Aliasing in Polymode module?

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ciopek
Posts: 1
Joined: Sat Mar 20, 2021 10:11 am

Aliasing in Polymode module?

Post by ciopek »

Hello,

first off I wanna say cherry audio & voltage modular are great and I <3 them.
However recently i have bought the Polymode module and while I really enjoy it I found it has quite audible aliasing noise when playing higher notes (C6-C8 range) - some other modules I tried also have a bit of aliasing but it's quiet enough it doesn't really matter in musical context while in case of Polymode the aliasing noise is sometimes almost as loud as the note itself :O

I have put up an example in the attachment - my daw is reaper @48Khz. (had to zip it, couldnt attach flac xd)

Please forgive my ignorance in case there's some obvious workaround I don't kno about xd

EDIT:
it seems like the standalone VST version of polymode doesnt have this problem :/ guess i should have bought that instead ᗒ ͟ʖᗕ
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polymode_aliasing.zip
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polymode_oh_no.png
polymode_oh_no.png (189.74 KiB) Viewed 2846 times
pauls999
Posts: 8
Joined: Wed Oct 20, 2021 9:42 am

Re: Aliasing in Polymode module?

Post by pauls999 »

I'm glad some one else has seen/heard this issue.
I too have been using poly modules for build new patches and found that as soon as i mix two or more oscillators with some slight detune i get strong static flanging effect that varies as you go up the scale but is very apparent in the high registers and sound like the output is being playing in a resonate tube.

I have tried most of the poly osc modules on the core pack and mixers and they all do it be they in a VST host or stand alone.
I have tried running at 96k and even 192K but its still there so i must be the internal sample rate used by the modules and seems to be the underling structure of VM rather than any individual module. Its shame because there is nothing like it in any of cherry other stand alone instruments so I'm wondering why its so apparent in VM, any answers pls?
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utdgrant
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Re: Aliasing in Polymode module?

Post by utdgrant »

pauls999 wrote: Mon Mar 28, 2022 1:12 pm I have tried running at 96k and even 192K but its still there so i must be the internal sample rate used by the modules and seems to be the underling structure of VM rather than any individual module. Its shame because there is nothing like it in any of cherry other stand alone instruments so I'm wondering why its so apparent in VM, any answers pls?
This is the heart of the problem. The basic sample rate of VM is fixed at 48kHz throughout. Setting a higher sample rate within your DAW has no effect on the processing rate of VM as a whole, or any individual modules within it. The stand-alone instruments usually offer different over-sampling options and in addition, will switch the basic sampling / processing rate to match that of the host DAW.

Your only hope with VM is to use modules which have internal over-sampling and anti-aliasing implemented before the signal reaches the output jack(s). This is usually most important in oscillators, to eliminate sharp discontinuities in the output waveform. Alternatively, some oscillator modules use switchable wavetables which remove the upper harmonics as the base frequency increases.

You'd have to ask individual VM devs whether they use either approach described above, or check in their documentation. Confession time: the Big Rat generates horrific amounts of alias frequencies when using pulse or sawtooth waves in the audio range. This is freely admitted in the documentation!
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