Differences between Minelab SD and GP models

[Steve Herschbach]

This is not intended to get into every nitty-gritty little detail, but instead is a brief overview for those unfamiliar with the Minelab Pulse Induction (PI) detectors.

The Minelab SD2000 was the first of the series, a genuine breakthrough in metal detector technology. It is the basis on which all the other models were developed.

The SD2100 and SD2100v2 are fairly simple manual ground balance units. The frequency could be manually adjusted to avoid interference from outside sources, such as a nearby detector.

The SD2200 and SD2200v2 offer automatic ground balancing or a fixed/locked ground balance. They also introduced an iron disc feature of dubious reliability, audio boost, and automatic frequency offset.

The GP Extreme offered enhanced sensitivity to small gold that was lacking in the earlier units. There were quality control issues with the unit however. The GP 3000 is essentially just a refined GP Extreme and the GP 3000 performance is more consistent between units than was seen in the GP Extreme. Threshold smoothness was improved to be less erratic. The GP 3500 is again just a refinement, with the only feature of note a button on the handle to allow for easy switching between ground balance modes.

The GPX-4000 was a break from the past, going to a digital control system. This allows for more adjustments but also more complexity. The GPX can attain smooth thresholds on par with the best VLF units. The GPX-4500 is a refined 4000.

I disagree with those that say you can get more depth on large gold from earlier SD units than from the latest models. Having used all the models the largest improvement I've seen over time is vast improvements in threshold stability and the ability to adjust for more varied circumstances. It may be that in a particular location an SD will do just as well as a GPX. But not where I hunt. My SD units all had the famous Minelab "warble" whereby the threshold constantly wavered. This meant that small nuggets or very deep larger nuggets had to give enough of a signal to break through the waver. A far cry from listening to a rock solid threshold for the faintest whisper or "break" in the threshold. You can get just such a rock solid threshold with the GPX units. It is not that the GPX goes deeper, it is that you can hear nuggets you would miss with an SD as they could not be discerned as clear signals.

More important on my ground was that my SD units simply could not tune out the intense magnetic basalt cobbles we have to contend with. The cobbles give a faint gold hit. So you either dug them all (impossible) or simply ignored the faint signals. But some of them were small nuggets or very deep larger nuggets. When the GPX arrived at my property I saw so many more small nuggets and deeper large nuggets come out of areas well hunted to the point of being "hunted out" that it was obvious the GPX had a significant edge. I'm not talking a nugget or two - I'm talking pounds of gold. The new GPX timings can allow for a clean solid threshold in areas where that was impossible with earlier units. Those that do not hunt such locations do not see the value in a GPX. Those that do know what I'm talking about. There is no way I'd go back to using an earlier model than the GPX-4500.

It should be noted is there are quite a few people modifying older SD units to get better performance on par with later units, and I'll admit these modified units are a wild card. Some swear by them and I'm not going to doubt them. But modifying older detectors is beyond where most people want to go so I think there is little doubt these units will only see use by a certain hardcore group of knowledgeable detectorists.

[kiwijw]

Thanks Steve. A great summary.

JW

[Jim Hemmingway]

This write-up has really clarified things for me. I always wondered about the differences for these high priced puppies...and now I know more than I did a few moments ago. Thanks Steve

Jim.

[Jonathan Porter]

Couple of points on this one, the GP3500 had a couple of other things going for it over the GP3000 and Extreme, namely the manual Tune control which was a boon here in Australia and more importantly the three Ground Balance speed options and in particular the Medium speed which allowed operators to detect in Auto Tracking mode even in quite ground types.

The other point is the GP series (right through to present day with the GPX-4500) have DVT (Dual Voltage Technology) which does offer a depth improvement on all target sizes over the previous SD machines.

Hope this helps,

Jonathan Porter

[Steve Herschbach]

You are right of course Jonathan. I was trying to present a summary more than a detailed analysis and so it is taken more from an lay operators standpoint. DVT and other refinements are all good things but at the end of the day once I got things set it added up to a little more sensitivity.

One thing I must impress on people is that in my opinion Minelab units are very easy to operate. The older units have few settings and in most cases little need to fiddle with them. Once you come up with good settings for a given area, you can go for days without adjustments - just turn on and go. My SD2200 at Moore Creek I could have glued the controls in place. I'm sure that is less the case in Australia with its far more difficult ground, but conditions are generally more forgiving here in Alaska.

