James Hetfield

From a November 2011 article found on mesaboogie.com:

"The core of the preamp switching and FX integration happens via Mesa/Boogie Amp Switchers controlled with Digital Music Corp.’s GCX Expander switching units. The Boogie amps being switched are two Triaxis Preamp’s run into a 2:90 Power amp. One Triaxis is set to the Mark IIC+ mode while the second Triaxis is used for clean sounds in the Green Clean mode. Like Kirk, James also has DBX Quad gates and T.C. Electronic G Major FX Processors along with a few extra pedals kept in the rack. The signal runs out of the 2:90 into two Mesa Traditional Straight 4x12s for a true stereo mix." (original source: http://mesaboogie.com/news/2011/11/metallica-live-rigs/)

James was using quad preamps and studio preamps during justice - black album era

Both James Hetfield & Kirk Hammett were using ADA MP-1 & ADA MQ1 EQ in their racks during the ...And Justice for All and Black Album era.