The Boss NS-2 Noise Suppressor was seen on the last known version of Dimebag’s pedalboard, used with Damageplan. Photos of this pedal can be seen on this page – Visiting Dimebag Darrell’s Home | The Making of Stompbox Book (scroll all the way to the bottom).
Based on the photo, the threshold on the NS-2 was set to around 11, decay to 8, and the mode was set to “reduction”.
In case you’re not familiar with what the noise suppressor guitar pedal is used for – it is used to reduce or eliminate unwanted noise, such as hum or hiss. The pedal works by detecting the level of the incoming signal and then cutting off the signal when it falls below a certain threshold. This can be helpful when playing with high-gain settings or using distortion (which Dime obviously did) or other effects that can add unwanted noise to the signal.
Dime first used the Boss NS-2 while recording GSTK (after his 6 band EQ (and PQ-3*) in front of two “wet/dry” RG100HT rackmount amps), along with his stereo “Hush” IIC in each amp’s loop.. plus the MXR Flanger/Doubler and original MXR 10 band EQ (V shaped “scoop”) in the loop of one amp (according to Terry Date).
*Not even Grady knew where the PQ-3 and 4 (or the Aphex Aural Exciter and Rocktron “Hush” units) were placed in Dime’s signal chain. It’s possible that Dime used the PQ3 or PQ4 in the loop (in place of his Sony MCI 500 Parametric EQ’s that were used to cut 1.2kHz out of his signal), especially if he only used the MXR 10 band EQ in the studio. Also, the Aural Exciter is like a BBE Sonic Maximizer (or Presence and Resonance boost), which could’ve been used in the loop as well.. and the “Hush” units were all “stereo” noise reduction circuits that were designed to be used in the loop of 2 separate amps, but Grady believes Dime only used one channel.. in front of his amp splitter, which sounds very questionable.
(Also, boosting and cutting frequencies at the beginning of your signal chain has no effect on “gain staging”.)