If Opamps are OK instead of discrete transistor designs, you might want to check out my design. It easily beats the typical Baxandall circuits in both performance and sound quality. The latest new and improved version starts at Post #18 (Here: http://www.diyaudio.com/forums/chip-amps/199130-usable-tone-control-2.html) , but go back to the beginning to get the full story.
Mike
Mike
Yes, basically. But note that different component values at both sides of the control potentiometers. In a Baxandall tone control these should be symmetrical. Hece, I suspect a non- linear frequency response with the controls at 12 o'clock. What was the designer thinking?
What a pity that Radio RIM, Munich, was folded in the early 1990ies. I've been there several times and always was much impressed by their assortment of electronics.
Best regards!
Passive tone controls predate the Baxandalls, and the old passive ones almost always use log or audio pots and factor of 10 differences in cap values in order to get enough boost/cut range. They are also a bit nonlinear, even at flat position. Linear controls would have -6dB “gain” at center rotation, and +/-12 is often desired - and the log/audio pot will allow this because its down more than 6dB at center setting. Early Baxandall designs probably used the log pots out of habit more than anything else, even though linear ones could be made to work better. More common to see it in tube sets, but I’ve seen early transistor circuits using audio taper pots there.
Sinclair project 60 preamp. About as clean and simple as it gets:
http://diy.torrens.org/Sinclair/P60/issue_1/p06.jpg
http://diy.torrens.org/Sinclair/P60/issue_1/p06.jpg