Compass Au 2000
By Reg Sniff
From Page 8
August, 1994 issue of Lost Treasure
It is no secret that hunting for gold nuggets is one of my favorite aspects of treasure hunting, and I have found through experience that my most important tool is a good metal detector more importantly, a detector specifically designed for hunting nuggets. I say this because the most frequent size nugget found is very small, the type that nugget hunting instruments are designed to find.
To meet the needs of serious nugget hunters, one of the oldest names in the metal detector field, Compass Electronics of Forrest Grove, Oregon has just introduced two new nugget-hunting detectors, the Au 52 and the Au 2000. I have been fortunate enough to get the opportunity to field test the Au 2000.
For those of you who follow my field test reports on nugget hunting instruments, you have probably guessed where I elected to do my testing. Thats right Arizona! My reason is, I have been very fortunate to be successful on past trips. Was I successful with the Au 2000? Yes, but before discussing that aspect, I will first explain a little about this new detector.
The Au 2000 nugget-hunting detector is really a dual purpose unit that can also be used for coin hunting because of its excellent discriminating capabilities. This new instrument comes standard with the features of a 10 turn ground balance control, front end sensitivity control (called Power Level), and another control called Threshold control which selects between two different auto tuning speeds and threshold signal level.
What makes the Au 2000 stand out in a crowd is the two distinctly different frequencies of operation, 13.77 kHz and 52 kHz (13,770 and 52,000 cycles per second). The higher frequency, designed for gold hunting, gives the best response to nuggets, especially the extremely small ones. The lower frequency, recommended when the instrument is used for coin hunting, can be readily used for nuggets also in the more extremely mineralized areas. Flipping a small switch in the upper left corner of the control housing does the selection of frequencies.
As mentioned earlier, the detector has a discriminating mode, called the Trash Out feature by Compass. This mode can be used when hunting either coins or nuggets. The operator can switch between the all metal mode and the Trash Out mode by merely pressing the appropriate touch pad.
One positive feature of this discriminating mode is the wide discriminating range which allows the use of this feature while hunting for the tiniest of nuggets. This feature can allow a serious hunter to search in the most trashy of areas for nuggets and minimize the amount of trash dug.
An additional feature of the Au 2000 is something called VCO (which stands for Voltage controlled Oscillator). This feature allows a target to not only give an increase in volume but also a tone change when in the all metal mode of operations.
When the VCO is on, the pitch or tone of the audio signal increases when the audio level increases. The VCO switch, located in the upper right hand corner of the control unit, has 3 positions, HI, OFF, LOW. In off, the VCO feature is not functional and all targets respond only with a louder signal, similar to a typical metal detector.
In the low position, a target responds with a volume increase as well as a moderate increase in pitch. In the HI position a greater pitch change as well as an increase in volume occurs making weak targets more noticeable. Both VCO modes aid in both sensing a target but more importantly, pinpointing a target.
The Au 2000 also comes standard with a lightweight 9 elliptical wide scan search coil equipped with a long cable which is needed for hipmounting. To hipmount the instrument, the operator just slides the instrument off the specially designed handle and slips a belt through the appropriate slot located on the back of the control unit.
For those of you familiar with the different Compass models, the Au 2000 uses the same control housing as their Scanner series, and like them is powered by 3 nine volt batteries accessible through the back of the instrument. Also accessible through a small hole located on the back are two small switches. One of these two switches affects the ground balance and the other the discrimination feature.
To increase the range of the ground balance control, Compass has elected to use a small switch (mentioned above) to increase the ground adjust range. Of the two switches accessible from the back, the top switch, which can be best described as a coarse ground adjust, allows the operator to select between mineralized ground and saltwater conditions. Normal setting is the ground setting.
The lower switch, also accessible through the same hole, is noted as Hi/Low. This switch alters the discrimination mode of operations. When in the Hi (factory setting), the discrimination mode is less affected by the ground balance control. Using this mode loses some sensitivity but hotrocks are all but eliminated as false signals. In the Low setting, greater depth is possible but at the expense of incurring false signals from highly mineralized hotrocks. Also, with the setting in the low position, the discrimination mode is dependent on the ground balance control setting. If the ground balance control is improperly adjusted, false signals are very possible even from the mineralization of the ground.
My first series of tests (including a trip to Arizona) were made with one of the first Au 2000s produced. This instrument displayed great sensitivity, especially to extremely small nuggets and remarkable stability, except when the coil was bumped. Bumping the coil against a rock or a bush (a common condition when nugget hunting) could cause the detector to respond with a false signal.
