All About The New 2020 Upgrades

The upgrades/modifications that we perform on the SD/GP/GPX series detectors are designed to get the absolute maximum performance out of your detector. Let's start by pointing out the differences between the SD, GP, and GPX detectors. What are the differences between different models? Is the price difference of the GPX compared to the GP series worth the extra money, is it worth going out and spending $10,700 on the GPZ?

The actual performance of the GP and GPX on big deep Gold is much the same when using "normal mode," normal mode is the standard mode of operation for all the SD, GP and GPX detectors, it is the mode that has the greatest depth capability on Gold upwards of 1 gram or thereabout. There are many variables on detection depth, and that includes coil size and type DD or Mono coil and the mineral content of the ground.

When detecting average mineral type ground, and that is 80% of the goldfields, "normal mode" is what you want to be using if you are after bigger Gold that is deep. The "enhance mode" found on the GPX series is aimed at reducing ground noise and is specifically used to find Gold of a smaller size in heavy mineral ground. There is a drawback in using enhance and that it will not go as deep as "normal mode" on large Gold. The biggest problem when using normal mode on an SD or GP series is that these detectors do not have any way of controlling the amount of ground noise coming into the circuit; this is why the ground noise hides or obliterates any target signals.

To make these detectors perform like the newest, we modify and upgrade the detector's electronics, and performance is far better than a standard detector. It can be even better than the latest, more modern detectors. We install our specially designed 5th Gen gain sub-board, this is a low noise variable two-channel tracking variable gain amplifier. This addition to the SD, GP, and even the GPX detectors brings the performance of these detectors up to cutting edge standards. Old ground is new again, and many prospectors are finding gold nuggets with the latest upgrades that have been missed by standard detectors.

The GPX 4000's are in a class of their own, and a fantastic detector once upgraded with our variable gain sub-board and full-width variable frequency. The Sensitive extra mode can be tamed down so that it can operate with any size coil, and this mode is excellent on getting those hard to detect type gold nuggets. On a standard detector, the sensitive-extra mode is near impossible to use with a mono coil. Sensitive-smooth mode is excellent on larger Gold, but it can be made to go a lot deeper with the upgrades, larger coils have shown far greater depth on big deep Gold after the upgrades. The secret is in having the variable front end gain and variable frequency upgrades installed into the detector.

The GPX 4500 is probably, in my opinion, the best of the detectors as it will go deeper on big Gold compared to the GPX 5000. This comment is in reference to stock standard detectors. Both these detectors 4500 and 5000 have enhanced mode, and our variable gain amplifier sub-board will allow greater performance to get extra depth on small to medium-sized Gold. After full upgrades, the GPX 4500 and GPX 5000 have greater depth on any size gold and can detect Gold of small size on par with the SDC 2300 as proven in our side by side testing. Depth capability is on par with the GPZ 7000, and the GPX coils are cheap and easy to obtain. 

The GPX 5000 detector has another mode "fine gold" this is similar to the enhance mode but is designed for even smaller Gold, the fine-gold mode can be noisy in very not ground.

Fine Gold is very adaptable to different ground types when the upgraded variable frequency modification is used. By adjusting the variable frequency and front end variable gain, you will be able to detect Gold that other prospectors walk over.

As a point of interest, the deepest Minelab detector for big deep Gold is the oldest. It is actually the first P.I detector they brought out in 1994, the SD 2000. I found hundreds of ounces of Gold with this detector years ago when they first came out, but mine was upgraded with some extra electronics to make it go extra deep and also increased sensitivity. So if you are not interested in small Gold and only want the big stuff, then an old SD 2000 with our latest upgrades could be just the right detector for you.

A group of seasoned prospectors came together for a round of testing a few years ago, and the testing involved being able to detect a 13-ounce nugget at the greatest depth. We used big coils up to 36 inches in diameter, and my own SD 2000 that was modified was the only detector that could get a clear target response at the 3ft depth level. Yes, the old SD 2000 beat the GP and GPX detectors. To get the depth performance on GP and GPX detectors, we had to carry out extensive circuitry upgrades. The newest updates get these detectors to go deep and also be very sensitive to small Gold. A modified GP or GPX gives the prospector a lot of capability to get small and large deep Gold.

