing This means that they take the high impedance output from a guitar or keyboard and transform it to the low impedance signal used in balanced sound systems Balanced signals inherently cancel noise and due to their lower impedance can tr...

Page 7: ...s a mic level signal This allows the JDI to be used alongside other microphone signals without introducing cross talk or causing transformer saturation when driving the signal through the mic bridging transformers of a splitter The magic of a great transformer The Radial JDI is a passive direct box this means that it employs a transformer to convert the impedance and balance the signal At Radial w...

Page 8: ...nd buzz An audio laboratory test called The Green Report visit www radialeng com for details pitted the JDI against three other direct boxes commonly used in professional audio The tests showed that the JDI could handle more gain before distortion was more linear throughout the audio frequency range and showed significantly less phase distortion All boxes tested well at 1kHz but as the frequency dr...

Page 9: ...ruments such as acoustic guitar to be connected to the DI and then to the snake system using the Lo Z XLR output splitting the signal to feed the stage monitor mixer for foldback just as microphones are In this case the thru jack would not be used The MERGE switch The JDI features an innovative merge function that turns the input and the thru put into a left right to mono mix Depressing the merge ...

Page 10: ...d Connection is made to the mic level input of the mixing console or to a standard mic pre amplifier The JDI is ideally suited for interface with concert snake systems and splitters where mic and direct box signals are directed to several destinations at the same time such as recording monitor broadcast and front of house mix positions The POLARITY switch A polarity reverse toggles the XLR pin 2 an...

Page 11: ... at the mixing console If you are using the thru put to your personal amp then your amp and the mixer will have ground paths and lifting the ground would then be considered Parallel speaker connection and the SPEAKER switch IMPORTANT THE JDI IS NOT A LOAD BOX You must ensure that the amplifier is connected to it s speaker load first as the JDI is not designed to handle the load on its own There are ...

Page 12: ...ctors and an external book end design steel shell designed to protect the switches and jacks from overzealous roadies and other rigors of touring Both boxes are made from 14 gauge steel and protected by a heavy baked epoxy finish that will look great even after years of service Inside the mil spec PC board is two sided which means that all components are soldered twice Further the dual shell enclos...

Page 13: ...put using a female to female XLR turn around adaptor Keep your level down to ensure the signal will not overload the JDI s transformer Connect the input of the JDI to the input of the guitar amplifier and you are set to go Use the Radial JDI for long cable runs High impedance coax cables are susceptible to noise if they exceed 25 feet Balanced lines on the other hand split the signal into two low i...

Page 14: ...s such as phase distortion Best of all passive DI s eliminate ground loops Q Why do people use active direct boxes A There are two reasons that active DI boxes like the Radial J48 have become popular To get good sound with a passive direct box you need to use a high quality transformer like a Jensen which can be quite expensive This cost dissuades many manufacturers from building passive DI s a ba...

Page 15: ... typically 48 volts and about 5mA When phantom is on it will not harm the JDI Q What is phase distortion A Keeping your signal in phase is akin to making sure that when you play guitar the sound coming from the low E string plays at the same time as the G string as they come out of your amp You may take this for granted but the fact is phase distortion can cause an instrument to get lost in the mi...

Page 16: ...duce personality to the sound and should be viewed in the same way as one views a tube microphone Q If my JDI ever fails what do I do A In the past 10 years the JDI has been so reliable that it is a rare occurrence when we need to repair one If however something goes bad a switch for example simply call Radial and we will issue a return authorization number for you to send it back to us for repair...

Page 17: ...ced 140k Ohms typical Output impedance Balanced 150 Ohms typical Frequency response 10Hz to 40kHz Linear performance 0 22 dBr deviation 20kHz Total harmonic distortion 0 05 20Hz 0 005 1kHz Phase distortion 4º at 20Hz 0 3º at 1kHz CMR 100dB 60Hz Maximum input level 22dBu Size 3 5 wide 2 high 5 5 deep Weight 1kg 2 2lbs Construction Welded 14 gauge steel Finish Baked enamel finish JDI Block Diagram ...

Page 18: ...laim 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...

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