Problem

When sending MIDI messages from your controller to your MIDI devices, you can hear a “tick” sound in your audio signal. This problem is more obvious when sending a stream of MIDI messages like MIDI Clock messages or CC messages via your expression pedal.

This issue is more common in devices with TRS MIDI implementations. From our experience, pedals that use DIN5 MIDI implements the MIDI standard.

Cause

There is a ground loop in your setup, likely caused by MIDI devices receiving MIDI without an opto-isolator in the circuit, or perhaps not designed properly to isolate the digital signals from the audio signal.

We are not able to comment on why the MIDI device is not designed with an opto-isolator, or why your MIDI device is leaking digital noise into its audio signal path. Check with the manufacturer on that.

This problem has nothing to do with the MIDI Controller. The MIDI Controller simply sends a MIDI signal out from its MIDI ports. In the MIDI standard, the receiving device needs to implement proper isolation to prevent ground loops.

Solution

Here are some solutions which might work

1. Use a MIDI Box as an interface. Most (if not all) MIDI Boxes should have an isolated MIDI input which should break the ground loop between the MIDI Controller and your MIDI devices, provided all are isolated power sources and there isn’t a ground loop between your MIDI devices.

2. Try cutting the ground in your TRS cable might help break the ground loop and solve the noise issue.

3. Strymon sells a 5 PIN to TRS cable for their TRS MIDI devices that implements isolation in the cable itself. Please note that this cable is one way (5 pin >> TRS).