Baxandall mid control

[Mixa]

In a 3-band Baxandall, how do I place the Mid control at 1kHz and make it narrow (high Q)? Which component controls the Q?

[Vivek]

Great question !!!!


I first learnt about the Baxandall when I was 15.

NATIONAL SEMICONDUCTOR had release an excellent Audio handbook, it had great explanations on many audio circuits, with lots of Math and analysis. Ooooh, I love math !!!

One of the sections was about the Baxandall, with a great explanation, equations, graphs and calculations about the 2 band Baxandall.


Then they devoted a small section regarding the 3 band Baxandall. They said that the mid band had low Q and hence too much interaction with the Bass and Treble band. Therefore, it was difficult to have precise equations to calculate the Mid band.

They however gave an example circuit with values


http://bitsavers.trailing-edge.com/components/national/_dataBooks/1976_National_Audio_Handbook.pdf
https://usermanual.wiki/Document/1976NationalAudioHandbook.2082164334/view
http://bitsavers.trailing-edge.com/components/national/_dataBooks/1980_National_Audio_Radio_Handbook.pdf


It might be better to use SPICE to calculate the values of the Mid Control and see how it reacts with the other bands. I will be happy to do that for you if you send me your schematic and values.

Or it might be even better to use a different Mid Control with higher Q.

[Vivek]

Have a look at Tom's design of a (Non Baxandall) mid band at ELECTRIC DRUID web site

https://electricdruid.net/designing-the-hard-bargain-distortion-pedal/

[Vivek]

https://web.archive.org/web/20040812214630/http://www.albertkreuzer.com/pics/el/pre/schem/preamp_sch21.gif

Bass Preamp with switches to change Mid Freq

[marcelomd]

In a 3-band Baxandall, how do I place the Mid control at 1kHz and make it narrow (high Q)? Which component controls the Q?

As I´ve said before. Simulating a Baxandall is way easier than calculating one.

I never bothered with it, but I _guess_ the ratio of the capacitors controls the Q. They form, with the resistors, a high and a low pass filter. A ratio of 1:10 should be wider than 1:5, for example.

[iainpunk]

keep the ''original'' style baxandall for bass and treble, and add a gyrator based mid control, this makes the Q way better, and the interaction way less problematic.

cheers, Iain