Karplus-Strong Exciters

oddson · 22 Jan 2008

Karplus Plus

chironex · 23 Jan 2008

Let's just say I have a lot to learn.

Questions:

1. I don't understand the envelopes for the input generators. How they work, what "Tuned" does, etc.

2. What is DC burst?

3. Where can I find an oversaturator module?

😉

oddson · 23 Jan 2008

I don't understand the envelopes for the input generators. How they work, what "Tuned" does, etc.

The classic KS algorithm has a burst that's 'tuned' to the one wavelength worth of noise -- so it's longer for lower tones. The untuned envelope is 500 samples long in the middle with a control that shortens and lengthens it. The tuned value starts with the tuned length in the middle and shorter or longer with the control values altered but proportional so that lower notes always have longer envelopes than higher one and in proportion to their wave length. It turns out the effect is pretty subtle in a lot of cases but I kept it in there anyway.

What is DC burst?

Instead of a noise burst it's just a stream of 1s in the signal. I high-pass filter gets rid of it once it's in the feedback path but it gives a real hard pluck to the string sound. I usually use it in combination with other signal.

Where can I find an oversaturator module?

Inside! 😉

I used someone else's code.

streamin In; streamout out;

float temp1; float temp2; float temp3;

temp1=In>=0&In+In<0&-1*In; temp2=In>=0&1+In<0&-1; temp3=In*(1-temp1/4); out=temp1>=2&temp2+temp1<2&temp3;

//parabolic saturator

I think scaling the signal up and then down again pre/post processing might have been my idea or I might have stole that too.

...I have a lot to learn...

Me too! 🙂

I spent a lot of time figuring this stuff out and asked a lot of questions (a lot of them stupid) and got a lot of help from people like Sambean and Stefan.

Your interest in this subject got me to start a Karplus Strong tutorial last night. I've barely started but it might be helpful to get some feedback as I go.

It's on the WIKI under Tutorials-DSP-Ocsillators-Speciality Oscillators It's very rough for now... I tend to write drafts as I go and smooth them out later. I can lead to some pretty convoluted prose in the meantime.

chironex · 23 Jan 2008

Wow. Thanks! I hope the one I'm working on turns out well 🙂

Umm...and apparrently, three copies of this topic were made. 😕

Would you mind deleting them? I think it's because of my computer's sluggishness when connecting to this site. EDIT: Nevermind, I figured it out. I'm used to SMF. 😮

*Sigh* Anyway, I've been working on the synth...

So far, I have:

One noise exciter w/ detuning, 1 filter, and a funky envelope. The envelope works kind of like the one you showed me, except that the "envelope off" and "tuned" options are basically be mixed together with the Amnt. knob.

A decent amount of feedback effects, allowing color changing (damping backwards), inversion (I take pride in my button there 🙂 ), and a BR filter that can be mixed with the straight signal.

One ADSR envelope.

A voices knob, which goes from one to 33 in steps of 5.

A cool-looking interface. 😀

And, that's all.

(If you didn't notice, the picture is the hyperlink to the VST.)

What I plan in the future:

-Adding more exciter oscs.

-Adding a "mixing panel" to combine the exciter oscs how you wish. (Fm/Am/etc.)

-Adding an envelope to the excitor filter that's the same as the one in the oscs.

-Adding an envelope to the feedback filter.

-Adding routable LFOs.

-A bunch of effects! --With your help (I'll need it), it be really cool to have a "Strum Sequencer". When people strum an a guitar, for example, it makes a chord, but the notes are played one after another--just quickly. I want to try to implement this, it would be awesome!

As you can see, I have quite a goal for this thing. Let's hope I can reach it. 🙂