Phono pre-amplifiers

Selecting the source, processing the micro signal...    Caring for the music...

Behind every JMF Audio product development lies music lovers' motivation. While most historical recordings have been remastered and transferred to modern formats, we felt that the digital versions failed to carry the emotion and ambiances in their integrality. That the recordings from the golden era had to be enjoyed in the format they were intended for.

JMF Audio’s knowhow in analog had been recognized in world-class recording studios as well as by audio connoisseurs for more than 30 years. The definitive phono pre-amplifier’s circuits would be developed capitalizing on our experience and our latest innovations. As the PHS phono pre-amplifier would inherit from several of the PRS 1.5 line-level pre-amplifier’s aspects, the project could have been expected to be completed in less time than usual for JMF Audio. The research and development and the manufacturing of specific components eventually required some additional years of dedication… and lead to two models.

Minute signal extraction and faithfulness to the music being major challenges to achieve. 

The PHS phono preamplifiers were finally unveiled, and the performances were beyond the initial expectations… Whichever the recording era, the JMF Audio PHS Instruments for the music® reveal the vinyl record as a format capable of utmost musicality, involvement, liveliness, and ultimately serving the music.

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The JMF Audio PHS reference phono pre-amplifiers feature a dual mono design, fully balanced circuitry, short signal path, and rely on the innovative ALP linearization (Intellectual Property registration).

>  ALP is a purely passive linearization filter that compensates for the RIAA recording curve with precision.

>  ALP features zero distortion, infinite headroom, by design.

>  ALP is sealed and shielded under a machined block of aluminum of Orose® grade.

>  ALP is built around bespoke made components and JMF Audio made components.

>  ALP is buffered by JMF Audio's SSA Super Symmetrical Analog technology involving hand calibrated input and output stages.

In addition to the main aspects, the details are of significant importance regarding the musical result:  

Like a recording studio microphone:

A phono cartridge is an electromechanical component that converts variations in records’ grooves into variations of electrical signal. Similarly, a microphone converts variations of air pressure into variations of electrical signal.

Both these sensors are made of a coil that needs to be connected to a signal amplifier. The signals are of very low magnitude and need to be protected against electromagnetic interference before amplification. This is why microphones have always been connected through shielded balanced interconnections in the recording studio world. For cost reasons related to consumer applications and also because the original cartridges were of moving magnet type, phono interconnections have been widely made through un-balanced links with RCA connectors.

The greatest care should be taken with nowadays precision moving coil cartridges that output low level signals. Since phono cartridges are balanced by design, the JMF Audio PHS phono pre-amplifiers handle them as studio microphones:

The PHS phono pre-amplifiers take advantage of JMF Audio's innovative and still unrivaled hand calibrated precision balanced input stage technology which allows up to 100dB of interference rejection and consequently protects the least micro detail of music picked-up from the record. Moreover, the calibration method integrates psychoacoustic criteria.

The interface is ideally made with a JMF Audio phono cable from the tone-arm’s through DIN to XLR or RCA (hot-cold) to XLR. Optionally the PHS pre-amplifier can be ordered with input IN1 wired as RCA for the tone-arms that feature an attached cable. The signal would take advantage of the balanced input stage as well.

Multiple inputs and optimal cartridge loading:

The PHS phono pre-amplifiers can handle several tone-arms or record players through dedicated inputs. The load settings are assigned to each input which allows seamless switching from one tone-arm to another.

Quite a few modern cartridges feature rigid cantilevers and tend to present an un-even response with a significant rise of magnitude at the upper frequencies. Low value resistive loading is commonly admitted as the only way to obtain an acceptable response from these cartridges. The JMF Audio PHS phono pre-amplifiers propose an alternative through combined resistive and capacitive loading for precise dampening and tuning of the upper range of frequencies and achieve a linear overall response. By releasing the constraints on the cartridge, the musical rendering shows greater openness and liveliness. The load value being dependent on the cartridge, the setting is located near the corresponding input, which ensures the shortest signal path. All inputs load settings are easily controllable at sight from the rear panel.

High gain:

The JMF Audio PHS phono pre-amplifiers feature as high as 75dB of gain for the modern moving coil cartridges that require more amplification. A lever on the front panel allows to adapt the gain to suit MM and MC cartridges, the overall system’s gain or the line pre-amplifier’s sensitivity.

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 phono preamplifiers feature an absolute signal phase control. 

No additional electronic circuits or components are involved for absolute signal phase control in the PHS phono pre-amplifiers, 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. 

The processing is purely passive and no additional electronic circuits are involved for the subsonic filtering in the PHS phono pre-amplifiers.