Baxandall Tone control

[Sharpie]

Hi, Has anyone implemented an equivalent of a simple two stage Baxandall tone control in code for the Teensy and the Audio board? I've searched on Baxandall to no avail and read the information on the audio system design tool but I still haven't got a clue. Too few joined up grey cells I guess.

Thanks.

 

[Theremingenieur]

Understanding the principle of operation of the baxandall tone control which consists of combining two shelve filters (see http://makearadio.com/tech/tone.htm) will allow you to do the necessary transforms to calculate the corresponding coefficients for the biquad Filter object which already exists in the audio library.

 

[PaulStoffregen]

You could use 3 filters and a mixer, like this.



3 biquad filters are probably the most flexible way. The biquad filter as a convenient functions to set high and low shelf responses. (right side panel - scroll down to setLowShelf & setHighShelf)

https://www.pjrc.com/teensy/gui/?info=AudioFilterBiquad

Then to adjust the relative tone, just change the gain settings of the 3 mixer channels.

 

[Sharpie]

Thank you both

Thank you both. I'll experiment with the biquad filters setLowShelf and setHighShelf. I'm afraid I still don't see why you're using three biquad filters Paul.

You could use 3 filters and a mixer, like this.

View attachment 14718

3 biquad filters are probably the most flexible way. The biquad filter as a convenient functions to set high and low shelf responses. (right side panel - scroll down to setLowShelf & setHighShelf)

https://www.pjrc.com/teensy/gui/?info=AudioFilterBiquad

Then to adjust the relative tone, just change the gain settings of the 3 mixer channels.

 

[PaulStoffregen]

Some of the Baxandall schematics have 2 tone controls, others have 3.