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Marshall designed the Kerry King signature amp, the 2203KK JCM800 has been around since 2007. It only took a decade for people to start cloning the noise gate.
This noise gate was cloned in the Zuul, Cock Blocker, Phalanx, Endless Blockade, Tannhauser, etc....
"Marshall’s engineers developed a special noise gate circuit with a threshold control.
Most noise gates completely kill the sound once it drops below a certain threshold,” Bowcott says. “This noise gate has an ultrafast expander circuit that’s similar to what you’ll find in a studio-quality noise reduction unit. It will work extremely fast during tight, precise staccato rhythms, giving you those desired ‘holes of silence.’
When it comes to sustained notes, though, the expander gradually attenuates the signal by following the dynamics of the note, giving you a much more natural-sounding gating that won’t prematurely cut off the end of a note or chord that you want to ring.”
This is considered by many to be the best noise gate for guitar.
Personally I use a BOSS NS-2. It adds a bit of midrange. But the only time I use it is when using a OD / boost....and they all pretty much add midrange.