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A direct box is an impedance matching and signal-balancing device. DI's
convert hi-impedance instrument signals to mic-level balanced lines for
interface with pro-audio equipment such as mixing consoles. A good direct
box will ensure proper electrical signals are maintained throughout the
signal chain and allow long cable runs without added noise. A good DI
box is just as important as a good microphone.
Active direct boxes require power such as a separate power supply, 48V
phantom power, or a battery to activate their circuits while passive direct
boxes convert the signal from high-Z to low-Z using only a transformer.
Passive DI's do not require a power supply to work.
This can be thought in terms of a dynamic mic compared to a condenser
mic. There are good dynamic mics and there are good condenser mics. A
good passive direct box depends entirely on the transformer that is being
used. For instance, the Radial JDI uses the world's finest transformer,
a Jensen. These DI's sound fabulous! In fact way better than most active
direct boxes!
It comes down to the application. For keyboards, and simple live set-ups,
the JDI is fantastic. No power supply, no batteries to go dead. You just
plug it in and it sounds great. The JDV on the other hand will give you
more reach. You will enjoy more detail or as Khaliq Glover (Engineer for
Marcus Miller and Herbie Hancock) said: “the JDV is almost holographic
compared to the single dimension of most DIs.”
No. Typical 48V phantom power only has 5 milliamps of available current.
The JDV requires much more current than this to drive its 30 Volt rails.
Phantom power is simply unable to do the job.
Sound quality. There is nothing on the planet that will do a better job
than the JDV. It is designed from the ground up to be sonically pure,
exceptionally dynamic, and totally transparent. The combination feed-forward
design, class-A circuit and 30 volt internal rails combine to put the
JDV in a class of its own.
Class-A circuits do not employ multiple gain stages to achieve greater
efficiency. They are pure gain stages that have and continue to be the
choice for audiophiles and purists. Although more efficient, Class-B or
AB circuits suffer a problem called zero-cross distortion that Class-A
devices do not. In the JDV, we are not concerned about power-per-watt
output, we are only concerned about getting the best possible sound. We
go a step further in employing a unique feed-forward design.
The 'easy guide' to circuit design always includes a feedback loop in
the circuit to stabilize the circuit. The JDV does not take the easy way
out; there is no feedback loop. The JDV circuit is akin to a pure tube
circuit design. The result is razor sharp precision without overshoot,
ringing or rounded-off wave generation. This things is almost alive!
Because the JDV has such a huge internal rail voltage, instruments are
typically unable to drive sufficient current into the JDV to cause it
to overload. Kinda' like having 12 cylinders on a car. You don't need
them until you are racing. Kick 'em in and the extra horsepower makes
all of the difference!
We could only get the JDV input to overload when we drove the output from
the line level of a mixer directly into the JDV and turned the volume
up high. It is unlikely, under normal use, that you will ever overload
the JDV.
No. The JDV is not a load box. This means that you must connect the amp
to a load 1st (like a speaker) and then you can connect the JDV to the
load.
Yes. However you should be careful to ensure that the load box properly
emulates a speaker. Make sure the -30dB pad is engaged and monitor the
JDV's input to make sure the overload LED does not go on.
The JDV is a unity gain device. This means that although it is designed
to output a mic level signal, the output can be significantly higher depending
on what input is being sent to it. This is why there is an output PAD
on the JDV. This allows hot signals to be padded down so that they do
not overload the input to mixers or mic level isolation transformers.
Noise. Due to the JDV's abnormally high input impedance, the internal
working level of the JDV is extremely low. This means that we must do
everything we can to ensure unwanted noise stays out of the JDV circuitry.
Power supplies tend to be a major contributor to noise. Keeping the noise
outside is a good thing!
The original JDV and the new JDV share the same audio circuit topology
and philosophy. Both use the same Class-A feed forward designs. The old
JDV used a rechargeable battery as a primary supply while the new design
does not. We found that although the original JDV worked well, many users
were confused about charging the battery and unless you read the manual,
you could get some pretty awful distortion or worse yet, you would think
the unit was defective.
