A bit of interesting stuff to be read - Negative Feedback Tone Control

[kagliostro]

http://home.comcast.net/~stphkeri/NegativeFeedbackTone.pdf

K

[PRR]

This is Baxandall's classic 1952 paper.

Before this, tone controls were fairly crude. Because of the music sources, a scratch filter was essential, high-boost was useless. Bass-boost was common, bass-cut less common (except in PA which usually had a 300CPS bass-cut option).

James published a survey which outlined the passive symmetric bass/treb boost/cut using tapered pots.
http://home.comcast.net/~stphkeri/James_SimpleToneControl.pdf
This became common.

Within a decade after 1952, "all" Hi-Fi used Baxandall's plan. Especially Stereo: it is much easier to track two linear pots than two tapered pots.

Note that when guitar amps gave symetric bass/treb boost/cut, they usually used a James-like passive network. Maybe they didn't read Wireless World. Maybe they stuck with what they learned in the early 1950s. And the Bax gives unity gain and can have low input impedance; you can get more gain from the same tubes with a passive network.

[kagliostro]

Thanks PRR

You have always very interesting things to share

Franco