the audio tone (pitch) is based closely on the VDI number range.
You stated:
"... don't like relying souly on the VDI.For example,I dug a few nickels that read 10 last week.They were in iron.VDI said 10 but the tone id said nickel.If I had the tone id off,all I would see is a vdi of 10.I found a seated dime last week that vdi'd at 78,same as a penny.BUt it had a silver tone to it.I dug it.Again,without a tone id,I would have just saw 78"penny"."
I'll say:
It isn't going to be so neat and proper when you have targets mixed with trash or if there are ground mineral issues. If you had a solid '10' reading or a solid '78' reading, you would have had an audio tone appropriate for that reading and NOT an "nickel" tone or a "silver" tone.
Now, if you were to have said you had a miced VDI reading that was jumpy and hung around the '10' or '78' mark for thsoe two targets, AND if you would have said that the audio Tone ID was not stabilized but you had audio 'spikes' perhaps that sounded
to you that they were potentially good targets, then I might buy it.
But the Tones are associated with the VDI. The DFX, the XLT, and any operator isn't that good.
You could get an Iron readout and a low-sounding audio Tone and still be sweeping over a 4" silver dime and all you would have to go by is the basic audio response as well as any sizeing and shapeing you might do to discern a coin-sized target. In those bad ground situations, Tone ID is worthless and can often work against you!
The folks with an MXT or other model who are relying on just a signle audiop report will then use the visual reference and not have the distraction of a NOT-proper audio tone. If hunting such a site that has those challenges you use a low discriminate setting and move dirt or rock to investigate the targets anyway. Tone ID is of no initial value.
The DFX and XLT have a nice Tone ID range, are killer for plucking quarters in sportsfields, and can be 'fun' to use. The best Tone ID I have yet used that provided multi-tones and ID's the best at depth is the Explorer. It's not perfect, either, but better.
Most serious hunters who get involved in a wide variety of hunting environments and applications (coins, jewlery, relics, prospecting, beach hunting, etc., etc.) eventually favor and appreciate the benefits of hunting W/O Tone ID a lot of the time. One of the best function features of the XLT and DFX is the OFF option for Tone ID.
Monte