A noise gate can help with pickup hum/guitar grounding buzz, especially at high gain overdrive settings. All it does is cut the signal from the guitar when the input drops below the threshold.
It can also quiet a noisy preamp when the gate is used in the effects loop. Again, only when not playing, since when you are playing the gate is open.
If the noise is coming from the power amp, there is nothing a noise gate can do.
Yes I own the boss pedal, since about 1993/93. They are essential for high gain guitar. And I did use mine in my early bass days, where I had a huge pedalboard. The NS was integral, as a power supply for the rest of the boss pedals on the board, and I utilized its effects loop. The way to run it is to put the noisy pedals such as distortion, chorus flange etc in the loop, so when the guitar is gated, the noise and hiss generated from the pedals is also shut off. Delays and reverbs are best used after the gate, and not in the gates loop, so the reverb tails and delay repeats don't get cut off when the gate kicks in.
Using the boss suppressor in a guitar amps effects loop (a specific way to hook it up with the guitar feeding the input of the gate, and the gate loop and amp loop connected) is a good way to calm the hiss common to tube amps with high gain preamps, which is where most of the hiss comes from. But again, no gate or hush can quiet a noisy power section.
That is the correct way to do it on a single Channel guitar amp with master volume. Cranking the master and controlling volume from the gain or input volume control is the correct way to get the loudest clean tone from a guitar amp.
With bass it is a little different, but the same principal would apply to an SVT classic.
With a more modern hi fi type amp (swr etc), it is best to run the preamp gain to just before clipping, for the highest signal to noise ratio. Cranking the master on those is just a good way to amplify the noise floor of the preamp.
It is really different depending on the type of amp. Bass is a more HiFi application and many bass amps are more closely related to PA systems than guitar amps.
Rumbles are different as well. Since the gain is more of a variable attenuator and does not turn off the signal when turned all the way down. There is no need to crank the master on a rumble since the gain control is not prone to introduce distortion or ugly fatty clipping like the gain control on other amps do. Consider it a teenager proof feature perhaps. Personally I would like the option to overdrive the first gain stage, but the rumble does not allow that, at least not with a passive bass in my experience. But I can get close enough with the overdrive.
The rumble truly is a different beast, which is easier for the non technically inclined to get a good standard warm and clean bass tone. Unlike an SWR or Boogie where the good tones take a bit more expertise to pry out of the amp, and there are many wrong ways to dial the amp in that sound like butt
rumbles make it easy
