Ground Lift - Implementation in the Axe FX 3

1

1vl

Member
I wanted to put my regularly used axe inputs and outputs on a rack panel and was wondering how/if I could include the ground lift switches from outputs 1 and 2.

If I understand/measure correctly, the switch switches off the signal ground on pin1 of the XLRs, so this can easily implemented on the rack panel.

Or am I missing something?
 
I think you’re correct. But how/whether it works will also depend on how you are grounding (or not) your feedthroughs on the rack panel.

For example, are you planning to isolate the jacks in the rack panel from ground (ie, they just feed through with no ground connection happening via the rack panel), and instead of connecting the ground of an input jack (from the XLR out of the Fractal) to an output XLR jack, you will connect it first to the switch and then to the ground pin of the output jack?
 
Yeah, you'd need to leave the switch on the Axe FX in the LIFT position for the rack panel switch to be effective. In doing so you are moving the XLR connection to ground outside the shielded chassis of the Axe FX. I'm not certain, but this could maybe induce a ground loop in the rack itself and patch cables between when you set the patch panel ground switch to GND, depending on how large the rack is and how far away the panel is from the Axe FX. You might want to use an isolated switch and run a ground wire directly to the Axe FX chassis for the switch instead of allowing it to ground through the rack panel.

It's not as straight forward as cutting the shield connection on one end of a TS cable to break a loop. The shield of the XLR cable is still typically connected to chassis ground even if the lift switch is set to LIFT. What it's doing is separating the XLR signal ground from chassis ground.
 
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One thing to keep in mind is how your XLR cables are wired. Modern XLR cable wiring practice seems to be to leave the plug shell floating and not connected to PIN 1. The shell gets grounded to the chassis by the socket in the device when connected, so that direct connection to pin 1 is not needed.

Not all XLR cables are wired this way, so you'll need to check any cables you have to make sure the plug shell is not directly connected to Pin 1. You can do that with a multimeter checking for continuity between Pin 1 and a metal part of the XLR plug shell. If Pin 1 is directly connected to the plug shell, it will defeat the ground lift switch when plugged in through the socket's shell connection to chassis ground.
 
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