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
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
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
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,
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.
from recordings made out-of-phase and/or to match with next amplification
balanced connections follow a former standard, the
PHS 7.2 and PHS 7.3 phono preamplifiers feature an absolute signal phase
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.
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
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.
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
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
|Number of inputs
|Original input module types
||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
|Hand calibrated inputs and outputs
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
|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)
|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)
||>100dB (10V output 1kHz, Gain min)
|Maximum gain output/input
||75dB (low level MC cartridge)
||0, -10, -20dB (ctrl. with front panel switch)
||0 / 180° (ctrl. with front panel switch)
||-12dB/oct, 13Hz (ctrl. with front panel button)
||dual mono (ctrl. with front panel button)
|Burn-in duration at the manufacture
||100 hours minimum
|Mains voltage range
||90V minimum, 250V maximum
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.