Calling all guitar pedal geeks!

August 6, 2010 9:10 PM

I play the recorder, using a basic recorder -- mic -- pedals -- amp setup. Pedal 1 provides delay; pedal 2 is the tricky part. There's a specific processing effect I'm looking for, which is this: 1) Clip the input signal above a defined decibel limit (not frequency limit); 2) Feed to output ONLY the signal above this limit.

I can use Audacity to do this in post-processing (via the Hard Limiter filter), but I'd like to be able to lay this effect on in real time, via an effects pedal. Does such a pedal exist? I know about real-time processors such as Max/MSP, but I would rather perform without a laptop on stage.

Note: I've experimented with various compression/gain effects, but they don't quite give me the sound I'm looking for.

Merci beaucoup.

posted by YamwotIam to Media & Arts (8 answers total)

I think this effect is called a gate / gating.

That may help with the searches at least.
posted by intermod at 9:14 PM on August 6, 2010

Hmm, so the signal goes...

            _____
thres_    _/     \...
   _     /
__/ \___/

Do you want the output to go somthing like...

thres_    _________...
          |
__________|

Or something like...

            _____
___________/     \...

(e.g. substract everything that's not clipping). In other words, can you clarify?
posted by Monday, stony Monday at 9:22 PM on August 6, 2010

Response by poster: Thanks Monday, yes, to subtract everything that's not clipping (your second option), that's exactly what I'm looking for.

Intermod: looking into gating right now, thank you.
posted by YamwotIam at 9:27 PM on August 6, 2010

Yep, this is exactly what a gate is for.
posted by Sys Rq at 9:29 PM on August 6, 2010

Here's the relevant part from the code of the plugin(from plugin.co.uk) I think YamwotIam is using:

        unsigned long i;
        for (i = 0; i <>
        {
                float limit_g = pow(10, limit_db / 20);
                float sign = input[i] <>
                float data = input[i] * sign;
                float residue = data > limit_g ? data - limit_g : 0.0;
                data -= residue;
                buffer_write(output[i],
                         sign * (wet_gain * data + res_gain * residue));
        }

If YamwotIam is using the residue setting to get the sound, I don't think a gate is what they want. I've never really seen that functionality on a piece of gear, even though it's really simple to implement digitally. The way I can see implementing with gear is use a hard limiter, then substract the output of the limiter from its input using a summing circuit (but you have to worry that there isn't a phase shift or a delay in the limiter).
posted by Monday, stony Monday at 9:48 PM on August 6, 2010

A noise gate with a fast attack and fast release will chop all moments where the signal doesn't reach a predetermined input level. This is to say that the signal will be treated as a single stream, it won't subtract out a quiet tambourine or anything funny like that. If you wanted to strip out all frequencies that weren't above a certain gain level, then that's a bit more complicated and for which you'd probably want to use a computer. Maybe a nice compressor could do it.
posted by rhizome at 10:04 PM on August 6, 2010

Response by poster: Hmm, if I read your advice aright, it looks like either the Decimator Noise Reduction pedal or the Boss NS-2 will do the trick. I'll try 'em out and let you know. Thanks again, I learned a lot from you all, as usual.
posted by YamwotIam at 11:02 PM on August 6, 2010

I'd go for the one with the decay. NS-2 is US$90, and you can cheap out if you want to with a Behringer version for $30.
posted by rhizome at 12:02 AM on August 7, 2010