History of Phono EQ Curves — Reading Guide

The History of Phono EQ Curves

Your phono equalizer plays records according to a standard called "RIAA." But do you know why it's called "RIAA," or whether other standards ever existed?

Follow the thread, and it leads all the way back to the dawn of electrical recording in the 1920s. How did EQ curves — once different for every label and every era — converge into a single standard? That history is not as distant from today's record playback as you might think.

What kind of reader are you?

I want the big picture first (approx. 15–20 min)

What is an EQ curve, why was it needed, and how was it standardized? A century of history, condensed into three standalone parts.

→ Read the history in brief (In a Nutshell)

I'm looking for a specific answer (3–8 min per topic)

"What is the RIAA curve?" "How should I play pre-RIAA records?" Common questions answered one page at a time.

→ Browse the FAQ

I want all the details

The complete record of over two years of research. Written from primary sources — Bell Labs technical documents, patents, AES papers, and more — across 25 installments plus a prologue.

→ Overview and reading guide for "Things I learned on Phono EQ curves"

About this content

This section (this page, In a Nutshell, the FAQ, and Research Notes) was built on the content of the blog series, with Claude Code (Anthropic Opus 4.6, as of March–April 2026) used as an aid for structuring and drafting. Responsibility for factual accuracy and final editorial judgment rests with the author.

The blog series (Pt.0–Pt.25) on the parent site was researched and written by the author over more than two years, drawing on primary sources — circuit diagrams, technical documents, academic papers, industry journals, patents, and more — examined by hand.

"Established facts" and "the author's interpretation or conjecture" are explicitly distinguished throughout the text. If you spot any errors or have additional information, please get in touch.

Start with a popular FAQ

• What is the RIAA curve?
• Can you hear a difference when you change the EQ curve?
• How should I play pre-RIAA records?
• EQ curve vs. mastering — which determines the sound?
• Are all U.S. stereo LPs on the RIAA curve?