Guitarix Center Amp: Decibels out of control when changing preset. Noise on Cabinet knobs.

[fernando-inf]

Hi, in this comment #85 (comment) I made mention of noises when changing preset. After several trials I can reduce the error to the Guitarix Center Amp. In the attached video I show 3 things:

1- When changing from preset A to B or C there is an incredible increase in decibels, I think this is because the pre-amplification stage decreases its values after the Master Volume. The Reverb further increases the problem.

2- The Cabinet plug-in makes a considerable noise when changing its values on the knobs, mainly with Princeton Style.

3- There is a significant difference in gain between the different Cabinet simulators, mainly with Princeton Style.

Bank and video attachment:
Video: https://youtu.be/_tHzuNw-JEk
Bank: BANK-34.gx.zip

[brummer10]

Hi fernando
1.) Here we are exactly were we talk about on #85 Mainly, in the digital domain we need to roll back filters instead switch them on/off to avoid such popping noises. Basically the same is true in the analogue world. Think, you switch on a amplifier with a connected guitar with gain set to a high value, wont you expect exactly this kind of noise? Hence, that's why you usually don't do that. Now, in the digital domain we've the same problem, just that we could implement soft bypass modes to reduce this noise. But we reach fast the point were we need to decide which kind is more annoying. Have a huge gap in the sound, or risk to have a popping noise. To clarify what I mean, look what I do when provide a plug for the MOD:
https://github.com/brummer10/GxSupersonic.lv2/blob/83e25bfd2eccac4f518471bfaf5fe120da19cf26/plugin/gx_supersonic.cpp#L147
and compare it with what we do in guitarix.
In the supersonic (just as a example, nearly all plugs, regardless from which author, which provide ramping, use values in that rang) I use 8x higher ramp value then in guitarix, to ensure that no popping noise will come up.
But doing the same for guitarix will lead to a couple of requests to reduce the gap time when switch presets. So, it's a compromise to reduce the ramp time to a value which cover "most" situations. In your video, you just didn't switch from on amp to a other on, but you switch it on and off, would you ever do that in analogue?
Still, when you are able to provide a better solution, that will be very welcome, I'm all open to learn more.
2.) Here we are as well on a border line. There is no other convolution engine that will provide you this options, exactly for the reason, "this can't be done without noise". The cabinet controls rework the convolution kernel, not the result of the convolution. This means it work with the Impulse Response, so with the influence it have on the original sound instead just modify the result. That requires a restart of the convolution engine on any change you make within the cabinet controls. But this is the only way to allow fine tuning the cabinet files. You'll never tune then in a live situation, there you work with presets.
3.) Yes, that's how it is, it's not my choice, it's a fact. Create presets to cover that.

[fernando-inf]

Very well. So at least now I know who was causing the popping noises. I will reconfigure my presets to avoid them. I hope one day to contribute some new idea for this. Thanks for responding, greetings.