There is a difference in resistance on coils made by Whites and those made for the ML. Miner John uses specs more like what Eric used originally and this is even a little different than the White's but not much. Miner John uses a totally different form of shielding than used by White's or ML compatible coils and this is why his coils have a tendency to be quieter.
Miner John also uses quality coax that has a served shielding which makes it almost impossible to detect. Thus false signals should be non existent. Unfortunately, this coax is a little smaller in diameter and this concerned Miner John so he adds a layer of heatshrink for added strength and protection. I don't do that to my coils since I try to not put any stress on the coax anyway.
The idea of the design is to get the coil to stabilize faster so there is less ground signal to deal with. This is why they might appear to ground balance better.
Changing the subject to sweep speed, there is a reason for finding the ideal speed. To find that ideal speed one needs to practice with small targets at different depths. The problem lies in an interaction between the filtering throughout the detector. Actually, the filtering before the autotune is the culprit. You could slow down the autotune easily by adding a couple of caps. In fact, there are small traces available for that purpose.
There are two integrators before the autotune circuitry that are a little too slow for my liking. They are that way to reduce noise, but do make it more difficult to detect small gold without a slow sweep. So any mod to the integrators that reduces the value of the caps involved will make the detector more responsive to small gold but add a little more noise at the same time. The integrators are matched so the caps have to be matched to 1% if they are changed. Also, the pc board has provisions to add two caps. The caps in place are C20 and C21, both 0.47uf caps. Replace them with 0.22uf matched to 1% caps and the response to smaller gold is better. One could go one step more and use 0.15uf and help a little more but doing so will also increase noise. C18 and C19 are places where a different cap can be added. Look around U6 for the parts mentioned.
Reg
