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Is there now marketed or has there ever been available a detector which inverts the audio volume scale?  Many applications produce better finds from the weaker signals, either because those items are smaller (e.g. micro jewelry) or deeper (e.g. old coins and nuggets).  Having to listen through the din of trash to hear the weak signals for most detectors is mentally fatiguing.  I wouldn't be surprised if this is/was possible with analog electronics, but seems like a task that digital processing could handle easily(?).

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I guess in a way the Gold Bug 2 with Boost enabled does a similar thing to what you're after, the smaller faint targets are very loud once that's flicked on,  it doesn't reduce the volume of the bigger targets but it sure boosts the volume on the smaller ones so they're loud like the bigger targets.

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A few old models had a feature called “surface blanking.” It basically filtered out the strong signals, leaving the weak. It never found favor, perhaps because of how it worked or did not work. I never used one so I do not know how effective it was. But I’ve always had a desire to try one as it seems like it might be of some use. The only model I can think of off the top of my head that still has the feature is the Garrett GTI 2500. Garrett calls it “surface elimination.” From the GTI manual, page 43 - 44:

Surface Elimination
This Search Aid is for use where quantities of metallic trash are present on the surface or at shallow depths. This function eliminates detection of objects of all sizes to the specified depth. Use the MENU touchpad to display Surface Elim on the screen to turn on. It will be turned OFF at the factory settings.

If you desire to use this Search Aid, press the (+) and (-) touchpads to set the desired elimination depth. This depth (to 4 inches beneath the coil) will be shown on the Upper Scale and on the Imaging Grid.

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Thanks, Steve.  I'm out of likes else I would have given one to your response (not that you need #30,143 all that badly 😁).  I'm surprised the White's V3i doesn't have this as it seems to have about every other bell or whistle anyone could have wanted, and then some.

One of the things Carson recommends in his book I'm currently reading is to listen for the weak signals and ignore the strong ones.  Easier said than done.  I realize other have recommended the same thing (user Cabin Fever mentioned it's something he's done which has led to more old coin finds, for example).

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I will just point out that The Equinox 800 gives you the ability to set Target Tones and Volumes for the different I.D Numbers, so you can to some extent invert volumes if you want, but larger targets are still in general going to be louder, but as long as it is not overloaded like with large iron you can set certain numbers your getting to a lower volume or tone.

  If Minelab is listening -- Please add at least some of the adjustments available in the other modes to the Prospecting Modes, At Least Two Tones for Plus and Minus Numbers.!

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3 hours ago, GB_Amateur said:

One of the things Carson recommends in his book I'm currently reading is to listen for the weak signals and ignore the strong ones.  Easier said than done.  I realize other have recommended the same thing (user Cabin Fever mentioned it's something he's done which has led to more old coin finds, for example).

This was done in the early 1980s and I know of quite a few prospector that did this and their prospecting partners dug up the ignored signal got a 32,36,50+ ounces that were only an inch or two deep. They were lucky they were sharing finds. My first nugget over an ounce was a 4oz sitting 2 feet from the edge of a sealed bitumen road and I though it was a coke can. I was having a look at a flogged surface patch and decided to have a look on the other side of the road see what was there. At the time my prospecting mate was a local policeman and was working to lunch time and both of us were planning to have a look for a new area. I took the 4oz into the Cop Shop and we used a scrubbing brush to clean it up a bit. Only got a 12 gm piece on the other side of the road.

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9 hours ago, geof_junk said:

This was done in the early 1980s and I know of quite a few prospector that did this and their prospecting partners dug up the ignored signal got a 32,36,50+ ounces....

Yes, for gold detecting it's a questionable practice, particularly in fresh (never searched) sites.  But for previously hunted parks, schools, etc. where *most* of the desirable old coin targets are deep and masked, and the undesirable pulltabs (in particular) and modern coins are shallow, it can be a big help.

I was out on Tuesday trying to hunt a spot that had recently produced for me but for which I had covered twice.  I put the 6" round DD on the ML Equinox, switched to Gold1, and even notched out all VDI's below 11.  I got blasted (recall -- Gold modes have proportional audio) by trash.  I could have just given up on USA 'nickel' 5 centers (TID 12-13) and notched all they way through 20.  Then I would have had blanking and choppy audio all day long.  I hate discing out the low channels!

Since it appears (modern) detectors don't have inverted audio, I'm wondering if an aftermarket device might exist which could be inserted in front of the headphones that accomplishes this task.  (Probably not, but maybe I can find someone to make one....)  Am I the only person who's ever thought of this?  (Easy answer:  a big NO.)  Why haven't enough requested it that the detector manufacturers would have cooperated?  (We've been down that path before -- the seemingly closed ears of detector manufacturers....)  Or the more likely answer -- it just won't accomplish what I want it to.

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19 hours ago, Steve Herschbach said:

The only model I can think of off the top of my head that still has the feature is the Garrett GTI 2500. Garrett calls it “surface elimination.”

The GTI 2000, later the 2500, was the first top end detector I ever used (top end at the time).  The surface elimination function works ok but it's basically a screen for targets detected at the selected depths.  The GTI will simply mute most any target, except large can slaw and the like then it just chirps a lot, and attempt to give positives to deeper targets however its not an inverted audio.  Targets will still be masked using that function so its not something I used very much.  But it does work.

The only audio inversion I have ever come across was a coil for my GP3000.  I still have it but its been so long I cant remember if its a nugget finder.... any rate it was called a phase inversion coil, it was around in 2005 I believe.  It had a  switch on the coil that allowed one to "flip" the transmit and receive of the DD design making shallow targets sound like deep ones and vice versa.  It worked rather well, mine was the 16 inch, and the inversion function also helped deal with EMI.

Other than that I cant recall anything else aside from audio boosts like the affor-mentioned gold bug.  My thoughts.

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The AKA Berkut 5 has both Large signal and Small signal filters.  Someday I'll get my hands on one.   I think it would make a great gold jewelry detector.

If your ears and mind can deal with it, All metal VCO audio can be useful for what you are wanting to do.  Shallow signals squeal,  deeper signals don't and the sensitivity settings controls the depth of the squeal.   So you can set your squeal depth to say.....7" or so for a coin size target, then when you hear targets that don't squeal, you know that if they are coin size, they are deeper than 7".  Since most detectors today include visual target id for the all metal mode, you only have to look at the meter for the non-squealers.   Works very good in mixed mode as you can both size, estimate depth and conductivity of the target without having to check a meter.

Good luck.

HH
Mike  

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