Phono Preamp Reviews

The Decca Curve

The Phono Box RS2 has a rather rare playback option: the mono-era Decca LP EQ curve.

Prior to the mid-1950s, different record companies used different recording EQ curves (emphasis) and expected consumers to use corresponding (de-emphasis) curves when they played back the LPs. Many mono-era "hi-fi" preamps—for instance, the McIntosh C8 "Audio Compensator"—offered a variety of EQ options. Around 1954, the Recording Industry Association of America (RIAA) stepped in and convinced the various US labels to standardize on RCA's "New Orthophonic" curve, which became the RIAA curve still used today. Companies "soft-converted" to the new curve, selling through their pre-RIAA inventory and running existing metal parts in the pressing plants until worn out. In Europe, standardization was slower, according to some accounts. Stereo records worldwide have always been cut with the RIAA curve, interwebs chatter and rumors aside (footnote 1).

The Decca curve, used for early-era mono LPs, has less high-frequency preemphasis: It boosts the signal 3dB less at 10kHz during disc-cutting, and the playback curve attenuates 3dB less at playback. This was visible in JA's published test results.

According to a Pro-Ject staffer, Pro-Ject CEO Heinz Lichtenegger is "a collector and lover of classical music, especially the works of the Vienna Philharmonic" on Decca, including early 1950s LP records. McIntosh Group PR manager Julia Lescarbeau claims that some European classical records were made with that curve up to 1962, when the German DIN adopted the standard RIAA curve.

If you have an annoyingly bright-sounding record, regardless of when it was made, dulling the top octave by switching in the Decca curve may make it less strident. Of course, you could also use, with more control, a properly designed treble tone control on a preamp or integrated amp.—Tom Fine

Footnote 1: Michael Fremer has some very strong views on this topic, which I agree with. See analogplanet.com/content/phono-equalization-bs-continues.