I'll try to explain this a bit:
As I indicated earlier dirtscratcher, some preset ones do work better, and some don't, it depends a great deal on how far positive they are set at the factory. Frequencies used are another determinant. Again, the F2 does better with its slightly positive preset than the Aces and in this case too the Eurotech Pro too, with their excessive preset (internal) positive settings. The F2 is set to produce better results in a (broader) range of soils than the other two (the Euro, and the Aces). Tesoro uses a tank circuit which allows a faster retune to pre-ground balance, and that gives them an edge in good behavior over the others here mentioned, and so do the other low-end Tesoros. In fact, as I said earlier, the only real differences between the Compadre and the Eurotech is that the Europech likes iron and steel artifacts slightly better than the Compadre. The Compadre however again, is not over-driven with high gain like the Eurotech, so it runs a lot smoother here (and in Montana too) since it is preset to come back to normal so very quickly. This is what some people call "response time".. The Eurotech gives the detectorist an edge in depth there, but not here where you and I play. The Compadre punches through the ground fairly well, but discriminates even better, cleaner, quieter than the other aforementioned, it and the F2. If over-driven in gain, then the whole set of parameters becomes a different set of rules entirely. In air, the Compadre measures about an inch less than the Eurotech, but in the ground it's a match for depth here. And although pushing a detector's preset positive setting to the limit gives milder soil a better chance, it in turn robs the more mineralized soils the chance to utilize that extra power. It's one of those "borrow from Peter to pay Paul" scenarios. The F2 and the Compadre both outdo the Aces (AND) the Eurotech in high iron soilfor all-out good behavior, I have tested them all against each other so I know that this is absolutely true.
The Vaquero you own does better than the Tejon in Fe. I know, I owned a Tejon for awhile and traded it for a $1,000 Browning A-bolt 338 mag, and I got the best end of the deal, the Tejon's high gain nearly drove me to insanity as it tried to reject the bad ground, and it was noisier than an Ace too. The Vaquero is a much quieter machine in the iron belt (west of the great Divide) .. Remember, that the ground balance control in any detector is nothing more than a rough iron discrimination control, period. The Tejon really sucked on this side of the divide, noisy as all heck, but the Vaquero does much better as I have mentioned many times in the last 3-4 years. Whites Prisms though with their preset sit somewhere in the middle for decent operation because some of them have a "black sand" switch which moves the detector toward being even more negative, hence smoother in operation in iron, I have one hanging off a nail just in the other room.. I have never in my entire life ever seen a preset GB work very well in Oregon, Washington, Idaho, Montana, Nevada, Utah, California, Colorado, Wyoming, or New Mexico, unless hunting in wood chips or air. The manual GB ones ALWAYS work better. Some operate so-so, but never as well as manual GB ones. . I now own only about 30 metal detectors but I've worked in design & repairing, plus manufacturing thousands of them. Gold nugget hunters commonly use high frequency IB (vlf) detectors with manual ground balance, unless all they can afford is something that doesn't have it. Hope this helps.. PM me and I'll explain the hows and whys of manual vs preset or "automatic" GB, or you can read George Payne's dissertations on the subject by searching the net. Just type George Payne + Ground balance in your browser. George is why we have what we now have in detectors, he is the instigator, the Godfather of ground balance detectors. Here is one of the many notes he wrote
BTW, George is a rather pleasant chap, I met him when he first started his Teknetics Company in Lebanon, Oregon upstairs in a commercial office building near the old Wally-World store.
www.jb-ms.com/Baron/payne.htm
