Filter introduces low-end information to signal path

I have noticed that the Filter in the Effects signal path adds additional low-end information. This applies to all the standard filter types (digital, analogue, ladder, dirty), with the drive set at 0. I would have expected the digital one to be crystal clear. I have found that this is when the resonance is set to 0 or low levels. Is this by design? Why is this information introduced when the resonance is turned down? Should the signal path not be crystal clear when the filter is simply allowing audio to pass through it?

To recreate this, enable the init preset and enable all three oscillators. Add the filter in the Effects chain, followed by a compressor. Then turn the resonance in the filter down and play a chord, low end information is introduced. When you turn the filter off, you can hear that the signal path is now clear or these low-end artifacts.

I have uploaded a video showing this. I am turning the filter on and off, and you can see the low-end information introduced in by listening, and also in the analyzer in the top right. I have placed a compressor to exaggerate the effect.

Sorry - hard to tell since this is not a fully init patch and there’s reverb and compression going on.

I took a fully init patch playing a c major chord with 3 oscs, rendered to audio with filter on and filter off, and I didn’t see anything below the fundamentals on my spectrum analyzer to atleast -100db.

At the moment it looks like it’s the patch or the reverb.

Edit:
Watch your osc levels as well, pushing hot signal into the filter will inherently cause it to clip, which may add the low end info you are seeing?
Just a thought!

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Hi Larry, thanks, I am really looking to get to the bottom of this, and whether there are grounds for a bugfix. I have created a video straight from Init, adjusting to ensure there is no clipping prior to hitting the filter. All I do is place a compressor after the filter to make it more evident, however it will come into play the moment any gain effect is applied (for example a distortion after the filter, or a gain effect in the DAW signal path after Vital).

If you look in the top right you can see the low-end information disappearing once the filter is turned off, which raises questions regardless as the filter at it’s default settings should not affect the audio and definetly not introduce low-end information, given there are no bands in the low end in this setting. This is the same for all filter types (digital, ladder etc).

Just to add, I am a very big fan of Matt’s work, and for what it’s worth consider myself somewhat well versed with the ins and outs of Vital (have created perhaps over 2000-2500 Vital presets comissioned for commercial use), after the first 100 I noticed this and switched using the Filter with the EQ for my filter macros. I just wanted to raise this as I really want to make more use of the filter in the processing chain, to free up the EQ for sound design. The only other change apart from this I could think of would be disabling the chorus amount on the reverb by default. Aside from that, Vital is pretty much my favourite VST synth out there.

Hey
Thanks for the clear video! Definitely not questioning your ability just hard to differentiate from your first vid :slight_smile:

Try perhaps with the volume even lower on all three osc? I don’t think the filter clipping is tied to the master gain, in other words I think the filter will still clip even if not clipping the synth master gain.
I noticed even with one osc wave going into the filter I can see the edges start to clip even before I get to the default 70% volume. So I’m thinking the way the low end moves as the waves phase around, I’m wondering if this is maybe artifacts from aliasing?
Does the low end stuff change with increasing the oversampling in the settings?

Otherwise, I don’t think Vitals filters are meant to be clean clean, even the digital one is modelled off something, no?
I can’t find anything in writing but I swear there was a forum post here somewhere…
But that would also explain why the eq is ‘cleaner’ as it’s not modelled on anything

Hope this helps!

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It’s a consequence of drive. You can satisfy yourself that this is true by turning up velocity tracking, and playing progressively louder notes. This effect only occurs when playing chords; it’s intermodulation distortion (try it with one note, notice it isn’t there). If you turn off the compressor, slamming into notes hard enough will still produce an audible distortion effect, even though you do not redline Vital’s output. The reason you see it as “low end” after compressing is intermodulation distortion is producing LF content but it’s very minor, only the multiband compression is brickwalling it up to where it’s very noticeable.

The drive is built-in to the filter models. You can’t get rid of it. The drive knob changes how much gainstaging there is going into the drive, but there is no OFF setting, just “low enough you don’t notice” setting. If you’re wondering why this only happens on the FX filter, it’s because the FX filter is mono, rather than poly; the primary filters are per-voice, so they do not produce intermodulation distortion.

Since every filter type has a distortion model, every filter exhibits this behavior in some way or another if you play a loud enough chord into it.

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Good to know the primary filters are per voice!

That explains everything and if that’s the case then will adjust my workflow accordingly, by using the filter only on single voice presets where no chords are being played; otherwise will continue to use the EQ as the macro filter on multi-voice presets.

Really grateful for the input and detailed insight into the inner workings!

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