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I see the Minelab GPX 4500 is being discontinued. If the price goes down is it worth it to pick one up or has what replaced it that much better? Perhaps a premium will now be asked for the remaining new GPX 4500's? Is now the time to buy??

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The thing is some dealers still have them listed for sale. I just wonder if Minelab gives the dealers a heads up when they plan on discontinuing a high end items like a detector.

 Maybe they do them like they doing on the Vanquish and that’s keeping us in the dark. The whole time feeding us bull a little at a time using video.

 Every time Minelab sends me a email on the Vanquish using video I think of this girl back in high school done the same thing.

 Here I am begging to see more. I hope this is not a let down for me Minelab. She was !

 Chuck 

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The GPX 4500 was long ago superseded by the GPX 5000. In fact the 4500 was officially discontinued but then later reintroduced as a lower price alternative to the 5000 and perhaps as a counter to the Garrett ATX which came out around then. If you want a 4500 new with warranty, it would be time to buy before they are gone. I assume the GPX 5000 will continue to be available. I would not expect prices on remaining 4500s to change but once they are gone perhaps the GPX 5000 will be reduced in price. Or not. With Minelab you never know, they may increase the price! :laugh:

https://www.detectorprospector.com/forums/topic/5765-4500-vs-5000/

 

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If i were buying another 4500 it would be the older version not the re release.

I cant guarantee the following information is correct but its information i read in an Australian gold gem and treasure magazine a couple of years back 

"Quote: "After some time removing the white paint, that the feedback resisters located on the dual AD797 input opamps (voltage amplifying devices) were a lower value than on the original GPX 4500 models". (the board inside the GPX's are painted white - to cover up what components are used - presumably)

His feeling was that the lower capacity resisters (also on the 5000) made for a quieter detector  but resulted in  loss of depth on some targets. Testing showed that the newer 4500 lost about 15% depth on big, deep target responses compared to the original 4500 

He then replaced the resisters on the new release 4500 with the same ones used in the original 4500. The result being that the new 4500 now detected targets at depth the same as 2 other older 4500"s he had. 

Maybe thats why some people say the old 4500's  punched deeper than the newer ones or the 5000's

Source: Australian Gold Gem & Treasure - August 2017

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It's not the first time I've heard that Jin, although it's the first time I've heard it talked about in that way and actually verified.  When I was looking to buy a 4500 I read on various forums people talking about the older 4500's being more ratty but having better performance just from a user standpoint.  That's why I ended up getting an old Aussie made one even though it wasn't that much cheaper than a new one.

Also, this thread says the press statement for the new Minlab facility in Ethiopia will be making GPX 4500's. 

https://www.detectorprospector.com/forums/topic/10547-minelab-ethiopia/

 

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I don't doubt the the source figured out that different parts were used and managed to find the original parts, but the 15% depth reduction claims are simply laughable considering all the variables that affect depth, not to mention the myriad of other circuit components and settings involved in this detector than a single op amp and a few resistors.  But if it makes people feel better about getting the earlier version, then who can argue with that.  I'm sure minelab had their reasons, and it seems wise to reduce noise susceptibility.  So unless I am seeing an unwise tradeoff to incorporate less reliable or cheaper parts (on a 3 to 5K detector!), the old depth performance gain seems more like detectorist folklore, superstition, and OCD perception than a reality.    I got the red-headed stepchild 4800, so I wonder what funky parts were used in that one.  :laugh:

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I wonder if having a more stable machine could possibly result in more gold finds which would justify Minelab doing it even if it does mean a slight depth loss.  Isn't it the same thing DST did on the T2/F75? Made what was otherwise a ratty machine into a more stable machine at a slight loss in performance? Reading back on some old T2 posts people were wanting to get their hands older models prior to the DST changes or keep their old one without the upgrade as they felt they went deeper.  A lot of people don't like a noisy ratty machine and would prefer it stable though.  In some places my old school GPX 4500 is just unusable as it's so badly distrubed by EMI,  I have to completely dumb it down which makes using it pointless so I reach for a VLF and now the QED which perform much better in those conditions.   I'm just used to my GPX being a bit noisy and unstable.

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Simon - agree that the performance tradeoff to get noise susceptibility down was indeed what ML was after, but doubt they would have done it by knowingly introducing a 15% depth penalty. 

I have no doubt the author if the magazine article correctly identified ML part substitutions in the latter 4500 iteration, but usually those types of substitutions are benign and mainly due to obsolesence (couldn't get the original parts so used perfectly acceptable equivalent parts) or to reduce heat dissipation (e.g., lower reseistance values) which improves overall reliability. 

Although raw performance tradeoffs are enevitable when combatting negative issues such as noise immunity or heat dissipation with circuit tweaks, ideally a good designer would balance such competing effects so the tweak would not result in such a dramatic performance hit.  I have no reason to believe that a design team that could pull off the GPX detector series design in the first place, could screw it up with a few resistors and op amps.  Also, I suspect it would be hard to pin down the overall performance impact unless you had access to all the soil conditions, coils, and target types the GPX is designed for.

But I am not saying it couldn't happen either (there have been some prominent and even deadly tech busts in the news lately resulting from performance tweaks to proven designs by respected design teams outside of metal detecting).  It just seems very unlikely that such a dramatic hit in performance would not have gone unnoticed by the majority of GPX users.

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On 8/13/2019 at 10:10 AM, Jin said:

"Quote: "After some time removing the white paint, that the feedback resisters located on the dual AD797 input opamps (voltage amplifying devices) were a lower value than on the original GPX 4500 models".

Here are the next few lines from the above sentence.

"Quote: The feedback resisters set the gain of the input stage and while lowering the value of these parts does make for a quieter detector, which in some cases can be an advantage in very hot ground, there is an amplification loss of available signal in quieter ground"

  

 

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I tried to see if there was any online version of the article you cited, but no joy, so thanks for the additional details, Jin.  The resulting ultimate depth loss penalty would be hard to quantify with any certainty, so when a 15% figure gets thrown around I assume that it is an estimate based on the calculated gain loss of the input amplifier, but how it directly correlates to ultimate depth would require knowledge of the relationship of gain to depth and in some cases, that relationship is non-linear and/or could be compensated for by higher user settings provided ML built in enough head room in the settings above the defaults, I suppose.  

Bottom line, good information to have for anyone considering used or (until the existing inventory is depleted) a new 4500 purchase.  Thanks.

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