Common Causes of Gating?

[killerkev]

Can someone list the common causes of unwanted gating effect?

I did some preliminary searches on it and found perhaps transistor biasing? Continued to search what transistor biasing was but the literature I found I believe is over my head. A simple down to earth explanation for the mentally impaired or is that just not gonna happen?

[R.G.]

Unwanted gating is nearly always a biasing problem.

The whole point of biasing in amplifiers is to move the operation of the active devices into a region where they can amplify as needed. If the bias is off, the device may not be able to amplify except on signals bigger than some level. This can result in the signal seeming to start up suddenly when a signal is big enough, and then to suddenly quit when it gets smaller than what is needed to overcome the misbiasing.

In some cases really large signals can cause a bias shift because they overcome the input limitations of the active device, and cause the input capacitors on an amplifier to load up on too much voltage one direction or the other. This is known as blocking distortion in tube amps, or simply "farting".

[LucifersTrip]

you can also gate with an "inappropriate" size cap. a long time ago (in my circuit bending days) I modded a fuzz rite to have 2 types of gating

http://www.luciferstrip.com/fuzz/fuzzritegate.jpg

[killerkev]

R.G.

"Farting" is exactly the sound to describe it. I have three pedal with this problem but yet I've used all the components specified. An Ampeg Scrambler which sounds awesome until the gating comes in at the very end, a slight decay, an op-amp big muff which just gates like a mother F$%@, A triangle big muff that has electrophilic caps as specified just gating away...

How to remedy these? Adjusting resistor and capacitor values? Hard to find what stage its happening in with just an audio probe.......

[nordine]

R.G.

"Farting" is exactly the sound to describe it. I have three pedal with this problem but yet I've used all the components specified. An Ampeg Scrambler which sounds awesome until the gating comes in at the very end, a slight decay, an op-amp big muff which just gates like a mother F$%@, A triangle big muff that has electrophilic caps as specified just gating away...

How to remedy these? Adjusting resistor and capacitor values? Hard to find what stage its happening in with just an audio probe.......

You could upload some pics of the soldering work, maybe you made some common mistakes that are giving you that farting sound

Biasing is one culprit; another is, as stated, overly big caps but thats more of a swell effect than anything,; a third one, which i may check out due your three effects behaving simmilar, is power source... a feeble power source (speciffically one that gives less current or voltage than needed) can alter your sound, but id point it more as a muffled sound than gated... but checkit too, the think that makes me wonder is your three pedals doing the same...

[RandomGlitch]

Sometimes gating is nice.  I like it on bass.  On guitar not so much.
But of course it depends.

[R.G.]

Hard to find what stage its happening in with just an audio probe.......

Yes, it is. That's why the thread "Debugging: What to do when it doesn't work" relies on taking idle/no-signal DC voltage measurements so much. And I think in your case that is the next step.

What you describe is exactly what I'd expect from a misbiasing problem. As I mentioned, there are other ways this can happen, but misbiasing is by far the most common.

If you don't have a meter, you are pretty much limited to visual inspection and audio probe to find the problem. Both of these are useful, but they are both indirect about what problems are happening.