TRS vs XLR -- phantom power

Question

I watched a video about audio signal levels and at the 3:12 instructor tells basically this:

When you are connecting "line level equipment" to the "audio interface", always use TRS or TS jack cables at the "audio interface" side (never use XLR).

Soon after, she also says:

If you have a gear that has an "balanced line level outputs" these should never be connected to the "audio interface" using XLR/XLR cables, but with XLR/TRS cables.

I think she wants to tell me that XLR/XLR cables always transmitt "phantom power" and that it is possible for me to destroy my gear if I accidentally turn on the "phantom power" while gear is connected using XLR/XLR cables.

This is exactly what I am doing currently - I am using XLR/XLR cables to connect my gear to my "audio interface" that has "phantom power".

Should I rather buy XLR/TRS cables to completely prevent any kind of damage? Is it true that XLR/TRS cables by itself completely prevent "phantom power" distribution?

Answer 1

Phantom power is not the sole motivator (and can often be switched off). XLR inputs usually have microphone levels (which can mean -60dB) and microphone impedance (around the house number of 600Ohms), TRS inputs have line levels (+4dB with most professional gear) and line impedance (typically something like 2kOhm or more). XLR outputs tend to be designed resilient against phantom power (for obvious reasons) though they are mostly line level but low impedance outputs, TRS outputs possibly less so.

The cable does nothing to prove against phantom power but only XLR inputs ever have phantom power, never TRS inputs (part of the reason is that TRS inputs have some wild intermingled order of establishing contact while XLR does not touch unrelated leads).

So it tends to be sane to use TRS inputs for line level. Whether you need an XLR/TRS or an TRS/TRS cable depends on whether your output is XLR or TRS.