October 2024: Fractal Audio's VP4 Virtual Pedalboard has been added to the wiki.
Humbuster
Humbuster cables and outputs
Humbuster is Fractal Audio's electronics design for reducing unwanted noise caused by ground loops.
It requires the use of a Humbuster cable and a Humbuster-compatible output port on Fractal Audio devices. All 1/4” outputs on the Axe-Fx II, III, FM3, FM9, FX8 and AX8 are Humbuster-compatible. Read I/O connectivity and levels
for more information.
The VP4 doesn’t support Humbuster cabling.
A Humbuster cable has a TRS end and a TS end. The TRS/stereo-plug end goes into the Fractal Audio device. The TS/mono-plug end connects to the other side, possibly an amp.
WARNING: When connecting a Humbuster output to a balanced TRS 1/4” input on another device, use a standard shielded 1/4” TS to 1/4” TS instrument cable (patch cable). Do NOT use a Humbuster cable. Do NOT use a balanced 1/4” TRS to 1/4” TRS cable. [1]
See “Humbuster cables” in sections 1 and 4 in the manual for your unit for more information.
FRACTAL AUDIO QUOTES
[2] Won't do anything for pickup hum. It just fights ground loops.
[3] The plug that goes into the Axe-Fx can be either TS or TRS. TRS would be for Humbuster cables.
[4] Humbuster cables do not eliminate noise. Humbuster cables in conjunction with Humbuster outputs can significantly reduce hum due to ground loops. The outputs of Fractal Audio products have a special circuit that, in conjunction with a Humbuster cable, senses the difference in ground potential between the devices and cancels the difference thereby reducing hum. It's certainly not snake oil and you can find numerous testimonials on our forum that speak for the effectiveness.
[5] The Humbuster outputs sense the ground noise at the far end of the cable and cancel it out. Remember there is no such thing as a wire with zero impedance.
[6] If you pull the cable out halfway it will get twice as loud. This is due to the humbuster output design. Don't pull the cable out halfway.
[7] The 1/4" outputs have a "remote ground sense" feature. You take a TRS cable and on one end you put a TRS plug and on the other end you put a regular TS plug. On the TS end you tie the ring conductor to ground. Plug the TRS end into the Axe-Fx II. The ground noise of the attached equipment is sensed and added to the output signal thereby cancelling the common-mode noise (hum). This is especially useful when doing the 4CM since that's when you usually get the worst ground loops.
A Humbuster cable is grounded at both ends. It's a three-wire configuration. The third conductor samples the ground potential at the receiving end and sends that back to the transmitter where it is used to cancel the ground noise. The manual even shows you how to make your own.
[8] (about the VP4) Humbuster is not necessary because it's DC powered and the chassis is floating. Hum occurs due to ground loops. If equipment is AC powered the chassis must be grounded by law. This introduces ground loops when using unbalanced connections. The correct solution is for everything to be balanced but the industry seems reluctant to embrace that.
Buy Humbuster cables
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