A JMF stack!
JMF Audio of France was founded in 1985 by Jean-Marie Fusilier. The company’s electronics have found homes in recording studios around the world including Soundville Studios in Lucerne, Switzerland and The Mix Room in Burbank, CA.
Of course mentioning this fact infers an appreciation of reproduction with more than an ear toward transparency—the ability to hear into the mix unadorned—which some people confuse with an analytical unemotional sound. My experience says we can have our cake and eat it too when it comes hifi and some people simply mistake crappy sound for accuracy.
There’s a lot to say about the JMF PRS 1.5 preamplifier, something I’ll dig into a bit more in the review proper. In the mean time, the JMF website is full of details including the PRS 1.5’s dual-mono design and proprietary ‘CSV’ passive volume control that “features zero noise, zero distortion, zero phase shift, infinite headroom.”
The unbalanced inputs are “automatically balanced at the input and take advantage of the symmetrical amplification structure.”
From JMF:
The PRS 1.5 takes advantage of JMF Audio’s innovative and still unrivaled hand calibrated precision balanced input stage, enabling 100dB of typical interference rejection. This means 30 to 100 times better than professional balanced circuitry. This parameter has been enhanced based on psychoacoustic criteria.
The JMF HQS 6002 stereo amplifier is a direct-coupled, dual-mono design offering 220 Watts into 8 Ohms, 400W into 4, and 550W into 2 Ohms delivered by what the company calls improved class A operation.
There’s a lot going on inside this amp and I’ll let JMF hit a few highlights:
High reserve of energy for instant delivery at the output on fortissimo. Achieved with the proprietary RPS concept involving toroidal transformers and capacitors made in France to JMF Audio’s strict specifications.
High voltage electronics for superior headroom and higher efficiency. A linear amplification by design, a short signal path starting with a hand-calibrated precision balanced input stage. These are key features of the LDA driver board, the center piece.
High current output capability for best possible control, allowing the amplification structure not to rely on compensations, yet featuring a high damping factor by nature. The base of the proprietary MTP concept.
Both the input and output connectors are made by JMF as is the captive power cord. The cases for the preamp and amp are brushed anodized aluminum and come in, as you can see, silver or black (I kinda wished they matched for the photos, but I got over it once I plugged them in).
Soon after their arrival, I installed the JMF stack on the Barn’s A-Side and let them have their way with the YG Sonja 3.3 because I had a feeling this would be a marriage made in hifi heaven.
I wasn’t wrong. Stay tuned for more!
JMF Audio PRS 1.5 Preamplifier
Price: $39,000
JMF AudioHQS 6002 Amplifier
Price: $45,000
Company Website: JMF Audio
US Distributor Website: Audio Skies
JMF Audio PRS 1.5 Preamplifier Specifications
Features:
Balanced inputs: 3 (IN0, IN1, IN2)
Unbalanced inputs: 3 (IN3, IN4, IN5)
Balanced outputs: 2 (OUT1, OUT2) allowing bi-amplification
Unbalanced outputs: 1 (OUT3) modular, fixed or variable
Volume display: [30] to [99]
Relative volume setting between sources: [-9] to [ 6] display for -9 to +6dB
Source display: [i0] to [i5]
OUT3 set as variable output (default): For active sub-woofers or a headphone amplifier
OUT3 set as fixed line level output (direct): For a tape loop (reel-to-reel or recorder) or a headphone amplifier, upon pressing Direct button. [di] displayed on selection, recalled by a dot light during normal use
Bypass for surround sound AV processor: from IN5 (unbalanced) upon configuration or IN2 (balanced) in option
Ground connection (earth): dia. 4mm type
Remote control: JMF Audio MBR1, user selectable code-set to prevent from interference
Technical Specifications
Input impedance: Maximum input level at up to unity gain
Maximum input level at max volume: 9V (+20dBu, XLR bal) / 4V (+14dBu, RCA)
Maximum input level at max volume: 3V (+11dBu, XLR bal) / 1.4V (+5dBu, RCA), version F
Maximum output level: 10V (+22dBu) into 10k ohms load
Global signal bandwidth:
1Hz..150kHz (intentionally limited for RF immunity)
20Hz ..20kHz (+0.0 / –0.0dB)
Signal to noise ratio (SNR): 120dBA typ. (+22dBu), version F
Total harmonic distortion plus noise: 0.0002% typ. (+22dBu 1kHz in / bw. 22..22k Hz)
Channel Separation: >100dB (10V output 1kHz, gain min)
Interferences: rejection (balanced input): 100dB typ.
