Radial Engineering Ltd.
JDI Stereo™ Direct Box User Guide
5
PASSIVE VS. ACTIVE
THE VARIOUS INPUT IMPEDANCE
As a direct box, the JDI Stereo will work with almost any instrument. It is however important to understand a few fundamentals.
The JDI Stereo is passive. This means that it does not require any power to make it work. This also means that it employs the
signal from the source instrument as the ‘drive’ which produces the balanced signal for the PA system or recorder. This also
means that if the input signal is very low, there may not be a strong enough signal to effectively drive the JDI. This is why pas-
sive direct boxes are usually recommended with active sources and active direct boxes like the Radial J48 are recommended
for passive sources.
Examples of relatively low output passive sources include an old Fender bass, piezo pickups and some sound hole acoustic
guitar pickups. Examples of higher output active sources include basses and acoustic guitars with built-in electronics (and a
battery), electronic keyboards and DJ mixers. Active sources are ‘powered’ and are able to produce a more powerful signal
than passive sources.
Radial makes a number of direct boxes to handle just about any situation. These differ by being active or passive and will have
a different input impedance depending on the desired use. As a rule: the higher the input impedance the ‘brighter or glassier’
the tone. The lower the input impedance; the ‘warmer and smoother’ the tone.
You will note that some of this information is conflicting. This has to do with personal preference. For instance, sound engineers
tend to prefer to use an active direct box like the J48 with an acoustic guitar as it tends to give the sound more sparkle. Some
bass players prefer the sound of their old P-Bass through a passive direct box like the JDI as it sounds warm and smooth. So
these are merely guidelines.
With piezo transducers, the rules change as these devices tend to sound much warmer and less peaky when presented with
a very high input impedance. The Radial PZ-DI has a load switch that lets you select between 220kΩ like the J48 for magnetic
pickups 1MΩ to follow the original impedance as set by Leo Fender and a 10MΩ input for piezos.
Model
Input impedance
Application
JDI
130,000Ω (130kΩ)
Active/passive bass, acoustic guitar, keyboard, DJ mixer
J48
220,000Ω (220kΩ)
Passive bass, acoustic guitar
PZ-DI
10,000,000Ω (10MΩ)
Piezo transducer
Содержание JDI
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