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JDX™ Reactor™ Using & Applications

The JDX 500 series module is 100% compatible with older API Lunchbox™ modules and racks while being 'wired' to work with all of the extra features built into the advanced Workhorse 500 series rack and mixer. This short guide is written for those who are experienced with 500 series modules. Complete details on using the JDX 500 and making connections to and from your 500 series rack can be found in the manual (PDF download).

The JDX operates in basically two modes: Amp Mode and Guitar Mode. Amp mode converts the speaker-level output from an amplifier to a balanced line-level output with filtering to emulate a 12" or 15" loudspeaker. Guitar mode converts the hi-z unbalanced line-level output from guitar pedals, digital processors and keyboards to a balanced line-level output with the same speaker emulation filters. Guitar mode is also pressed into service to record and Reamp® clean guitar tracks from your DAW. Simply select the operating mode using the front panel Guitar switch. This switch is recessed for safety and equipped with a flashing LED to let you know when Guitar mode is active.

Amp Mode - Using The JDX With An Amplifier

The JDX is exceptionally proficient when it comes to capturing the sound of a guitar amp. This is because the sound it captures comes from the combined relationship of the amplifier with the back-electro-magnetic impulse from the loudspeaker.

Amp mode is selected when the GUITAR switch is set to the outward position and the LED indicator is not flashing. Amp mode allows the JDX to receive the speaker-level output from your amplifier using the front panel phone jacks. Always use heavy 12 gauge speaker cables to optimize signal transfer between amp and speaker.

  1. Plug your guitar into an amp as you normally would.
  2. Connect the output of your amplifier to the HEAD jack.
  3. Make a parallel connection from the SPEAKER jack to your cabinet.

WARNING: Keep in mind that the JDX is not a load box. The amplifier must be connected through the JDX to a speaker or some form of a load. Failure to provide a proper load for the amplifier can cause damage to the amp and JDX.

Once the JDX is patched between your amplifier and cabinet connect the balanced line output to your recording or PA system. The JDX output can also be patched into more 500 series modules for further processing before recording. Use the JDX functions to fine tune the sound. For greater effect, try combining a mic with the direct feed from the JDX. This can often lead to exciting new tones.

Guitar Mode - Using The JDX Without An Amplifier

Alternately, the JDX can be used in 'guitar mode' whereby the amplifier and cabinet are not used. Instead, the guitar is connected directly to the JDX, via some effect pedals, to take advantage of the advanced multistage speaker emulation filtering.

Guitar mode is selected by pushing the GUITAR switch to the inward position. The LED indicator will flash to let you know when Guitar mode is active. Do not connect the speaker output of an amplifier when Guitar mode is active and the LED is flashing. Always use instrument cables to connect the JDX in Guitar mode.

  1. Plug your guitar into a distortion pedal like the Tonebone® Hot British™
  2. Connect the pedals output to the JDX front panel jack.
  3. The front panel jacks are paralleled and the unused jack can connect to the input of a guitar amplifier if desired.

WARNING: The flashing LED is a safety warning that alerts you when the JDX is set to guitar mode. Do not connect the speaker output from an amplifier when the LED is flashing.

The advantage with this set up is efficiency. Using the JDX in guitar mode is a great approach to laying down quick tracks when writing. Simply connect your guitar to some pedals then into the JDX and you are set to record, even late at night.

Adjusting The Sound

Tone Shift Filter

Once you start listening to the JDX, you will certainly want to tweak the tone to suit. The TONE SHIFT control is a variable low pass filter designed to gently roll off top end and smooth out the tone so that it better replicates the sound of your guitar amp. Simply depress the LPF switch and then rotate the TONE SHIFT control counter-clockwise (starting at 5:00 o'clock) until it sounds right. The TONE SHIFT can be used in both Amp mode and Guitar mode to adjust the sound.

Extending The Bass - LF-EXT

The JDX is designed to simulate the frequency response of a 4x12 cabinet. To add versatility, the JDX module is equipped with a LF-EXT or low frequency extension switch that widens the frequency response of the speaker simulator and reaches down further to emulate a 15" loudspeaker. This adds an octave or more to the bottom end to create bigger tones for guitars and lets bass players use the JDX too. On keyboards the low extension can fatten up a Hammond organ and 7-string guitars will have the lower register power needed to descend into the trenches of filth and degradation.

Low frequency output is increasd when LF-EXT is engaged.

Extending The Power

The original JDX was designed for 100 watt guitar amps. But as we later discovered many artists using it with high-power bass amps. These powerful amps caused the JDX to output signal levels significantly greater than what 100 watts amps produce. As a safety measure, and to reduce the risk of overloading, the JDX 500 module has been outfitted with a 300W switch. This introduces an attenuating pad at the ¼" HEAD input to lower the sensitivity. This recessed switch should be engaged when connecting amps over 100 watts or when the line-level output is driving the DAW input to hard.

Using The JDX 500 With PhazeQ 500

Some of the fattest guitar tones can be created when the JDX 500 is combined with a Radial PhazeQ 500 module. This set up consists of two signal paths that are eventually combined into one track or channel at the mixing console. The first signal path is the direct feed from the amp through the JDX and the PhazeQ. The second signal path is created using a microphone and a mic-preamp like the PowerPre 500 series module.

PhazeQ 500 Module

One difference between these two chains is the speed the signal travels at. The signal travels the JDX direct chain at near the speed of light all the way to the DAW. The signal takes longer to pass through the second chain because it slows down to the speed of sound between the speaker cabinet and microphone. This means the direct JDX signal will arrive at the recorder slightly before the microphone's signal. This creates a phase alignment distortion called comb-filtering that can sound odd or hollow when the signals are mixed together.

The PhazeQ is adjusted to bring the fundamentals frequencies of the direct signal path into alignment with the microphone signal. This produces rich tones that otherwise can take hours to find by moving the mics around the room. The PhazeQ can also be used to create alternate tones like thinning out the sound by purposely miss-aligning signals partially out of phase. This is definitely addictive!

Using the JDX to Re-amp®

Recording A Dry Track

While in guitar mode the JDX can also be used to Re-amp your signal. This process involves recording a dry track while auditioning the performance using a guitar amplifier. A direct box like the Radial J48, JDV or JDI are often used to record the dry track but the JDX can be used for this too.

Recording a clean "dry" track through the JDX

Reamping Through The JDX

Once the dry track has been recorded, send the track back to the JDX where it can then be reprocessed through the low-pass filter and speaker simulator. You can also use the parallel ¼" SPEAKER jack to drive the input of a guitar amp and record its sound with a mic preamp like the PowerPre 500. The output from the JDX can be patched to other 500 modules for further processing to create exciting effects before being re-recorded to a new track on your DAW.

Re-amp by sending the dry track back to the JDX and amp. 
Record the amp to a new track with a mic and pre


All Radial 500 series modules have access to the Omniport when installed in a Workhorse 500 series rack. In the case of the JDX 500 the Omniport is configured as a mic-level direct box output. This allows you to patch the JDX directly into a snake system and the mic input of a mixing console for live performance or connect a different preamp to impart it tonal characteristics.

When installed in a Radial Workhorse 500 series rack the
JDX Omniport produces an additional mic-level DI out.