Simple noise gate  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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bmxguitarsbmx
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Post by bmxguitarsbmx »

Amazingly enough, this simple circuit works quite well. There isn't crosstalk in mine. Not sure if you realize this is using a level shifter for envelope generation, not using a halfwave or full wave rectifier. Maybe there would be crosstalk if it was doing rectification. You are right about the threshold control and bias being tangled together but as I said before, it simply works.

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Post by dylan159 »

bmxguitarsbmx wrote: 09 Dec 2022, 15:09 Amazingly enough, this simple circuit works quite well. There isn't crosstalk in mine. Not sure if you realize this is using a level shifter for envelope generation, not using a halfwave or full wave rectifier. Maybe there would be crosstalk if it was doing rectification. You are right about the threshold control and bias being tangled together but as I said before, it simply works.
The crosstalk would be from using a dual op amp to buffer the sidechain input, something considered in the first post.
Level shifter, call it how you want, but It morphs into an half wave output at low threshold settings, which is for the best since it means negative peaks can't let the capacitors charge again as much.
I have no doubt the circuit does what it says it does, OP is happy with it and so are others, but we're here to discuss after all.
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AxelKay
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Post by AxelKay »

Final edit: nevermind I got it. It's like the g string 🫥

Trying to figure out the ins and outs gave me a headache 🤣
Ok so supposedly I want to do the 4 cable method, do I simply hookup my cables according to the schematic? The "guitar in" and "to amp in" tips are connected... I'm missing something 🤔

Edit: also, the way I see the pcb, you can't wire a 3pdt for true bypass (?)

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Post by toxonic »

I'm pretty much a noob in electrics and building pedals and also new here in the forum.
I really like the circuit, because it seems to be quite simple to build, but it seems that i can't get it working.
I tried to breadbord the circuit an since i actually have no amp with fx loop i connected the KEY_OUT to SIG_IN, but for some reason it's not gating the signal.
Instead i get a real nasty fuzzy distorted version of the input signal.
I tried an audio probe inside the circuit, but it seems that there's no audible result on the output pin 6 of the opamp and behind it.
But i don't really know what i have to expect - can somebody help?
Maybe a high res image of the circuit on a breadbord or something?
VCC is 8,96 V, Vref is about the half (4,4 V), is this correct so far?
I already breadborded the circuit 3 times and always compared it to the schematic - sadly, i always get the same result.

By the way, is it a normal behavior, that the signal is simply passed between source and drain of the JFET, as long as the gate is not connected?

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bmxguitarsbmx
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Post by bmxguitarsbmx »

Hey Toxonic, Welcome to the forum!

Please clarify your problem:

Is it nasty when your signal is low and you would expect the pedal to mute the signal?

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Post by bmxguitarsbmx »

I can think of 3 reasons you might get nasty fuzzy sound:
1) you need to select a different JFET that will turn fully OFF and fully ON at the right gate voltage (gate referring to the gate pin of the JFET).
2) too much gain in the op-amp and transistor part of the circuit. Double check gain setting resistor values and maybe swap in a different transistor. (this would result in nasty fuzz when you expect the pedal to MUTE)
3) not enough gain in the op-amp and transistor part of the circuit. (this would result in nastiness when you expect to hear nice loud guitars)

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toxonic
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Post by toxonic »

bmxguitarsbmx wrote: 18 Feb 2024, 19:11 I can think of 3 reasons you might get nasty fuzzy sound:
1) you need to select a different JFET that will turn fully OFF and fully ON at the right gate voltage (gate referring to the gate pin of the JFET).
2) too much gain in the op-amp and transistor part of the circuit. Double check gain setting resistor values and maybe swap in a different transistor. (this would result in nasty fuzz when you expect the pedal to MUTE)
3) not enough gain in the op-amp and transistor part of the circuit. (this would result in nastiness when you expect to hear nice loud guitars)
Thank you much for your reply! The nasty, distorted sound occurs the whole time, it's not gating at all. But maybe i have done something wrong - however, i will rebuild it again asap, in the next days i will be too busy to get it done, but i will let you know, if it worked.
PS: I already swapped the jfet several times with no effect (always j175 type, cause it's the only p-type jfet i have at home).

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Post by bmxguitarsbmx »

toxonic wrote: 22 Feb 2024, 21:25 ... The nasty, distorted sound occurs the whole time, it's not gating at all. But maybe i have done something wrong - however, i will rebuild it again asap, in the next days i will be too busy to get it done, but i will let you know, if it worked.
PS: I already swapped the jfet several times with no effect (always j175 type, cause it's the only p-type jfet i have at home).
ok, good info. The JFET may not be ground referenced. Stick a 1M to ground on both the Drain connection and the Source connection. Just to eliminate that problem. The JFET can't have a Gate to Source voltage, if the Source is not connected to Ground.

Additionally, double check your connections to Vref. That could be a easy mistake that would put the JFET out of useful operating region.

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