RUN: A word of warning

The Situation

A small number of users have reported damaged / non-functioning modules after patching with Just Friends. The problem arises when patching another module's output to the 'RUN' input of Just Friends. The source module is typically a digital output (including 'analog' gate outputs). Typically the damage is instant & the source module is non-functioning afterward.


The Cause

Just Friends has -12v normalled to the input of the 'RUN' jack in order to detect whether a cable is present. Due to the nature of the normal-switch, there is a brief moment during patching this input where -12v is seen on the patch cable. In most cases, outputs are capable of handling a brief event like this, however some modules are not prepared for this and can be damaged.



The choice to implement jack-detection in this manner is owed to a combination of a lack of standards and assumptions I made during design. Eurorack in general suffers from a lack of clear standards, leading to different manufacturers making different assumptions about how the instrument will be used. The Mannequins line of modules is designed to handle inputs across the full Eurorack power supply ranges. Additionally these modules are designed to allow passive mixing of outputs (output to output connection) without damage. While the above are the assumptions I made for my designs, I understand how others could come to different conclusions about the necessity of such things. In this context I don't think it makes sense to place blame squarely on one party or the other.


Workaround / Best Practice

The easiest workaround is to always patch a loose cable to the RUN jack first, before connecting a voltage source. While this may be less flexible than traditional patching, this approach makes sense for the modal-type interactions of the RUN input.

Additionally we're offering a free service modification for existing modules, which involves replacing the RUN jack with a current-limited version. Further details can be found here: RUN Jack Upgrade.


For existing units we'll be including a small warning message about the issue, and encouraging our retailers to do the same for existing stock. We'll be reworking the jack-detection mechanism to avoid this issue in the future, confirming with affected manufacturers the safety of this new approach.