Risk of long-term shorting XLR cable

Question

I'm adding a 'mute switch' into my XLR cable.

To mute an XLR cable/Phantom powered microphone you temporarily connect pin 2 and 3 in the cable to short the connection. I have seen plenty of youtube videos and tutorials online of people doing this to add quick mute buttons and stuff into their podcast setups.

The difference with what i'm planning is instead of a momentary switch like a lot of people make, i'm going to add an SPST switch, so that I can flick a switch and mute my microphone for long periods of time, and only enable it when I want to.

Will there be any risk to my equipment when I mute the microphone and short pins 2 and 3 for long periods of time?

If it helps, the microphone and usb interface in my setup are

https://eu.audio-technica.com/AT2020

https://focusrite.com/en/usb-audio-interface/scarlett/scarlett-solo

Answer 1

For long-term muting, you could just turn the 48V phantom power off from the Focusrite. Or, make the switch disconnect pins 2&3 from the mic, to turn it off and save power.

Answer 2

This may be most easily understood by looking at an old-fashioned transformer balanced configuration.

^{simulate this circuit – Schematic created using CircuitLab}

Figure 1. A phantom-powered microphone circuit using balanced / unbalanced transformers and a mute switch.

How it works:

• The 48 V supply is fed in the centre-tap of XFMR2. Current splits both ways in the transformer with the result that the DC current is running opposite directions in each half of the winding so the flux in the core cancels out and the transformer doesn't saturate.
• At the microphone end the reverse happens and the 48 V is collected, smoothed and used to power the microphone preamp.
• Return current is through the screen or shield wire (pin 1 on an XLR).

Now have a look at your MUTE switch. It shorts out the audio but for the DC it is only connecting one 48 V line to the other. It does not load the power supply or short-circuit it in any way.

Also note that the preamp remains powered so unlike your other question where you proposed to cut the phantom power lines this circuit should not give an audible "pop" when un-muted.