Thanks for chiming in JP - your comments are always appreciated. For those that do not know JP has an inside lead on all things Minelab and produces an invaluable set of DVDs on the fine details of operating Minelab detectors.

I have to say that I always consider the GP3500 the best of the analog units and kind of miss its audio. The GPX audio lacks a certain feel that is hard to describe. I think the digital processing scrubs out certain nuances. But the GPX just offers so much more control there is no going back. My main wish would be for separate channel 1 and channel 2 manual ground balancing to be reimplemented as an option. I'm not sure how much I would use it but it is like a feature I once had and now do not, and with digital you can pretty much have it all.

Now if we could only get units. I'm a Minelab dealer in name only these days. Detectors have long been unavailable, and now if anyone wants a spare coil or a battry or a power cable they better hustle quick. All available supplies are drying up and everything seems to be on backorder. A few more weeks at this rate and I won't have anything left.

[Paratrooper]

Just a quick question . As I remember there were many units nicknamed "Unstable Extremes". I was told that there was no rhyme or reason to this since one unit serial# was a good unit and the next was a bear to use . Has the cause and solution been discovered ?

[Jonathan Porter]

The GP extreme got a bad rap right from the start due to some faults turning up in the initial batch of detectors released to market, once the word spread people for whatever reason started to become experts on which ones were good and which were bad (serial number wise), this was exacerbated when people started re-selling and used as a sales pitch the claim the detector fell within the "GOOD" serial number range etc. Any GP extreme sent back to Minelab would be fixed properly as they well and truly know what to fix and why after all this time. Like all things electronic you get your lemons but on the whole the GP extreme was a very good detector and in some ways was better than the later GP 3000 and 3500.

If you have purchased a second hand GP extreme then a service trip to Minelab to have it checked out would not go astray to make sure it is within spec and for peace of mind, the only thing to watch out for is if the detector has been modified in any way as I am pretty sure Minelab will now not work on modified detectors.

JP

[Reno Chris]

I have a GP Extreme I have used for years and its served me really well and found some nice gold. I ended up sending it back in not too long after I bought it (used), because I accidentally bumped the on switch while changing a coil (I'll never do that again!). Its run great ever since I got it back from the shop in Vegas.

However as a potential buyer, I'm kind of stuck on a fence right now. I'm ready to consider an upgrade, but essentially none are available. The few I've seen for immediate sale were offered at crazy high prices like seven or eight thousand (no thanks!). The other possibility is to make a down payment to a dealer and wait about forever - maybe 6 months or more - maybe a lot more. Well, the truth is that 6 or 10 months from now the GP 5000 will be out (or just around the corner even if it isn't out). So maybe I'll just wait for the 5000. I'm not going to pay sky high "scalper" prices, and I figure by the time the 4500 log jam is cleared out, ML will be releasing the 5000 not too long thereafter. So here I sit waiting to see what happens, and doing nothing. I think there may be a lot of other buyers in the same boat....

Just my thoughts and ruminations.......

Chris

[Steve Herschbach]

Hi JP,

"but on the whole the GP extreme was a very good detector and in some ways was better than the later GP 3000 and 3500"

Surely you know that was going to get a rise! Care to elaborate?

[Jonathan Porter]

Hi JP,

"but on the whole the GP extreme was a very good detector and in some ways was better than the later GP 3000 and 3500"

Surely you know that was going to get a rise! Care to eloaborate?

G'day Steve, yes a rise is a good description of a trout poking its head up to investigate what might be drifting past on the current. The GP extreme in its natural state is and was very well designed but due to parts becoming unavailable right around its release compromises had to be made to the basic design to allow for the replacement parts. I have done a few direct comparisons between the GP series and have found a correctly running GP extreme to be more stable and have slightly more depth over the later GP variants, we are splitting hairs here but it is noticeable looking at it from my professional perspective. Obviously I don't want my words to echo on down through the annals of time here so I should point out the differences are only small but suffice to say a GP extreme is a very well balanced detector when working correctly (as in sticking faithfully to the original design parameters). Electronic components move rapidly (Moores law) so from the original design phase to the replacement part stage things had moved on.

Hope this answers more questions than it raises.

JP