JDX 48™ Reactor™ Using & Applications

This short guide is written for those who are experienced with pro-audio and direct boxes. Complete details about the many features built into the JDX 48 Reactor amplifier direct box and how best to use it can be found in the user guide by clicking the icon at left.

Making Connections

As with any electronic audio device, make sure all levels are turned down and/or power is off before making connections. This avoids power-on transients or capacitor discharge from harming speaker components. Always test at a low volume to make sure connections and cables are working properly.

Because the JDX 48 connects between the amp head and speaker cabinet, all of the power is also going through the JDX and cables. It is therefore important to use high quality 12-gauge speaker cables to make the speaker and amp connections. These should be terminated with standard ¼" phone plugs. Connection from the JDX 48 to your mixer is done using a standard balanced XLR cable.

The JDX 48 can be powered using 48 volt phantom from your console or by connecting the included 15 VDC power supply. There is no power switch. Once power has been applied, the LED indicator on the JDX 48 will illuminate to let you know power has been received and you are ready to go.

JDX 48 Standard Instrument Setup
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Standard Setup

  1. Connect an XLR cable from the JDX 48 balanced output to the input of a mic-preamp, mixing console or computer interface.
  2. Turn on the phantom power at the mixing console or connect the external 15VDC power supply to the JDX 48.
  3. Check to make sure the power LED indicator is illuminated to confirm power is present.
  4. Connect a ¼" 12-gauge SPEAKER cable from your amplifier's output to the JDX 48 amplifier input labeled 'FROM AMP'.
  5. Connect another ¼" 12 gauge speaker cable from the JDX 48 'TO SPEAKER' jack to your speaker cabinet. The JDX 48 speaker jacks form a parallel connection straight through the JDX 48. This is easily tested by turning your amp up to a low level. If you hear no sound, check the cables and connections.
  6. Slowly turn the volume up on your mixer to a low level and test the guitar amp to make sure signal is present. If you encounter any buzz or hum, try lifting the ground. You are set to go!

CAUTION - THE JDX 48 IS NOT A LOAD BOX! A speaker or equivalent load must be connected to the JDX 48 'TO SPEAKER' connector at all times during use.

Combining the JDX 48 with a Microphone

Combining the JDX 48 with a mic
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To add greater depth and 'fat' to your guitar tone, try combining the sound of the JDX 48 with a microphone. The two signals can be mixed together to create rich textures. Try moving the microphone around the room to find the sweet spot where the fundamental frequencies or harmonics line up to create a satisfying tone. Another studio trick involves 'sliding the JDX 48 track' using a digital recording system. By delaying the direct track, you are essentially performing the same function as using the Radial Phazer (described below) and aligning the fundamental frequencies to create a fatter tone.


Using the JDX 48 with a Radial Phazer™ 360º Phase Alignment Tool

JDX 48 used with mic and Radial Phazer
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Combining the sound of a microphone with the JDX 48 can be very rewarding. But to really go all the way, you have to consider the problem you have created by combining both sounds: The signal coming from the amp through the JDX 48 is traveling at the speed of light (via electron flow), while the corresponding sound arriving at the mic capsule via the speaker is travelling at the speed of sound. Thus, the mic'd signal will arrive later than the direct JDX 48 signal due to the time it takes it to travel through the air. This difference in phase alignment causes cancellation at various frequencies commonly known as 'comb filtering'.

You can 'correct' the situation by aligning the two signals 'in time' so that their fundamental frequencies are in phase. This sounds complicated but the good news is that you need only use your ears to make it work—it's that easy To make this all work, you will of course need to use two channels on your mixer: one for the mic'd signal and the other for the direct feed from the JDX 48 plus a Radial Phazer.

The Phazer™ is a line level, analog phase alignment tool that allows you to adjust the direct feed from the JDX 48 so that it is in phase (in time) with the mic'd signal. Connect the Phazer to your mixing console using the insert point on the JDX 48's channel strip. This can be done with balanced or unbalanced cables or using a typical insert cable with TRS at one end, and two 1/4'" plugs at the other. Once connected, simply turn the phase adjustment knob clockwise - slowly - starting from the left until you find the sweet spot. This will be when the two sounds combine to create a fat rich bottom end. Be careful! The Phazer is addictive… you will soon want to use it on everything!