Oscillator output appears to be bandlimited at ~17 kHz

[pedrocot]

Hello – I'm a brand new user of Voltage Modular, in fact this is my first ever foray into modular.

I'm running the VST3 version of VM 2.7.0 for Mac OS.

I noticed that the output of the standard Cherry Audio Oscillator module appears to be bandlimited in some way around 17 kHz – see attached screenshot. Side note – this frequency seems to fluctuate somewhat when I use another Oscillator to frequency mod the primary output Oscillator, however the bandlimit frequency doesn't appear to fluctuate in a way that correlates with the Oscillator that is freq modding the primary Oscillator.

I'm just wondering if this bandlimiting behavior is intentional.

Voltage Modular version 2.7.0
Mac OS Catalina 10.15.7
FL Studio for Mac 21.2.2

Thanks!

[utdgrant]

Yes, it's deliberate and it completely eliminates aliasing in the signal at source. Of course, if you introduce non-linear distortion, then aliasing has a chance to creep in again, due to harmonics appearing above the Nyquist frequency (24 kHz).

If you connect a channel of ACE Constants and Multipliers to the Pitch CV input of an Oscillator, then crank the base frequency up higher and higher, you can see the upper harmonics drop out of the signal. Once you reach above about 10kHz, you're left with just a single sine wave, regardless of the waveform you're monitoring.

[pedrocot]

Thanks for your quick reply. Out of curiosity, is there an oscillator module that will generate non-bandlimited waveforms?

[utdgrant]

Thanks for your quick reply. Out of curiosity, is there an oscillator module that will generate non-bandlimited waveforms?

I created an experimental oscillator which allowed you to switch between the Cherry Audio Digital Oscillator and Analog Oscillator models as an audio-range VCO. The results were pretty ugly when switched to the digital oscillator model and playing high-pitched notes.

NOTE: MRB has updated all the oscillators in the VM2500 collection since this video, and they now sound perfect across all frequency ranges.

https://www.youtube.com/watch?v=i_dLPSYm5Aw

[utdgrant]

I decided to create another video tonight to demonstrate how the CA Analog oscillator 'drops' the upper harmonics as you increase the fundamental pitch.

https://www.youtube.com/watch?v=WjWGBTPxPCw

[pedrocot]

Thank you, I appreciate the demonstration(s).

[ChR_is]

Out of curiosity, is there an oscillator module that will generate non-bandlimited waveforms?

you most likely do not want a non-bandlimited oscillator. a non-bandlimited oscillator will alias severely.

if you want more high-end in the spectrum, you can try the free Micro Oscillator:

Micro Oscillator Bandwidth

MicroOscBandwidth.png (680.54 KiB) Viewed 4658 times

Micro Oscillator also completely eliminates aliasing in the signal at source even more

If you really want a non-bandlimited oscillator you can use formula to create one:

Formula Naive Saw Oscillator

Formula_NaiveSawWave.png (990.36 KiB) Viewed 4658 times

Here's the formula to paste:

Code: Select all

5*2*mod(0.2*0.5*(y+5)+(2^x)*65.4064/48000,1)-5

make sure to connect the output back into the Y input. use the X input to control the pitch. base tuning is C2.