Unwanted artifacts with LFO

I am trying to learn how to implement an LFO into a synth I am building. I am having a problem with a buzzing sound when the LFO is oscillating at a relatively high amplitude and/or frequency. A quick description of my setup: The Sin output of the LFO is added with the output of my Envelope and sent to the Amplitude input of a quad oscillator (sine, saw, tri, pls). The Frequency and Width inputs on the LFO have their controls connected directly, but the Amplitude control is connected to a multiplication module, the envelope output is connected to that same multiplication module, and the multiplication output is connected to the LFO's amplitude input. The Sync and Sync Phase inputs on the LFO are unused as of right now, as I don't know their purpose. The artifacts are most apparent when my main oscillator is playing a sine wave. Any help is greatly appreciated

 

the regualr LFO operates at the control rate, so it will sound horrible at high frequencies - if your control rate is set to 200 hz, then 100 hz is the nyquist rate at which aliasing starts, and technically i think complex waves will alias at lower frequencies. aliasing adds inharmonic/randomsounding artifacts. so id imagine thats the problem.

if you are working at audio rate (and i think you are if you are using an envelope) use a regular osc for the LFO, it will work fine at any frequency. the corecell LFO is nice for this, in the corecell->control menu.

 

OK, that definitely helps, but I'm still having some problems. When I use the corecell LFO and attach it to the amplitude input of my oscillator, I can't get it to stop sending a constant gate signal –it plays sound all the time, not just when I press a key. I've tried everything I can think of to no avail. I also have a couple questions if you've got the time to field them. I was under the impression that an LFO was just that– low frequency. Like, not even in the realm of percievable sound. I was also under the impression that aliasing only occurs when the frequency becomes so high that the sample rate cannot keep up with the oscillation of the wave. So wouldn't this not be a problem with an LFO? I could be way off on all my info, since I'm just getting it from reading sound textbooks without anyone to ask for guidance. Thanks for replying to my thread!

 

yeah, im sorry, i shoulda mentioned that - an uadio signal is no good if its being used for gates, usually. thats really an event thing. try an A to E, then step filter. that should help, its my usual route to get events out of audio corecells.

 

The LFO alternates between -1 and +1. For the oscillator is A=+1 or A=-1 the same amplitude. So when the LFO signal changes the amplitude doesn't.
Add after the LFO output an audio core cell which adds 1 (now the LFO changes between 0 and 2) and multiplies with 0.5 (now the LFO changes between 0 and +1.

ciao herw

 

duh, "my bad" (as the kids around here say)! thanks herw, i was thinking about envelope gating, not AM.

 

I've tried everything both of you have mentioned and I still get a constant signal when the LFO is hooked up to the amplitude input of the oscillator. Herw, I even hooked up a new instrument exactly according to the screenshot you were so kind to post, and even that plays a constant note without pressing a button. I've tried running it through every audio to event module including audio to gate and nothing works. I am banging my head against the wall on this one, it is very frustrating.
Do you have any recommendations on an instrument that utilizes a simple LFO so that perhaps I can take it apart and see how it works? The ones in the library that comes with the program are too complicated for me to quickly take apart.

 

im not entirely sure what you mean now? do you mean that it wont stop making sound? did you put an envelope after the oscillator?

 

i will upload this simple ens here - have just no time but after next 8 hours.
ciao herw

 

Yeah, I mean that it won't stop making sound. Sorry about the lack of clarity. That ensemble would be great, herw. I'm looking forward to it.

 

see attachment - ask if you have questions

ciao herw

 

Herw– the first thing that happens when I open this ensemble is it makes constant sound. It sounds like the LFO is working, but I need an instrument to accept midi input and be silent when I am not depressing a key. I really haven't gotten into sequencing yet, and I am wondering if this ensemble is perhaps set up to be used with a sequencer. This ensemble rather nicely illustrates my problem, but not a solution to it. Does it not make constant sound when you run it?

 

yes - i think we all have misunderstood your "is sending a constant sound - the sound is interrupted by the LFO

see attachment. your mistake was to use an add-module. You have to multiply both (gate module and LFO). Another solution is as kid_sputnik described (post #8) to use an envelope generator after the oscillator (see attachment)

ciao herw

 

You guys are awesome. Thanks so much. Everything is working properly now, except for one thing. The LFO doesn't seem to be affecting the release portion of the audio signal. My envelope is functioning, because the attack portion still comes in slowly, but no matter how I set it up, it will not perform AM on the release. I have tried add and multiply modules on both sides of the instrument. That is, I have tried adding the gate with the lfo, and multiplying the gate with the lfo, then sending the output to the envelope. I have also tried adding the envelope with the lfo and multiplying the envelope with the lfo and sending it to the oscillator. I have tried every combination of the aforementiond adds and multiplies.

 

Hooray! I figured it out. Not quite sure what my problem was, but after simplifying my instrument I've got it working the way I want it to. You both have been a lot of help. I would buy you both a sandwich if we were in closer proximity

 

It's hard to make me happy. The LFO is missing one feature, the range of modulation. Not the speed at which the LFO modulates, but the range of how loud and soft it gets. This was achieved with the non-core LFO by attaching a control to the LFO's amplitude input, but the core module is missing an amplitude input. How can I get amp modulation out of this thing?

 

pastrami with spicy mustard will be fine. =)

 

same solution as for the osc. Multiply the out of the LFO with a knob's out. If you want only an oscillating around a level you can add another knob's value.
ciao herw

PS: i would like to get carpaccio ;-)

 

Awesome. Now I can breathe easy. Until I start trying to buid more mods on my synth, that is. You guys have been a tremendous help.