Output impedance: 50 ohms
Maximum gain output/input:
12dB (XLR bal in) +18dB (RCA in), version F
0dB (XLR bal in) +6dB (RCA in), prior to version F
Volume control range: 70 steps of 1dB
Volume control step precision: better than 0.05dB above volume [40]
Volume control left/right level mismatch: < 0.1dB above volume [40]
Specific to modular output OUT3:
Maximum gain in variable mode: 12dB (RCA in / RCA out), version F
Output impedance in variable mode: 50 ohms
Gain in direct mode: 0dB (RCA in/RCA out) -6dB (XLR in/RCA out)
Output impedance in direct mode: 600 ohms
AC mains power supply: 100, 120, 220-240 V AC – 50/60Hz (according to country of destination), version G
Power consumption: < 30W in operation (< 2W in standby), version G
Enclosure: Orose® up to 16mm thick machined anodized aluminum, machined steel buttons and rose-gold
Dimensions: 482 wide (front panel) x 320 deep x 106 high mm including feet (19” x 12.6” x 4.2” high)
Net weight: 14 kg (31 lbs), version G
Finishes: Silver or Black anodizing
Measurements with Audio Precision APX555 equipment. Voltage values are RMS. Specifications are based on the manufactured products at date of writing and may change with product evolution.
JMF AudioHQS 6002 Amplifier Specifications
Input
Impedance: 20kΩ
Output current capability: 80A per channel
Connection: XLR – metal case, gold contacts
Interference rejection: 100dB typ., based on psychoacoustic criteria
Type: Hand calibrated precision balanced input stage (impedance matched to PRS 1.5)
Monitoring: Level metering (-15dB to +3dB, deactivatable), Input offset, Overload, High temperature
Gain: 34.6 dB (all models have the same voltage gain which eases multi-amplification)
Output:
Output power RMS: 20W / 8Ω 400W / 4Ω 550W / 2Ω for one channel
Output current capability: 80A per channel
Load impedance: > 2Ω recommended (tested down to 1Ω at full output power at the manufacture)
Connection: JMF Audio LSS dia. 6mm (120A continuous rated) and gold plated WBT for forks or wires
Bandwidth: Better than 0.1dB 3Hz..20kHz for 250W / 4Ω, small signals better than -1dB at 100kHz
THD+N: Better than 0.01% for 250W / 4Ω at 1kHz (0.001% typ. un-loaded) BW. 20Hz-20kHz
Signal to noise ratio: 110dB typ. un-weighted BW. 20Hz-20kHz
Damping Factor: Better than 1000 at 8Ω, wide-band, for one channel
Audio signal coupling: Direct coupling
Protection Circuits:
Automatic protection against high frequency large signals
Automatic protection against input offset voltage and subsonic (fc 3Hz)
Automatic protection against overheating
Automatic protection against overload and short circuits
Mains voltage supervision (protections activation reported on front panel)
AC Mains Power Supply: 100, 120, 220-240 V AC – 50/60Hz (according to country of destination)
Cooling: Passive cooling | Sealed case design (no air path inside amplifier, preventing from dust)
Enclosure: Orose® up to 16mm thick anodized aluminum external enclosure including steel controls and rose-gold
Dimensions (Version G): 482 wide (front panel) x 539 deep x 149 high mm including feet (19” wide x 21.5” deep x 5.9” high)
Net Weight (Version G): 34 kg /pc (75 lbs /pc)
Finishes: Silver or Black anodizing
Voltage values are RMS. Measures on 230V AC power supply after 100 hours of operation. Specifications are based on the manufactured products at date of writing and may change with product evolution. Measurements with Audio Precision APX 555 equipment.