Upgraded detector settings

I am going to start with the GP series detectors, always run the detector in deep and normal, do not use the switch positions of Sensitive or Salt, these positions are next to useless in the real world and will cost you Gold. On the GP-Extreme, did you know the switch position named Normal is for DD type coils, and the switch position called Enhance is for Mono coils? If you use a DD coil in Enhance, only half of the loop is used in a mono mode, with the other half of the DD coil doing nothing at all. Note that Minelab used the word "Enhance" on the GP and GPX, and it means two different things, so make sure you understand this, or it will get confusing when operators of GP extremes and GPX detectors get together and talk about settings.

When using the upgraded variable gain do not go and crank it to the maximum, the size of the coil and the type of ground will dictate how far you can turn up the gain, cranking the gain up on bad ground is like trying to drive a V8 car in the wet with bald tires. Back it off, and you will see a significant improvement. Gain is not everything, the magic is in the signal to noise ratio, if the signal is weak and the noise is high then the signal is lost in the noise, reducing the noise and still having some signal from a target is the difference between finding Gold or walking over it. 

I cannot stress enough the importance of having a quiet detector. There are mental aspects as well; having your ears bombarded with noise causes hearing fatigue, and your brain will start treating all sound like background noise.

You can walk over the target, and you will not notice it. Trust me that all noise is terrible, some prospectors will say they listen to the ground noise to work out the ground.

They are going to suffer hearing fatigue and miss targets. Other prospectors fully turn the threshold down so far as it cannot be heard, sure this will alert you to any noise, but some targets cause an inverse signal sound and this signal sometimes does not break the threshold. Big deep targets can give an inverted signal. I do not recommend using a detector with zero threshold sound.

The Variable frequency mod... Long pulses (low numbers) have some characteristics you need to understand. Big deep Gold of the multi ounce size needs big pulses of energy from the detector to "light it up" as small pulses will not create enough energy to charge a big gold nugget fully. Obviously, one needs a big coil to be able to get these big nuggets, and the big winding size of the loop excites a lot of ground with the big pulse from the detector. When you charge up much of the ground from using a big coil, it can cause a large amount of ground noise, so back off the gain, if you need to quiet things down.

 When using the low frequencies, the time the detector receiver turns back on is delayed as a ratio of the frequency; this allows the ground noise to decay while the target is still giving a signal, this also allows you to in many circumstances to increase the 'Front End Gain" not the Minelab gain found on the back menu of a GPX series detector. Front end gain is the one we add with the silver single-turn potentiometer. Accurately setting the input gain in relation to the amount of ground noise is paramount to your gold nugget hunting success. 

Front End or input gain has to be balanced in regards to amplifying the ground noise and getting enough signal from the target. By adjusting the Variable gain control that we have added to the detector achieves this requirement perfectly. Do not crank up the Minelab gain in the back menu as this will just swamp the circuitry, it will reduce the depth and increase picking up all hot rocks, the Minelab gain should be run at a low number like 3 or 4 some operators run it at 1 and some run it at 5, just keep in mind that noise is your absolute enemy, a quiet setup that is matched to the coil and ground will win you Gold.

Be aware of using certain coils; there are electrical characteristics inherited by some coils that limit their function in some situations. Some coils cannot operate correctly at high frequencies and high gain; it is not the detector's fault. However, it is that the coil cannot switch fast enough, and this allows residual self-generated coil signals to get into the input stage of the detector and cause either noise or total desensitisation. The newer coils made for GPX detectors work quite well; be aware that some old coils are what I classify as NQR (not quite right), some of the designs are borderline at best.

We still do provide upgrades to the SD series detectors, and the cost is $650 to $1500 depending on if the detector is SD 2000 SD 2100 SD 2200 and what you want to be done with it.

All GP series detectors are $1850, and GPX detectors are $2250, and this gives you the Full Upgrades. We can break it down into individual enhancements, depending on your situation. Talk to us about what’s best for you. 03 5340 0993

All work on all detectors is covered by a 5-year workmanship warranty, if you, at any stage, want to sell the detector, the remainder of the warranty transfers to the new owner.

I get a lot of people (mainly dealers) telling customers that ML will not repair modded detectors; this is not an issue as we repair all Minelab SD, GP, and GPX detectors and have spare parts and even better components to increase the performance.

We currently do detectors for Australia, New Zealand, USA, Chile, Mongolia, Russia, Ukraine, UAE, Somalia via South Africa. Please have a look at our photo page on There is plenty of customers gold found with upgraded detectors.