If you use a speaker instead of headphones then this is a quick modification to it to add a bypass switch to dull the output. Pictured is one of the units that the B&Z setup utilises. Even though the B&Z has a bypass switch (it kills most all output) it will still benefit from this, and if you're using the GPX4500 battery with the inbuilt booster this is worth the effort to stop that annoying start up squeal.

We file or drill a section of the speaker housingin the spot pictured and trim the boss that the screw goes through to allow room for the switch. We solder a resistor (anywhere from 150 Ohms to 250 Ohms is fine) across the switch contacts and connect the switch in series (in line) with the speaker wiring.

If you run dual speakers like I do then the switch is connected into the wiring lead coming from the battery or booster. The output side of the switch then connects to both speakers allowing both to be dulled when the switch is activated. When the switch is opened the resistor is effectively placed in series with the speaker wiring dulling the output, and when the switch is closed it bypasses (shorts out) the resistor and restores full output to the speakers.

This is useful for when you are firing up your detector to avoid the noise, or pinpointing a large and loud target, or for when you have company and want to be a little bit secretive.