Do you need a variable-EQ phono equalizer — decision criteria based on your collection

Do I need a variable-EQ phono equalizer?

Question answered on this page: Should I buy a phono equalizer that allows switching turnover and high-frequency pre-emphasis values? Who would benefit from one, and what are the limitations?

Answer: it depends on your collection

Whether a variable-EQ phono equalizer is useful is largely determined by the era and format of the records you own.

If you listen to U.S. stereo LPs (1958 onward)

You do not need variable EQ.

Cutting equipment for U.S. stereo LPs was designed with the RIAA curve as the standard, leaving no room for cutting stereo discs with any other curve. A standard RIAA-compatible phono equalizer is all you need.

Note: European stereo LPs are outside the scope of this site's research and are not addressed here.

→ Are all U.S. stereo LPs on the RIAA curve?

If you listen to monaural LPs (1948–1958)

It can be somewhat useful.

During this period, each label used a different curve, and the transition to RIAA was gradual. If the label and approximate date are known, the recording curve can sometimes be estimated.

However, due to factors such as continued use of old stampers and outsourced cutting, it is not easy to determine the curve of a specific pressing with certainty.

→ What curves were used on mono LPs from 1948 to 1958?

If you listen to 78 rpm records

This is where it appears most useful — but the limitations are also greatest.

The 78 rpm era saw little standardization, and a wide variety of recording characteristics existed. A variable-EQ unit is a useful tool, but in most cases the "correct setting" is a matter of debate.

→ What curve should I use for 78 rpm records?

Historical background

The variable-EQ phono equalizer is not a new idea.

In the 1950s, preamplifiers with multiple curve-switching capabilities were commercially available, including the Marantz Audio Consolette (6 turnover positions × 6 rolloff positions), McIntosh C-8, H.H. Scott 121-C, and Fisher 80-C. At the time, different labels used different curves, so this was a practical necessity. Moreover, since the specifications of many labels' curves were not publicly disclosed, amplifier manufacturers had to rely on estimates and compromises in their implementations.

As RIAA became universal, curve-switching features disappeared from most models. In recent years, however, renewed interest in playing pre-RIAA records has led to variable-EQ phono equalizers being manufactured once again.

Technical limitations to be aware of

There is an important technical fact to know when using a modern variable-EQ phono equalizer.

Modern units all use RC circuits — equalization circuits built with resistors (R) and capacitors (C).

However, much of the professional recording equipment from the pre-RIAA era used LRC circuits. While an RC circuit can approximate the frequency amplitude response of an LRC circuit (how much each frequency is boosted or cut), subtle differences in phase response (the time shift at each frequency) and frequency response characteristics are said to arise.

If one accepts this view, then even with the "correct" parameters set, perfectly restoring an LRC-era recording to its original state is, in principle, impossible.

This point is discussed in detail in the work of Nicholas Bergh.

This does not negate the value of a variable-EQ phono equalizer. Approximating the frequency amplitude response alone can yield a meaningful audible improvement. However, the expectation of "perfect restoration" is not technically accurate.

For details → Pt.22, Pt.23

One more caveat

When you switch settings on a variable-EQ phono equalizer, the sound changes. This is only natural — you are changing the frequency response, so it would be strange if the sound did not change.

However, "the sound changed" and "the correct curve has been found" are two different things.

There is nothing wrong with listening at your preferred settings, but to conclude that "this setting is the correct curve for this record" requires evidence beyond listening impressions (documentation, records).

→ Can you hear a difference when you change the EQ curve?

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