Radial JD6 Six Channel Rack Mount DI User Guide

Introduction

Congratulations on your purchase of the Radial JD6 multi-channel direct box. The JD6 is a world-class 19" rack-mountable DI system optimized for keyboards, audio-visual equipment, computer sound cards, samplers, electronic drums, and instruments of all types.

This manual provides details on the JD6's design and features. Key among these are internal grounding options, particularly useful for integrating the JD6 with keyboard racks and audio-visual systems.

For questions or applications not covered, visit www.radialeng.com for the Questions and Answers section, or email info@radialeng.com.

The JD6 Design Concept

The modern live sound environment increasingly integrates portable computers and sound cards, alongside DJ equipment. This shift necessitates new interfaces to manage these diverse audio sources. The JD6 addresses this need, bridging the gap between road-ready touring gear and project studio setups.

The design prioritizes ease of use, adaptability to various setups, compact rack density, and exceptional sound quality. Crucially, it aims to solve common ground loop problems that affect keyboard technicians.

Development of the JD6

The Radial JD6 is a 6-channel evolution of the successful Radial JDI direct box, replacing the Radial JD4 as the standard 19" rack-mounted direct box. Channels 1 and 2 offer enhanced functionality, acting as problem solvers for stage and studio. These channels feature a high-frequency filter, a merge function to combine stereo inputs to mono, and selectable 1/4" or RCA inputs for improved AV and computer interfacing. Channels 3 through 6 provide standard DI functionality for keyboards, electronic drums, and other devices.

The JD6 is a passive direct box utilizing high-quality Jensen™ audio transformers for superior performance, handling high signal levels without saturation and exhibiting minimal distortion (<0.006% at 20Hz) and phase deviation (<4° at 20Hz). This ensures accurate reproduction of dynamic signals like a sampled grand piano without altering tone or introducing distortion.

Channels 1 and 2 feature priority switching jacks, where front panel jacks take precedence over rear panel jacks. This is advantageous in studio setups for quick signal path reconfiguration, acting like a patch bay.

For touring efficiency, optional extension panels are available. Each channel also has internal grounding switches, allowing engineers to select between floating and chassis grounding for maximum flexibility.

Built for demanding environments, the JD6 features a welded 14-gauge steel chassis, baked enamel finish, high-cycle switches, and glass-filled polymer connectors with nickel silver contacts for durability. It comes with a 3-year limited warranty.

Features and Functions

The front panel of the JD6 features controls for each channel. Key features include:

• -15dB Pad: Reduces signal level from high-output sources like CD players or headphone outputs. It is generally not needed for instruments like basses or guitars. Note: When using a headphone output, set the headphone level to zero before activating the -15dB pad.
• 8kHz Filter (Channels 1 & 2): A low-pass filter that rolls off frequencies above 8kHz, designed to remove hiss and noise from older equipment or high-frequency hash from modern electronics. It can also help reduce noise from electromagnetic fields. This filter is engaged by pressing the -15dB pad button.
• 180° Polarity Reverse: Reverses the polarity (absolute phase) at the XLR output (pin-2 and pin-3). Useful for interfacing with older equipment or creatively mixing direct and mic'd sources.
• Ground Lift: Disconnects pin-1 at the XLR output, providing 100% isolation. This helps eliminate noise from ground loops and hum. Lifting the ground connection assumes the JD6 will be grounded at the input. Note: Internal chassis ground lift switches are factory set to 'float' for isolation between channels.
• Input Connectors (Channels 1 & 2): Features both front and rear 1/4" input and thru-put connectors. Front jacks have priority switching, meaning they temporarily disconnect the rear jacks when a plug is inserted. This is useful for studio patch bay functionality.
• Thru-put Connector: Passes the direct signal to an instrument amplifier or sub-mixer. On channels 1 & 2, these are duplicated on the front and rear with priority switching.
• Merge Function (Channels 1 & 2): Combines left and right inputs into a mono signal at the XLR output. This passive summing function is useful for mixing stereo sources from keyboards or sound modules when mixer channels are limited. The dual RCA inputs also perform this function.
• Input Selector Switch (Channels 1 & 2): Toggles between the 1/4" input and the RCA jacks, allowing quick switching between different audio sources.
• RCA Inputs (Channels 1 & 2): Located on the front panel for interfacing with CD players, computer audio cards, and other AV equipment. Depressing the RCA selector switch diverts both front and rear 1/4" inputs to the RCA jacks. The dual RCA inputs are pre-merged to mono.
• Easy ID Label Zones: Areas on the front and rear panels for labeling channels with a wet-erase or wax pencil, aiding in complex setups.

Rear Panel Connections

The rear panel connections are similar for all channels, featuring XLR balanced outputs and 1/4" input and thru-put connectors. Channels 1 and 2 have switching jacks with front panel priority.

