As a standard facility of most mixing consoles and DAWs, we all tend to take EQ for granted, even though there are many different types of equaliser with varying levels of sophistication and application. While the true origins of the first audio equaliser are shrouded in the mists of time, two names stand out for me as pioneers of audio equalisation: Peter Baxandall from the UK, and the American, Eugene Shenk. Baxandall was an electronics engineer (and friend of our esteemed Editor In Chief) who came up with a very elegant circuit for an active bass and treble equaliser. He published his design, royalty-free, in 1952 and it has subsequently been employed almost universally in mixing consoles and hi-fi amplifiers, bearing his name as the Baxandall equaliser or ‘tone control’. Amazingly, at around the same time in America, Gene Shenk developed a passive design which has become the legendary studio equaliser — the PulTec EQP-1.
The Pultec is fabled. I use my emulation all the time. This review is an excellent guide to what it is and why it works.