Why did phono EQ curves converge on the RIAA standard? A primary-source history from 1925 through the 1954 RIAA standard and the stereo-LP era that followed, with a 3-part overview, a topic-based FAQ, and a research blog.

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"

Recent updates

• April 28, 2026
  • 🔔 Newly published: What can — and cannot — be learned from a 46-issue close reading of "Dialing Your Disks", a recurring 1950s column in High Fidelity magazine
• April 27, 2026
  • ✏️ When was the RIAA curve established — years of pre-history leading up to January 29, 1954 — Added McKnight (J. Audio Eng. Soc. 30(4), p.244, April 1982) account in the standardization-timeline section, noting that AES TSA-1-1954 and the RIAA's 1954 standard adopted the same characteristic in the same year and that the "Bulletin No. E1" name and revision dates were assigned retrospectively
  • ✏️ Why the RIAA curve became the industry standard — technology, politics, and economics — Added McKnight (J. Audio Eng. Soc. 30(4), p.244, April 1982) account at the end of Factor 2, noting that AES and RIAA — separate organizations — adopted the same characteristic in the same year as a symbol of cross-industry consensus-building
  • ✏️ (In a Nutshell Part 2) How did unification finally happen? — From the postwar era to the birth of the RIAA curve (1942–1954) — Added McKnight (J. Audio Eng. Soc. 30(4), p.244, April 1982) account at the end of §4 "Three standards, one curve," noting that AES TSA-1-1954 and RIAA adopted the same characteristic in the same year and that the "Bulletin No. E1" name was assigned retrospectively
• April 19, 2026
  • ✏️ Records have physical limits: low frequencies make the groove swing too wide, highs get buried in noise. Recording cuts the lows and boosts the highs; playback reverses it. That's phono equalization — the modern standard is the RIAA curve. — Added note on the 1956 Saturday Review description
  • ✏️ What EQ curves were used before RIAA, and why were there so many — Added Burke's account from the 1956 Saturday Review book (five playback curves a domestic control unit should provide, plus the equalizer-as-necessity truism)
• April 18, 2026
  • ✏️ The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964) — Expanded the 1949 revision section in four layers based on close reading of Broadcasting Telecasting (1948–1949): the two-layer approval flow (RRSC executive committee → full committee on April 9, 1949 → NAB Board of Directors on April 14–15, 1949) with the April 7 open meeting; primary-source backing for the disc-curve carry-over (March 28, 1949 "reaffirmed a majority" quote; April 18, 1949 composite-groove study quote); the trade-press silence in the second half of 1949 (May–June follow-up gap, July Portsmouth engineering-department downgrade, November consolidation of standing committees, absence from year-end reviews); and the Howard → McNaughten engineering-director turnover three to four months after adoption
  • ✏️ Why did the U.S. and Europe use different EQ curves — the divergence in turnover frequencies and its background — Corrected the date of A.E. Barrett's (BBC) remark on NAB pre-emphasis from 1949 to 1947 (source: NAB Recording Standards Meeting, Audio Engineering, October 1947)
• April 17, 2026
  • ✏️ Are U.S. stereo LPs recorded with RIAA curves, or with per-label EQ curves? What do label-by-label curve charts actually show? Answered from cutting system design and engineers' own testimonies. — Minor revision of the summary
  • ✏️ What is the RIAA curve? The standard equalization for analog records, established in 1954 and defined by three time constants (3,180μs / 318μs / 75μs). Covers the history of its adoption and its current status. — Minor revision of the summary

→ Past revision history

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) used as an aid for structuring and drafting. Codex (OpenAI) is also used alongside Claude Code, as a sub-agent for close reading of primary sources. Responsibility for factual accuracy and final editorial judgment rests with the author.

→ How is generative AI used in producing this site?

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.

Wherever possible, "established facts" and "the author's interpretation or conjecture" are explicitly distinguished throughout the text.

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?