Radial Engineering J48 MK2 Manual de usuario
User Guide
Radial Engineering
1638 Kebet Way, Port Coquitlam BC V3C 5W9 tel: 604-942-1001 • fax: 604-942-1010
email: [email protected] • web: www.radialeng.com
Radial Engineering is a division of C•TEC (JP CableTek Electronics Ltd.)
J48
www.radialeng.com
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: 604-942-1001 • fax: 604-942-1010
email: [email protected] • 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.
J48 MK2 - Manual V3.1 05/20/05 part #: R800-9616-00
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-modu-
lation 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 info@radialeng.com.
We love to hear from you!
Enjoy.
True to the Music
Radial Engineering J48 User Guide
1
True to the Music
INPUT AND OUTPUT PANEL FEATURE SET
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.
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.
Radial Engineering J48 User Guide
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Radial Engineering J48 User Guide
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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 posi-
tions.
13. Double sided PC board
The military grade double-sided PC board provides
maximum durability and added resistance against
cold solder joints.
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.
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, sam-
plers 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 electri-
cal 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.
True to the Music
Radial Engineering J48 User Guide
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True to the Music
Radial Engineering J48 User Guide
5
DIRECT BOX BASICS
What is a direct box anyway?
The name ‘direct box’ comes from direct insert 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. We take this very seriously with all our direct boxes and as such, have designed these to reproduce
the most accurate ‘picture’ of the source signal no matter what the instrument.
Direct boxes perform several important functions: they are designed as impedance matching and signal balancing devices.
This means that they take the high impedance of a guitar or keyboard and ‘transform’ it to the low impedance used in bal-
anced sound systems. Balanced signals inherently cancel noise and, due to their lower impedance, are capable of very
long cable runs. Balanced signals are the norm in professional recording, broadcast and live sound. By properly matching
the impedance you will enjoy better sound, less noise and an extended frequency response.
Typical DI box setup
True to the Music
Radial Engineering J48 User Guide
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Getting to know your Radial J48
As a rule, all direct boxes follow the same basic procedures when connecting them to a sound system. The instrument plugs
into the IN, the musicians’ instrument amplifier connects to the THRU, while the mixer or recorder is connected from the
XLR ‘OUTPUT’. Since the XLR output connection to the mixer taps the signal before it goes to the musician’s amplifier, this
allows the mixing engineer to ‘capture’ the signal before it is modified by the musician, thus resulting in the purest source
possible. It is important to note that what may sound good on stage may not necessarily sound good in the venue.
By sending an unaltered signal to the front of house mix position (FOH), the engineer is able to get the sound he is look-
ing for with minimal phase and harmonic distortion. This is likely the main reason why Radial direct boxes are so popular.
Radial DI’s do not alter the sound in any way before it gets to the mix position.
High to low impedance conversion and balancing
The Radial J48 features a 220kOhm input impedance for the instrument. As the signal passes through the J48 to the XLR
output, it is converted to a balanced 600-Ohm low impedance signal. This allows long cable runs without introducing noise
into the audio signal path. It is important to note that the output of the Radial J48 is mic level. This allows the J48 to be
used alongside microphone signals without introducing cross-talk or causing saturation when driving the signal through the
mic-bridging transformers of a splitter snake.
Phantom powering
The Radial J48 is an active direct box. This means that it employs a powered circuit to convert the impedance and balance
the signal. The J48 derives its power from the mixing console using remote phantom power. Phantom power is a clever
48V-DC supply that comes from the mixer and runs on top of the audio through the XLR mic cable without affecting the
audio. It was originally designed to provide power to capacitive or condenser microphones.
When direct boxes first appeared they used batteries. The problem with batteries is that when they run low, they cause the
circuit to distort. It’s pretty simple: less power – less headroom. Phantom power solved the problem by providing a remote
power source that could eliminate the battery. Eureka! Phantom power gave us a stable power supply and no batteries to
worry about.
True to the Music
Radial Engineering J48 User Guide
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Dynamic headroom
Years ago when the first phantom powered active direct boxes came around, the “instrument” of the day was a passive
Fender Bass. These instruments would typically generate 1 or 2 peak volts at best. This seemed to work well. Then all of
a sudden, someone decided to put a battery powered pre-amp in the instrument and the output levels increased. Today
basses and acoustic guitars will easily output voltages as high as 7 volts. The result: overload!
With more input voltage, you need more dynamic handling to handle the transients. This means you need a higher inter-
nal rail voltage. The Radial J48 converts the 48V phantom using a similar approach to today’s super-high output power
amplifiers whereby a digital switching power supply is employed to raise the internal rail voltage from the typical 3 volts to
9 volts. Headroom!
Because the J48 is able to handle these transients without overloading, you eliminate square wave distortion. Because of
larger internal capacitors, the circuit is not constantly working at its peak. Harmonic distortion is reduced, inter-modulation
distortion goes down and phase distortion is minimized. The Radial J48 coasts along producing a less stressed and more
musical sound.
Buzz and hum caused by ground loops
Probably the most challenging aspect when setting up a sound system is reducing system noise. The most common problem
is buzz and hum due to ground loops. This is generally caused by two separate ground paths with different voltage poten-
tials interacting together, such as an AC powered keyboard connected through a DI to a mixer. Although lifting the ground
can help, this is often not sufficient. Often times, engineers will revert to passive direct boxes such as the Radial JDI just
to avoid ground loops. The Radial J48 employs a transformer as part of the internal switching power supply design. The
transformer isolates the current from the phantom power supply, eliminating the ground loop. Clever.
Plug and play easy
Ultimately, a good direct box should be plug and play easy to use. The J48 is a sophisticated device on the inside that
is designed to be easy to use on the outside. By understanding the design, we feel that you can make better use of the
features that are built into this marvelous direct box.
THE J48 FEATURES AND FUNCTIONS
The ¼” input and thru-put connectors
The J48 features two ¼” jacks on the input panel. These are designed to accept normal instrument input levels such as
from basses, acoustic guitars, keyboards, and drum machines. The left ¼” input is normally connected to the source instru-
ment. The second right-hand ¼” connector is normally used as a ‘thru’ connector and feeds the instrument signal to the
musician’s amplifier.
For instance, when using the J48 with a bass guitar, this set-up allows both the musician and the engineer to work with
the original (direct) signal from the bass. This way, the musician can set up his sound on stage with his own EQ while the
engineer can EQ the bass to better work in the hall.
True to the Music
Radial Engineering J48 User Guide
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Note: On live stages, it is common that instruments such as acoustic guitars would connect directly to a snake system
and the signal would be split like the microphones to the stage monitors for fold-back. In these cases, the thru jack
would not be connected.
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