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Re: Please, make a moog model 55 vst
Posted: Sat Nov 26, 2022 12:01 pm
by UrbanCyborg
Aliasing isn't caused by rounding errors, but by unrepresentable frequencies "folding over" into lower frequencies. Any frequency over the Nyquist frequency (half the sampling frequency) can't be represented, and if present will show up in the form of aliased frequencies.
Incidentally, quoting from the downloadable VM900 manual,
The VM900 CP3 is a recreation of the classic Moog
"Console Panel Mixer." At high inputs levels, it had a
tendency to clip the tops and bottoms of waveforms for a
characteristic overdriven tone. We've also included a
switch that allows selection between the more overdriven
tone and the later, cleaner-sounding version.
Note that CP3 is DC-coupled and can be used to mix audio
or sub-audio CV signals.
Model- Selects the audio characteristics of the earlier or later production CP3 circuit. Rev. 1
has more of a tendency to clip waveforms, whereas Rev. 2 is less inclined to break up.
Click Filter- When engaged, this rounds of sharp waveform edges to reduce clicking - it's
intended for use with edgy control signals to reduce clicking when patched to something
such as a VCA CV. The Click Filter is generally not recommended for use with audio signals.
So the CP3 rev 1 has
designed-in non-linearities. I included the quotes about the click filter because that would clearly exacerbate the problem, if used with audio signals. I don't know if any of this is of help, but figured it's always a good idea to get a good fix on the ground state, so we're sure we're all talking in the same mental space.
Reid
Re: Please, make a moog model 55 vst
Posted: Sat Nov 26, 2022 2:31 pm
by Steve W
Thanks for the comment, but it seems you missed my point. Or, to you use your wording, you misrepresented the mental space I was coming from.
Re: Please, make a moog model 55 vst
Posted: Sat Nov 26, 2022 8:06 pm
by UrbanCyborg
Might have done. How did I miss it?
Reid
Re: Please, make a moog model 55 vst
Posted: Sun Nov 27, 2022 9:44 pm
by utdgrant
Steve W wrote: ↑Fri Nov 25, 2022 7:11 pm
I recreated the patch and hear the two tones, the beating, and the "third tone." I have seen mathematical-based explanations, but I am too old to understand complex math. So, is aliasing the result of phase differences* that cause in essence "a fourth tone?" If so, is antialiasing the use of mathematics to compensate for this "fourth tone" so to speak?
If I do not understand it correctly, please keep your explanation/correction understandable. Thanks.
Hi Steve,
I've created three videos on YouTube which demonstrate some of the phenomena we've been talking about in this thread. I hope you find something useful in there.
Video 1. A demonstration of how distortion can add harmonics to a pure sine wave (basic 'West Coast Synthesis'). The latter part of the video shows how distorting the sum of two sine waves leads to a mushy sound due to intermodulation and the generation of non-harmonic sidebands.
Video 2. A demonstration of generating harmonics which are above the Nyquist frequency, and so get reflected 'backwards' into the audio spectrum. This is textbook 'aliasing'.
Video 3. A demonstration of a distorted sine wave and its harmonics starting below the Nyqusist frequency then going above it. You can see and hear the sidebands going all over the place as they cross the Nyquist frequency.
Re: Please, make a moog model 55 vst
Posted: Sun Nov 27, 2022 10:06 pm
by Steve W
utdgrant wrote: ↑Sun Nov 27, 2022 9:44 pm
I've created three videos on YouTube which demonstrate some of the phenomena we've been talking about in this thread. I hope you find something useful in there.
Thanks, but you really shouldn't have gone to that extent for my sake. Based on the weblinks provided above as well as my own internet reading, I am comfortable with my understanding of what aliasing is, why it has been given the name "aliasing," how it comes about in audio and visual media, some of the perceptual issues it causes, etc. Maybe others will benefit from it as long as you went to all that effort.
PS: I just spot checked the 1st video (a few seconds here and there) and around 13:38 (+/-) you demonstrate what I was initially calling the "third tone" as well as the "fourth tone." Ergo, I conclude maybe you didn't miss my point after all! I will spot check more as I have "spare" time.
Re: Please, make a moog model 55 vst
Posted: Sun Nov 27, 2022 10:13 pm
by utdgrant
Steve W wrote: ↑Sun Nov 27, 2022 10:06 pm
Thanks, but you really shouldn't have gone to that extent for my sake. Based on the weblinks provided above as well as my own internet reading, I am comfortable with my understanding of what aliasing is, why it has been given the name "aliasing," how it comes about in audio and visual media, some of the perceptual issues it causes, etc. Maybe others will benefit from it as long as you went to all that effort.
No worries, Steve. I did it to refresh my own knowledge, and it was fun. It was just done off-the-cuff with no editing (pretty obviously!
), so didn't take long.
Re: Please, make a moog model 55 vst
Posted: Mon Nov 28, 2022 9:34 am
by PoorFellow
utdgrant wrote: ↑Sun Nov 27, 2022 10:13 pmNo worries, Steve. I did it to refresh my own knowledge, and it was fun. It was just done off-the-cuff with no editing (pretty obviously!
), so didn't take long.
I took a look also , but alas for me it is a bit too hard to process it all at the moment as I am still struggling with the basics of Voltage Modular.
If not stuck then I am still at a level where I am trying to understand and learn the basics of sound creating and modification using Voltage Modular.
But at least it made me familiar with your Youtube channel (which I for some reason missed up until now) and I have saved a lot for reference and eventual later viewing.
Thank you !
Re: Please, make a moog model 55 vst
Posted: Mon Nov 28, 2022 3:45 pm
by Steve W
PoorFellow wrote: ↑Mon Nov 28, 2022 9:34 am
I took a look also , but alas for me it is a bit too hard to process it all at the moment as I am still struggling with the basics of Voltage Modular.
If not stuck then I am still at a level where I am trying to understand and learn the basics of sound creating and modification using Voltage Modular.
I'd recommend working on those (basics and sound creation). As someone mentioned, if you hear the effects of what's called "aliasing" you are more likely to hear it. Its like anything. I learned intervals, so when I hear a Perfect Fifth, I recognize it. I did not learn pitches, so when I hear an F, I don't recognize it as an F. I learned to hear and recognize beating (when two tones are very close to each other but not 100% "in tune." I will add the exact time in Video 1 where you can hear the beating (somewhere around 13:38) if you don't know what that is. Or just take 2 oscillators on the same frequency and detune one ever so slightly until you hear a single tone that is "phasing" in and out at a rate that depends on the miniscule difference between two frequencies.
Re: Please, make a moog model 55 vst
Posted: Mon Nov 28, 2022 5:41 pm
by PoorFellow
Thank you Steve W ,
It's not that I am tone deaf , I am really not ,on the contrary I think , but to even begin to try to relate to the discussion here via those videos and to understand it all then I would first have to try to correlate all the sounds in the videos and all the expressions used here and that would be mostly/almost impossible to me at the moment. I might be able to if I sat down and made it a study that I wanted to drive all the time needed into no matter how long...
But at the moment I think I need to get a either firm grip on the basics of both sound generating and sound generating with Voltage Modular or at least get a better/some grip of it (including all them things that some take for granted while others don't understand them !)
Re: Please, make a moog model 55 vst
Posted: Wed May 24, 2023 4:48 pm
by SynthBaron
Bump. I really wish the aliasing problem on the CP3 would get fixed.