Stopping softsynth aliasing?

[nineofkings]

Is there a way to cut down on aliasing? Maybe an oversampling VST or something? I want to use it on fuzzpillz oatmeal, because while it sounds good filtered and with effects, the raw waves alias like hell.

[chuck death]

Arkecode VST Oversampler.

[Aloysius]

Or

http://www.kvraudio.com/get/2667.html

[chuck death]

Um, that plugin is garbage, aliasing is not something you can remove automatically with a fixed filter, you have to remove it at source (by oversampling the VST for example). It was completely debunked when it was released, it really doesn't work.

[LBN]

Wusik VM is a neat wrapper that, in addition to its other utilities, has oversampling options. IIRC it lets you oversample 2x and 4x.

http://www.wusik.com/ww/products/wusikvm

[Bronto Scorpio]

Oversampling just does one thing: It sets the samplerate for a synth/fx higher.
You can do that yourself. Just render at 96khz (or higher), you should always do that! (there are a few exceptions, but that won't matter here)

Cheers
Dennis

[antto]

+1
i usually always start my projects at 88.2kHz or higher sampling rate
this gives you more room in the high freqs to manipulate hihats and noises without supa-dupa EQs

[Urs]

Here's the revelation: Oversampling alone does not remove much aliasing in a synth.

Aliasing typically happens in oscillators and in filters. If the oscillators utilise full bandwidth (which is why they alias in the first place) then they will be a bit better by oversampling. But the filter will still fold all those frequencies back into the audible spectrum. No matter how much you oversample, a simple x^3 waveshaper in the filter will ruin it. All you ever gain is a few more semitones on the keyboard which will remain in the bearable zone. The more you oversample, the closer it gets to a single octave of feasable bandwidth.

In order to remove aliasing in a synth you need to oversample *each* aliasing-prone section independently. Which a wrapper obviously can't (and neither do some synth engines, but that's a whole different story)

[penguinfromdeep]

[nineofkings]

OK, so that's why only unfiltered waves with sharp edges alias on Oatmeal, because they have more high-frequency content. Also, just oversampling the output doesn't work. So I'll just have to deal with the nasty mid-range? (for some reason it happens in the mid-range more than the highs and lows)

[Richard_Synapse]

Typical waveforms like sawtooth or square fall off at only 6 dB per octave, so doubling the sample rate accomplishes very little here. I like to push back aliasing by 50 dB or more, which would correspond to 256 times oversampling. Not really an option, so the problem has to be fixed at the source end. This is what most professional synths do, avoid the aliasing to begin with.

Doubling the sample rate is nevertheless a good idea, especially effects can benefit from that.

Richard

[Urs]

I like to push back aliasing by 50 dB or more, which would correspond to 256 times oversampling.

Which is basically what BLIT synthesis and its derivates do. We even do 512x oversampling of steps, pulses and discontinuities

[Big Tick]

Wusik VM is a neat wrapper that, in addition to its other utilities, has oversampling options. IIRC it lets you oversample 2x and 4x.

The next Zen update will do this too, btw. However, Urs is absolutely right about the way to get 100% alias-free output from a synth - no oversampler can achieve that.