All channels provide a transformer-isolated 600-ohm mic-level output via XLR, capable of driving cables up to 500 feet (165 meters) without introducing noise. The output is designed to be connected to a mixer's mic input or a mic pre-amplifier for optimal level matching and impedance.

Using the JD6

Before connecting, ensure all system levels are off to prevent pops. All switches should be in the OUT (disengaged) position during setup. The JD6 is passive and requires no power. 48V phantom power will not harm the unit.

Connection: Connect the source instrument to the input, an instrument amplifier or personal mixer to the thru-put, and the XLR output to the main mixer.

Troubleshooting:

• If noise is encountered, try lifting the ground.
• If a channel's level seems too high, engage the -15dB pad.
• When recording both a direct feed and a microphone feed, try reversing the polarity for potentially dramatic results.

Grounding Options for the System Engineer

The JD6 offers flexible grounding schemes for noise-free performance. Each channel has a separate XLR pin-1 ground lift. All channels are 100% isolated from each other to prevent crosstalk and ground issues.

Internal ground switches allow bonding circuit ground to the chassis. By default, each channel is 'floating' (isolated). System engineers can configure 'star grounds' by connecting all channel grounds to a single point. These switches are accessible by opening the unit. A ground lug on the rear panel can be used to connect the JD6 chassis to a rack or ground bus.

Channel 1 also features a side-access ground switch for single-channel chassis grounding, activated with a small screwdriver.

Note: Chassis grounding is typically not required due to the JD6's inherent isolation. It is recommended to leave internal switches in their factory-set 'float' position unless you are a qualified system engineer.

Typical Stage Set-up

A common stage setup involves connecting a computer sound card to channels 1 & 2, keyboards to channels 3 & 4, and sound modules to channels 5 & 6. The computer can use either the front panel 1/4" jacks or the RCA jacks.

Diagram Description: The diagram illustrates a concert setting where multiple audio sources (computer, keyboards, samplers) are connected to the Radial JD6. Balanced outputs from the JD6 are routed to the house mixing console. A separate connection is shown from the JD6 to the musician's personal mixer.

Optional Output Panels

For touring convenience, Radial offers hook-up panels to extend JD6 outputs:

• JD6-X6: A simple XLR breakout panel with 3-foot and 6-foot extensions, allowing mounting on the keyboard rack for easier connections and reduced cable clutter.
• JD6-X12: Designed for systems using two JD6 units (12 channels). It uses a 37-pin multi-connector with multi-pin to XLR male breakouts, enabling quick connection of 12 keyboard signals with a single twist, significantly speeding up setup and teardown on multi-date tours.

The Advantage of Going Passive!

The Radial JD6 is completely passive, requiring no external power. It utilizes high-quality Jensen JT-DBE audio transformers to bridge the input and XLR output. Passive designs offer advantages over active devices, primarily by eliminating noise, ground loops, and stray voltages due to the isolation provided by the transformer's primary and secondary coils.

The quality of the transformer is crucial for a passive DI. The JD6 uses Jensen transformers, known for their smooth, distortion-free response across a wide frequency range (10Hz to 40kHz), ensuring accurate audio reproduction.

Radial JD6 - Questions & Answers

Can I also use the JD6 with guitars and basses? Yes, the JD6 uses the same audio circuit as the Radial JDI and is suitable for guitars, basses, and most instruments.

Can I use the JD6 backwards like a re-amping device? Yes. Record a dry guitar track, send it back to the JD6's XLR output (as input), and connect the JD6's guitar input (as output) to your amplifier.

What about combining left and right keyboard outputs? Directly 'Y-jacking' stereo signals can cause issues like phase cancellation and potential damage to the keyboard. The JD6's merge function acts as a resistive mixer to prevent this.

If I use the front panel input on channel-1, will both thru-puts still work? No. Channels 1 and 2 have switching jacks with front panel priority. Connecting a plug to the front jack diverts the signal and disconnects the rear connection until the front plug is removed.

How many keyboard players does it take to change a light bulb? Just hit auto transpose and it makes the changes for you!

Are active direct boxes better than passive DIs? It depends. Passive DIs can eliminate noise and hum while sounding great, largely due to the transformer quality. Active DIs are suited for passive instruments or devices not connected to the power grid. For keyboards, a good passive DI is often preferred.

Why is a passive direct box better for keyboards? Keyboards, computers, and AV equipment are prone to noise and ground loops from being connected to power outlets. Passive DIs with isolation transformers prevent these stray fields and voltage differentials from causing system noise.

Will phantom power hurt the JD6? No, the JD6 is passive and is not affected by 48V phantom power.

Radial JD6 Six Channel DI Specifications

Specifications are subject to change without notice.