THE J48 QUICK START
This section is for advanced users. It provides a quick set of instructions for those that are familiar with direct boxes. For
up and coming engineers, we suggest that you read through the manual before using your Radial J48.
Caution!
When connecting or disconnecting any audio device always ensure the power is off or all levels are set to
zero. This practice will reduce the probability of noise, such as a capacitor discharge, from being sent through the
amplifier to the speakers, which could cause a big “bang” in your sound system or even cause a speaker to blow. This
is especially true with phantom powered equipment.
The Radial J48 is an active direct box and as such requires standard 48V phantom for powering as found on most consoles
and pre-amps. Before you start, make sure the phantom power has been turned on at the console. You can check for the
presence of 48V phantom by depressing the low-cut filter switch. If phantom is present, the LED on the front panel will
illuminate for a moment.
Now, make sure all switches are set in the ‘out’ position. Plug the instrument into the INPUT. Connect the THRU to the guitar
amplifier or keyboard mixer, and the XLR OUTPUT to the PA or recording mixing console.
With the PAD set to 0dB ( out position), slowly turn up the input level at the mixer and listen. The J48 should be able to
handle most instrument levels without any problems. For exceptionally high signal levels such as from digital pianos, sam-
plers and high-output basses, inserting the –15dB pad will reduce the input level to the active circuit. If you hear distortion,
simply depress the –15dB pad. To reduce low frequency mud and run-away acoustic resonance, the J48 is equipped with
a low-cut filter that gently rolls off bass (-6db at 80Hz). This has the added benefit of increasing the dynamic range when
depressed.
Since the Radial J48 employs a transformer in the power supply, you are actually isolating the input and the output electri-
cal connection. This will eliminate most buzz and hum caused by so-called ground loops. If you encounter 60-cycle hum
or noise, it is likely that you have a different ground potential at the input and output of the J48. Depressing the ground lift
(break) switch will generally solve the problem.
The J48 also features a polarity reverse. This reverses pin-2 and pin-3 at the XLR. As the J48 is set following the AES
standard with pin-2 hot, reversing the polarity is generally not required unless the instrument is being both DI’d and mic’d.
If so, the polarity reverse switch would allow both the mic and the J48 to be set ‘in-phase’ should these be reversed.
You are now ready to go! Now, close your eyes and listen. The J48 is without a doubt one of the most musical DI boxes
manufactured today.
True to the Music
Radial Engineering
J48 User Guide
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