Below is a paragraph from a Garrett (maker of the Ace 400) catalog about the importance of ground balance in VLF detectors:
"VLF Tip: Ground Balance Feature'
Soil mineralization levels often change in the field, and this can create unstable detector performance. Higher-end detector models with Ground Balance features allow the user to adjust the detector's ground balance as these conditions change. Ground balancing a detector calibrates it to the soil conditions, resulting in deeper target detection, more accurate target information, and stable detector operation."
I completely agree with that statement, EXCEPT, the part about "Higher-end detector models". There is a bunch of entry level priced machines out there from a variety of manufacturers with adjustable GB. If it's available at an affordable price point, it makes all the sense in the world to me to get a detector with that ability to maintain a steady performance level in varying ground mineralization.