The Tesoro Diablo Ii

By Reginald G. Sniff
From page 24 of the February, 1993 issue of Lost Treasure
Copyright © 1993 Lost Treasure, Inc. all rights reserved

It is no secret that nugget hunting is about my favorite type of treasure hunting. In fact, just the thought of finding a gold nugget starts me thinking of ways to make another trip. Since most of my trips are to Arizona, about 800 miles away, I want every advantage I can to increase the odds of finding a gold nugget. For me this means using a metal detector designed specifically for hunting gold such as Tesoros Diablo II.

The Diablo II, like other nugget hunting instruments, has been designed to detect small nuggets deep. This is their main advantage over a typical metal detector. In other words, the Diablo II can detect extremely small nuggets that wont cause any response on most coin hunting instruments. In fact, on my last trip to Arizona, new owners of Diablo IIs were bragging about finding nuggets less than a grain in weight or about the size of the head of a straight pin.

This instrument is equipped with all the basic controls that make up a good nugget hunting instrument; a 10 turn ground balance, a sensitivity control, and a threshold control. Other controls included on the Diablo II are a 3 position tuning switch labeled RETUNE, NORMAL, AUTO, and a new 3 position switch (called minerals condition switch) labeled EXTREME, LOW, NORMAL which will be discussed in greater detail later.

One feature normally found on a coin hunting instrument, the discrimination mode, is not used on the Diablo II. Because this detector lacks the discrimination feature, it is not recommended for general coin hunting.

The Diablo II is one of the latest models in the Tesoro line to use their new plastic control housing designed with special shielding capabilities built into the plastic. This new instrument comes equipped with Tesoro s standard 10 elliptical wide scan search coil, a non metallic lower stem, and is powered by two 9 volt batteries. A wide selection of optional coils include 7,10, and 15 inch elliptical coils in both the wide scan and concentric design.

Tipping the scales at about 3 pounds, the Diablo II is both light weight and well balanced making long outings less tiring. Adding to the convenience factor is the ability to hip mount the instrument without the addition of extension cables, since the standard coil comes with an extra long cable.


My initial testing of the Diablo II was done as a field test for Tesoro and was included in one of their Metal Detector Information magazines. This field test report contains some of the previously published information as well as new information.

I found the setup of the Diablo II to be extremely simple. Turn on the instrument, wait for the battery check to conclude and proceed in setting up the controls for the preferred sensitivity, ground balancing, and threshold setting.

Although I found the ground balancing of the Diablo II simple, I should mention that due to the increased sensitivity of this instrument, newcomers may find the ground balancing touchier than on a typical coin hunting instrument. Unfortunately, the ground response is nothing more than another target, so, the Diablo II not only senses extremely small nuggets well but also senses the mineralization of the soil with greater sensitivity. Fortunately, the 10 turn ground balance control makes precision tuning a lot easier than instruments with a single turn ground balance control.

One control that helps alleviate the ground problem is the previously mentioned 3 position minerals condition switch. The labeling, EXTREME, LOW, NORMAL, are selections that refer to the ground conditions.

When hunting in areas where the ground is constantly changing, making hunting frustrating, a quick change from the LOW setting to either the NORMAL or EXTREME setting will help minimize the changes caused by the ground minerals. When combined with the standard single turn sensitivity control, almost any combination of sensitivity settings can be made to compensate for the ground conditions.

I did find that when I changed the minerals condition switch from LOW to one of the other settings, I noticed a slight but noticeable decrease in sensitivity in air tests. However, I found the true loss in sensitivity of buried targets was generally minimal when switching from low to normal. More specifically, I found that, under certain conditions, reducing the sensitivity enhanced the possibility of finding nuggets. I know this sounds strange, but after running several tests using nuggets as targets, I found that in bad ground, switching from low to normal allowed me to hear faint responses from small deep nuggets that I couldnt hear when the switch was set on the low position.

On deep small targets that I could hear in both the low and normal positions I found that when switched to normal, the targets seemed to respond with a clearer but somewhat weaker audio signal.

When I switched to the extreme position I did see some depth loss but the responses to the ground minerals were greatly reduced.

One control I found very important to adjust properly was the threshold control. The setting of this control is a matter of personal preference, but care should be taken to adjust it to hear the slightest audio changes. For me, this required the threshold to be set so I could just barely hear an audio response. I found that when the audio threshold was too high, it was more difficult to hear the really deep targets.

