First Equalizer


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Filters and EQ have a long history.


George Ashley Campbell, working at AT&T, persuaded electrical reactance to be repurposed as audio resonance, inventing the essential building block of EQ:  the L-C circuit (inductor and capacitor).



The Pultec EQP-1 becomes the first program EQ built for audio.  Adding a fixed make-up gain to the passive filter section, it becomes the EQP-1A.  Studio HVAC bills will never be the same.



Peter Baxandall publishes his paper in Wireless World, “Negative Feedback Tone Control” and ‘tone’ controls start appearing on home hi-fi equipment.



George Massenburg publishes his AES paper, “Parametric Equalization,” giving recording engineers just about as much signal processing flexibility in the frequency domain as they’ll ever need.