Strange sounds when the guitar signal fades out

Quad Cortex Bug Reports
1

Hi everyone, I would like your opinion because I don’t know if what I hear is a normal behavior of the Quad Cortex or if it is related to a problem. As you can hear from the attached audio file, when the guitar sound naturally decreases or fades out during the release of a chord (in the attached file it is quite clear what I mean), an annoying hiss/digital distortion noise appears (I don’t know how to define it better). I tried changing the cable, resetting the unit, I checked that the inputs and outputs were correctly set and that they did not clip, I used various factory presets, modified factory presets and very basic presets created by me, activated and deactivated the noise gate, but the noise was always there in all these cases.

In the attached audio file you can hear:

Sound 1 - Factory Preset 1A without any modifications.

Sound 2 - Factory Preset 1H modified with gain at 8.0.

Sound 3 - Preset with EVHIII Red amp, factory settings.

Sound 4 - Preset with Freedman amp and overdrive.

I attach some photos with the various presets and one with the input settings.

This unwanted noise can be heard clearly in all the sounds, in some you have to turn up the volume a bit to hear it more clearly, in others it is much more evident. Sound 4 is the one in which the noise is most emphasized, you can hear quite clearly how it fades out and then disappears and stops. It seems like a sort of annoying digital distortion that is triggered when the sound of the guitar begins to fade out. But, as I said, by turning up the volume you can notice how it is present in all the sounds. Even trying with much less distorted and more crunchy sounds, that strange digital noise persists when the sound goes down, in this case, of course, it has a much lower volume and is less perceptible.

Here the link to all the files:
https://drive.google.com/drive/folders/1oSbMMusprYy-WThJOgRuaqzJdS3VLO1X

Thanks for your valuable answers and for your possible advice.

PS. The unity has the latest software upgrade CorOs 3.0.1

2

There are two types of noise here. You can also make them audible all the time by disabling the noise gate on the input and the utility gates in the presets.

  1. Constant “hissing” white noise
  2. The “digital chirping” noise which sounds like it has a specific frequency.

The first one is normal. It’s just always there to a degree and gets amplified the more gain is in your chain.

The second one sounds like interference from another electronic device. To make sure we are talking about the same thing, I recorded a sample of me, doing my best to mute the strings while walking towards my computer/screen, which makes a very similar noise. (Factory Preset 1A, Noise gates off)

In the beginning you hear the normal white noise. After about 4-5 seconds the EMI noise from the computer starts to get louder.
https://www.dropbox.com/scl/fi/052odpvs3z112okx15ffs/emi_noise.mp3?rlkey=vgb593l2y3bn4itk76i23uz5k&e=1&st=bd2j854g&dl=0

Is this what you were pointing at?
If so there is probably something nearby or something connected to your power line that induces this noise. (light with transformer/LED, air conditioning, computers, screens)

To find the source, you could try the following:

  1. Use a preset without noise gate where you hear the noise all the time.
  2. Take your guitar, volume up move around in the room to see if the noise changes. If the noise changes, you should be able to locate the source of the noise and avoid it. Also badly shielded pickups and passive/single coils can make things worse in this case.
  3. If the noise stays constant when you move your guitar you could try switching off devices in your home one by one. Alternatively you could try moving to another room or another building/location to see if the noise persists.

Hope that helps. Good luck!

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3

Hi,
And thank you so much for your reply. No, my noise is not a white noise or a interference problem. It’s some sort of digital crackling (i don’t know how i can describe it in a better way, but i you listen to the audio file you can ear it at the end of every chord) that appears when the note, or the chord, fades out. I also disabled the noise gate and trying various settings, but nothing change. I don’t know if this is the normal behaviour of the converter or the software that control the QC, but in this case is not a good rappresentation of a real amp, or if that depends on some sort of issue of the unit.

Thank you again

4

I had this problem. The culprit was the electric garlands on the Christmas tree. After I turned them off, all the audible noise and interference disappeared. :slightly_smiling_face: :+1:

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5

Really? I regret a little bit more every day to have spent €1600, more or less, for a unit that has this kind of issue caused from a poor hardware design. They already have to fix my switch board due to a rotary encoder that doesn’t work. I have to try to build a Fadaray cage, maybe this could solve the problem, even if i don’t think that the interference of an electromagnetical field is my problem because it only appear when the notes start to fade out.