During my initial testing I noticed another minor limitation concerning the threshold control. An operator could only select between fast autotuning which had a preset threshold or slow autotuning and adjustable threshold. When using very sensitive high impedance earphones like my Koss units, the preset threshold level of the fast autotuning mode was a little too loud for me. Checking the Au 2000 with other earphones having lower impedance didnt display the loudness problem.
A call to the factory revealed that changes were in the works to correct the coil problem. Because I was already preparing a second trip to my favorite nugget hunting area in Arizona, I sent the instrument back for the necessary changes. My new test unit came back with a new coil which had internal reinforcement to eliminate the falsing when the coil was bumped or banged against an object.
Also changed was the threshold control. This new test unit was equipped with push-pull selector which allowed me to use either the preset threshold level or adjust the level to suit my preference while selecting between either a slow or fast autotuning. This change made a dramatic improvement when using my Koss earphones. (1 should note, that this second change is planned for future units and may be in production by the time this article is presented.)
Initial testing was done with a selection of targets including several different sizes of nuggets acquired on previous Arizona trips. What I found during the initial tests was the 52 kHz frequency really excelled in detecting extremely small nuggets, and did an exceptional job on detecting larger deeper targets also.
The lower frequency, 13.77 kHz, was tested on different test targets including coins buried at various depths as well as nuggets. This frequency seemed to excel in the discrimination mode capabilities, and I found it easy to to detect my 6-1/2 deep dime buried in highly mineralized ground, matching some of the more expensive coin detectors.
I should note that when making my initial checks I selected the Low setting of the Trashout select located at the rear of the unit. (With this switch in the Hi setting, I was unable to detect my 6-1/2 deep dime). Since I am accustomed to false signals from hotrocks and know what to expect, I opted to leave the switch selected to low to obtain the additional depth.
Comparing the different frequencies on really small nuggets, the pinhead size displayed the strengths of the higher frequency. The 52 kHz setting responded with a louder more positive response on the extremely small nuggets. Also, while checking one of my deeper buried targets with this frequency (a nickel buried at 9), I noticed a small sharp blip of a response, something not noticed by my other gold detectors. A little investigation revealed an extremely small piece of tinfoil had been blown in and settled over my deeper target.
Getting back to discussing the discrimination mode of the Au 2000, I found the discrimination feature of this instrument to be extremely accurate. More importantly, I was very impressed with the extremely wide range of discrimination adjustment. For nuggets, I found that using the preset setting allowed the detector to reliably detect even the tiniest of nuggets (pinhead in size) while rejecting most iron trash.
My coin hunting testing was confined to careful checking of my test targets and one trip to a nearby park. Setting the discrimination control at the appropriate rejection positions of FOIL, TAB, and S CAP, resulted in the appropriate rejection of these targets.
My park trip didnt result in any remarkable finds but did display to me that this detector is right at home in a coin hunting environment. Also, during my nugget hunting outings, the discrimination feature was as smooth and accurate as any I have used under such adverse conditions. One thing that will probably occur with the Au 2000 is the detection of old pop bottle caps as good targets, a problem with all wide scan coils.
OFF TO ARIZONA:
My trip to Arizona left me wondering if my luck would continue to hold and I would again be lucky enough to find a nugget or two. In all fairness, I should state that nugget hunting is one of the more tiring and frustrating forms of metal detecting, however the rewards when successful are also more rewarding.
Actually, I made two trips to Arizona with the Au 2000, first with the initial unit before the modifications and a second one with the later revisions. The first trip was unsuccessful as far as finding nuggets but I did get a good feel of the instruments capabilities.
The second trip did prove more favorable in the fact that I did manage to find a total of 6 small nuggets. What made this a great trip was the fact that all of these nuggets were taken from a couple of heavily hunted areas. Five of the 6 nuggets found were very small mundane shaped pieces of gold, each weighing between I and about 5 grains. The 6th nugget, which was my best find, was a little beauty weighing a little more than a pennyweight. This nugget is pretty in the fact that it is very rough and is wrapped around a piece of quartz.
I mentioned the nuggets first so I could concentrate more on the little techniques I found very useful on the Au 2000.
Initially I set the detector for 52 kHz, near maximum sensitivity, fast autotuning, minimum threshold, and high VCO. I also should mention that almost all of my hunting was done using the all metal mode of operations and only using the discrimination feature to verify strong targets.
The reason for this procedure is because, unlike any form of coin hunting, nuggets are rare, elusive, and the various ground problems including a wide variety of hotrocks can easily cause the most accurate of discriminators to fail to accurately respond.
