That one looks like it can be slid off the detector stalk and belt mounted..
When doing this, make sure not to flex the cable where it goes into the head or the disc, I ruined a $400 unit like this
Radio Shack Koss headphones will do fine..
Digging utensilts can be metal, better though if tough plastic, especially a "sifter" with a screen so you can wave it over the top of the detector and tell if the target is in it or still in the ground.
I've had em so sensitive that they would pick up a piece of tinfoil from a cigarette or gum pack, 1/2 the size of a BB !!
Forget the lying advertising about units that tell you exactly what you have in target, they Lie big time.
As a target lies in the ground it will corrode slightly, any metal except Gold and a few other Noble metals will.. This causes the ground to become saturated with small amounts of the metal and causes the reading to be stronger than normal..
The longer the item has been buried, the more mineralization is formed..
Your biggest enemy out there in general digging is Pull Tabs, there are Billions of them even miles from the nearest road.. Some birds take fancy to the shiny tabs and play with them, dropping them far from civilization.
This is very hard work.. sometimes rewarding, though seldom.
In the neighboring county a treasure hunter was working a creek in the national forrest.
He detected a tin can, onward he went until he remembered the code he swore to.
"You shall take out any trash you find"
So begrudgingly he dug up a 3 lb rock with over One Kilo of pure Gold inside, U of Ga said it was worth over $20 k