6

This is a lot of artifacts that it is the same concept i’m saying in these days.
In real world this is a unbiased amp =) not normal behaviour… cut… and intermodulation… and … dragons!!..
No… if i have a amp that has this behaviour SO evident (i can accept a little bit of… but no at this level) i have to REBIAS preamp or poweramp tubes!

Aliasing ? (a lot) ? i think yes. Or neural networks not so evolved at time of capture/for/modelling.

Headrush flex in this field is really MORE real, for example. A natural fade out of higain amp. Real behaviour. Your sample has a lot of artifacts (we are not alone =) ) ;-D

And i’m not referring to background noise or elaboration noise… but at guitar/amp sound. (and also… elaboration noise it too much high imho, but this is another problem)

The problem is that when you start to ear it, you always ear it afterwards, good luck.

I think that NeuralDSP knows about this thing, but is keeping quiet to keep it under the carpet and gain time to update the models with new captures of Tina. Ndsp cannot have failed to notice it… they knows.
You can notice this problem working with dynamic pick… when you rise down… you don’t have the natural string soul with clipping… but a lot of FCZFCZCZCHIUUZ :grinning:

Captures are in another league.
But i’m for amp modelling, the best way to tune the sound of our guitars.

I hope that my thoughts will be interpreted in a constructive way

7

I agree with you for the most part, but the only thing that i want to know is if this is a normal behavior for this unit (that is for sure not so good because shows some basic errors in the programming or in the construction of this product), or if is only my unit that produces these weird fade out because is broken again in another part.

8

I’m honestly not sure if I hear what you mean.
So I recorded a sample similar to yours and you can tell me if you hear the problem in there too.

I built your Friedmann Lead preset from the screenshots and turned off the Exotic Z Boost to reduce the influence of noise.

First one is with input noise gate on, the second one is with noise gate off.
https://www.dropbox.com/scl/fi/0ondb9x8uct87ico6yvu7/friedman_noise.mp3?rlkey=jlumtm8xnhn4t0pnwpjqxjx3u&st=ov9b7nsu&dl=0

Apart from the noise gate struggling and “crackling” a bit at the end, I don’t really hear a problem.

9

Yes it’s that crackling at the end of the first chord. In your sample is less evident (the noise seem to has less volume) than in mine but it’s still there, maybe is less emphasized because of the boost turn off. Thank you so much for your sample.

10

Yes that’s definitely the noise gate at work. And the more noise floor you have, the more you hear it. When I turn the boost on I definitely get more of a sizzling sound at the end. The interference I talked about earlier can also add into that.

There have been other threads on here about the different noise gates. Some people say they have analog pedals that do a better job.
Some people say the problem is the noise gate built into the input block and that they are happier with a “simple gate” block (which just abruptly cuts volume at a certain threshold or the newer “adaptive gate (S/C)” in the end of the chain but with sidechain set to input 1.

Personally I have never seen a device do this perfectly. You always have to compromise at some point.

Here is a recent thread about the topic:
https://unity.neuraldsp.com/t/noise-gate-on-input-block-not-working-correctly/12686

11

Is the input noise gate the one you are referring to and that you use in your sample, right? Because in my sample i turn off the adaptive noise gate. Thanks again for your help.

12

Yes in the sample I used the built-in noise gate in the input block

image
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I also tried other variants:

  1. Adaptive Gate in the front: Gave similar results to the input gate
  2. Simple Gate in the front: Cuts sound abruptly, but doesnt “fizzle out”
  3. Adaptive Gate (S/C) in the end with sidechain source set to input 1: I feel like this has less crackling at the end. Maybe worth a try, if you haven’t tried it yet.
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13

try recto or soldano, friedman seems ok

14

First of all thank you so much for your help and support. My first and most important concern was about some software and hardware issues to the unit itself, like i said in my previous message they already replace the switch board due to a problem with some of the switches/rotative encoders. But, comparing your sample with mine, seem that my QC works properly and that this is not at all an issue due to a malfunction. It’s more like a not so well programmed part in the DSP software. I also tried the noise gate at the end of the chain, still crackling but in a more sottle and soft way, seems less random and more vibrating with the notes of the chord. Thank you so much again.

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