Clicking noise in audio path with every MIDI message sent or received by the Axe-Fx.

JSXtremist

JSXtremist

Inspired
As many Axe-Fx users have reported over the years...


The issue...

I'm experiencing a clicking noise in my audio path that occurs with every MIDI message sent or received by my Axe-Fx. For example, whenever the...
(1) Axe-Fx sends any MIDI messages, such as tempo or tuner sysex data to a compatible MIDI foot controller:
(a) On the Axe-Fx, if setting I/O > MIDI > Send Realtime Sysex to Tempo or Both, there is clicking in sync with the tempo of the Axe-Fx; refresh rate sent to the controller for blinking the controller's preassigned tap tempo button.​
(b) On the Axe-Fx, if setting I/O > MIDI > Send Realtime Sysex to Tuner or Both, there is rapid clicking if the Axe-Fx tuner is engaged; refresh rate sent to the controller for a readout of the Axe-Fx tuner on the controller's main display.​
Note: Tempo and tuner sysex messaging can be disabled on the Axe-Fx by setting I/O > MIDI > Send Realtime Sysex to None and rebooting the unit. Unfortunately, this disables the tuner readout and tempo blink functionality on the controller. As an alternative workaround, to preserve at least tuner readout on the controller, set Send Realtime Sysex to Tuner, then set the tuner to mute audio (hides the rapid clicking while tuning). Often, however, despite this being set to None or Tuner, the Axe-Fx will boot up with clicking in sync with tempo back in the audio path, not blinking on the controller, and the Axe-Fx must be rebooted for this sysex setting to load correctly; for tempo clicking to stop.​
(2) Axe-Fx receives any MIDI messages, such as those sent by a MIDI foot controller:
(a) As any expression pedals connected to the controller are moved; each value (0 to 127), from heel to toe position produces a click. This, in turn, creates a “zipper effect” of rapid clicking across the entire range of each expression pedal, regardless of the modifier they were programmed to control on the Axe-Fx.​
Note: This is the biggest issue as I've found no fix or workaround for it. Setting up expression pedal dampening on the Axe-Fx doesn’t hide this clicking, nor will a Noise Gate, which I prefer to avoid anyway.​
(b) Clicking with each MIDI message sent to the Axe-Fx on other MIDI channels.​


The rig...

Audio Path: Only 2 audio connections (cables) are necessary, both connected at the front of the Axe-Fx. Audio simply goes directly from a guitar, to the Axe-Fx, and out to headphones.
(1) An unbalanced cable to the front input jack.
Note: Using either Mogami 2524 with Neutrik plugs or Lava Mini ELC with its solderless plugs. With or without a guitar connected to this cable, all clicking results are the same.​
(2) A pair of headphones plugged into the headphone jack.
Note: The audio path is kept at least 3 to 4 feet away from all MIDI cables, the MIDI foot controller itself, and all expression pedals connected to it to avoid clicking. This, however, isn't possible when I'm performing at the controller, and the clicking gets much louder once I make skin contact with it or any of its expression pedals.

Foot Controller and Expression Pedals: I have the option of connecting either an RJM Mastermind GT/22 (current), FAMC Liquid Foot+ 12+ (previous), or Axess Electronics FX-1 + Expander (previous) to the Axe-Fx, which I run directly off their power bricks, and 4 of the Fractal EV-1 Expression/Volume Pedals, which connect to the controller with Mogami 2552 cable and TRS plugs.

MIDI Cable: A 5-pin MIDI cable connects to the rear MIDI input of the Axe-Fx for bi-directional communication. Note: I've tried several 5-pin MIDI cables, mostly constructed from VTG 4-conductor 24 AWG with 95% coverage shield and Neutrik MIDI plugs. Each MIDI cable has its shield connected either to pin #2 on both ends or only on the controller end.

Power: Both units always connect to either a single power conditioner or basic power strip. Note: All outlets are tested for ground using an outlet tester.


