j48 stereo user guide jensen transformer equipped active 48v phantom powered direct box Radial Engineering Ltd. 1588 Kebet Way, Port Coquitlam BC V3C 5M5 Tel: 604-942-1001 • Fax: 604-942-1010 • Email: info@radialeng.
j48 stereo direct box user guide Introduction......................................................................... 1 J48 Stereo Features........................................................... 2 Making Connections........................................................... 3 Using the PAD.................................................................... 4 Using the Ground Lift......................................................... 4 Using Various Instruments........................................
FEATURES 1. ¼” THRU-PUTS: Left and right parallel outputs used to connect the hi-Z instrument signal to an amplifier, tuner or personal monitoring system. 2. ¼” INPUTS: Left and right unbalanced, hi-Z inputs used to connect instruments. 3. -15dB PAD: Reduces the input sensitivity to prevent overload. 4. +48V: LED indicator will glow when the J48 Stereo is receiving phantom power. 5. HPF: High-pass filter switch gently rolls off bass to remove rumble and resonant feedback (-3dB @ 80Hz). 6.
OVERVIEW The Radial J48 Stereo is an active direct box that derives its power from the 48 volt phantom supply from the mixing console or mic preamp. You simply plug in and it will quietly go to work. Making connections As with all audio gear, always ensure audio system levels are turned down or equipment turned off before making connections. This will avoid plug-in or turn-on transients from damaging more sensitive components such as tweeters. There are two channels on the J48.
USING THE -15dB PAD Inside the J48 Stereo is a unique switching power supply that is designed to provide plenty of headroom even when pushed very hard. There are however, instances when the output from an instrument can be extreme. To prevent distortion, the J48 Stereo has a -15dB input pad that reduces the input sensitivity. Examples could be a very high output digital piano, active bass guitar or maybe the overly aggressive output from a DJ mixer. If you hear distortion, simply depress the PAD.
GROUND LOOPS A common problem occurs when connecting a stage amp to the direct box whereby a so called ground loop can present itself. This is often caused by DC offsets or voltage differentials that can introduce hum and buzz in the sound system. The first line of defence is to lift the audio ground - pin-1 on the XLR. With most direct boxes, when you lift the ground you also disconnect phantom power.
USING VARIOUS INSTRUMENTS The J48 Stereo is active. This means that it has a built-in preamp or buffer circuit that drives the signal. This is the benefit of an active direct box over a passive counterpart. In other words, if you have a passive source such as an old Fender bass, the J48 Stereo presents a very effective interface.
USING THE HIGH-PASS FILTER A very handy feature that is built into the J48 Stereo is the high-pass filter. When activated, it gently rolls off low frequencies below 80Hz and helps eliminate resonance and feedback. This handy feature is particularly effective at cleaning up the low registers, making it easier to mix. The other benefit with eliminating bass is that you actually increase the available dynamics. Low frequencies and their huge waves require more power than their high frequency counterparts.
OPTIONAL RACK MOUNTING KITS The J-Rak 8 and J-Rak 4 are an innovative rack mount chassis. The J-Rak 8 has eight vertical slots for Radial J48 Stereo direct boxes or the other Radial J-Class products. The J-Rak 4 has four horizontal slots. J-Rak 8 J-Rak 4 Each direct box can be front or rear mounted allowing the system designer to have the XLR’s on the front of the rack or rear, depending on the application.
SPECIFICATIONS Audio circuit type:......................................................................................
BLOCK DIAGRAM J48 Stereo Block Diagram INPUT PAD SWITCH HIGH-PASS FILTER SWITCH BUFFER CHASSIS GROUND PHASE INVERTER THRU IN+ IN- INPUT PAD SWITCH HIGH-PASS FILTER SWITCH 180° POLARITY REVERSE SWITCH BUFFER + VCC TO CIRCUIT - GROUND LIFT PHASE INVERTER THRU Radial Engineering Ltd.
RADIAL ENGINEERING 3 YEAR TRANSFERABLE WARRANTY RADIAL ENGINEERING LTD. (“Radial”) warrants this product to be free from defects in material and workmanship and will remedy any such defects free of charge according to the terms of this warranty. Radial will repair or replace (at its option) any defective component(s) of this product (excluding finish and wear and tear on components under normal use) for a period of three (3) years from the original date of purchase.
