RE: Input and Biquad/QuadBiquad.h and Source...

It seems like the difficulty you are facing is related to getting started with Bela, understanding the way it is designed to be used. If my guess is correct, then below might help you get the code running.

This first statement is to describe the assumption I am making about which Zip file you are talking about. The way to get a Zip file from the github repository I sent in a link is like this,
https://github.com/transmogrifox/Bela_Misc
,then there will be an option "Code" and "Download Zip".

Is that the Zip file to which you have made reference?

If this is what you mean, then you may unzip this zip file you will have a directory structure of the repository, which looks like the corresponding github page -- within there are multiple directories each having a different sketch. Each one is its own Bela project and I am uncertain what Bela would do with the whole of Bela_Misc copied to a single project directory.

You need a new project that includes all the .cpp, .h and .txt files you see here:
https://github.com/transmogrifox/Bela_Misc/tree/master/klingon_tone

This means on our PC you would browse to the kingon_tone directory under the unzipped Bela_Misc directory and upload those files to a new project from the Bela IDE, like below.

1) Download Bela_Misc repository zip from https://github.com/transmogrifox/Bela_Misc
2) Extract zip to your PC
3) Open web browser to Bela IDE -> create new project, name it whatever you want
4) Delete the default (auto-generated) render.cpp
5) Use menu option to upload project files
6) Browse to extracted zip directory, klingon_tone
7) Upload all .cpp, .h, .txt files from directory klingon_tone to this new project directory
8) Build and run
9) If 8 works, then you can modify code using the IDE editor to observe how it may change the sound, and/or adjust project settings in the IDE (e.g AGC gain, DAC gain). Defaults will be ok for testing basic compilation and verify sound has changed.

If you have more experience with Bela, there are more elegant ways you can learn to copy the code to the correct place The above method is one way that is easy to explain, and it works.

ryjobil Each one is its own Bela project and I am uncertain what Bela would do with the whole of Bela_Misc copied to a single project directory.

it would place them all in the same project and fail gloriously at link time with multiple duplicate symbols!

silver2row Your code is printing to the console too quickly. Check your audio thread for print messages.

Getting this message confirms you followed the instructions correctly, the code compiled and it is running. The message is a side-effect of not having any pots connected to analog inputs. The application prints each time it detects the pot gets turned. When there is nothing connected to the input, the noise appears as if the pot is constantly being turned back and forth from one extreme to the other faster than a human could ever turn it, and it prints more messages than Bela can keep up with.

Below shows how to disable reading the pots when nothing is connected to the Analog Inputs:

In render.cpp:

void render(BelaContext *context, void *userData)
{
    //separate audio inputs into their own buffers
    format_audio_buffer(context, ch1, 1);
    format_audio_buffer(context, ch0, 0);

Comment these lines as shown below

    //Scan analog inputs and set settings
   // for(int i = 0; i < N_KNOBS; i++)
     //   format_analog_buffer(context, kp[i]);

The remainder of this function posted to help you see where the commented line is found, but you don't need to change anything else below.

    //Run the klingon on ch0
    klingon_tick(kot, ch0);

    //Send it to the output
    for(unsigned int n = 0; n < context->audioFrames; n++)
    {
        // Write klingon through ch0, pass-through ch1
        audioWrite(context, n, 0, ch0[n]);
        audioWrite(context, n, 1, ch1[n]);
    }
}

Once that is working, then you can make modifications to the code I gave previously for making the effect more extreme.

silver2row I tried and this is the return output I get:
This output is helpful. Thanks for posting it.

Delete the file test_tonestack.cpp It is the only code in the directory that can generate an output formatted like that, and with those numbers. This is a file that I should have put into the "analysis" directory because it's an offline test utility for the tonestack code, but was not meant to be executed in real time. Sorry about that.

@giuliomoro it is noteworthy that Bela seems to be compiling and executing that program without generating an error (except too many print statements at runtime).

Remember earlier I mentioned channel 0 has klingon tone and channel 2 is just pass-through. Depending how you have hooked up the guitar it might pass-through or it might get the effect.

If using both in parallel it will be a mix of clean and bluesey.

The default settings are for a "bluesy" sound with guitar. If you hear some distortion that is somewhat mild, that is what I expect.

You can get more extreme settings from what was posted above. The first step was just getting the code to execute, and then now maybe you can do some things to make the change in sound more obvious.

Here's an example of what it will sound like if you get the guitar level turned up high enough on the input:

Actually "Klingon Tone" is a play on words for "King of Tone". It's a digitized model of the "King of Tone" pedal https://happybluesman.com/why-king-of-tone-pedal-famous/ . The analog circuit is very similar to the Marshall Bluesbreaker in case that helps describe what to expect.

The default settings are adjusted so that a guitar with nearly full-range input will "break up". You have to crank up the gain and mix to all hard clipping for it to sound distorted on a weak signal.

If you have plugged your guitar direct to Bela input with no amplification then you will need to set the input gain in project settings to about 12 dB. That audio level meter I showed in the video is nice for helping set up the input level, but that is yet another project and it makes sense to get one working correctly before moving on to another.