I know how the ProRackG works (filters noise from the pre-amp using information about the noise coming from the guitar), but does it also filter this noise during playing?
In other words, does it clean up the sound when the guitar is played or does it shut off like the Boss NS-2?

Also, do professional studio's use noise gates when recording guitars, and does it help getting a clearer sound?
Jackson KV 2, Jackson COW 7 (both in B), Jackson Demmelition V
Bogner Überschall (blue rev)
Marshall 1960B Vintage (2x V30 & 2x G12T75)
TC Electronic G Major
BBE Sonic Maximizer 422A
Weber Mass 150w
ISP ProRackG
T.Racks Dinopower
I'm not familiar with the ProRackG (never used one)... but I just read up a little about it,...,

A typical noise gate basically works like this... when the signal reaches a certain level (usually a low level), the device kicks in and it cuts off the signal (basically, if you play guitar, the signal is high, so sound goes through; but when you stop playing, signal drops, noise gate cuts in and stops sound, so you don't have misc noise when not playing). But it should also be noted that most nice noise gates (particularly rack-form, not pedal) feature a variety of controls to allow you to adjust the gate's parameters... such as the level where it actives, how long it takes to activate, how gradual it cuts out, and more.

Reading about the ProRackG... it sounds like it isn't even really a "noise gate" at all... it really sounds like all it is a "noise filter" (or at least, it may have a real noise-gate built in, but it sounds like its primary use and design purpose is for "filtering"). Basically, you plug your guitar in one channel... it detects and eliminates "noise"... you throw the signal into your amp... and then you throw the amps output (I believe through its effects loop or such) through the 2nd channel... and it detects and eliminates "noise" at this stage. So really... it sounds like it is working/processing while you are playing.

As for professional studios... I'm not sure about ALL... but I imagine most studio engineers will employ a noise gate somewhere in the signal chain of amp; particularly when it is high gain oriented (where just slightly touching a string makes a very audible noise lol). But in this environment, they are not likely to use something like the ProRackG, or those pedal types... they're more likely to use a noise gate with a lot more features/settings. For example... some noise gates have a very FAST and quick cut-off when the threshold is passed; this may not be desirable when recording, lol... So better noise gates that employ better timing/fading/etc are more likely to be used. But this isn't to say it is all done this way.... I know if I were recording with my high gain amp, I would definitely use a noise gate to reduce unwanted noise when I'm not playing; otherwise, I'd probably spend too much time trying to edit it out in any sort of silent-passes lol...

Anyway, enjoy your ProRackG!