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GPZ 7000 Threshold Setting Concerns


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For years I ran the GPX 5000 Threshold setting with a faint audible level by following the book; which is condensed as follows;

Through a process of dynamic noise compensation, Smart Electronic Timing Alignment (SETA) ensures that the threshold stability is improved and maintained, allowing you to operate the GPX 5000 with maximum efficiency under all conditions.

Threshold is the constant audible background hum or noise produced by the detector.

On the front panel rotate the variable Threshold control to achieve a very faint but still audible noise level. It should be smooth with only minor fluctuations.

The Threshold is your reference point and lets you know what the coil is sensing, whether it may be a target, ground noise, or electrical interference, so it is important to set the threshold so it can be heard. When a target is detected, the Threshold changes in volume and pitch. Listen to the threshold carefully. Concentration is an important part of detecting. A very deep or small target may only cause a very small change to the Threshold noise.

Listening for a target signal with a high level of Threshold noise would be like trying to hear a whisper within a crowded noisy room. A high Threshold may also be uncomfortable to your hearing.

If the Threshold level is set too low (less noise) very soft target signals, from small or very deep targets, may not be heard.
It is important to reset the Threshold level as conditions change. For example, your ears may adjust to the low levels of audio after an hour or so, or the conditions may have become windy.

So here are my concerns;

With the GPZ 7000 I find it difficult to achieve the low quiet hum of the GPX 5000. I get the trying to hear a whisper within a crowded noisy room effect. The constant high noise level makes it difficult to listen for small changes that would indicate a small shallow or large deep nugget. So I tend to run it far below the default setting of 27. And much of the time I run at a setting of 1.
 
Another problem is related to the control differences between the two machines. The GPX 5000 has a simple variable Threshold control with no numbers to be concerned with. 

The GPZ 7000 has digital values which appear to be inverted in function. Attached is an edited illustration from the GPZ 7000 manual that displays my view or understanding of how it should be described.

Threshold settings.png

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  • Steve Herschbach changed the title to GPZ 7000 Threshold Setting Concerns

8 hours ago, Chet said:

The constant high noise level makes it difficult to listen for small changes that would indicate a small shallow or large deep nugget. So I tend to run it far below the default setting of 27. And much of the time I run at a setting of 1.

Hi Chet.  

I stayed with 27 for a fair while when I got my Z but over time I brought it down to 26 and only occasionally, 25.  I tried using a 'Bogenes' type of setting but did not like it.  

My concern is that it sounds like you have a "constant high noise level" when you are at 27?  I never found 27 gave a high noise level and wonder if there is (and maybe always has been if nothing has changed) an issue with your detector? 

I suppose we should also ask what are you running your Volume and Sensitivity settings at (usually)?  And do you use a booster of any sort?  

Cheers, N.E.  

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Hi Chet

For me the 7000 in a noisier machine than the 5000. 2 different beasts and I nearly wrapped it round a tree when I first got mine. I have actually upped my threshold to around the 27 after running it lower for a while. Northeast raises a good point with the volume settings. 'Noise' control has a lot to do with the audio settings rather than the threshold. With the visuals you have posted I wonder if you are looking at the peaks (the blue mountain tops for want of a better dedcription) rather than the horizontal line drawn through the diagrams which represents the threshold level. You see the height of the line corresponds with the threshold level. 

J.

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Chet,

Someplace I have Lunk's latest settings but this is his discussion about your topic:

 

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I think you found a spelling error in the manual too. (to/too) 😄

But I agree, they have it backwards in the manual from a human/human ear perspective and the numbering system on the machine itself. Low/High seems to match the diagram in the sense that they are speaking about the threshold level relative to the expected lowest or highest target or EMI signal levels though.

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I had a similar problem with my first Zed. It would occasionally run quiet, but usually was noisy no matter what settings we tried. Gerry, Lunk, and Mark all tried to smooth out the machine for me. End of story was a return to factory and a replacement machine. 

 

Mike

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Northeast and Arky, I am hard of hearing so I run the volume around 14 with the WM12 speaker. With mild ground I run the Sensitivity at 20. My first 7000 also had a noise problem when the battery would get around 50 percent down. It would get very noisy; if I put it on the car charger for 10 minutes it would quiet down until the battery got low again. Minelab replaced it quickly with help from Gerry’s.

OZMOG’ I agree the 7000 is in general noisier than the 5000. On the right side chart where I have added the Bold Threshold numbers; my machine sounds like its running near the top rather than at 27.

Mitchel, Lunk was one of my trainers; I have tried his settings but his Threshold of 35 is just too noisy for me. 

Jason, you pass the test on also catching the To/Too.😎

Steve, the “-“ sign would correct the number/value problem; but Tarsacci might have a copyright on it.😂 

Thank all of you for the great comments; my plan now is to jot them down and try to apply them this spring on a trip to Nevada.

Also I will compare machines and settings with someone else that is running quiet. 

Have a good day,
Chet
 

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58 minutes ago, Chet said:

I am hard of hearing so I run the volume around 14

Somewhere in the deepest, darkest DP Forum threads JP mentions something like 'raising Volume by 1 notch is akin to raising the Sensitivity by 2'.  I wonder if it is your Volume that is causing the issues.  I never had mine that high but I'm guessing Volume at 14 would make things a bit unstable. 

Have you tried a booster?   I used the B&Z and ran my Z Volume at 1 and just turned the B&Z up to the level where it was perfect for my hearing.  

The only issue with boosters is more stuff on your person but done right they can still be fairly compact and user friendly.  Personally I wouldn't use a Z without one.

I hope you get it sorted   👍

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I have been using the SP01 with two shoulder speakers for some time. And the separate volume control is better than just the 7000 volume control.

Recently to reduce weight I removed the SP01 and speakers and went back to a single WM12 on my right shoulder. I also removed a bunch more stuff off of my harness and belt. It feels a lot better now. I may go back to the SP01 latter.
 

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