What does it mean "gate" in fuzz boxes?

[tenser75]

What's the principle behind the GATE knob?
is a RC filter?

does it lower the noise level?

I notice the big muff is super noisy and is almost "open"
where Fuzz Factory which has the gate knob seems "compact/closed"
Does the gating affect the sustain?

Id' love to learn the circuit and principle behind it

thanks

[digi2t]

I believe it's more focused on voltage control, either supply voltage, or bias voltage. From my limited experience, either lowering the supply voltage, or varying the bias voltage, will gate the sustain. That's to say, limit the amount of sustain the circuit can deliver at a particular voltage, "closing the gate" on a note, in a manner of speaking.

[Mark Hammer]

If I cast my mind back to my early days, one of the characteristics of early fuzz units was that they gated a bit.  As players, it kind of bugged us that the note would suddenly cut out, obliging us to pick harder to keep it alive longer.  As a design element, it was a primitive noise-management feature.

In part, I suspect this may have been because so many guitars were equipped with pickups that did a poor job of rejecting hum and any other interference.  Fuzzes, being quintessentially high-gain devices, ran the risk of amplifying hum and other noise, so instead of applying noise gate pedals to keep that stuff under control (which tended not to happen in pedal form for another decade or so, even though studios had used noise gates for a while already), the gating was built into the very source of the objectionable noise - the fuzz.

In another way as well, so many fuzz pedals would exhibit interesting "misbehaviour" as the battery ran down, often resulting in a sort of "micro-gating" or sputter behaviour.

After making myself a Woolly Mammoth clone, which includes a control for precisely this aspect, I found myself playing around with the Q2-emitter-to-Q1-base path in the standard Fuzz Face topology that shows up in so many pedal designs.  Increasing the resistance of that path can yield some interesting forms of such gated sputteriness.  It doesn't completely cut out (although I suppose this would depend on particulars of the design and resistance value), but let's say there are interesting "hesitancies" created in the tone that interact pleasingly with the gain setting.

Aesthetically, providing a means for gating would seem to be in direct contravention of the principles of fuzz pedals, given that such pedals have generally been used to keep notes alive and sustaining for much longer periods, with an aggressive demanding tone.  But more and more players seem to find use for tones that sound like the guitar is "giving up", running out of energy, "zombified", or whatever.  And the sputtering gated quality gives it that effect.

[nocentelli]

In a Big Muff, replacing the 100k resistor to ground on the second clipping stage with a 100k pot gives you a simple/crude gate control.

[tenser75]

wow, very interesting... now i wanna try all this mods!

[tenser75]

although I feel the gate is not the supply voltage... i have seen it called "starve" or "stab(ility)"
but the gate pot seems always connected one of the Tranny legs... I was wondering if there is a rule about it

is it simply that more or less voltage pushes the signal/wave in one direction?

again I'm a newbie in electronics so i'm not sure what talking about!

[aron]

To me it usually means it will control the sustain of the note as you hold it. So adjusting it can make the note cut off faster or slower or sometimes it makes a sputtering sound.