While playing with this setting the one weak point of the Diablo II was noted. At very low threshold settings, there were times I could hear slight but distinct variations in the audio. At times this could best described as a low growl. Concerning at first, I became used to it and this signal variation became almost unnoticeable.

During my various testing of this instrument I tried 5 different coils including the both wide scan and concentric 10 inch and 7 inch elliptical coils plus the 15 inch widescan elliptical model.

All coils worked perfectly with the detector but some ground balance adjustments were necessary when changing from coil to coil.

I found that the concentric coils seemed to be a little more sensitive to extremely small nuggets than the widescan coils, but they also seemed to respond more to the ground mineralization. After extensive testing I decided that I preferred the widescan models due to their reduced response

to the ground minerals. My favorite coil turned out to be the optional 7 inch widescan coil over all others because of its lighter weight and ability to get into tight places. Surprisingly,, this small coil sacrificed little in overall depth also.


My initial testing took me to the mountains of Colorado where the Diablo II proved it could tackle the most severe mineralization. Although I didnt find any gold on my initial outings, I did find several very small sized pieces of lead and other metals. This initial field testing displayed that the Diablo II could find as small a nugget as the average person would want to find.

One of the serious problems of nugget hunting is dealing with hotrocks of which Colorado seems to have more than its share. During my initial outings I tackled the area with the ground balance control adjusted a little differently than what might be considered normal. Instead of adjusting for proper balance over the ground, I set the ground balance control to null the most common negative responding hotrock. The reason for this setup was to assure I would get a response from a target next to such a rock. A negative response from hotrock can easily mask a weak signal from a small target such as a nugget hidden beneath or along side of the rock.


My next series of tests took me to Arizona, a mere 800 miles away. Since I was already familiar with Tesoro nugget hunting instruments, I knew what to expect in this area, and quickly adapted to the varying ground problems.

As to be expected, my first couple of days were filled with digging a lot of small pieces of trash including boot tacks, pieces of lead bullets and other pieces of metallic junk.

Although unfamiliar to average coin hunters, the digging of trash is a common occurrence when nugget hunting. To a beginner, this may seem frustrating until they are rewarded by finding one small nugget. Somehow, the sight of gold glistening in the sunlight all but erases the frustration of digging junk.

As mentioned earlier, the Diablo II doesnt have a discrimination mode so a person should dig every target to be sure of its nature. This lack of discrimination isnt so bad when one realizes that most nuggets I have found seem to be hiding next to a rock and a lot of the rocks in nugget country are some form of a hotrock.

As mentioned earlier, a hotrock can give a very strong negative response. This response is especially critical to the discriminating circuitry. Using the discriminating mode of a detector, so equipped, to determine whether to dig a target can easily cause a nice nugget to be rejected.

To put nugget hunting in perspective, we have to realize that nuggets are rare. In fact it has been stated that finding a quarter ounce nugget is as rare as finding a 5 carat diamond. So the last thing a person wants to do is to hunt all day, week or month and pass up the one nice nugget they pass over on a nugget hunting excursion because they think it responds as trash.

Getting back to my outing in Arizona, by the third day, I was getting as frustrated as any serious nugget hunter does. The day had been the usual, digging the few and far between targets only to find that they were trash.

Occasionally I would get a weak positive response that would cause the old heart to skip a beat or two only to find the signal was coming from some of the reddish rocks found in the area. After a while, I got to where I could easily determine if a rock was causing the signal. One way I found to check to see if the target was a positive responding hotrock was to adjust the ground balance slightly to see if the rock would null out. Another way was to see how quickly the target response would die off as I passed over the target with the coil at different heights above the target.

If the signal would change dramatically with a small change in coil height, I was fairly certain that the target was a rock. Just to be sure I would investigate each and every signal regardless if I was certain it was a rock.

Finally, late in the afternoon, I received a nice solid response. Somehow, I knew what this target was before it was dug up. Sure enough, after some brief digging I was rewarded with the sight of a respectable nugget (about 2 pennyweight in size). This turned out to be my only real find of the trip but somehow it was all worth it.


The Diablo II isnt the fanciest nugget hunting instrument around, nor is it the most expensive. It is, however, a very powerful instrument equipped with all the necessary features needed to find nuggets.

One of the big advantages of the Diablo II is the wide variety of searchcoils available. As mentioned earlier, a person can select from three different sizes and two different styles, making this instrument one of the favorite basic nugget hunting detectors for all conditions.

If youre looking for an economical nugget hunting instrument with plenty of punching power in the worst of grounds, you should stop by your Tesoro dealer for a demonstration, or contact Tesoro at 1-800-528-3352.