FAQ on phono EQ curves: what the RIAA curve is, what came before, when each label switched, stereo LPs, 78 rpm playback, listening tests vs. documents, and a glossary. Organized in four sections: basics, history, audibility, and practice.
Phono EQ Curve FAQ
Questions about EQ curves, answered one topic at a time. Each page can be read independently.
Fundamentals
- What is phono equalization, and why is it necessary?
- What is the RIAA curve?
- When was the RIAA curve established?
- What EQ curves existed before RIAA?
- Why did RIAA become the standard?
- How did record playback technology evolve?
- What is hot stylus recording?
- Glossary
History
- Who invented the LP?
- Why did lateral-cut become the standard rather than vertical-cut?
- What was the "Battle of the Speeds"?
- Why did Columbia and RCA Victor release separate formats if their engineers were cooperating?
- What was the Columbia LP curve?
- The first-ever recording standard — the 1942 NAB
- Why was the 1942 NAB standard defined as a curve with a ±2 dB tolerance rather than in time constants?
- Why did the U.S. and Europe use different EQ curves?
- How did listeners play records back then?
- What was the "Sapphire Group"?
- Stokowski and Bell Labs: the experimental recordings
- What equipment did Rudy Van Gelder use for cutting?
- What was "Dialing Your Disks"? What can it tell us, and what can't it?
Sound and perception
- Can you hear a difference when you change the EQ curve?
- EQ curve vs. mastering — which determines the sound?
- What factors besides the EQ curve affect the sound of a record?
- Listening tests vs. documentation — which should you trust for identifying EQ curves?
Practical guide
- How should I play pre-RIAA records?
- When did each label switch to the RIAA curve?
- What EQ curves were used on mono LPs from 1948 to 1958?
- What curve should I use for 78 rpm records?
- Do I need a variable-EQ phono equalizer?
- Is there a reliable EQ curve reference?
- What sources did I use for this research?
Stereo LPs and EQ curves
About this site
→ Read the history in brief (In a Nutshell)
Revision History
- April 28, 2026: Added "What was Dialing Your Disks? What can it tell us, and what can't it?" to the History section
- April 15, 2026: Moved "The first-ever recording standard — the 1942 NAB" and "Why was the 1942 NAB standard defined as a curve with a ±2 dB tolerance rather than in time constants?" from Fundamentals to the History section
- April 15, 2026: Added "Why was the 1942 NAB standard defined as a curve with a ±2 dB tolerance rather than in time constants?"
- April 15, 2026: Added "Why did Columbia and RCA Victor release separate formats if their engineers were cooperating?"
- April 10, 2026: Added "How is generative AI used in producing this site?"
- April 10, 2026: Added "The first-ever recording standard — the 1942 NAB" and "Why did lateral-cut become the standard rather than vertical-cut?"
- April 9, 2026: Added "What sources did I use for this research?"
- April 8, 2026: Initial publication