From Russia With Noise Gate

[Paul Marossy]

The designer of this circuit, Eugene Zhernovoi, emailed me to tell me about his noise gate design, which as far as I know hasn't been introduced here at this forum. Looks interesting. The website is in Russian, but here is the schematic for it:

http://stellar.ho.ua/NoiseGate/Doc/NoiseGate.pdf

[tednet]

Looks very promising. Got a pcb layout by any chance?

[sean k]

Wow, you just gotta call it the KGB. That which quiets down that which one doesn't want to hear!

[Paul Marossy]

Looks very promising. Got a pcb layout by any chance?

There is none that I know of.

[Morocotopo]

How do you use it? The FX´s go in the send/receive jacks?

[Paul Marossy]

How do you use it? The FX´s go in the send/receive jacks?

I think that is the idea.

[PRR]

> How do you use it? The FX´s go in the send/receive jacks?

The send/receive jacks are convenience frills. You could omit them: Q1 Source to C16.

They ARE convenient when you have a hissy effect. This connection watches the guitar level. When guitar shuts-up, the gate shuts-up, even if the FX continues to hiss.

U1A and U2A is a HIGH-gain audio amp. So much gain that anything bigger than gitar-hiss will make Volts of signal. D1 U2B D2 make a DC voltage, C17 holds that voltage between cycles (and an adjustable bit more).

Q2 sits normally-"shorted", against R19 signal-resistor, muting the output.

Guitar signal swings C17 in a direction to un-"short" Q2, and signal passes R19.

Since the 220K R19 leaves a signal too weak to drive long cables, U1B buffers it to drive almost anything you'd find on a stage.

Layout and bypassing will be fussy. U1A U2A have HIGH gain and any sneakage around them will oscillate. When we did this job with a row of discrete transistors, we used a long narrow board and a separate power supply. Chips make it easier, but not a no-brainer.

There's nothing radical here. Study other noise-gate layouts for guidance, especially around the high-gain path from input to rectifier.

[jkokura]

Wow, you just gotta call it the KGB. That which quiets down that which one doesn't want to hear!

Perfect name. Mind if I use it if I build it?

[sean k]

No ownership on my part and it's just a suggestion so go ahead.

The man who designed it may not think the association is kosher and may prefer the FBI or CIA 

[Paul Marossy]

I figured this would be a good place for everyone to analyze the circuit and determine what its weaknesses might be.   

[jkokura]

No ownership on my part and it's just a suggestion so go ahead.

The man who designed it may not think the association is kosher and may prefer the FBI or CIA 

I'm in Canada. Closest we got is the RCMP. Maybe CSIS. Terrible names though.

KGB works good if you build a Russian Muff and whatever other Russian circuits we can think of. What do you think of assembling an all Russian cast for a pedalboard eh?!? Comrade?!?