PHS 7.3 phono pre-amplifier

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Notes for the records collectors:

When micro groove vinyl records were introduced in the late 1940's, most record companies and their mastering facilities already applied recording curves to cut records masters. By reducing the levels in low frequencies and increasing the levels in high frequencies, the groove's width was narrowed and evened over the bandwidth. This allowed more music to be recorded on the disc and lead to less overall distortion thanks to reduced cutter and pickup excursions. Applying the inverse curve at playback would permit to recover the original tone along with reducing the perceived surface noise thanks to the low-pass effect.

However most record companies, American, English and European, applied proprietary curves before adopting, with more or less eagerness, the RIAA curve defined in the mid 1950's.

Along with the introduction of the micro groove vinyl record, larger bandwidth microphones and recording equipment also became more widely used and high-fidelity audio emerged; allowing jazz and classical music icons to release recordings that have become of historical value.

Although playing back these valuable records is possible using a RIAA tuned phono preamplifier, the overall emotional content would fail to be translated to the listener due to incorrect tonal balance and its side effects.

A lot of information on historical recording curves and their application can be found and heard from record collectors and products manufacturers, but many sources tend to disagree or copy each other. Many beliefs also seemed unrealistic to us. Therefore, JMF Audio spent years studying the subject and the most relevant solution for a phono preamplifier to serve the music and the demanding record collectors.

Visiting record shops, seeking first pressing records from the 50's and 60's at sellers located in the US, UK, Europe, Hong Kong, Japan; seeking books and publications by past and present specialists; meeting with record collectors and discussing with re-mastering engineers from England and Germany… The JMF Audio records and books collections increased tremendously over the years, with countless accompanying notes and data.

Methods for determining the most suitable compensation curves, based on measurements and comparisons in JMF Audio's studios, backed with statistics, were developed. These methods have been registered for intellectual property.

Weighting the results with the value of the records on musical and historical criteria, by artist, by label, it was concluded that only a few alternative curves could cover all cases of interest, while ensuring ease of use. These curves were labelled Columbia, Decca and AES.

According to our experience, some record companies could have announced RIAA compliance (printed on sleeves) earlier than actuality as our evaluations drew that the mastering remained made with a proprietary curve. Other record labels seemed to have released different records using different curves in relatively short periods of time.

With these alternative curves, it has been made possible to follow the career of major artists in the original tonality, with preserved intend and emotional move. Going through recordings from Frank Sinatra, Duke Ellington, Benny Goodman, Charlie Parker, Dave Brubeck, Louis Armstrong and many more requires the use of the four curves featured in the PHS 7.3. The alternative curves respect the three original parameters (turn-over, roll-off and bass shelf).

Registered owners will access a detailed list of suggested applicable curves according to the records label with estimated change-over date, records identification as well as guides through notions such as recording, mixing, mastering, pressing, re-pressing, licensing, re-issues, re-recording, re-mastering…

The alternative recording curve matching belonging to the mono records era, PHS 7.3 users will advantageously select the mono mode when applying alternative curves.