Our Number 1 Mod

This mod has proven to be the ultimate mod for depth & sensitivity. I have now performed the GPM mod internationally and have never had one comment that it did not perform brilliantly.

Main Benefits

Depth & Audio Enhancer

This unit (seen in the picture above on the side of the SD2000 control box) combines a 12V step down adjustable regulator and Audio Signal Enhancer. No other units compare with this one. Highly reliable and rugged to take most punishment out in the field. All circuitry is Surface Mounted technology and heat isn't a problem. The regulator is adjustable from 6.9V to 8.5V (± 0.1V) to suit all types of terrain and coils. Tests that we have done improve depth considerably. A test we performed using a Coiltek 24" UFO coil on a 5oz nugget in average mineralised ground improved depth by an incredible 5" over 7.3V systems and over 6" on standard battery system. The beauty of this system is you can use it at the lowest setting and run all day at a constant voltage of 6.9V, just as if you had a fully charged 6V battery online. The Audio Enhancer is filtered and compares with the best in the market.

Sensitivity Control

The next part of the mod is the 2 variable sensitivity controls that are located on the front of the detector. These control the biasing to the Op Amp receive circuitry that in turn enhances the signal received from the coil. This ultimately leads to 2 major enhancements, Sensitivity and response from targets and Depth increase. Tests by ourselves and others (notably Jack Lange, from Jack Lang Detectors) show that without using the Depth and Audio Enhancer (DAE) with the standard 11" DD coil provided by Minelabs with the detectors gives a depth increase of 4" + over the SD2200. Couple this with the DAE and a large coil and you really have an Extreme metal detector in your hands. For further information on this please download the Instruction Manual in the downloads area or contact me personally at
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This is a better view of the Power panel side. The extra controls on the face of the detector are the original Barry Johnson Audio Mods not something that is included. Also it has 2 Extra Frequencies.