Test results...

All clicking is much louder if I...
(1) Plug an instrument cable into the front input of the Axe-Fx, with or without the other end plugged into a guitar, then make skin contact (including bare feet) with metal anywhere on the:
(a) Foot controller.​
(b) Expression pedals I connect to the foot controller.​

All clicking is no longer audible whatsoever (momentary fix) if I...
(1) Plug an instrument cable into the front input of the Axe-Fx, with or without the other end plugged into a guitar, then place one if not both of my hands on or around the:
(a) Metal housing of a plug at either end of the instrument cable.​
(b) Axe-Fx chassis.​
(2) Using an instrument cable, connect a guitar (humbuckers or single coils) to the front input of the Axe-Fx, then make sufficient skin contact with the guitar strings (multiple fingers) or metal parts of the guitar.
(3) Don't plug an instrument cable into any inputs on the Axe-Fx.

All clicking isn't any more or less audible if I...
(1) Use an AC ground lift plug adapter (aka "cheater plug" or three-prong/two-prong adapter) in powering the Axe-Fx.
(2) Try several different power outlets in different rooms throughout my home.
(3) Have the instrument cable near the foot controller.
(4) Connect an unbalanced cable, or even a Humbuster cable, to either set of inputs on the rear of the Axe-Fx, rather than the front input.

As listed above, judging by my test results so far, there seems to be either...
(1) A grounding issue with the inputs of the Axe-Fx.
(2) Lack of isolation between MIDI and audio signals passing within the Axe-Fx.
(3) Crosstalk between MIDI and audio signals passing within the Axe-Fx.


My goal...

I want to permanently resolve all clicking without sacrificing any functionality.

Could an isolation transformer help? What else could I try?
 
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Have you tried/tested this issue on a different outlet or location?
If it actually is a ground issue, at least you would know for sure by moving your rig.
 
I've had a similar problem with the expression pedals of my ART X-15 MIDI controller: If I've moved the pedals, there has been always a "zipper noise". Finally I've met a very skilled guy at the ART area in the Musikmesse Frankfurt and he recommended to set the "inter message delay" of the X-15 from 80ms (default value) to a higher value (160ms worked for me). Problem solved for me!
If your MIDI controllers don't have such a setting, maybe you could simulate it with your sequencer software. If it works then, I'm pretty sure that there are little MIDI helpers available that could filter the messages in such a way.
Of course I can't tell whether it'll help you, for from your description it sounds more like a grounding issue in your case - anyway I've wanted to share my experience with you, perhaps it's the same...
 
Yes. I've found in testing, at least with the cables I am using, that the audio path must be kept at least 3 to 4 feet away from all MIDI cables, the MIDI foot controller itself, and all expression pedals connected to it. This, however, isn't possible when I'm performing at the controller, and the clicking gets much louder once I make skin contact with the controller or any of its expression pedals. Since grounding either end of the unbalanced cable at the audio input of the Axe-Fx with a sufficient amount of skin contact completely resolves all clicking issues, does anyone know if an isolation transformer would permanently resolve the whole problem altogether?
 
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So then it is crosstalk that shouldn't be audible with a balanced audio path. So if you need to run audio and MIDI in parallel you should think of a balanced connection (XLR out) and a "reverse DI box" to make the signal unbalanced in the last possible position of the signal path. If you could use the balanced signal it would of course be the best solution, but that depends on the inputs the AXE FX is connected to.
 
Be sure you use a well screened midi cable with metal connectors. Screen linked to mass on both sides if single screen. If double screen: interior screen (magnetic protection) linked to mass on both sides, exterior screen (mechanic protection) linked to mass at one side only. BTW never had such serious problems, but when I had some small problems it happened with 4 euro midi cables. Try not to have the midi and instrument cable in parallel over long distances. They may cross perpendicular. If the problem persists you might want to try soldering a cable with twisted pairs, like cat5 or cat6 or flexible core wire phone cable.
 
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