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The information on this page supplements the official manuals.


CPU usage with USB connection

Connecting the AX8, FX8 or Axe-Fx II through USB increases CPU utilization. This is by design. If a preset uses much CPU, you may run into CPU overload problems with an USB connection. source source

AX8 and FX8 and USB

The AX8 and FX8 have an USB 2.0 type B port (host). It's fully class-compliant. There's no driver required. USB is used to connect the unit to a computer and to run the software editor and Fractal-Bot.

USB Audio is not supported.

Axe-Fx II and USB

To connect the Axe-Fx II through USB a driver must be downloaded to the device first from a computer. USB drivers for Mac and Windows are available for download here. If the USB driver is not installed, utilities such as Axe-Edit, Fractal-Bot and Cab-Lab won't recognize the Axe-Fx II. Also, tablets such as an iPad do not connect to the Axe-Fx II, until the driver has been downloaded to the unit first (without power cycling).

Fractal Audio:
"The driver that we supply for OS-X computers is NOT an audio driver. It is a firmware installer. The Axe-Fx II uses a "soft" USB controller. It gets its code from the host computer. When you turn the Axe-Fx II on it requests firmware from the host. This is superior to a hard-coded controller in that updates merely require a new host image rather than reflashing the controller."

The USB connection supports USB-to-MIDI, so there's no need to use a MIDI interface in most cases.

USB Audio is supported. An external audio interface is required when connecting the analog Axe-Fx II outputs to a computer.

USB features.png

USB Adapter Mode

The Axe-Fx II can be used as an USB-to-MIDI interface to update the firmware on the MFC-101, using Fractal-Bot. This is explained in the Fractal-Bot manual.

Fractal Audio: "The USB Adapter feature was added for simple USB-to-MIDI functionality, specifically firmware updates for the MFC-101. It is a low priority task since audio processing is the Axe-Fx's primary usage. Latency is not guaranteed. It is not intended as anything more than a no-frills, simple MIDI adapter for non-critical tasks." source

Troubleshooting USB

High-pitched noise may be caused by a ground loop.

Fractal Audio:
"The USB spec calls for grounding the cable at both ends (mistake). This can create an USB ground loop. Make sure everything is plugged into the same outlet strip." source

Fractal Audio:
"An occasional flicker when hooked up to USB is not unusual. This is due to the screen redraw being interrupted by the USB thread." source

When experiencing problems such as dropped connections or an Axe-Fx II which freezes after connecting USB, always replace the USB cable first. Example


The Axe-Fx II can work as an audio and MIDI interface just as it does on Windows or OS X, although Linux is not supported officially.


Loading the USB firmware:

Since the Axe-Fx II is an Audio Class 2.0 compliant device no additional drivers are needed. The Linux kernel already supports such devices. However, depending on your kernel version, there can be some issues:

Threads about using Axe-Fx II with Linux:

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