the source, controlling the volume... Caring
for the music...
quality of the power amplifiers propelled JMF Audio to the reference recording studios
of Nashville, USA, in 1989, as
reported in the History of the brand. Although
capitalizing on more than 30 years of experience in analog designs for music
research and development for the PRS 1.5 pre-amplifier took many
years, as the first owners who followed the genesis can attest...
impossible had to be made possible: to insert an element
without loosing any detail of music.
The JMF Audio power amplifiers owners
had dreamed of the matching control unit. It had to be up to our
expectations. We think it was also worth the wait.
JMF Audio had designed
excellent preamplifiers in the past. However the new challenges for the
reference JMF Audio preamplifier were extremely high:
1. For sound quality
the goal was to equal a fixed passive attenuator carefully designed by
2. For precision, left/right perfect symmetry, low glitch on
changes, precisely defined steps had to be assured.
3. For ease of use, remote control operation had to be possible as
with our DXC D/A converters.
Point 1. was a test
that none of the preamplifiers we tested passed successfully. (obviously,
Point 2. was easy to fulfill for integrated circuits based
preamplifiers but rarely possible on the best sounding ones which
volume control were based on resistor ladders or potentiometers.
Resistor ladder units featured large glitches.
Point 3. was not a problem for many preamplifiers but the best
sounding ones were passive and not remote controllable though.
The PRS1.5 eventually saw
the light. Not only it is the only preamplifier to
successfully fulfill point 1, but it also surpasses by far this target
; mostly thanks to the hand calibrated input/output stages and
impedance matching provided by JMF Audio's SSA Super Symmetrical
PRS1.5 is a dual mono, fully balanced design that embeds the
innovative CSV volume control.
CSV is a fully passive volume control system based on a digitally
controlled switches network.
CSV by concept features zero noise,
zero distortion, zero phase shift, infinite headroom!
CSV is sealed and shielded in a machined block
of aluminum, JMF Audio engraved.
CSV features a quadruple redundancy for an expected
life time far superior to the best potentiometers.
> CSV is input and output buffered in the PRS1.5 by
JMF Audio's SSA Super Symmetrical Analog technology.
the major aspects, the details are of significant importance
regarding the musical result:
PRS 1.5 has taken advantage of the result of the long researches of
JMF Audio on the
sound neutrality of passive components, semiconductors and materials, as
described in the section about the power amplifiers.
The PRS 1.5 pre-amplifier utilizes selected and uncommon components for audio
applications: instrumentation semiconductors, bespoke passive
components, selected and noble materials...
After selection on
technical aspects, refined selection on measurement, the final
decision on absolutely all the audio components that the PRS 1.5
contains has been taken after long listening tests in the newly built
JMF Audio's studio.
Engraved walnut front panel
The PRS 1.5 inherits of
the JMF Audio' power amplifiers innovative and still
unrivaled hand calibrated precision input stage technology, enabling 100dB of common
mode rejection of interferences carried by the input cables, this means
more than 30 times better than found in professional balanced circuitry. This
parameter having been enhanced by integrating psychoustic criteria.
The proprietary DC
coupling circuit allows a direct signal path (enhanced and improved with
Un-balanced incoming signals automatically take
advantage of the symetrical structure right from the input.
The same care has been
taken for the output section for enhanced balancing precision.
This defined JMF
Audio's SSA Super Symmetrical
Analog technology, possibly unique...
A total of 8 adjustment points require manual calibration after a 100
hour burn-in period on each preamplifier.
The preamplifier's mono audio boards feature metal case ulta low noise discrete
components (military grade) and bespoke capacitors on the power supplies
(starting from revision D). Every components and connectors on the audio path have been selected for their reliability and
on listening for their natural sound characteristics.
The JMF Audio proprietary PGP pure gold finish of the printed circuit
board is incompatible with the automated processes. The hundreds of components
populating both sides of the boards and in the CSV volume section are
hand mounted and soldered one by one by our specialized technicians with JMF Audio's bespoke
solder, using a magnifying glass. A work that recalls jewels manufacturing.
the most transparent line stage,
the PRS 1.5 is also the matching driver for the JMF Audio HQS power
The JMF Audio elements are entirely hand crafted in our workshops and pass severe
tests. Since revision B, every pre-amplifier has even been verified by listening in our
studios after an operational period of over 100 hours, so as to ensure its
future owner will receive the best.
||3 (IN0, IN1, IN2)
||3 (IN3, IN4, IN5)
||2 (OUT1, OUT2)
|| to 
|Relative gain setting between sources
|| [-9] to [ 6] display for -9 to +6dB gains
||[i0] to [i5]
|*Out3 can be set to follow the volume control
or set as direct (DI)
for a tape loop
or to drive a headphone amplifier
|[di] display on selection,
recalled by a dot light on normal use
|Ground connection (earth)
||dia. 4mm banana type
||IR, all functions using MBR-1
|Massive aluminum volume control button
bearing / massive aluminum compartment / smooth rotation.
|Machined 10mm thick anodized
and brushed aluminum chassis, mounted on special damped and anti skidding JMF Audio feet.
|Gold plated analog mono boards embedding
CSV and mounted on suspensions for acoustical isolation.
