PHS 7.3 and PHS 7.2  phono pre-amplifiers

MODELS

SPECIFICATIONS

TESTIMONIALS

REVISIONS

PHS 7.3 dual mono phono preamplifier - Orose Silver

The PHS 7.2 and PHS 7.3 are dual-mono phono preamplifiers, featuring JMF Audio's unique ALP and ALP-EM linearization technologies. These phono preamplifiers can handle up to 2 (PHS 7.2) or 3 (PHS 7.3) tone-arms or record players. Their advanced hand-calibrated balanced input stage and high gain take full advantage of low-level moving coil cartridges, without the need for step-up transformers. The innovative input module interfaces provide 16 resistive and 16 capacitive loads for each input and corresponding cartridge, for precise dampening and tuning of the upper range of frequencies to achieve a linear overall response. The load settings are assigned to each input which allows seamless switching from one tone-arm to another. The record collector oriented PHS 7.3 features a special mono mode and three optimized alternative compensation curves for the enjoyment of pre-RIAA era recordings.

The PHS 7.2 and PHS 7.3 were developed as instruments for the music and inherit from JMF Audio's decades of know-how and the relentless work of its research and development department. Starting from a blank sheet of paper, over three years of development were necessary for these products to see the light and reach the first customer; two more years than first planned… Music deserves all our attention.

 The information on this page will be further developed soon.

 

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.

These alternative curves take advantage of the JMF Audio passive components that are part of the RIAA circuit, without affecting it, thus guarantying the highest quality. The JMF Audio implementation of the alternative curves is named ALP-EM for Enhanced Matrix and is controlled by a dedicated custom programmed logic circuit. This unique implementation has also been registered for intellectual property.

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 4 curves featured in the PHS 7.3.

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.

JMF Audio PGP gold substrate circuit boards. Hand positioning and soldering of precision components on both sides. Two boards will be necessary to build a dual-mono PHS 7.3 or PHS 7.2 phono preamplifier, made up of more than 700 parts.

Absolute phase:

To compensate from recordings made out-of-phase and/or to match with next amplification stages which balanced connections follow a former standard, the PHS 7.2 and PHS 7.3 phono preamplifiers feature an absolute signal phase control. 

We'd like to point out that no additional electronic circuits or components are involved for absolute signal phase control in the PHS 7.2 and PHS 7.3 phono preamplifiers, ensuring total transparency without change in performance.

Subsonic filter:

Very low frequency content, usually due to record wrap, recording flaw or acoustic induced vibrations, may alter the musical rendering along with putting unnecessary high demand on the power amplification. Elimination of the lowest frequencies is made possible by activating the subsonic filter with the Filter push button. 

For this feature also, no additional electronic circuits are involved for the subsonic filtering in the PHS 7.2 and PHS 7.3 phono preamplifiers.

Mono mode:

To reveal all the musicality of the golden age vinyl mono recordings, the PHS 7.3 features a unique mode, activated by the extreme right button of the front panel, labeled as Mono. This mode takes full advantage of the dual-mono concept of the PHS 7.3, by reducing the overall noise, enhancing the rendering with stereo cartridges (without any change on the cabling) and taking absolute advantage of mono cartridges, vintage or cutting-edge. In mono mode, the audio signal is equally balanced to the left and right stereo outputs.

Another challenge taken up, no additional electronic circuits are involved for the mono mode of the PHS 7.3 phono preamplifier, ensuring total transparency without change in performance.

 

The information on this page will be further developed soon.

PHS 7.2 dual mono phono preamplifier - Orose Silver

The JMF Audio products feature a sealed case design, which prevents dust and moisture from entering the chassis. The push buttons are precisely machined in a block of steel, inserted in sliding cylinders, providing smooth and precise operation. The toggle switches, individually housed in a metal frame, are made to measure for JMF Audio. The internal proprietary ALP and ALP-EM linearization circuits are enclosed in a sealed machined block of aluminum for optimal isolation. The mono audio circuit boards are mounted on semi-floating sub-chassis for superior immunity to vibrations. The PHS 7.2 and PHS 7.3 inherit from the dual chassis concept already developed for the PRS 1.5 preamplifier; the external housing being made of up to 10mm thick machined aluminum blocks. These instruments rest on JMF Audio proprietary decoupling and anti-skidding feet.

