I may be a bit confused now. Which coil were you using when you encountered the chatter? I'd need to know that to be able to say whether or not you'd be losing depth with the stock coil. As a general rule, concentric coils will hunt deeper in moderate soil conditions. But in highly mineralized soils, the DD's will outperform the concentrics. If you are hunting a gold field, and have the typical high mineralization levels, using a high frequency coil would be beneficial. If the coil you referred to as "noisy" is a higher frequency coil and the stock coil is not, I'd guess there is a problem with the noisy coil. If it is the elliptical coil at 18.75, you need to know that it is not waterproof. Only water resistant. Some folks have reported good "results" by running a bead of silicon caulking around the lip of the coil cover and around the connection where the cable goes into the coil. If these things do not apply or the coil simply does not work, again, I'd say there is a problem with that specific coil. If so, it needs to be sent in for service or replacement. Without more descriptive information of which coil you are having the problems with, and the settings you've been using, it is tough to diagnose here. JMHO HH Randy