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 JDV-
Pre 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!