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Yes. The JD7 is a high-impedance, unity gain distribution amplifier. This
means that it takes the original signal and then amplifies it at so that
each output to the amplifiers is the same as the original input device.
The problem you were experiencing in the past was caused by what is commonly
known as a ground loop. Each amplifier is different and as such, has different
chassis voltages referenced to ground. When you connect these together
these voltages combine to cause noise and hum. The Radial JD7 is equipped
with isolation transformers on most of the outputs. These electrically
isolate the amplifiers from each other thus solving the ground loop problem.
If you simply Y-jack the output of your guitar, the signal going to each
amp is cut in half or to be more precise, you will experience a 3dB loss
at the input. You loose punch, dynamics and drive which makes your guitar
sound lifeless and thin. Most A+B boxes are simple passive devices that
cause this problem. The next level AB box uses inexpensive drive circuits
(op amps and IC’s) to step-up the power so that you do not experience
the power loss. These circuits are cheap to build and unfortunately sound
like it. They are brittle and unnatural and ruin the sound of the guitar.
The JD7 is as perfect as perfect can be! The JD7 has been designed to
reproduce your guitar as faithfully as technology will allow. In other
words, although nothing is perfect, the JD7 is as close to perfect as
possible. The JD7 does not employ any op amps or ICs – it is 100%
discreet Class-A. This is what audiophiles insist on for best reproduction.
Further, the JD7 uses the worlds finest Jensen Transformers. The best
circuit with the best components produces the best results.
After we built the 1st JD7 prototype, we knew it was exceptionally accurate.
It was perfect. In fact it was too perfect. The problem was that it did
not sound right. After many hours of testing, we found that there was
a relationship between the guitar and the amplifier that was being lost.
When a guitar is connected to an amplifier, the amplifier’s input
section, tubes and transformers combine to create a load on the pick-up.
This ‘loading effect’ combined with the type and length of
cable further causes a noticeable tonal change, especially on lower output
single coil or vintage humbucking pick-ups. Although subtle, the change
was more than tonal; it had to do with the feel and grind of the guitar.
This was the problem: When the guitar was connected through the JD7, the
natural loading and resistance was lost. The guitar no longer saw the
amplifier; it was seeing the perfect input on the JD7 while the amp was
seeing the JD7’s perfect output. The relationship was lost. The
amp was no longer ‘dragging’ down the pick-up. Drag control
recreates this effect by allowing the musician to adjust with the guitar’s
impedance and resistance before it is sent out to the amplifiers. Drag
is subtle yet absolutely awesome!
Active DI's can be good but they can have several disadvantages: First
and foremost, active direct boxes require power. This means that they
must either run off batteries, phantom power from the console or use a
power source like a 'wall-wart' or AC/DC supply. When the power is low,
they distort. This means that for the direct box to work well, you must
keep the batteries at full charge which is impractical if not impossible.
No. Not really. It is designed for passive pickups and it has virtually
no effect on active devices or keyboards.
No. The JD7 was not intended for live use as few if any guitarists (except
at the very high end) that would ever use more than two amps on stage
at any time. This being said, there are some professionals that employ
JD7s on stage in conjunction with custom effect board switchers. To address
this need, Radial offers an ABY foot pedal in their Tonebone series called
the Radial JX2 Switchbone that is a pared down version of the JD7 for
live use. It allows one guitar to drive 2 amplifiers.
Not from the front panel. The problem is that when you change the level
going to the guitar amplifier, you are in fact changing the tone and saturation
at the amp’s input. For minute adjustments in the control room,
one would normally increase the volume on the mixer for the given microphone
on the target amplifier.
Yes. Maybe we should have called the JD7 the JD10… The effect loop
outputs on channels 5 and 6 are always engaged. Depressing the loop switch
on the channel front panel turns the ‘receive’ on. This means
that you can use these outputs for other devices. Keep in mind however
that these are not transformer isolated outputs and will be subject to
ground loops if one is not careful.
Yes or course. However please keep in mind that in order to keep noise
down and to avoid getting a shock, you should always use properly designed
equipment with 3 prong plugs. The 3rd ground plug is there for safety
and using older 2-pronged amplifiers can be both dangerous and noisy.
Always connect channel-1 to a relatively new amplifier with proper grounding.
This is where the JD7 derives its ground. You must make sure that any
old amplifiers be set to the correct electrical polarity. Read the owner’s
manual on this matter as this will not only protect you from electrical
shocks, but it will also reduce noise.
Absolutely! You can use any guitar level device at any input or output
as all of these are guitar levels. You can even use higher level instruments
on input B by depressing the PAD.
No. It is mic level. The output is about the same as what you would get
from a direct box. This allows the JD7 to be used in a concert or recording
splitter snake system. The JD7 balanced output should be connected to
a mic preamp or mixer mic input.
This is the preferred amplifier design for circuits where sound quality
is more important than high-power. In fact, audiophiles love the way Class-A
circuits sound, as they do not introduce anomalies such as zero-cross
distortion which of course cause phase distortion and inter-modulation
distortion.
Many amplifier and effect pedal manufacturers assume that you will only
be using their product and as such, they may end up being ‘out of
phase’ or to be more precise, be polarity reversed from one and
other. This of course only matters when you play several of these together
at the same time. As this is the intended function of the JD7, the polarity
reverse allows you to ‘line-up’ all of the amplifiers and
pedals so that you get them all working together.
The A-B selector will allow you to select between A or B or if B is not
used (1/4” not connected), the rear XLR jack becomes active when
input B selector is depressed. This is a line level input with variable
trim to prevent high output levels from recorders from overloading the
JD7 input circuit.
Radial - True to the Music™
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