Pink and red chroma (very) noisy...?


When my new unit arrived yesterday, the pot defaults were all 12oclock. This meant pink (bit-crusher) chroma with 50% depth and feedback but man, this becomes extremely noisy just after a second, even without any input. So starting Nautilus for the first time scared the hell out of me! Also red (distortion) acts the same. It’s not the effect itself, but ‘extra’ white-ish noise.

Also after a ‘purge’ it starts building up again and in medium volume input you also hear the noise build up, which makes it unusable… It seems to pick up the LEDs blinking, as it builds up at the rate of flashing.

All the other chroma’s are fine and quiet with a very low noise floor…

Anyone else also has this behaviour?

Cheers, Airell

Here’s a short wav.

Depth and Feedback 50%.
Starts with chroma blue.
At 4 seconds switch to chroma green.
At 9 seconds switch to chroma pink.
At 15 and 18 seconds I pressed purge.

It feels it isn’t applied to the sound, but it picks it up out of nowhere.


Should Pink and Red Chroma also distort without any sound coming in?
It seems it’s ‘inserting’ something to distort…?

Hey @Airell, good observation about the distortion modes on Nautilus. This is a unique occurrence when you introduce gain in the feedback loop, what you are essentially hearing is the noise floor getting louder over time as it feeds back through Nautilus.

Hope this makes sense, and let me know if you have any other questions about Nautilus!

Hi @michael , Thanks you your answer.

So I guess this feedback differ from the other modes, as the others do not ‘introduce’ the noise floor as much as the feedback in ‘pink and red’. When I attenuate the incoming sound into the Nautilus, (more quiet/low volume sounds coming in), is there a sort of makeup gain to boost more quiet sounds in pink and red? As the ‘noise floor feedback’ seems to be much more present when incoming volume is 0, and ‘goes away’ when one slightly increases the volume of the incoming sound?

You can adjust the input signals gain by holding the Tap button and turning the Dispersal Attenuverter knob. The range on the knob is -12dB to +12dB

I actually do want to get low volume signals coming in. I have a VCA before the input of the Nautilus which attenuate the signal in self-generating patches. It’s not that my signal needs to be boosted. I wanted to know if the Nautilus itself is doing a ‘gain boost’ (independent from the Tap+Dispersal gain) in these modes.

So it seems distortion modes are more prone to feedback the noise floor than the other modes. I’ll try to avoid these modes when I know signals will not be that hot.

Ahh, I see what you are saying. Yes, the distortion modes on Nautilus introduce gain boosting, but relative to the Depth knob position. The effect, and the gain boost, is off when Depth is fully CCW or at 0V on these Chroma effects.

Here is a rough visualization of what is happening in these modes:

This same principal applies to the lowpass and highpass filter effects which is why, even with infinite feedback, the delays eventually fade out.

For the lo-fi “Refraction Interference” mode, the nature of the effect is a bit different.
It’s not explicitly gain boosting, but sample-rate reducing and bit depth reducing which results in:

  1. added noise, not present when at higher resolution/bitdepth
  2. bitdepth reduction quantizing things to the nearest “bit” and will result in a perceived loudness increase as harmonically simple signals (e.g. sine waves) are transformed into stepped signals, and at lowest bitdepths essentially square waves.
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Yes, this describes what I observe.
Thank you for your comprehensive answer!
Cheers, Ian