This guitar-to-MIDI converter transmits MIDI data directly to your computer over a USB cable.
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Web Clips: Listen to audio clips of a chord played on Logic Pro''s built-in ES2, and a synth violin part played on the included WAVE XTable VI software instrument

TerraTec's Axon AX 50 USB guitar-to-MIDI converter ($549) is the company's second product to be based on Axon's neural-network-detection algorithms. It uses the same conversion technology as the Axon AX 100 mkII, which I reviewed in the March 2007 issue of EM (available online at www.emusician.com), and ships with a similar software editor.

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The Axon AX 50 USB is a guitar-to-MIDI converter that transmits MIDI data directly to your computer over a USB cable.

Because the guitar-to-MIDI conversion technology was covered in the last review, I'll focus on the specific features of the Axon AX 50 USB here. You can also find a detailed description of the software editor in the March 2007 review.

Half Pint

The Axon AX 50 USB forgoes having editing buttons on the box for a sleek look and a half-rackspace footprint. The front panel of the unit includes a 13-pin input that can accept the output from any 13-pin compatible magnetic or piezo hexaphonic pickup. The front panel features a 3-digit, 7-segment LED window that doubles as the tuner and patch-number display. Next to the LED display is a tiny button that does triple duty: it activates the integrated tuner, adjusts the LED brightness, and prepares the device for firmware updates. The front panel also contains a large power button.

The rear panel is equally sparse. There is an input for the included 12V wall wart (which, by the way, is huge, even by wall-wart standards), an output for the normal magnetic pickup signal of the guitar, and MIDI In/Out/Thru jacks. Last but certainly not least, the middle of the rear panel features the centerpiece of the entire device: the USB jack for connection to a Mac or PC.

Direct Connect

One of the most glaring omissions in the Axon AX 100 mkII was a direct USB connection to a computer. The Axon AX 50 USB not only transfers MIDI data to and from the computer over a single USB cable, but it also uses the built-in USB MIDI support in Mac OS X and Windows XP, eliminating MIDI driver issues and making this a truly plug-and-play device. I plugged the unit into my Mac Pro, and all my software was able to see it. Perfect.

The software editor included with the Axon AX 50 USB features the Axon AX 100 mkII's unrivaled string, fret, and pick split functionality and parameters, with the added bonus that you can configure different splits not only by MIDI channel but by USB port as well. The Axon AX 50 USB appears to your computer as five separate USB MIDI devices. This gives you the flexibility to route your various splits to different applications or to different tracks within one application.

The Axon AX 50 USB software editor also differs from its big brother in that it doesn't include the latter's arpeggiator, step sequencer, and Hold-mode functions, due to the AX 50's lack of a momentary switch input. Considering that most software instruments and DAWs have their own arpeggiators and step sequencers, I didn't miss this functionality within the Axon editor.

Sound Improvement

One of the weak spots of the AX 100 mkII was its bland complement of internal GM wavetable sounds. The Axon AX 50 USB includes no internal sounds, instead shipping with Wave XTable VI, a sample-based virtual instrument that runs in Native Instruments' Kontakt Player 2. It contains nearly 900 MB of GM-compatible samples divided into 128 single instruments and 9 drum and sound-effects kits. All the sounds in Wave XTable VI are quite usable, high-quality samples. This is a vast improvement over the internal sounds in the wavetable chip inside the AX 100 mkII.

You can run Wave XTable VI standalone, utilizing the Axon AX 50 USB/Wave XTable VI combo as a true computer-based guitar synthesizer, or you can instantiate Kontakt Player 2 inside your host software. You can also load the Wave XTable library into a full version of Kontakt 2 for more-serious editing and sound design.


It took a bit of work to optimize the Velocity sensitivity of the Axon to my playing style, but once I did, I found the Axon's speed and accuracy a dream. I used my Koll Tornado, which is equipped with a Ghost Hexpander 13-pin pickup, to play both Wave XTable VI standalone and software instruments in Apple Logic Pro, and what I played was always what I heard (see Web Clip 1).

I do wish that the sensitivity sliders in the software editor offered meters to aid in calibration, and that the manual provided more detail. But overall, guitarists interested in using their main instrument to control software instruments owe it to themselves to give the Axon AX 50 USB a serious look.

Value (1 through 5): 4

Web Clips: Listen to audio clips of a chord played on Logic Pro''s built-in ES2, and a synth violin part played on the included WAVE XTable VI software instrument