What EQ curve should you use for 78 rpm records — an honest look at an open question

What EQ curve should I use for 78 rpm records?

Question answered on this page: When playing a 78 rpm shellac record, what curve should the phono equalizer be set to?

The honest answer: this is an open question

There is no simple answer along the lines of "use this curve for this label from this year to that year." Apart from a limited number of cases where primary sources survive, research has yielded competing conclusions, and there is no single definitive "correct" answer. Given the circumstances of the era, this is unavoidable.

Throughout the 78 rpm era — even limiting the scope to the electrical recording period, roughly 1925–1957 — standardization of recording characteristics was incomplete, and in the majority of cases the characteristics actually used were never accurately documented.

The situation by era

Acoustic recording era (up to c. 1925)

Electrical equalization did not exist. The mechanical characteristics of the recording horn and soundbox were imprinted directly into the groove. The concept of a "playback EQ curve" simply does not apply.

Early electrical recording (c. 1925–1942)

Recording characteristics varied depending on the equipment used — Western Electric's rubber-line recorders, RCA's proprietary systems, and independent recording setups at various companies.

However, precision in this era was relatively loose. Values in the literature and technical documents of the time are often stated with broad ranges such as "turnover around 200–300 Hz," and characteristics were not controlled to the decimal-point precision of modern standards.

After the NAB standard (1942–)

In 1942, the NAB standardized recording characteristics, but this standard was intended for broadcast transcription discs (professional use) and did not directly apply to consumer shellac records.

In practice, some labels converged toward similar characteristics under the NAB standard's influence, but many others continued to use their own proprietary curves, and no true unification occurred.

Industry secrecy

One reason standardization gained little momentum was that companies treated their recording technology as closely guarded secrets. Recording system and cutting equipment specifications were handled as trade secrets, and technical details were almost never made public. This not only allowed a multitude of different curves to coexist, but also makes it difficult to determine after the fact what characteristics were actually used.

(→ The Sapphire Group — from secrecy to standardization)

A practical starting point

Even if there is no single correct answer, a starting point can be offered.

For U.S. electrical-era 78 rpm records, a practical approach is to begin with 500N-FLAT (turnover 500 Hz / no high-frequency pre-emphasis) and then explore the curve best suited to each individual record, consulting various research resources along the way.

European 78 rpm records tended to use lower turnovers than U.S. records (around 250–300 Hz). High-frequency pre-emphasis was also generally less pronounced, or absent.

Both of these are general tendencies and not guarantees for any individual record.

About detailed curve charts

Detailed charts listing EQ curves by label and year can be found on the internet. These are useful as practical reference material, but should be used with caution.

Do not demand of the chart a precision that the original recordings did not possess. As noted above, recording characteristics in the 78 rpm era were, by modern standards, approximate. A chart that appears to identify a specific curve based solely on label name and year may be implying a degree of precision greater than the original recordings actually had.

Turnover and rolloff alone do not tell the whole story. Recording characteristics of the period were not determined solely by the electrical settings of the cutter head. For instance, the resonance characteristics of condenser microphones or the mid-to-high-frequency boost from ribbon microphone preamplifiers could produce an effect similar to high-frequency pre-emphasis. These were not part of the intentional "recording curve," but they do affect the tonal balance on playback. For this reason, two views coexist: one that respects only the cutter head's recorded characteristics and labels the result as "FLAT," and another that includes the microphone chain's characteristics and labels it as "with rolloff." This is one reason why different charts list different values for the same label and the same period.

(→ Pt.3 section 3.4.5 — for a detailed discussion of the relationship between microphone characteristics and recording curves)

For guidance on choosing reliable sources: → Are there reliable references for EQ curves?

Listening still has value

"Not knowing the correct answer" does not mean "it makes no difference what you do."

Adjusting the settings on a variable-EQ phono preamplifier while listening can genuinely improve the tonal balance of a 78 rpm record. Whether or not the result matches the original recording settings, if it lets you enjoy the music more, that has value in itself.

What matters is to keep the distinction between "a setting that sounds pleasing" and "a historically correct setting" clearly in mind.

→ Do I need a variable-EQ phono preamplifier?

→ What EQ curves existed before RIAA?

For details → Pt.1–Pt.9, Pt.21

← Back to FAQ