Comparing FM behavior across 8 VCOs -- who knew they'd be so different?!

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This is a bit of a sidebar from a video about Frequency Modulation on my main channel, ‪@SoundVoltage‬. This demonstrates how 8 different eurorack modules behave given the exact same inputs. Craziness ensues.
00:00 - Intro
01:36 - Humble Audio "Quad Operator"
02:30 - After Later Audio "Cascades"
03:09 - Cre8audio "Capt'n Big-O"
03:49 - NLC "CEM-3340"
04:23 - Tiptop-Buchla "258t Dual Oscillator"
05:14 - Pittsburgh Modular "Local Parks"
06:09 - New Systems Instruments "Harmonic Shift Oscillator"
07:06 - NLC "Kareishuu"

Опубликовано:

11 июн 2024

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Комментарии : 17

@tru7hhimself 4 дня назад

the spectrum is nice. but i'd really have liked to also see the waveform at the same time. anyway, thanks for this nice comparison!

@FelipeTellez 6 дней назад

You "WROTE" your freq analysis tool!? If you did, that is mega cool. Loving your explanations😊

@SoundsofVoltage 6 дней назад

@FelipeTellez - I did :) A bit of Python code to open the WAV file and capture the frequency peaks, and then a bit of javascript to generate the animations that I then record. I think it turned out pretty ok :) Glad you're enjoying them!

@FelipeTellez 6 дней назад

@@SoundsofVoltage It looks very profesh! kudos!

@harry2house536 6 дней назад

Thank you

@d42kn355 20 дней назад

Great video.

@SoundsofVoltage 20 дней назад

Thanks!

@VBlack-xc9mu 6 дней назад

Hi, I make some quick FM calculations and your sidebands spectrum shown on at time 1:15 - 1:25 is wrong, because there can not be frequencies 330 and 660 Hz.

@SoundsofVoltage 6 дней назад

You're right, the image I was showing at the time was just a "stock image" that I had ready, not something from the specific "carrier at 440 & modulator at 330" tests I would run. That's a good catch.

@kitkatandy929 21 день назад

Nice, scientific summary! So the result is "happily", oscillators are behaving mostly very different at least at fm-ing. The tune-drift of some of the OSCs are just an offset I estimate and you can adjust the tuning to be in tune with other OSCs again? To avoid this completely, you could also use SYNC, which results in other/more dynamic "material". What I found quite interesting overall is the fact, that while adjusting the modulation depth, some of the sidebands "wandering" downwards the frequency and some upwards. Somehow a bit like a carousel. Should use the spectrum analyzer more often...

@SoundsofVoltage 20 дней назад

@kitkatandy909 - The downward wandering took me a while to figure out... it sure looked weird to see some going down while others were going up, but this is result of that carrier drift. Let's say you've got a carrier at 440 and a modulator at 330. The upper side bands would be 770, 1100, 1430, 1760... The lower sidebands start at 110 and then, when the math says it would go to 110-330 = negative 220, it reflects back around to 220. Then -550 goes to 550, and -880 goes to 880. (This is all going to be my main video). Now imagine that the carrier drifts upward from 440 to 490. Those reflected sidebands would start by appearing to go down -- the sideband at -110 would drift upward to -60. But because it's reflected around zero, it actually appears to drift down from 110 to 60. So some of the sidebands are going up, but any of the reflected sidebands will appear to drift down -- and then back up again when it hits zero. Wacky. :)

@kitkatandy929 20 дней назад

@@SoundsofVoltage Quite interesting at first sight! Thanks about clarification of the "maths" behind this. Thats why I love your videos so much 👍

@andrewduncan529 5 дней назад

Are all of these examples linear FM? Are they AC coupled? I have some Animodule VCOs that I really like, but the triangle wave is slightly offset so I need to use a high pass (I actually have a purpose-built passive filter in order to AC couple) if I'm doing linear FM with them. I wouldn't expect the humble audio sine to be offset, but it might be.

@SoundsofVoltage 5 дней назад

@andrewduncan529 - Yes, these were all linear FM. And I *think* they were all AC coupled. it's quite common for the FM input to go through a small value capacitor to filter out the any DC offset. I know there are a couple that let you switch between them, but none of these do.

@Fluxwithit 20 дней назад

nice video. what scope are you using , very clean layout.

@SoundsofVoltage 20 дней назад

@Fluxwithit - It's actually something I built. I capture the audio, run it through a program that does the spectrum analysis/FFT and outputs data that is used to generate the visuals. It's a bit more work, but this way I can make it look/act exactly as I want.

@Fluxwithit 20 дней назад

@@SoundsofVoltage brilliant