hi,
i want to create a LFO that could change the volume of a signal with a sinusoidal wave
i have some questions about that,
i use a osc~ object for creating low frequences, and it has a signal outlet,
input of volume number is control inlet,
i used env~ but it looks like it uses a lot of CPU, is there any other objects that i can use for that job,

and my other problem about env~:
osc~ goes sinusoidally from 1 to 0,0 to -1, -1 to 0 ... and so,
but env~ object outputs always positive values as amplitude (normally), so when osc~ is at 1 env~ outputs 99.99, when osc~ is at -1 env~ outputs 99.99 again, so its not the sine wave that controls the volume, its only the half of it...
i dont know if i could tell my problem, a made an image of it =)

you have any suggestions?

http://www.pdpatchrepo.info/hurleur/oscenv.bmp

This exact question came up yesterday and I posted a solution. I've attached it again.

[env~] gives the RMS (root mean square) value. That means the square root of the average of the squared signal. If you square anything (real) you always have a positive number, so the output of [env~] is always positive.

If you wish to have the instantaneous value of an audio signal use [snapshot~]

best,

andy

http://www.pdpatchrepo.info/hurleur/klfosin.pd

thank u very much,
i solved the problem with a
metro and snapshot~

It seem easier to multiply signals [*~] by signals to modulate amplitude, using snapshot~ to get control rate volume info will produce barely audible 'jumps' in the audio.

It took me a moment to understand what you mean Nestor, but you are correct. I'm not sure if that's what Kuzu is doing but it's always best to keep signals in the audio domain wherever possible, if they are already audio signals. In other words, convering to a control/message rate and back to a signal is bad (from a sound quality POV). I guess it's a common misunderstanding that just because a signal like an LFO moves slowly it should be at message rate.

here's a control based lfo. it starts to get really steppy above 5 hz, but usually you want your lfo's slower than that anyway.

http://www.pdpatchrepo.info/hurleur/vlfo.pd

and here's the helpfile for the lfo:

http://www.pdpatchrepo.info/hurleur/vlfo-help.pd

thank you all,
nestor's idea is very useful also but i wanted to control a 'number' using a lfo so that i would be able to change not only the volume but also other parametres of a signal (like frequency... or maybe a delay time etc..)
i send my version as attachement which oscillates between 0 and 1
(i used metro 10 it sounds fine for up to 10hz (but it could be a metro 50))

http://www.pdpatchrepo.info/hurleur/lfo.pd

Thanks, hardoff. I use your vlfo in my project, too (modified, obviously).

If I want lfo above 5Hz, I should decrease the metro time, shouldn't I?

You don't know yet how your patchs helped me... I should send you a chocolate cake, as gratitude.