Since you have a 950 coil attached, I'll assume you are using the 5900 Di Pro SL CB.
This is a fine machine, though a little heavy. This model was also my first detector with an arm cuff, which took some getting used to after years of using the "blue box" White's detectors.
As mentioned before, an accurate ground balance is critical to maximizing depth. Second most important is the Sig Bal. I place this second because it will, to a great extent, determine what mode you choose to hunt with. If you are able to get a good GB with Sig Bal at maximum, you will want to consider using TR/Disc mode. But first, a word about GEB/Disc - this is the normal hunting mode if you want to discriminate out iron and such. It is also a motion mode - which means you have to keep the coil moving to detect anything. This is significant because this detector requires a rather fast sweep in order to achieve any kind of depth. In fact, it is difficult to swing this detector too fast. So, because this mode provides discrimination and requires a very fast sweep (which most people are too slow), I figure this is just about the worst mode as far as depth goes. OK, back to TR/Disc - if you are able to get a good ground balance with Sig Bal at maximum, go to TR/Disc. It is still a discrimination mode, but is not a true motion mode, so you don't want to move the coil too quickly. Once the TR/Disc is selected, lower the coil to about an inch above ground, pull the trigger, then lower the coil to the ground and start searching. It is important to keep the coil very close to the ground. IIRC, TR/Disc can achieve around 30% greater depth than GEB/Disc in ground that is not high in mineralization.
Threshold - most folks set this too high. If you want to find deep targets, you have to be able to hear them, set the threshold as low as you can and still hear it. Too loud, and deep targets will get drowned out. Discrimination - even though the 5900 is not a tone machine, I can tell you that nickels and pull tabs do sound different. Put a nickel on the ground and keep adjusting the Disc setting until you can just pick it up. This will disc out most pull tabs and small aluminum. However, be aware that any discrimination other than iron risks missing small gold jewelry. No matter what detector you use, if you are looking for gold, you are going to dig tabs - period. Finally, headphones. You don't mention them, but they not only extend battery life, a good set is imperative for finding deep targets. I used a set of White's Royal GT headphones for a long time. They are, IMHO, much maligned for an inexpensive set of phones. Simply pulling the speakers out and installing dense foam in the cups will improve the sound quality immensely.
Good luck and good hunting!
