Full past revision history of this site — all changes older than the "Recent updates" shown on the top page

Past revision history

What you'll find on this page: A full chronological list of all changes made to the lower-level pages (In a Nutshell, FAQ, Research Notes) of this site that are no longer shown in the "Recent updates" section on the top page.

For the latest updates, see the "Recent updates" section on the top page.

• April 18, 2026
  • ✏️ 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
  • ✏️ Do you need a variable-EQ phono equalizer? What about 78 rpm records or pre-1954 monaural LPs? What about stereo-LP collections? Decision criteria organized by collection type. — Minor revision of the summary
  • ✏️ Why so much disagreement about EQ curves? Where does the idea that each label had its own curve come from? — organizing the structure of the debate — Minor revision of the summary; added link to the FAQ page on EQ curve references; updated the series link to point to the research-notes page
  • ✏️ How generative AI is used in producing this site — what AI handles, and what it does not — Changed the list of models used into a bullet list and added Claude Opus 4.7
• April 16, 2026
  • ✏️ (In a Nutshell Part 2) How did unification finally happen? — From the postwar era to the birth of the RIAA curve (1942–1954) — Added a new subsection to §3 on the vocabulary shift from graph to time-constant definitions (AES 1951 "impossible task" and Moyer 1953 "curve alone" primary-source quotes)
• April 15, 2026
  • 🔔 Newly published: Why was the 1942 NAB standard defined as a curve with a ±2 dB tolerance rather than in time constants? Testing two working hypotheses against the primary sources.
  • ✏️ (In a Nutshell Part 1) Why wasn't there a unified standard from the start? — From the birth of electrical recording (1925) to the NAB standard (1942) — Added primary-source context on the 1942 NAB standard's background — ten equalizer settings in use, the RRSC's charge to "minimize adjustments on the reproducing system," and Smeby's acknowledgment of the diversity of existing characteristics. Corrected the adoption date to March 19–20, 1942 per the NAB Engineering Handbook (1945, 3rd Edition)
  • 🔔 Newly published: Columbia and RCA Victor engineers shared information through NAB, the Sapphire Group, and the AES — so why did the two companies release incompatible formats?
• April 14, 2026
  • ✏️ When did major U.S. labels move to the RIAA curve — a list based on verifiable documents — Added figures
  • ✏️ What is the hot stylus — the technology that transformed recording quality and helped standardize EQ curves — Added figures
  • ✏️ Stokowski and Bell Labs experimental recordings — how a conductor and engineers pioneered high-fidelity recording — Added figures
  • ✏️ Who invented the LP — the contributions of three key figures and how to read their conflicting accounts — Added figures
  • ✏️ Rudy Van Gelder's cutting equipment and EQ curves — what the equipment records and his own testimony tell us — Added figures
  • ✏️ How record playback technology evolved — the interplay of stylus pressure, disc materials, and recording characteristics — Added figures
  • ✏️ What was the Battle of the Speeds — Columbia LP vs RCA Victor 45, how it was resolved, and its connection to EQ curves — Added figures
  • ✏️ Why lateral-cut rather than vertical-cut became the standard — the commercial outcome and the 1938 physical justification — Minor wording fixes; added figures
  • ✏️ 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. — Added figures
  • ✏️ 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 figures
  • ✏️ How generative AI is used in producing this site — what AI handles, and what it does not — Updated the description of the Codex / Claude Code role split and quality control practices to reflect the current workflow
• April 13, 2026
  • ✏️ The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964) — Inserted the recording frequency-characteristic chart from the 1942 NAB standard paper (Chinn 1942, Broadcast Engineers' Journal) and the lateral-cut recording chart from the 1953 NARTB standards document. Both visually show that the graph definitions carried a ±2 dB tolerance band
  • ✏️ The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964) — Noted that the 1942 graph definition carried a ±2 dB tolerance, citing the Fig. 1 / Fig. 2 captions of Smeby's paper
  • ✏️ The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964) — Reflected the following from the contents of NAB Reports 1941-1942. Precised the 1941 RRSC timeline (May 23 → June 13 → June 26 → August 20 → October 23), added four direct NAB Reports quotes (task definition, "ten different equalizer settings," "highly controversial subject," wartime deferral), introduced a new subsection on the October 23 main-committee adoption, and connected the graph→time-constant section to the 1942 rationale. Minor wording fixes elsewhere
  • ✏️ The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964) — Strengthened the rationale for the graph→time-constant shift with Moyer 1953 and Roys 1968. Added a direct Smeby quote on why the 1942 standard used graph form. Added Boegli (April 1953) on conditions just before the NARTB revision
• April 12, 2026
