I know I am jumping in late on this but on my Garrett Ace 350, I found the headphone connector to be very inconveniently located and generally an annoyance. That said, I made a patch cable relocating the headphone jack to under the arm cuff where I can more easily unplug the headphones and get fewer cable snags. With the headphones unplugged and my patch cable plugged into the original jack, no audio comes out of the speaker. I must pull the plug out of the detector (which is no big deal) altogether to get audio from the internal speaker. As long as anything at all is plugged into the Jack I get no audio. A bare TRS plug should not change the resistance enough to do that in my way of thinking. Just my two cents.