The table below summarizes the differences and common key points between the PHS 7.2 and the PHS 7.3.

PHS 7.2 PHS 7.3
Number of inputs 2 3
Original input module types MC/MM (x2) MC optimized (x2) and MC/MM (x1)
Input stage type JMF Audio balanced and adaptive JMF Audio balanced and adaptive
Analog circuit board technology JMF Audio PGP gold JMF Audio PGP gold
Linearization filter type JMF Audio ALP JMF Audio ALP-EM
Linearization passive components JMF Audio Precision grade JMF Audio Reference grade
Number of alternative curves 0 3
Mono mode No Yes
Subsonic filter Yes Yes
Hand calibrated inputs and outputs Yes Yes

PHS 7.3 dual mono phono preamplifier - Orose Black

PHS 7.3 and PHS 7.2 mono printed circuit boards, featuring proprietray ALP-EM and ALP record linearization, on JMF Audio PGP gold substrate. Two boards will be necessary to build a dual-mono PHS 7.3 or PHS 7.2 phono preamplifier.

Technical specifications:

Input impedance range defined by input module type and settings
Maximum input level 200mV (typ. MM cart), 20mV (typ. MC cart), Gain min
Maximum output level 10V (+22dBu) into 10k ohms load
Global circuits bandwidth 1Hz..150kHz (intentionally limited for RF immunity)
RIAA deemphasis curve conformance +/- 0.05dB (1k..20k Hz), +/- 0.1dB (20..20k Hz)
Inputs common mode rejection ratio (CMRR) 100dB typ.
Signal to noise ratio (SNR) >96dBA (10V output, Gain min, typ. MC cart)
Total harmonic distortion (THD) <0.002% (10V output 1kHz, Gain min, BW.20kHz)
Channel separation >100dB (10V output 1kHz, Gain min)
Output impedance 50 ohms
Maximum gain output/input 75dB (low level MC cartridge)
Gain range 0, -10, -20dB (ctrl. with front panel switch)
Phase range 0 / 180° (ctrl. with front panel switch)
Subsonic filter -12dB/oct, 13Hz (ctrl. with front panel button)
Mono mode dual mono (ctrl. with front panel button)
Burn-in duration at the manufacture 100 hours minimum
Power consumption <20W
Mains voltage range 90V minimum, 250V maximum
Net weight 12kg

 

JMF Audio PHS 7.3 serial number 001. The flagship phono preamplifier in the new Orose Silver finish, presented in JMF Audio studio B. This highly anticipated instrument would soon sit in its owner's music room in Asia, next to the long time playing JMF Audio HQS 9001, PRS 1.5, PCD 302, SR8, CM8, DP5... The owner placed the order after listening to the prototype and requested this particular serial number. It was in 2019... We are thankful to Mr. S.W. for his trust and patience. We put all our expertise and care in designing and crafting this new instrument and are honored to pass it to good hands, ears and heart. Photo July 1st 2021.

 

JMF Audio's PHS 7.2 phono preamplifier, world's first presentation at Hifideluxe Munich 2019 :  

At JMF Audio we think that the recordings from the golden years should be enjoyed in the format they were intended for.

Of course, most of the historical recordings have been remastered and transferred to CD or hi-res. However, we find that the digital versions have failed to carry the emotion and ambiances in their integrality. In our opinion the recordings from the 50’s to the 70’s, and most 80’s, were meant to be played on vinyl. Only vinyl would translate all the music and spirit to the listener and place him in the suitable state of mind.

This was the initial motivation for the development of the JMF Audio phono pre-amplifier / linearizer.

We took over the development of the new phono linearizer based on our last achievements which dated 1997. The results soon confirmed our expectations. Recordings from the analog era sounded pleasing, with warmth and natural. Next, as prototypes were improving by application of JMF Audio’s past decades’ acquired experience and knowhow, complemented with dedicated research and development, we found ourselves fascinated with the resulting natural and life-like rendering… including on today’s recordings...

 

More information below: 

 

> PHS 7.2 preliminary leaflet

> Hifideluxe 2019 report article

> Hifideluxe 2019 report video

    Prototype presented in Munich, Hifideluxe 2019

 

 

 

 

 

 

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