Also, during my trip I was continually experimenting with different instrument settings including changing frequencies. This testing proved that selecting the lower frequency did minimize the ground responses making searching extremely mineralized areas more comfortable but made the detection of extremely small nuggets more difficult. Both large and very small nuggets can be readily found by the lower frequency, but the sharpest response from very small nuggets came from the higher frequency.
One location, was a place recently scraped with a dozer. It contained ground so hot that operating in the 52 kHz frequencies was extremely difficult. I opted to use the lower frequency at this location.
In the areas having extreme mineralization and quickly varying ground mineralization, I also noticed that I could still could get excellent results in terms of depth capabilities with lower sensitivity settings. Although targets such as small deep gold nuggets did respond with a smoother less distinct response, the response to various ground problems was also much less.
In the areas where I found my nuggets, I had the sensitivity set between the preset mark and maximum, depending on the particular location I was hunting.
It wasnt until my 4th day of hunting that I decided to follow one of my cardinal rules of nugget hunting, which is, to search an area very slowly. This search speed is probably best described as searching at a snails pace. Once I slowed down, everything seemed to fall into place.
One other trick I implemented was to swing the coil carefully and trying to maintain a constant coil height above the ground. This combination of techniques, combined with fast autotuning and the minimum threshold settings, allowed me to hear the whisper of change in audio response from each of the nuggets.
The fast autotune circuitry readily compensated for the different ground changes and minimized the negative boing from some of the more radical negative hotrocks. With the slow coil movement and practice over the offending rocks, I was, able to distinguish the different audio changes caused by a metallic object and the rocks.
One little trick I used, especially near the end of a day when I was extremely tired and didnt have the energy to dig every suspected target was, once I got a questionable response (I didnt know for sure if it was coming from a rock or a very deep target), I would approach the suspected target slowly and carefully from different directions.
With this technique, a signal response from a rock would generally disappear or seem to move, while a response from a metal target such as gold would remain. The real trick to this technique was to go slowly.
In fact, this slow technique allowed me to detect one of my very small nuggets that were buried between two offending rocks. The trick was to carefully listen to the different signals.
Metallic targets responded with a positive response as I approached the target from different directions. The rocks would give a positive response after I passed by the rock. Also, once I got what I thought was a good signal in an area I would swing the coil just enough to clear the suspected target and then swing back.
As mentioned earlier, I used the discrimination mode to verify a strong response only. If the signal was weak or there were a lot of adverse rocks in the area, I would dig the suspected target out of the hole and then check the pile of dirt with the discrimination mode.
One might ask why a person would check once the nugget was out of the ground. Well, in the area I was hunting, the nuggets were coated with a red clay making it impossible to recognize them as nuggets until they were cleaned a little.
Although I found the Au 2000s discrimination circuitry very positive and as accurate as any I have used while nugget hunting, I know from past experience with every other discriminating detector I used for gold hunting that, too many things can influence the discrimination mode. As those of you who have hunted for gold nuggets can verify, gold is rare and missing one nugget because of an error in the discrimination mode because of something like a nearby hotrock can mean the difference between success and failure.
My general procedure proved right since 4 of the 6 nuggets initially did not give what could be called a positive response in the discrimination mode. Judging from the ground conditions, there were different reasons. In a couple of cases, the target was too to deep for the discrimination mode to reliably detect the target, and on the others, the response from nearby hotrocks masked the nuggets response.
My recommendation for the Au 2000 and any other discriminating detector is to only use the discrimination mode for verification of sharp strong responses of suspected gold targets. Even then, I would recommend that when sweeping a suspected target that only the minimum of side to side motion be used to avoid sweeping over nearby hotrocks that could influence a good targets response.
The Au 2000 is an exceptionally sensitive dual-purpose nugget hunting instrument that is right at home coin hunting. The dual frequency, VCO capabilities, and wide range discrimination give this instrument extreme versatility in all types of hunting and ground conditions.
The 9 elliptical coil is lightweight, easy to maneuver in tight places. The detector is also lightweight, well balanced and the ease of hipmounting makes it possible to operate the Au 2000 in almost any environment comfortably.
The discrimination feature of this gold hunting instrument is very accurate and in the adverse conditions found in gold areas, it is as good as any I have tried.
Simply stated, I heartily recommend the Au 2000 to anybody who is serious about nugget hunting and wants to find those nuggets left behind by others.
For more information about the Au 2000, the Au 52 or any other of the Compass line of detectors, you can contact Compass at: Compass Electronics, 3700 24th Ave., P. 0. Box 366, Forrest Grove, OR 97116. Phone: (503) 357-2111 or FAX(503) 357-1919.