I have checked in on this thread whilst at work today and had time to ponder. It's been a hard day 😉
There is a possibility that all the gold is gone. It was only shallow and the GPX got it all. But based on Steve H, JP, KiwiJW and heaps of others writing over time how the GPZ re-ignited patches that they felt were dead and buried - it seems unlikely that your little patch has flat-lined just yet.
This quote intrigues me.
These bits are supposed to be the domain of the Z (or an SDC)! These are the same bits that the GPX series supposedly struggle on. So that just brings me back to the feeling that something is not right with the settings or some part of the set-up.
If heading back to this same spot I would use:
Ground Mode - Normal (as long as it is usable).
Gold Mode - High Yield.
Threshold - 27 ish.
Sensitivity - only take it to a point where it is just starting to get unstable and then go back 1 setting. I do understand that running hotter can also be advantageous and Steve H has outlined his insanely hot settings and Kiwi gets away with them too (and I've used these to clean out patches of tiny bits). But just to start, this is where I would go and allow myself to listen for the tiniest change to that flat line threshold - rather than trying to listen for the 1 dollar coin in a tumble dryer full of 5 cent pieces 🤣
Volume - about 8.
Volume Limit - about 10.
Audio Smoothing - Off.
Ground Balance - Semi - auto.
I know you also mentioned here and in your email that you tried Extra Deep. From the GPZ manual -
This setting is specifically designed for searching for deeply buried nuggets. Large, deep nuggets (typically ≥ 50 grams) produce complex and subtle audio responses, so this setting should only be used by skilled operators. Shallow targets may be missed with this setting when compared to the ‘High Yield’ or ‘General’ settings. This setting is not recommended for general use.
The bold bits make me think 3 things.
You mentioned that you reckon the run of gold is shallow. So maybe not the best mode.
A good mode for nuggets bigger than 50 grams (wouldn't that be sweet!). Has this patch produced anything near that range or bigger?
Complex and subtle audio responses - may be getting masked by the hot settings background noise?
Lastly, I would take the SP01 out of the equation for a bit. This is in no way a slight at Pat or Nenad. Regardless of brand I would suggest the same thing. It is a matter of eliminating possibilities where something might be falling down. Maybe the filter choice is not right, maybe the SP01 is faulty, maybe the WM12 is faulty, maybe there are battery issues, connections, etc. I would just go back to the basic set-up and see what happens. Boosters can be great but the basic Z and WM12 combo works pretty well too.
Most importantly, don't give up on the GPZ yet. It may be an ergonomic nightmare, have limited coil choice and be the price of a small car but it is an awesome gold finding machine and if I knew I had the time and the disposable cash I would have mine back in a heartbeat 😊
I hope something in all that dribble helps you to find the yellow stuff 😉