Always consult the Owners Manuals


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USB connection and CPU usage

Read this: CPU Load.

USB connection and Axe-Fx III

The Axe-Fx III has a dedicated 16-core, 500 MHz USB microcontroller.

USB 2.0 is used to connect the unit to a computer, to run software editors and Fractal-Bot. USB Audio is supported.

Computer requirements:

"Still USB-over-MIDI but at least 10x faster." source
"The Axe-Fx III has a new driver. I just tested it under Reaper and was able to set the buffer size to 8 with no problems. I typically have it at 256 because I monitor directly from the output but it seems to be working fine on the lowest setting." source

USB connection and Axe-Fx II

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 downloading 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).

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

USB Audio is supported.

USB features.png

USB connection and AX8/FX8

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

USB Audio is not supported.

USB Adapter Mode (Axe-Fx II)

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.

"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

This has not been implemented on the Axe-Fx III.

USB Audio

Read this: USB Audio, AES and SPDIF.

USB troubleshooting

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

"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
"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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