  • ✏️ How did listeners actually play records before RIAA unification — casual listeners, audiophiles, and professionals — Added note on RIAA standard document circulation date (June 1954)
  • ✏️ Key terms in phono EQ curves — turnover, time constants, curve notation, and more — Added note on Japanese "SP record" terminology
  • ✏️ What EQ curve should you use for 78 rpm records — an honest look at an open question — Strengthened the description of European 78 rpm records with Copeland 2008; added the Decca ffrr exception
  • ✏️ What was the Battle of the Speeds — Columbia LP vs RCA Victor 45, how it was resolved, and its connection to EQ curves — Added the design philosophy of the New Orthophonic curve (Moyer 1957)
  • ✏️ 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. — Added note on RIAA standard document circulation date (June 1954)
  • ✏️ The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964) — Added the 1953 NARTB standards book and the 1964 NAB standards book (ed. Hess) as primary-source citations
  • ✏️ What EQ curves were used before RIAA, and why were there so many — Added a brief reference to Moyer 1957 (at least eight recognized characteristics; parameter ranges)
  • ✏️ (In a Nutshell Part 2) How did unification finally happen? — From the postwar era to the birth of the RIAA curve (1942–1954) — Added note on RIAA standard document circulation date (June 1954)
• April 11, 2026
  • ✏️ How record playback technology evolved — the interplay of stylus pressure, disc materials, and recording characteristics — Added Pierce & Hunt's findings on vertical compliance; minor wording fixes
  • ✏️ Why lateral-cut rather than vertical-cut became the standard — the commercial outcome and the 1938 physical justification — Added quantitative distortion data from Pierce & Hunt 1938 (p. 169)
  • ✏️ Why did the U.S. and Europe use different EQ curves — the divergence in turnover frequencies and its background — Added CCIR background and Copeland (2008) bibliographic details
  • ✏️ Why the RIAA curve became the industry standard — technology, politics, and economics — Added Moyer (1957) "eight characteristics" and "compromise" citations to Factor 2
  • ✏️ What sources did I use for this research? — An overview of the primary sources, books, papers, and interviews encountered over two years of investigation — Added Copeland (2008) to technical references and Moyer (1957) to trade magazines
  • ✏️ What sources did I use for this research? — An overview of the primary sources, books, papers, and interviews encountered over two years of investigation — Added Japanese-language resources section
• April 10, 2026
  • 🔔 Newly published: Why lateral-cut rather than vertical-cut became the standard — the commercial outcome and the 1938 physical justification
  • ✏️ 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. — Added primary sources (Westrex 1958 quotation in Evidence 1, new Evidence 5 on the standardization process and Evidence 6 on playback equipment), with tone adjustments
  • 🔔 Newly published: The first-ever recording standard — the 1942 NAB and its revisions (1949, 1953 NARTB, 1964)
  • ✏️ When was the RIAA curve established — years of pre-history leading up to January 29, 1954 — Clarified the significance of the June 1954 RIAA standard document; added post-approval transition details from "The Curve That Conforms" (1954)
  • 🔔 Newly published: How generative AI is used in producing this site — what AI handles, and what it does not
• April 9, 2026
  • ✏️ How did listeners actually play records before RIAA unification — casual listeners, audiophiles, and professionals — Added Boegli (1953) and Kendall (1954) citations to consumer amplifiers section
  • ✏️ 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. — Added section on the "label = curve" assumption
  • ✏️ Why so much disagreement about EQ curves? Where does the idea that each label had its own curve come from? — organizing the structure of the debate — Expanded "The course of overseas debate" section with a concrete example
  • ✏️ Why the RIAA curve became the industry standard — technology, politics, and economics — Added Boegli (1953) citation to Factor 2
  • 🔔 Newly published: What sources did I use for this research? — An overview of the primary sources, books, papers, and interviews encountered over two years of investigation
  • ✏️ Overview and reading guide for "Things I learned on Phono EQ Curves," a 25-part blog series (plus a prologue) researched from primary sources over more than two years. Includes a per-part summary, links to related FAQs, and pointers to source material. — Added link to research sources FAQ in the reading guide
  • ✏️ (In a Nutshell Part 1) Why wasn't there a unified standard from the start? — From the birth of electrical recording (1925) to the NAB standard (1942) — Added "rolloff" terminology for the playback inverse characteristic; added context on recording technology as trade secrets
  • ✏️ (In a Nutshell Part 2) How did unification finally happen? — From the postwar era to the birth of the RIAA curve (1942–1954) — Corrected the date of the Hollywood Sapphire Group's first meeting
• April 8, 2026
  • 🔔 Newly published: A 100-year history of phono EQ curves in three parts: from electrical recording to NAB (1925-1942), postwar to RIAA (1942-1954), and stereo LPs to today (1954-present).