5k ohm / XLR and RCA inputs
XLR bal / +16dBu RCA
normal output OUT1 (OUT2), at volume max:
||1Hz .. 100kHz (+0.0 / –0.1dB)
..20kHz (+0.0 / –0.0dB)
|Signal to noise ratio
(+22dBu 1kHz narrow band)
typ. (+22dBu 1kHz in
/ bw. 22..22k Hz)
||0.0005% typ. (+22dBu
1kHz in / bw. 22..22k Hz)
|Maximum gain output/input
||0dB (XLR bal in) +6dB (RCA in)
|Volume control range
||70 steps of 1dB
|Volume control step precision
||better than 0.05dB above volume 
control left/right level mismatch
0.1dB above volume 
to modular output OUT3:
gain in variable mode (at volume max)
(RCA in) - 6dB (XLR bal in)
impedance in variable mode
in direct mode (DI)
(RCA in) - 6dB (XLR bal in)
impedance in direct mode (DI)
||< 25W in operation (<
1W in standby)
The JMF Audio PRS 1.5 has seduced music lovers from all areas. Whether these
experienced audiophiles and sound engineers used to defend fully
passive designs, tube based designs or whether they used to trust famed brands in solid-state
have found in the JMF Audio PRS 1.5 the precision, timbres rightness,
amplitude, greatness in the presentation of music.
We are thankful to the enthusiastic JMF Audio instruments-for-the-music owners for their feedbacks,
comments and the wish for some of them to get the information published.
However it has been
limit the comments on this page to just a few. Music enthusiasts are invited to discover and
experience for themselves. JMF Audio would be pleased to guide and
advise a representative.
Please refer to the Contact
page and our Policy.
Mr. C.M. (HQS9001, PRS1.5,
"Saturday I plugged the
[PRS 1.5] preamp in my Mark Levinson 436. Right from the first notes: clearly
superior [...], better hold low frequencies and more dynamic, unique
JMF Audio mids for musicality, wider and nearer sound stage. In summary:
more music and less hifi. A reference preamp to be associated to all power
amplifiers. Congratulations on this success!" (via e-mail)
Mr. C.M. soon after
purchased HQS7001 power amplifiers, and later upgraded to HQS9001.
M.I. (HQS7001, PRS1.5, CM4, SR8, PC2), Asia, on JBL speakers:
were shocked [when we first listened with the PRS1.5 and CM4 cables]. What
I can say is that the sound is very flat over the frequencies and the sound
has become soft. At the same time, it sounds as if it is with very very very
high resolution. [...] I am experiencing what you meant by 'wider
sound stage, three dimentional rendering, air' [...]. Thank you for
providing jewelry products." (via e-mail)
R.Y. (HQS6002, PRS1.5, SR8, CM4), Singapore.
"I’ve been using a Japanese brand (tube
preamplifier and amplifiers) and cables were either [from Denmark] or
[from Netherlands]. The most notable difference was the liveliness of the music, the soundstage and details. Your
electronics is also quieter."
via e-mail (2011)
A.M. (HQS9001, PRS1.5, DXC2.2 MKII, SR8, CM4)
can listen louder, the sound is clearer, wider, more lively; there is so
much more information... Congratulations for having taken up this challenge.
I can believe that the previous clients were amazed..."
(PRS1.5, PC3) France
"Owner of a high quality
[English made] system linked to a Lenco 75 JTN (I am a vinyl addict), I
had been looking at replacing my preamp for years. After analyzing the market and a few tests [...], I was not satisfied about the results,
especially for the price. A friend suggested me JMF Audio [...]. After one week of direct comparison, I concluded: what a superb transparency! More details.
Simply Music. The three dimensional rendering is gigantic. Loudspeakers and walls just disappeared… It confirmed me
that even if the source quality is very important, the preamp quality shall not be neglected. For myself, I have
found my happiness
[EDIT] the last preamp of my life... My system is now musical… Before acquiring a new high price preamp, I strongly advise to evaluate JMF Audio…"
(via e-mail, 2014)
Mr. Mic A.
multiplatinum records sound engineer and producer, New York
(PRS1.5 revision D), after a 30 year quest for the ultimate
"I was blown away... The sound character, tone, detail, musicality, timing was like nothing I ever experienced . It was shocking! You created a monster! I heard so much detail on the disc I never heard before.. and the way I heard it is really impressive.
And placement of instruments....wow is all I can say!!!!! really... you did it! Congratulations !!"
Read full article
|PRS 1.5 -D
||Major upgrade, 2017. The original PRS1.5 outperformed a
passive attenuator. The PRS1.5-D equals a direct link made of the JMF
Audio CM8-C cable, a feat.
> Read the first
impressions in New York studios
> Article on the test conditions
and truth demonstrations (coming soon)
|PRS 1.5 -C
||Major upgrade. Finalization and homogenization of the
global isolation and shielding concept initiated in 1985. Applies to
all JMF Audio products.
|PRS 1.5 -B
||Rear panel with one additional balanced input
JMF Audio products are designed to be references and to last. The
base of these instruments is safe and modular. Upgrades are proposed
for clients to take advantage of the results of our continuous
research and development efforts, without the need for product change.
It means "details", but details make the differences and
can lead to the exceptional. The device revision (B, C, D...) is indicated by a silver badge located on
the rear panel and is linked to the product serial number in JMF
Audio's tracking files.
> More information about our upgrade policy.