CW makes a good point.
Minelabs have automatic ground balance and it is one of the very finest, maybe even the best, but it also causes small targets to get overlooked sometimes, due to it's particular slow operative characteristics and behavior.
Tesoros though seems to do better than most others with their ultra-fast auto-return-to-threshold on the cheaper models coupled with their preset (that's not what it really is, it's actually a parameter of a certain time lapse using a capacitive discharge circuit, showing up as a charge/discharge system exibiting height and strength of the sine wave pattern controlling the highs and lows of it's positive and negative voltage to coil).
This is primarily true with the Compadre, Silver uMax, and a couple of others rather than with their high-priced detectors having manual ground balance. Tesoro keeps a very tight reign on things, meaning that with an Explorer for example, the auto GB allows up to a 3 inch positive and a 3 inch negative level , while Tesoro keeps a mere 1/2" level and very quickly too, much tighter, and that gives the Tesoro a better shot at tiny targets. Just imagine yourself tuning your detector to 3" under-ground, to 3" over-ground level and at a slow rate. Then shorten the time lapse and the high and low doing the same thing. That's right, the short, quick one recovers faster and gets a better chance at hard to find small targets. It also is why a Sov or Expl sometimes misses a dime for example, after passing over a pulltab, so you have to hunt real slow. This does not happen with Tesoros or Fishers or Whites, especially Tesoros. Manual ground balance is an essential for nugget hunting though, because of the ability to control the GB even more, however, this needs to be tended to like a new born baby too, otherwise you could REALLY be on the highs and lows of GB and MISS those tiny flakes. Many people complain about the Fisher GB II because it has to be retuned so often, but it does get the real tiny ones, for sure. Garretts are a whole different story though, but the high end ones do a lot better with tiny targets than their low priced ones do.
In other words, Tesoros do BETTER WITHOUT manual ground balance in bad soil on coins than WITH manual ground balance, and for many reasons too, including max output voltage, etc. They do better hunting nuggets though with a manual ground balance, just like any other detector. Lucky for me though, I use a Compass and it has BOTH manual AND auto retune to GB, and it's a quick one too.
With these modern detectors there actually is no really good set of rules to go by because all it takes to make a 3 Khz detector behave like a 30 Khz one is by adding or changing a bit of circuitry, and nothing more. Minelabs have a real good con going on right now, and it's about their different frequencies for different coils. Read Tesoros comments on how much frequencies affect detector capabilities, and you will learn (under general information) that 3-30 KHz will all do the same thing if the engineering is right, regardless of what frequency they use. BTW, Minelabs DO NOT USE ALL THOSE FREQUENCIES AT THE SAME TIME. They simply use whatever freq the detector decides might be optimum at a given nanosecond, nothing more. And they can and do make mistakes too, but their auto ground balance is the best on the market today, albeit a bit flawed..