  • 🔔 Newly published: What was the Columbia LP curve (500C-16) — its technical characteristics, adoption history, and transition to RIAA
  • 🔔 Newly published: Can you hear a difference when you change the EQ curve? Yes — but "the sound changed" and "the right curve was found" are two different things
  • 🔔 Newly published: Is it the EQ curve or mastering that determines the sound of a record — from the perspective of the entire signal chain
  • 🔔 Newly published: Should you trust listening tests or historical documents when identifying EQ curves — the difference in what each method can answer
  • 🔔 Newly published: What EQ curves were used on 1948–1958 mono LPs — why there is no single right answer
  • 🔔 Newly published: How should pre-RIAA records be played on modern equipment — sorting out practical options
  • 🔔 Newly published: Are there reliable references for EQ curves — research-based resources and criteria for evaluating source reliability
  • 🔔 Newly published: What was the Sapphire Group — the gatherings that broke down industry secrecy and paved the way for standardization
  • 🔔 Newly published: What factors besides the EQ curve affect the sound of a record — an overview of the signal chain from recording to cutting
  • 🔔 Newly published: How did listeners actually play records before RIAA unification — casual listeners, audiophiles, and professionals
  • 🔔 Newly published: Key terms in phono EQ curves — turnover, time constants, curve notation, and more
  • 🔔 Newly published: What EQ curve should you use for 78 rpm records — an honest look at an open question
  • 🔔 Newly published: When did major U.S. labels move to the RIAA curve — a list based on verifiable documents
  • 🔔 Newly published: What is the hot stylus — the technology that transformed recording quality and helped standardize EQ curves
  • 🔔 Newly published: Stokowski and Bell Labs experimental recordings — how a conductor and engineers pioneered high-fidelity recording
  • 🔔 Newly published: Who invented the LP — the contributions of three key figures and how to read their conflicting accounts
  • 🔔 Newly published: Rudy Van Gelder's cutting equipment and EQ curves — what the equipment records and his own testimony tell us
  • 🔔 Newly published: How record playback technology evolved — the interplay of stylus pressure, disc materials, and recording characteristics
  • 🔔 Newly published: What was the Battle of the Speeds — Columbia LP vs RCA Victor 45, how it was resolved, and its connection to EQ curves
  • 🔔 Newly published: 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.
  • 🔔 Newly published: 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.
  • 🔔 Newly published: Do you need a variable-EQ phono equalizer? What about 78 rpm records or pre-1954 monaural LPs? What about stereo-LP collections? Decision criteria organized by collection type.
  • 🔔 Newly published: Why so much disagreement about EQ curves? Where does the idea that each label had its own curve come from? — organizing the structure of the debate
  • 🔔 Newly published: Why did the U.S. and Europe use different EQ curves — the divergence in turnover frequencies and its background
  • 🔔 Newly published: 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.
  • 🔔 Newly published: What EQ curves were used before RIAA, and why were there so many
  • 🔔 Newly published: When was the RIAA curve established — years of pre-history leading up to January 29, 1954
  • 🔔 Newly published: Why the RIAA curve became the industry standard — technology, politics, and economics
  • 🔔 Newly published: Overview and reading guide for "Things I learned on Phono EQ Curves," a 25-part blog series (plus a prologue) researched from primary sources over more than two years. Includes a per-part summary, links to related FAQs, and pointers to source material.
  • 🔔 Newly published: (In a Nutshell Part 1) Why wasn't there a unified standard from the start? — From the birth of electrical recording (1925) to the NAB standard (1942)
  • 🔔 Newly published: (In a Nutshell Part 3) What does this history mean for playing records today? — Post-RIAA transition, stereo LPs, and the open questions that remain
  • 🔔 Newly published: (In a Nutshell Part 2) How did unification finally happen? — From the postwar era to the birth of the RIAA curve (1942–1954)