www.radialeng.com JDI and Mk3 DUPLEX User Guide 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 is a division of C•TEC (JP CableTek Electronics Ltd.
RADIAL JDI & DUPLEX USER GUIDE TABLE OF CONTENTS PAGE 1. Introduction .................................................................................1 2. JDI feature set ............................................................................2 3. JDI quick start ...........................................................................3 4. Direct box basics .........................................................................4 5. Features and functions ............................................
True to the Music Part 1 - Introduction Congratulations on your purchase of the world’s finest direct box! The Radial JDI Mk3 is the latest version of the highly acclaimed JDI and is without a doubt the finest passive direct box available today. The JDI is very unique in that it does not color or alter the sound in any way. This ensures the natural tone and harmonic balance is retained, bringing out the very essence of the instrument.
True to the Music Part 2 – The JDI Feature Set (1) 15dB PAD switch - a -15dB pad can be introduced to reduce the input voltage and ensure a clean, distortionfree signal. (8) Double sided PC board - military grade circuit board features a full ground plane for maximum protection against stray magnetic fields and RF noise. (2) MERGE switch - left-right merge function turns the input and thru-put connectors into a pair of left-right inputs with a mono output at the XLR.
True to the Music 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.
True to the Music Part 4 – Direct Box Basics What is a direct box anyway? The name ‘direct box’ comes from ‘direct insertion 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.
True to the Music Getting to know your Radial JDI Mk3 As a rule, all direct boxes follow the same basic procedures when connecting them to a sound system. The instrument plugs into the INPUT, the musicians’ instrument amplifier connects to the THRU and the mixer or recorder is connected to the XLR ‘OUTPUT’.
True to the Music flow. Varying the number of windings on the input and the output allows us to control the input and output impedance ratio. This is where the specification ‘10k : 150-Ohms’ comes from. The beauty of a transformer is that there is no electrical connection between the primary and the secondary. The signal is ‘transformed’ from electrical energy to magnetic, then back to electrical; in effect, a ‘magnetic bridge’.
True to the Music Part 5 – Features and Functions The ¼” INPUT and THRU connectors The JDI features two ¼” jacks on the input panel. These are designed to accept normal instrument input levels from basses, guitars, keyboards, drum machines, etc. The left-most ¼” input is normally connected to the source instrument. The ¼” connector to the right of the input is normally used as a ‘thru’ connector and feeds the instrument signal to the musician’s amplifier.
True to the Music Understanding input distortion and using the –15dB PAD switch Today, many acoustic guitars and basses have battery powered active pre-amplifiers that boost their pickup output signal. These high gain pre-amps often generate between 2-volts and 7-volts at their outputs. This high voltage can saturate the input of most direct boxes causing a harsh square wave distortion.
True to the Music The Radial JDI features an isolation transformer that will generally eliminate most of this type of noise. But in severe cases, lifting the ground on pin-1 at the XLR by depressing the GROUND switch can help. When lifted, this assumes the ground will be derived by connection of the THRU, through the cable shield, to grounded equipment such as an amp.
True to the Music The JDI’s parallel speaker connection feature lets you do this by connecting the JDI directly to the speaker cabinet. It is important to note that the JDI is NOT a load box; you must have a load such as a speaker connected to the amplifier, as connecting the JDI directly without a load could cause severe damage to the equipment. Connect your amp as usual, then connect a ¼” to ¼” cable from the second (parallel) speaker cabinet jack to the JDI.
True to the Music Part 6 – Other cool uses for your JDI Use the Radial JDI to re-amplify your signal! Today, a popular studio effect is to record a signal such as guitar, voice or keyboard on a track and then run the pre-recorded track back through a guitar amplifier or effect pedal. This effect is known as reamping or re-amplifying and was started by Les Paul in the 1950’s and was widely used on recordings by the Beatles in the 60’s, and by Steely Dan in the 1970’s.
True to the Music Part 7 - FAQ’s or Frequently Asked Questions Q: What is the difference between active & passive? A: Active DI’s have a built-in pre-amp that requires battery or 48V phantom power to run, while passive DI’s use a transformer to convert the signal and do not require any power supply. Both ‘transform’ or convert the instrument’s high-impedance output to a low impedance balanced microphone level. This allows long cable runs without adding unwanted noise.
True to the Music Q: Why is loading no longer a concern? A: Back in the 1970’s, acoustic guitars did not have the sophisticated pickups and built-in pre-amps that are standard now. Today, most electric basses incorporate high-output pickups or have active electronics built in. Acoustic guitar pre-amps and keyboards can have equally high output levels. These high output levels are so powerful that loading is no longer the concern. The ‘fix’ has in fact caused a new problem – input distortion or saturation.
True to the Music Q: Is a flat frequency response better than a colored response? A: This is a good question. When buying a large condenser microphone, you are most often not getting a flat response mic, but a mic colored or flavored to add to your sound palette. Most studios boast a selection of mics and the sign of a good engineer is one that knows ‘which mic to use on what’ in order to get a particular tone. With direct boxes, this is usually not the case.
True to the Music Part 7 – Block diagram and specifications JDI Block Diagram JDI Mk3 (and JDI Duplex) Specifications Type Passive Jensen Transformer equipped Input impedance Unbalanced 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.
RADIAL ENGINEERING (a division of J.P Cabletek Electronics Ltd.) warrants this product to be free from defects in material and workmanship to the original owner 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.
