[quote Hombre]Howdy Monte!
I have been playing with my IDX PRO modified, and I noticed that if the GB is off a little bit it downscales the target ID. It seems to like a rather positive GB to upscale the target ID. Do you power ballance the IDX?[/quote][size=medium]... Hombre, the TID is going to be affected by an errant GB setting. The cause for a flaky TID can often be attributed to a too-low GB setting for the motion Discriminate mode. The Classic series were designed slightly different from many other popular silent-search discriminators of that era. Let me explain.
Since many hobbyists are familiar with the Tesoro brand, and since most of their models have been turn-on-and-go but function the same as their manual GB models, they make a good brand to use in the explanation. Tesoro has used a circuitry design with the Discriminate mode's GB reference set a little positive from the manual setting for the All Metal/Pinpoint mode. It might be viewed as a positive off-set to the primary GB setting. This design ensure that there's less likely to be any when the coil is lifted from the ground or you sweep the coil over a hole, which can occur with a somewhat negative GB adjustment.
So, most typical Tesoro models were GB'ed to be 'spot-on' in the All Metal mode, they would be a bit positive in the Disc. mode and the operator wouldn't hear any annoying chatter during operation, especially over somewhat mineralized ground. While this is a good thing from a manufacturing standpoint because the fewer complains about ratty operation the better, it doesn't provide peak performance for the most dedicated metal detectorist.
I can't tell you how many times I used an original Tesoro Lobo, Bandido, original Eldorado or more current model in some tough ground conditions and "Power Balanced" to get improved performance. The problem, however, is that due to the circuit-designed offset, the best GB attained in the silent-search motion Discriminate mode meant that the All Metal/Pinpoint mode was rendered less useful because the GB was too negative.
This is one reason why I have enjoyed the Bill Lahr-designed Classic circuitry for so many years now. The Classic circuitry design actually results in a slightly negative GB reference for the Discriminate mode when you have a 'spot-on' GB in All Metal. Therefore, it requires a slightly positive G in All Metal to have a sufficient GB for the Disc. mode to eliminate falsing in the motion discriminate mode. The result? A functional GB in All Metal mode that might be just a bit positive, but the very good auto tune circuitry does it's job just fine and searches in All Metal are generally no problem.
With the Classic ID and IDX/IDX Pro, the right-on GB in All metal results in a too negative GB reference for the Disc. mode and therefore the TID is going to be a bit flaky. So, yes, having the proper, slightly positive GB in All Metal takes care of the errant TID problem.
Do I Power balance the ID & IDX Pro's? Yes, on a rare occasions I might. The nice thing with the Classic circuitry design is that it is not really squirrelly in operation. I prefer the modified models because Bill Crabtree's additions work well and let me tailor the GB adjustment to the coil in use, and on occasion to a particular site. For the most part, however, I just 'set-it-and-forget-it.' I use the manual GB control to establish a slightly positive GB so that I am functional and stable in both modes, then I leave it alone. I only change it if there is a radical change due to using a different search coil, or an occasional ground mineral issue.
Monte
PS: For those who are not sure what was meant by "Power Balancing", it is a term I coined over a quarter century ago to describe the method of adjusting the Ground Balance in the motion Discriminate mode. It's quite simple, really.