Operator Adjustable Equalizers: An Overview

• References Introduction This paper presents an overview of operator adjustable equalizers in the professional audio industry. The term “operator adjustable equalizers” is no doubt a bit vague and cumbersome. For this, the author apologizes. Needed was a term to differentiate between fixed equalizers and variable equalizers. Fixed equalizers, such as pre-emphasis and de-emphasis circuits, phono RIAA and tape NAB circuits, and others, are subject matter unto themselves, but not the concern of this survey. Variable equalizers, however, such as graphics and parametrics are very much the subject of this paper, hence the term, “operator adjustable equalizers.” That is what they are—equalizers adjustable by operators—as opposed to built-in, non-adjustable, fixed circuits. Without belaboring the point too much, it is important in the beginning to clarify and use precise terminology. Much confusion surrounds users of variable equalizers due to poorly understood terminology. What types of variable equalizers exist? Why so many? Which one is best? What type of circuits prevail? What kind of filters? Who makes what? Hopefully, the answers lie within these pages, but first, a little history.