The 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 stepped attenuators.
> CSV by concept features zero noise, zero distortion, zero phase shift, infinite headroom.
> CSV is sealed and shielded in a machined block of aluminum.
> CSV features a quadruple redundancy for an expected life time far superior to the best potentiometers.
> CSV is input and output buffered in the PRS 1.5 by JMF Audio's SSA Super Symmetrical Analog technology.
Complementing the major aspects, the details are of significant importance regarding the musical result:
The 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.
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 psychoacoustic criteria.
The proprietary DC coupling circuit allows a direct signal path (enhanced and improved with revision D).
Un-balanced incoming signals automatically take advantage of the symmetrical 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.
Features:
Balanced inputs
3 (IN0, IN1, IN2)
Unbalanced inputs
3 (IN3, IN4, IN5)
Balanced outputs
2 (OUT1, OUT2)
Unbalanced outputs
1 (OUT3*)
Volume display
[30] to [99]
Relative gain setting between sources
[-9] to [ 6] display for -9 to +6dB gains
Source display
[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
JMF Audio MBR1
Remote control
Volume control button machined in a solid block of steel, hold in a double bearing compartment, providing a smooth rotation and best feel of power control. Orose® case machined 10 to 16mm thick anodized and brushed aluminum chassis, mounted on special damped and anti skidding JMF Audio feet.
PGP gold analog mono printed circuit boards embedding the CSV volume control units mounted on suspensions for improved immunity to vibrations.
Technical specifications:
Input impedance
Maximum input level
at low volume
> 10k ohm (XLR and RCA inputs)
9V (+20dBu, XLR bal) / 4V (+14dBu, RCA)
Total harmonic distortion plus noise
0.0002% typ. (+22dBu 1kHz in / bw. 22..22k Hz)
Interferences rejection (balanced input)
100dB typ.
3V (+11dBu, XLR bal) / 1.4V (+5dBu, RCA), version F
Maximum input level
at max volume
10V (+22dBu) into 10k ohms load
Maximum output level
1Hz..150kHz (intentionally limited for RF immunity)
20Hz ..20kHz (+0.0 / –0.0dB)
Global signal bandwidth
130dB typ. (+22dBu 1kHz narrow band)
120dBA typ. (+22dBu), version F
Signal to noise ratio (SNR)
>100dB (10V output 1kHz, Gain min)
Channel separation
50 ohms
Output impedance
12dB (XLR bal in) +18dB (RCA in), version F
0dB (XLR bal in) +6dB (RCA in), prior to version F
Maximum gain output/input
70 steps of 1dB
Volume control range
better than 0.05dB above volume [40]
Volume control step precision
< 0.1dB above volume [40]
Volume control left/right level mismatch
Specific to modular output OUT3:
Maximum gain in variable mode
Output impedance in variable mode
Gain in direct mode
0dB (RCA in/RCA out) -6dB (XLR in/RCA out)
12dB (RCA in / RCA out), version F
50 ohms
Output impedance in direct mode
600 ohms
100 hours minimum
Burn-in duration
at the manufacture
< 25W in operation (1W in standby)
Power consumption
Weight: 12kg