All about the new 2015 upgrades

The upgrades and modifications that we perform on the Minelab SD, GP and GPX series detectors are designed to get the absolute maximum performance out of your detector. Lets 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 7000?

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 there about. There are many variables on detection depth and that includes coil size and type, double D or mono coils, and the mineral content of the ground.

When detecting average mineral type ground, (which 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 a SD or GP series is that these detectors do not have any way of controlling the amount of ground noise coming into the detector, this is why the ground noise hides or obliterates any target signals.

To make these detectors perform like the newest offerings we modify and upgrade the detectors electronics, performance is far better than a standard detector and can be even better than the latest newer detectors. We install our specially designed 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 new upgrades that have been missed by standard detectors.

The GPX 4000 is in a class of its 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 be used with any size coil and this mode is great 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 great 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 the GPX 4500 and 5000 have enhance 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 GPX4500 and GPX 5000 have greater depth on any size gold and can detect gold of a 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 called “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 just walk over.

As a point of interest, the deepest Minelab detector for big deep gold is the oldest.  It is actually the first PI 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 really 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 upgrades 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. Did you know, on the GP extreme, the switch position named “normal” is for double D type coils and the switch position named “enhance” is for mono coils? If you use a double D coil in enhance only half of the coil is used in a mono mode with the other half of the double D 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 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 big 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 noise as background noise.

You can actually walk over the target and you will not notice it. Trust me that all noise is bad, 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. There are other prospectors that fully turn the threshold down so far as it cannot be heard, sure this will alert you to any noise but some targets cause a inverse signal sound and this signal sometimes does not break the threshold. Big deep targets can give an inverse signal. I really do not recommend using a detector with zero threshold sound.

Variable frequency

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 to fully charge a big gold nugget. Obviously one needs a big coil to be able to get these big nuggets and the big winding size of the coil excites a lot of ground with the big pulse from the detector.  When you charge up a lot of 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 in many circumstances to increase the front end gain. (not the Minelab gain found on the back menu of a GPX series detector) 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 detectors fault but 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 not quite right, some of the designs are borderline at best.

We still do full upgrades to the SD series detectors. All work on all detectors is covered by a 5 year warranty, if you at one 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 Minelab 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, and even Somalia via South Africa. Have a look at our photos, there is plenty gold there found by customers with upgraded detectors.