What's the most basic implementation of resonant lowpass filter?

[Architeuthis]

If you say so, why not. This thread now looks like a mess, perhaps you should start a new thread with a clearer description. I'm not upset.

Cheers,

You were only upset in my scenario.

You say "why not", I'm waiting for someone to tell me how!
Edit: And if no one can tell me how, I'll have some details in a few months if things work out.

[stratum]

You say "why not", I'm waiting for someone to tell me how!

Here is how http://www.srmuniv.ac.in/downloads/lab1.pdf

But now you'll need to figure out why this is an answer to your question.

[Architeuthis]

That's very clever... so you've answered the riddle. Your reasoning is that if an oscillator is used to remove harmonics (or sidebands in this case) then you can consider it to be a filter. Ok... we'll leave it at that... for now...

[xoxos]

sympathy as i've seen you code and develop. sometimes we can use some obviated bumps to integrate our perspectives. i'll try not to judge you for what i don't appreciate

"fast sine osc"
s0 -= f * s1;
s1 += f * s0;

(the leg needs to be taken periodically.. heheheh)

"dude no. can you turn an oscillator into a filter?"

sure can.
s0 -= f * s1 + input;
s1 += f * s0;

you see how i did that? i didn't read a book or ask an expert, i just wrote it that way, like a rebel.

what you have here would be delightfully termed a *resonator* by many persons. problem is, it's a resonant filter at 100 % gain.

how do you add gain to this?

there are many ways to add gain to that. could ask, how don't you add gain to that? add a scalar to both (or just one) terms. urs might not use it on his next bestselling synth but it still works

s0 -= w * s1 * gain + input;
s1 += w * s0 * gain;


we always hang in a buffalo stance. yeah timmy, now the tambourine.

no money man.

[stratum]

That's very clever... so you've answered the riddle. Your reasoning is that if an oscillator is used to remove harmonics (or sidebands in this case) then you can consider it to be a filter. Ok... we'll leave it at that... for now...

I wonder why you are interested in this riddle if you weren't confused about these things. Is it some kind of game for times that you feel bored? There are better things that you can do, what about trying to help understand this http://www.kvraudio.com/forum/viewtopic ... 3&t=477919

[Architeuthis]

"fast sine osc"
s0 -= f * s1;
s1 += f * s0;

Xoxos, thanks for the explanation.

I wonder why you are interested in this riddle if you weren't confused about these things. Is it some kind of game for times that you feel bored?

No. Not a game. It's also not a riddle. I simply want to know if someone has detailed how to turn any old oscillator into a filter. I could have created a new thread specifically for asking this, but this thread kinda lead into this question and has served its purpose. I started off asking what the simplest lowpass filter was because I think one answer to this question is "an oscillator makes for the simplest lowpass filter if used in the correct way". I learned a few things from those who responded, so thank you. I didn't recognize it before but Xoxos' answer is pretty good.

Let's leave it here. I'll create a new thread in the future when I can detail the answer to my question.

[Architeuthis]

There are better things that you can do, what about trying to help understand this http://www.kvraudio.com/forum/viewtopic ... 3&t=477919

o, yeah, no I'm too uneducated for such things.

[stratum]

If you unsolder the positive feedback path in an analog oscillator, the resulting circuit can be used as a filter.

A digital filter which has became an oscillator basically has the same kind of positive feedback.

On the other hand, a simple formula like sin(x), which is an oscillator, is just a formula. It does not have anything you can "unsolder" so that it would become a filter.

o, yeah, no I'm too uneducated for such things.

Me too. But I have seen a few "educated" ones who were actually uneducated and a few "uneducated" ones who were actually well educated but no formal paper officially recognized that they were. I don't really care one way or the other, as there isn't a significant number of employers in my home country to whom I could apply if I had a signal processing degree.