JDX™ Direct-Drive™ Using & Applications

The JDX Direct-Drive™ is a unique device that emulates the sound of a guitar amplifier while doubling up as a direct box. In other words, with the Direct-Drive on a pedalboard, you can do a gig without carrying an amp to the club or record silently using all your favorite pedals. The design begins with a ¼" guitar input and passive thru-put to feed a stage amp plus a dedicated tuner output. The signal then passes through a series of filters to create Radial's signature JDX™ tone. This is modelled after the sound of a Shure SM57™ in front of a Marshall™ 4x12 cabinet. This is augmented with two amp settings that add the character of a Marshall JCM™ head or Fender Twin™ combo to the mix. These can be further tailored using a presence switch to add extra sparkle. The amp tone signal exits the Direct-Drive via either a ¼" guitar level output or via a balanced XLR to feed the PA. The Direct-Drive may be powered using a standard 9V power supply or typical pedalboard power brick.  (PDF download).

Making Connections

Before making connections, it is good practice to turn your PA or recording system down as this will prevent connection and power-up transients from damaging more sensitive components such as tweeters. Plug a 9V power supply into the Direct-Drive. You can use any standard Boss-style PSU or power brick to supply power; the power supply is not included. Once plugged in, the LED will illuminate to let you know power is being received. A cable clamp is available should you wish to lock in the power connection. Simply loosen the screw, pass the power adaptor cable through the hole and re-tighten.

Set the four top-mounted switches to the off or bottom 'start' position. To test, connect your guitar directly to the Direct-Drive input and the XLR output to your PA or recording system. Begin playing as you slowly increase the level on your audio system. Try the VOICING switch by changing the amplifier tones.


Tone Voicing

  1. Bottom: JDX
    This emulates the sound of a 4x12 cabinet with a mic. It tends to have a fair bit of mid-range and works very well to cut through the mix.
  2. Middle: STACK
    This will bring out a ton of bottom end to produce a big fat tone. Try adding a bit of top-end using the bright switch. This works like a presence switch on an amp.
  3. Top: COMBO
    This creates a brighter more open tone. It sounds great on cleaner signals using a delay and chorus. If you want more upper shimmer, try using the bright switch.

You are now ready to add your guitar pedals. For fun, plug your guitar into your overdrive, chorus and delay. Now go back and retest the amp settings using distortion and effects. This is where the Direct-Drive truly comes to life!

Rear Panel 1/4" Connections

There are four ¼" connectors on the rear panel along with the balanced XLR out:

  1. INPUT
    Used to connect your guitar or signal chain from effect pedals.
  2. THRU
    Bypasses all amp simulation and sends an untouched signal to your stage amp.
  3. TUNER
    Used to connect a tuner – keeping it out of the signal path.
  4. OUT
    Used to send the wet amp tone to recorder or second amplifier.

Rear Panel Balanced Output

This active output is used to feed a PA or recording system. This follows the AES standard with pin-1 ground, pin-2 (+) and pin-3 (-). It is a mic level output and thus should be connected to a standard mic input on a mixer or studio preamp. The XLR out has two top panel functions:

Polarity Reverse
This toggles pins-2 and 3 at the XLR output and is primarily used as a creative tool to phase correct the direct output so that it better aligns with a microphone in front of an amp. This of course assumes you are using the 'thru' out to feed a stage amp and will be combining the two channels. It can also be used if interfacing your Direct-Drive with an older vintage preamp that may not follow the AES standard.

Ground Lift
This disconnects pin-1 on the XLR to help reduce hum and buzz caused by ground loops. Hum often finds its way into audio systems due to voltage discrepancies within the power system. Lifting the ground disconnects the audio ground in between the Direct-Drive and the PA or recording system which can often alleviate noise. If you hear buzz, try pushing the switch upwards.


If using a multi-pedal power supply, you must ensure the DC outputs are isolated. If not properly isolated, the power supply can damage the JDX Direct Drive. Please consult the power supply manufacturer to ensure the outputs are isolated before connecting.

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