Radial Engineering Reamp kit User's Guide

www.radialeng.com

J48

User Guide

Radial Engineering
1638 Kebet Way, Port Coquitlam BC V3C 5W9 tel: [phone] • fax: [phone]
email: [e-mail] • web: www.radialeng.com

Radial Engineering is a division of C•TEC (JP CableTek Electronics Ltd.)

RADIAL J48 MK2 USER GUIDE

TABLE OF CONTENTS PAGE

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

Input & output panel feature set .............................................2

J48 - Quick start for pros ........................................................4

Direct box basics .....................................................................5

Features and functions ............................................................8

Frequently asked questions ....................................................13

Block diagram and specifications ............................................15

Warranty ..................................................................................Back cover

Radial Engineering
1638 Kebet Way, Port Coquitlam BC V3C 5W9
tel: [phone] • fax: [phone]
email: [e-mail] • web: www.radialeng.com

Radial Engineering Ltd. is a division of

Features and specifications are subject to change without notice.
J48 MK2 - Manual V3.1 05/20/05 part #: R800-9616-00

C•TEC

(JP CableTek Electronics Ltd.)

INTRODUCTION

Congratulations on your purchase of the Radial J48™ direct box.
Three years in the making, the J48™ is a unique direct box that has been
designed to handle the new generation of active battery-equipped
acoustic guitars and basses that often overload typical direct
boxes and cause distortion. Best of all, the J48 does so without
the use of batteries.

The secret is the J48’s internal digital switching power
supply that converts 48V-DC phantom power to produce
a higher internal rail voltage. This allows the J48 to
handle transients of up to 9 Volts without choking.
More dynamic headroom results in less square wave
distortion. In fact, every aspect of the J48™ design
has been optimized for maximum headroom while
introducing minimal phase, harmonic and inter-modu­lation distortion.

But this is not all: the Radial J48 features a transformer
that isolates 48V phantom power to help eliminate
ground loops while removing hash and system noise.
This ensures that what you put in - you get out. Nothing
altered, nothing changed: just the pure and natural tone
of the instrument.

We invite you to read through this manual before using your
Radial J48 so that you can maximize it’s potential. Please log onto
www.radialeng.com for further details and updates. We also invite you
to forward any comments, questions or suggestions to [e-mail].
We love to hear from you!

True to the Music

Enjoy.

Radial Engineering J48 User Guide

1

INPUT AND OUTPUT PANEL FEATURE SET

True to the Music

1. -15dB pad switch
A provisional -15dB pad reduces the input signal to the
circuit to ensure a clean and distortion-free signal is
obtained.

2. 48V check LED
Used in conjunction with the low-cut filter switch to
check for phantom power.

3. Left-right merge switch
A unique ‘merge’ function turns the input and thru-put
connectors into a pair of left-right inputs with mono
output at the XLR.

4. 1/4” input and thru-put jacks
These are used to connect the instrument to the direct
box and the direct box to the instrument amplifier.

5. Protective bookend cover
The innovative bookend cover provides protection to
switches and connectors against damage during hectic
stage set-ups.

Radial Engineering J48 User Guide

6. XLR male output
This male XLR output connector is wired to the AES
standard with pin-1 ground and pin-2 hot and puts out a
600-ohm mic level signal.

7. Polarity reverse 180º
This toggles the XLR pin-2 and pin-3 to interface
with older equipment. Also used when combining two
sources (mic & DI) on the same instrument to avoid
phase cancellation.

8. Low-cut filter (-6dB down at 80Hz)
Gently rolls off bass to reduce rumble and acoustic
resonance. Dual function switch also used to check
presence of 48V phantom power.

9. Ground-lift switch
This ground-lift switch breaks the ground between the
input & the output to eliminate hum and noise caused
by ground loops.

10. Full bottom no-slip pad

Provides mechanical isolation to reduce slipping and
electrical isolation from amplifier frames and handles.

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True to the Music

11. Welded I beam construction
For maximum durability, a 14 gauge steel welded
I-beam construction for a lifetime of trouble free
performance.

12. Silent, high cycle switches
Super high repetition switches withstand heavy use
and heavy fingers. “Make before break” design
eliminates pops and clicks when toggling switch posi­tions.

13. Double sided PC board
The military grade double-sided PC board provides
maximum durability and added resistance against
cold solder joints.

Radial Engineering J48 User Guide

14. Power supply transformer
The transformer in the power supply helps eliminate
ground loops by isolating the power coming in from the
XLR’s 48V phantom feed.

15. Digital DC to DC switching power supply
Steps up phantom power to produce higher internal
rail voltage. This provides more headroom and results
in less distortion and a more natural sound.

16. Oversized capacitors
Oversized capacitors produce maximum headroom.

17. Baked-on enamel finish
Great looks on stage or in the studio for years to
come.

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True to the Music

THE J48 QUICK START

This section is for advanced users. It provides a quick set of instructions for those that are familiar with direct boxes. For
up and coming engineers, we suggest that you read through the manual before using your Radial J48.

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 probability of 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 J48 is an active direct box and as such requires standard 48V phantom for powering as found on most consoles
and pre-amps. Before you start, make sure the phantom power has been turned on at the console. You can check for the
presence of 48V phantom by depressing the low-cut filter switch. If phantom is present, the LED on the front panel will
illuminate for a moment.

Now, make sure all switches are set 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 recording mixing console.

With the PAD set to 0dB ( out position), slowly turn up the input level at the mixer and listen. The J48 should be able to
handle most instrument levels without any problems. For exceptionally high signal levels such as from digital pianos, sam­plers and high-output basses, inserting the –15dB pad will reduce the input level to the active circuit. If you hear distortion,
simply depress the –15dB pad. To reduce low frequency mud and run-away acoustic resonance, the J48 is equipped with
a low-cut filter that gently rolls off bass (-6db at 80Hz). This has the added benefit of increasing the dynamic range when
depressed.

Since the Radial J48 employs a transformer in the power supply, you are actually isolating the input and the output electri­cal connection. This will eliminate most buzz and hum caused by so-called ground loops. If you encounter 60-cycle hum
or noise, it is likely that you have a different ground potential at the input and output of the J48. Depressing the ground lift
(break) switch will generally solve the problem.

The J48 also features a polarity reverse. This reverses pin-2 and pin-3 at the XLR. As the J48 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.
If so, the polarity reverse switch would allow both the mic and the J48 to be set ‘in-phase’ should these be reversed.

You are now ready to go! Now, close your eyes and listen. The J48 is without a doubt one of the most musical DI boxes
manufactured today.

Radial Engineering J48 User Guide

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