Display machines can be incredibly frustrating. But the plain truth is no display machine will be 100% accurate 100% of the time. The fewer segments or VDI numbers, the less accurate it's going to be. Your best machines have a VDI range of -99 to 99 or 0 to 99. Even with a range of 200, you'll still get lots of false readings because there are more than 200 conductivity ranges of metal depending upon a whole host of factors.
Yeah, I agree with you about the Ace series, random and (at last with the 250 I had) the display, and tones, often bounced all over the place. My Coinmaster with 8 segments vs the Ace 250's 12 segments tends to be more stable.
Your best information is going to come from your ears. Notice how none of the display machines have eliminated the audio circuit?
Anyway right now you should be digging every signal. That way you really learn your machine. Give this machine 100 hours of honest effort. On a few hunts cover the display and use your ears only. You'll be surprised at what you learn. I primarily (85%) use a machine with no display. I find the shallow cents often have to brighter sound than a quarter at the same depth. I've learned the sound of zinc covered fencing parts. I can often tell the size of items, particularly at depths 4" or less. Which translates I can tell if it's a coin or not. At a new site, usually within an hour, I can start picking out how various targets "unique" to that site sound.
If you want to find gold. You are going to have to keep your discrimination down, I keep my right at the edge of foil. I eliminate about half the foil, but still detect balled up foil. That way I have a chance of finding fine gold chains. Yes, I dig a ton of pull tabs and other junk. But in about a year I found 3 pieces of gold jewelry. One small gold ring was among a pile of pull tabs.
Also keep your sensitivity up. Only turn it down if you are getting EMI interference.