The Radial JDV Mk3 is the third generation JDV and in developing this
box, we set goals in place that included making the unit more user friendly,
lowering the self-noise and expanding the dynamic range. All of the good
things that were in the original have been maintained or wherever possible
improved upon.
Obviously the new JDV has many more features. But that is not all: The
new JDV has gone from using SMT (surface mount technology) to the higher
capacity and precision of discreet components. In order to expand the
headroom, we developed a totally new power supply with a floating ground
scheme for less noise, and we got rid of the rechargeable batteries!
Originally, the Drag control was supposed to be recessed so that once
set, the control would not be touched. However we found that it was so
darn musical that people would be adjusting it all the time. Because the
JDV will probably live on the floor most of the time, we felt that a knob
would stick out and get kicked and broken. So no knob. Kinda' looks weird
at first, but you'll get used to it.
The speaker pad switch has the most potential to cause damage to the JDV
if used incorrectly. Connecting a speaker output directly to the JDV without
the load the speaker pad provides will likely blow the JDV’s input
circuitry. By recessing this switch, we reduce the chance that users will
use it in error or without thinking of the consequences.
The Avalon is a good box. We tested it, took pictures, took it apart and
then put it back together. We consider the folks at Avalon as good competitors.
They make a credible product and their equipment is professional and sounds
that way. Is the JDV better than the Avalon U5? No, we cannot in all honesty
say that the JDV is better. We can tell you that our tests showed the
JDV is probably more accurate but at this level, we are splitting hairs.
Here's our perception: People buy Radial direct boxes for two primary
reasons.
Reason #1, Sound: ...or as we say, "the Radial un-sound™".
Our boxes are extremely accurate and we do everything we can to ensure
the integrity of the instrument is maintained without any added artifact
or coloration whatsoever. We believe that our task is to deliver the sound
pure and simple. The Avalon is equipped with a whole bunch of pre-set
curves that allow the user to pick the sound he likes. The JDV is probably
more natural while the U5 also has its place.
Reason #2 Construction:
The JDV is not as pretty as the Avalon. We recently challenged an Avalon
user to drop his DI from 4 feet on the ground after we did this to the
JDV. He declined. The Avalon is designed to be in the protective care
of an engineer. The JDV will get kicked, jumped on, stacked and thrown
around. I guess we're from the other side of the tracks where we expect
our box to be subjected to real world abuse. This ain't no pretty boy!
Check the recessed speaker pad switch. If this is pushed in, the input
level will be way down. This is usually the offender because it is hard
to see. Also, check the output pad to make sure it is not depressed.
If the Vary-Z is engaged and the Drag control is completely counter-clockwise,
the sound can be muffled as you are dropping the input impedance well
below normal. Also check to make sure the lo-pass filter is not on.
Yes but this quality will be more on the lines of regular direct boxes.
The tuner out is guitar level and is perfectly fine for effects and having
fun. Of course its primary function is to keep you tuned without allowing
the tuner circuit to get in the way of the sound.
The reason for this is simple, yet the application is open for debate.
Here's the deal...
On stage, a bass player or guitarist should be setting his sound so that
he is comfortable. The volume, the tone, angle of projection should be
made so that the stage environment is as conducive to a great performance
as possible. In the venue, the PA system is used to provide great sound
for the audience. For example, more mid range on stage for the bass player
may or may not fit well with the PA system mix. As such the engineer generally
prefers to have as clean of a signal as possible from the bass. This avoids
added distortion caused by introducing multiple layers of EQ or gain or
effects such as compression in the signal path.
Today, you will often see the bass going direct while a microphone is
also placed in front of the bass amp to get the post amplifier sound.
The engineer will generally mix these together or sometimes switch sources
depending on the song and the desired effect.
Ultimately, this is a creative decision. To help make this decision easier,
the Radial JDV Mk3 is equipped with a standard DI (instrument level) set-up
and a parallel speaker set-up to take the post amplifier sound. With a
JDV, you get it all! |
