The manual is a bit off on this point. The C&J and Relic primary and alternate search modes all use a style of mixed-mode audio. The mixed-mode operation on the MXT is different from previous White's products in two respects. First, the all-metal portion of the audio response uses a much higher default S.A.T. setting than, for example, the DFX or XLT. Because of this, the all-metal portion of the mixed-mode response has a motion requirement. The other unique aspect to the MXT's mixed-mode operation is that the MXT automatically switches from all-metal mode to discriminate mode dynamically based on target strength. On the XLT/DFX mixed-mode, both all-metal and discriminate audio are always heard.
<b>"If I hunt in the relic mode with "0" discrimination and trigger in the center, would that be a true "all metal" mode on the MXT?"</b>
That depends on the precise definition of "true all-metal." With the disc. at 0, C&J Primary and Relic Primary and Alt modes will all provide a response to targets too weak for their VDI number to be determined (as will Prospecting mode, I might add). But the ground-balance will cause sensitivity to be lost for targets with a VDI number to which it is set.
Enjoy.