Question on gain in active bax

[bufferz]

hello,

could somebody help me with the following question:

If I wanted to reduce the gain on the treble band in the following bax circuit should I increase/decrease the 10k resistor or change the pot value?

Id like to mod it so that the treb band only boosts half relative to bass - thanks for any help

[PRR]

You put stopper resistors on each end of the pot.

Where did you get the scheme you posted? The analysis is not clear, and there is a simpler way to do this.

Finding examples has become HARD since (according to Google) NObody knows the difference between a Bax and a James. They are very similar from the front of the hi-fi, but very different in the circuits.

[PRR]

FWIW, here is Baxandall's original plan, re-drawn with a triangle instead of a tube:
https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part8/Page2.html

For half-boost, the "2k2" resistors would be changed to about half (each) the pot value, 23.5K; and the cap values might want to be trimmed.

[bufferz]

Thanks for your help.

here is a schem in context


so if i wanted to reduce the treb to half gain increase but keep full cut would i add the 2k2 stopper resistor to one side?

[bufferz]

or "25k" stopper resistor to one side?

[PRR]

If you don't ues equal values on both ends of the pot, the "mid-point" response is not flat.

Frankly the easiest thing is to not turn the knob all the way.

If you are having oscillations when Treb is maxed, try taking some supersonic response out of the path, or re-layout so output never gets near input.

[bufferz]

Thanks again for your response!

Ya, was thinking about redoing the layout - too many parallel wires as well. In the meantime could you explain how to remove supersonic response?

[Pojo]

Should be able to just add some lowpass filtering or modify an existing filter. Convenient locations I look for are where there's an existing series resistor in the signal path and just add a cap to ground right after it (or increase the size if such a cap already exists). The 10k at the input (R2) looks like a good candidate. To focus on supersonic frequencies only and not darken the tone, size the cap so the new filter starts rolling off anywhere from say 15khz to 20khz. 1nF would set it at 15khz.

That is unless Paul has something else in mind, in which case I'd go with his advice instead