Panel mounting type RCA pin jack, φ3.5 jack, terminal, etc. are available in "Insulation type" and "Non-insulation type."
When this jack/terminal is attached to a metal panel, it indicates whether or not the GND terminal side is conductive to the panel.
In the case of the insulated type, the GND terminal of the jack/terminal is not electrically conductive to the metal panel.
In the non-insulated type, the metal panel and GND terminal are electrically connected.
Use insulated connectors when you do not want to create a GND (ground) loop.
Also, the speaker output may not be GND on the -side, and since a large current flows, it is recommended to use an insulation type that does not drop on the panel.
Generally, the input terminal of the RCA is not shared with the chassis (panel) GND.
* A GND loop is a loop (circle) of wiring. In particular, a loop of a GND wire is called a "GND loop."
If you experience symptoms such as noise contamination or hum, use an insulated mold to cut the GND loop.