Where is that jitter coming from? Why is it not a perfect waveform before filter?
What jitter are you talking about ? The default patch always sounded good to me…
I’m not even sure what you are asking about, but to answer the title :
The default patch is a small demo synth. A synth always has a VCF.
Now if you experience jitter, maybe you need to change some settings like audio engine, or buffer size, let us know if we can help you with that 
The Fundamental VCO-1 has two settings ‘Analog’ and ‘Digital’. The analog waveform is deliberately imperfect: https://vcvrack.com/Fundamental.html.
The digital waveform becomes ‘cleaner’ as you increase the sample rate as noted above.
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Yes, it was caused by the sample rate.
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