Input Gain: Hammett used the "Normal" input on his Mesa/Boogie Mark IIc+. The gain setting on this amp is highly dependent on personal preference, but it's generally kept in the mid-to-high range.
Channel: The Mesa/Boogie Mark IIc+ has two channels: a "Clean" channel and a "Lead" channel. Hammett primarily used the "Lead" channel for the Master of Puppets album.
Mid-Boost: The Mesa/Boogie Mark IIc+ has a mid-boost switch, which can enhance the mid-frequency range. Hammett often engaged this switch to add clarity and cut to his guitar sound.
Master Volume: The Master Volume controls the overall loudness of the amplifier. For heavy rhythms like those found in Master of Puppets, it is typically set higher to achieve a more saturated and heavy tone.
Tone Controls: Hammett used the graphic EQ section on the Mesa/Boogie Mark IIc+ to sculpt his tone. The 12-band EQ allows for precise adjustment of frequencies. Without specific details, it's difficult to replicate his exact tone settings.
Guitar: Besides amps and pedals, Hammett's guitar choice also plays a significant role in achieving the Master of Puppets tone. He used a modified Gibson Les Paul Custom equipped with EMG 81 and EMG 85 active humbucker pickups.
Remember that these are general guidelines, and your tone will ultimately depend on your specific setup, guitar, pickups, and playing style. Experimenting with different settings is key to finding a tone that suits your preferences.