Phase inversion method not working
Hey there,
I like to use a method for sound design that involves summing a signal with its phase inverted version and then manipulating one of them to isolate the difference between the two signals.
it seems like that doesn’t work in Drambo. I can cancel a signal by inverting and summing, but when I process one of them, I hear both signals again.
maybe it’s a latency issue that shifts the phase again? Or a classic user error?
cheers :)
Comments
I’ve run into this before and depending how you have it setup it could be a few different things.
Let’s assume the simplest version of this. 1 mini oscillator on a sine wave, an inverter and a mixer module. You run then sine into the inverter and then route the output of the inverter and the original sine into the mixer. This will always work, if this isn’t working for you then something is going on with your system I don’t understand, but I wanted to establish that this works.
The weirdness starts in two places. If you instead have two mini oscillators outputting sine waves, invert one of them and combine them the mixer, this won’t work most of the time. This is because the phase of an oscillator in Drambo compared to another one isn’t perfectly synced. They’re phase begins whenever they loaded in and the chances that is the exact same time are slim. Now if you save the patch that I just described and reopened it, it would work! Because the oscillators would have loaded in at the same time with their phase aligned.
The second weird thing is latency like you suspected. Some modules and especially auv3s introduce latency and Drambo has no latency compensation like a lot of other daws. What this means is if you are using one of the modules that introduces latency then the phases will never align properly. So if we go back to the first example of the patch that works consistently and introduce a peaking eq module (one which always adds a tiny fraction of latency) into either of the chains, it will suddenly stop working. A work around for this is to introduce the peaking eq into both chains as they introduce the same amount of latency and suddenly the phase lines up again.
Not every module in Drambo introduces latency like that. I don’t know of a definitive list showing which do and don’t so it’s kind of trial an error. Hope this helps!
@parkerfrost you can hard sync the oscillators in dRambo.
There's a gate input to trigger the oscillators so you could have the oscillators hard sync at every gate signal
or use the cv sequencer or gate+velocity sequencer to sync once every beat/bar/phrase.
I'm focused on manually correcting for latency right now so I'll browse the modules and see which ones are adding latency.
The Compression module certainly does add latency when "Look ahead" is switched on.
@gravitas oh that’s so awesome to know! That will save me so many headaches in the future. And yeah compressor on lookahead, and peaking eq are the only ones I know for sure do
@prehm I've done it many times and it does work if you do it correctly.
In other words: Please be more specific if you want a specific answer 😉
Specifically: BP filtered white noise.
Test setup: noise to invert and bp filter, invert and filter to mixer
oh. I think I can see my error 😅 a peaking eq would be better I guess
I think the sound you’re after is osc hard sync, like @gravitas mentioned
phase cancellation needs to be sample accurate, so if you process one of the waves it will introduce a delay (you can try using a very short delay on the other wave)
anyway a picture is worth a thousand words
You can do it using 2 identical BP filters:
Well the BP filter cuts out everything else, so there is no noise left to cancel out..
it kinda works with a peaking eq, but there is some noise left. Putting a delay of ~0.04 ms after the invert gets rid of almost all of the noise, so the peaking eq definitely introduces some latency.
@prehm
Well the BP filter cuts out everything else, so there is no noise left to cancel out..
Ah, I thought that was what you were looking for, reading your original post.
it kinda works with a peaking eq, but there is some noise left. Putting a delay of ~0.04 ms after the invert gets rid of almost all of the noise, so the peaking eq definitely introduces some latency.
Sure it does - but tbh I'm still not sure what you want to achieve in the end.
i wanted to know wether the phase cancellation method works in Drambo or not (because I couldn’t get it to work), which I now know :)
in terms of what sound I want to create, I am working on a synthesizer that uses a bunch of sine waves atm and I am looking for ways to get the sound to be less sterile, without creating additional harmonics. Using a pure BP filter on white noise leaves too much noise to be usable in my case.
I tend to make a lot of random lfos and put the tiniest amount of them on a bunch of parameters. It really breathes life into a patch. Like click in and write out 0.03 on the amount. Doing that on a few shapers in series with different random sources will really add some organic vibes, but honestly just add the tiniest fraction of modulation to like 20 parameters and it’s so nice.