Some kind of noise gate...

[Drake120]

Hi,

I'm looking for a way to do that:


For example, you plug two guitars there - if one (A) is below threshold level, then B is muted. Of course, it's not the exact way how I will use it, but it is just an example.

Probably it can be done by modifying an existing circuit.

Thanks

(JD)^S

[ashcat_lt]

Just about any rackmounted compressor/gate will do this.  Split signal A into the sidechain (sometimes called key) input.  Run signal B to through the input and output.  You'll likely want to buffer, and possibly amplify, a guitar signal beforehand, but then you didn't specify what these "signals" are...

[Mark Hammer]

What you refer to often gets called "external keying".  That is, the audio signal of interest is the one that gets gated, but it is being gated by an entirely separate signal, not by itself.

I have a couple of noise-gate projects posted on my site.  In this one - http://hammer.ampage.org/files/LPM-23-NoiseGate.PDF - you can see that there is a 10k resistor and a .047uf cap on the emitter of that transistor on the input.  If you cut the connection to the .047uf cap, and routed it to a separate jack, you could plug whatever you want into that jack and "key" the audio signal that you have plugged into the main jack.  In this example - http://hammer.ampage.org/files/GainesNoiseGate.PDF - you can even see that very input provided in the project.

People use external keying frequently as a means to sync up things.  You have probably heard the David Bowie song "Let's Dance".  The horns have a familiar-but-different kind of feel to them.  During production, Nile Rodgers mixed the horns down to a blended track and keyed them with his guitar strumming so that they had a kind of funky rhythm guitar feel.