Radial Engineering JDV-Pre 500 User Manual

True to the Music

www.radialeng.com

®

True to the Music

®

User Guide

JDV-Pre

™

500

Instrument Preamp and DI

500 Series Module

www.radialeng.com

Radial Engineering Ltd.
1588 Kebet Way, Port Coquitlam
British Columbia, Canada, V3C 5M5
tel: [phone] • fax: [phone]
email: [e-mail]

WARNING NOTICE TO USER!

The Radial JDX 500 is not a load box. This means that if you are using it with a guitar
amplifi er it must be connected to a speaker cabinet or some type of load box. Failure
to do so could result in damaging the JDX and your amplifi er which of course would not
be covered under warranty. Always ensure you have proper cables and connections
have been checked. We recommend using high quality 12 gauge speaker cables.

Because the JDX 500 can also be used as a direct input from a guitar, we have
instituted a slow fl ashing LED to let you know when you are in this mode. This safety
measure reminds you that you should not connect a guitar amplifi er output to the JDX
when in guitar mode as this may damage the JDX.

Although preventative safety measures have been designed into Radial 500 series
products we strictly advise against hot-swapping modules or plugging and
unplugging them when the Workhorse or other 500 series rack is powered on. Hot
swapping can cause connection sparks at the card-edge connector that could send
damaging transients to other equipment. This also greatly reduces the life span of the
contacts. Damage due to hot swapping is not covered under warranty. There are no
user serviceable parts inside.

Radial® JDV-Pre™ 500 User Guide

Table of Contents ......................................................Page

Feature Set .................................................................... 1

Overview ........................................................................ 2

Getting Started ............................................................... 4

Using and Adjustments .................................................. 6

Specifi cations ................................................................. 9

Block Diagram ................................................................ 9

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

Congratulations… you’ve done it! You have invested in what we believe is one of the
most musical sounding instrument preamps ever made. The JDV-Pre went through many
design revisions before we fi nally decided to release it to market. Why so long? Each time
we plugged it in, we found ourselves asking for extra bits that could make the JDV that much
better.

What this really means is that behind what appears to be a simple control panel are lots of
extra cool features that have been carefully incorporated into the design. And the only way
to take full advantage of them is to actually read this manual. Once you have done so, there
may be questions that have not been answered. For these, we kindly ask that you visit the
JDV-Pre FAQ page. This is where we answer questions from users, like yourself, with the
latest information that can be helpful when using the JDV-Pre live on-stage or in the studio.
If of course you cannot fi nd what you are looking for, either post a question on the FAQ or
feel free to send us an email at [e-mail] and we will do our very best to get back
to you in short order.

Now close your eyes and listen. You are about to hear your vintage Fender Jazz bass for
the very fi rst time.

True to the Music

®

Radial Engineering Ltd.

JDV-Pre

™ 500 Module

10

1

9

8

Rear Panel

7

1

4

3

2

6

5

FEATURE SET

1. GAIN: AccuState level control simultaneously adjusts the
gain and input sensitivity to ensure lowest noise at all gain
settings.

2. INVERT: Reverses the polarity on the JDV output. Ideally
suited for reducing feedback on stage or can be used in the
studio to better phase align two signals for improved stereo
imaging.

3. HP FILTER: High-pass fi lter reduces low frequency
resonance, helps clean up the sound of acoustic instruments
and eliminates run-away feedback. Great for layering tracks
when recording.

4. DRAG: Engages the Drag control. This shifts the impedance of
the front panel ¼” input from a fi xed 3.9meg-Ohms for passive
piezo pickups to a variable load for magnetic pickups.

5. LOAD ADJUST: Varies the load from 22k-Ohms (fully counter­clockwise) to 500k-Ohms (fully clockwise). Replicates the load
of a tube amplifi er on a magnetic pickups for a smoother, more
natural tone. Great for bass and guitar!

6. LED INDICATORS: For power, signal present, peak-overload,
and phantom power provide visual feedback of the JDV-Pre
operating status.

7. INPUT: Used to connect high impedance instruments to the
JDV-Pre. This front switching jack has priority over the XLR
mic input on rear panel of 500 series rack.

8. AUX OUT: Buffered output used to feed a guitar amplifi er.
Transformer isolated to eliminate buzz and hum caused by
ground loops.

9. OMNIPORT: Balanced, low impedance direct box output (mic­level) designed to feed a snake system and mixing console
in a live touring environment. Available when used with the
Workhorse rack.

10. XLR INPUT (rear panel of rack): Microphone input with
phantom power. Enables the JDV-Pre to be used with
instrument condenser mics. Transformer coupled for optimal
signal fl ow. This input is disabled when a plug is inserted into
the front panel ¼” input.

11. PHANTOM POWER - Turns on/off the +48V power supplied
through the rear panel XLR microphone input. When engaged
the front panel LED indicator will illuminate. Used to power
condenser microphones connected to the XLR mic input.

Phantom On

11

Radial Engineering Ltd.

JDV-Pre™ 500 Module

True to the Music

®

2

JDV-PRE OVERVIEW

The JDV-Pre is a preamp dedicated to instruments. In other words, when we designed the
JDV-Pre, our goal was to deliver a device that would be equally effective at amplifying a
guitar, violin, mandolin or a contra-bass. So we started by optimizing the front end for the
most natural tone and widest possible bandwidth. We then added a variable low-cut fi lter that
would enable the engineer to ‘size’ the preamp so that it would translate the instrument’s true
character while eliminating problem resonance.

As we developed the design, it became abundantly clear that instruments are amplifi ed in
many different ways depending on the transducer. In our audio world, a transducer captures
vibrations and converts them into an electrical impulse. This can be in the form of a magnetic
pickup that captures the vibrations of a string, a piezo element that captures the vibrations
at the bridge or even a microphone capturing the vibrations of sound as it travels through
the air.

Passive Piezo

Element

Magnetic &

Active Pickups

Condenser

Instrument Mic

Instrument

Amplifi er

Live PA
System

Multi-track

Recorder

Each transducer reacts differently to an electrical circuit. For instance a magnetic pickup
sounds warmest when the impedance is set around the 200k-Ohm mark. A piezo really
works best when the impedance approaches 4meg-ohms. And with condenser and dynamic
microphones, one has to consider 48V phantom power, the input impedance and of course
how much gain you introduce. The more gain, the more opportunity for noise. The more noise
fi ltering you employ, the more you can affect the instrument’s natural harmonics. Great care
is needed all the way along.

Once you captured the source, the next goal is to send it along to one or more destinations.
For instance when recording, the JDV-Pre must produce a +4dB balanced line output to feed
digital audio workstation and a thru-put for the musician’s amplifi er. On a live stage, the JDV­Pre must also be able to feed the artist’s instrument amp and produce a mic-level output like
a direct box so that it can feed a snake system.

The JDV-Pre user’s guide follows the fl ow chart above and discusses how each of these
functions is addressed. Let’s get started!