The HQS 7001 is a reference mono power amplifier, which remarkable performance is bettered only by JMF Audio’s flagship HQS 9001 reference mono amplifier.
Driving the loudspeakers... Caring for the music...
The JMF Audio HQS pure analog power amplifiers have been acclaimed for their high output power combined with a faithful, natural rendering of music. Since 1988, the most influential audio professionals, such as American studio designer Tom Hidley, and world-class studios (Nashville, New-York, London, Capri, Tokyo, Moscow, Toulouse, Paris...) have trusted the HQS power amplifiers to monitor the quality of the recordings and productions, with great pleasure of listening.
While it first met with success in the studios, the JMF Audio technology was humbly aimed at celebrating music, for all music lovers.
Jean-Marie Fusilier designed and built the HQS power amplifiers without the preconceptions, the marketing considerations, the deadlines or budgets that generally limit commercial designs. Being an expert engineer in high-frequency, infra-red and power electronics, a mother and a brother organ/piano players, Jean-Marie Fusilier approached audio differently, by passion, with pragmatism, and developed innovative solutions. These set the fundamentals of the JMF Audio manufacture, established in 1985.
The JMF Audio founder desired a lively yet controlled rendering for all types of musics... Even with high sensitivity loudspeakers, this meant significant driving force, precision and very low noise floor. The tube technology which he used to cherish was therefore left aside. Regarding the solid state technology, it was common belief that only a pair of matched output transistors could lead to musicality, which was still only suitable for intimistic listening.
Jean-Marie Fusilier took up the challenge to design a power amplifier that would be faithful to the music in all circumstances.
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The approach behind the JMF Audio HQS power amplifiers can be summarized as follows:
> 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.
An approach that was set in the beginning and is still followed today, sometimes with the exact same components.
Complementing the major aspects, the details are of significant importance regarding the musical result:
Since their introduction, the JMF Audio HQS power amplifiers have taken advantage of the long researches of their designers on the sound neutrality of passive components, semiconductors and materials as well as on the amplification structure allowing fast response, stability and linearity at every stage. The JMF Audio HQS power amplifiers utilize selected and uncommon components for audio applications: high frequency precision transistors, matched differential pairs, bespoke passive components, proprietary printed circuits boards substrates...
Due to the requirements for specific components from the aeronautic, aerospace and fast-train industries located in France, some companies have specialized in manufacturing custom parts. Thanks to our initial activities in high-frequency electronics, as told in the History of the Brand, we have collaborated with such specialists for over 30 years, which has allowed JMF Audio to obtain made to measure components and parts, especially passive, that best suited our criteria, for the music.
The JMF Audio HQS power amplifiers are able to deliver formidable currents, with serenity. Large signals never happen to mask small signals. Possibly unique... and especially desirable when enjoying music at moderate levels. The notes last longer with JMF Audio power amplifiers.
We have pointed out that the reaction of the loudspeakers (the counter electromotive force) was a commonly underestimated phenomenon. The loudspeakers have to be under control. Even at living room levels, the JMF Audio HQS power amplifiers allow an ample rendering of music, in an absolute comfort.
JMF Audio defines dynamics as linearity down to the lowest levels, especially when the message is complex. This is another aspect that we consider very important. Linearity allows the reproduction of the least details, the subtle ambiances and the wide and coherent natural sound stage as caught at the recording. A challenge...
The LDA mono driver board, the center piece inside the power amplifier, based on a symmetrical structure, it is in charge of the voltage amplification of the delicate incoming line signal by a factor of over 30dB. Since 1985, the driver stage has featured the 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 proprietary DCS coupling allows a direct signal path, free of link capacitor.
The LDA multi-layer mono driver board features metal case ultra low noise discrete military grade components, made in France bespoke capacitors, temperature compensated current biasing. 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’s proprietary PGP 24 carat gold printed circuit board substrate is incompatible with the automated processes. The hundreds of components populating both sides of the board are hand mounted and soldered one by one by our specialized technicians using JMF Audio's specific solder, under a magnifying glass. A process that requires skills and patience and results in the application of jewels manufacturing methods.
A total of 6 adjustment points are hand calibrated on each driver board after 100 hours of operation at the manufacture.
The proprietary MTP output stage, in charge of the signal amplification in current, employs multiple selected transistors which have their own biasing, thermal compensation, fail-safe circuit. The biasing being independently calibrated to match the transistors and associated driver board's characteristics. Our researches on the class A operation of the AB class output stage have lead to a proprietary design more than a decade ago. Small signals, such as the decays and the details of ambiances, have since been reproduced through improved class A.
Thanks to the naturally stable design of the power amplifiers, the output stages provide a direct path from the transistors to the output terminal, without the added inductive component that is normally mandatary in solid state designs.
The JMF Audio Instruments for the music® are entirely hand crafted in our workshops and pass stringent tests. Since 2009, every manufactured power amplifier has been verified by listening in our studios after an operating period of over 100 hours and placed in comparison with our references.
The dual chassis design, with the Orose® enclosure made of 10 to 16mm thick anodized and brushed aluminum parts, lays on JMF Audio’s proprietary decoupling feet. Whichever the chosen anodizing color Silver or Black, the engravings are filled with rose-gold and the controls, inserted in guided cylinders for smooth operation, are precisely machined in solid blocks of steel. The toggle switches, individually housed in a metal frame, are made in France to JMF Audio’s specifications.
Key features:
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RPS high stability power supplies. Made to measure capacitors and toroidal transformers.
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LDA driver boards, symmetrical, linear and short signal path amplification structure.
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DCS servo, direct coupling, zero capacitor link on the signal path.
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DPO direct output design, zero inductance on the signal path.
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MTP output stage: multiple transistors, individually controlled, 330A capability for HQS 9001, improved class A operation.
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TRB temperature regulated circuits (with accelerated thermal stabilization starting from version C)
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PGP proprietary 24 carat gold analog printed circuit board substrates (LDA amplification an MTP output stage).
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SCD sealed case design, preventing dust from entering the chassis.
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LSS made to measure dia. 6mm output terminals (120A rated) with specific PGP gold, or WBT for forks.
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Protection against input offset, too high frequency, high temperature, overload. Signal level meter (deactivable from version F).
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All models feature the same voltage gain, which facilitates multi amplifiers and active setups.
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All power amplifiers are upgradable (starting from version B).
Technical specifications:
Hand calibrated precision balanced input stage (impedance matched to PRS 1.5)
- Type
Level metering (-15dB to +3dB, deactivatable), Input offset, Overload, High temperature
Monitoring
300W / 8Ω 500W / 4Ω 850W / 2Ω
- Output power RMS
> 1.5Ω recommended (tested down to 1Ω at full output power at the manufacture)
- Load impedance
JMF Audio LSS dia. 6mm (120A continuous rated) and gold plated WBT for forks or wires
- Connection
Better than 0.1dB 3Hz..20kHz for 250W / 4Ω, small signals better than -1dB at 100kHz
Bandwidth
Better than 0.01% for 250W / 4Ω at 1kHz (0.001% typ. un-loaded) BW. 20Hz-20kHz
THD+N
110dB typ. un-weighted BW. 20Hz-20kHz
Signal to noise ratio
Better than 1200 at 8Ω, wide-band
Damping factor
Direct coupling
Audio signal coupling
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)
Protection circuits
100, 120, 220-240 V AC - 50/60Hz (according to country of destination)
AC mains power supply
Passive cooling
Sealed case design (no air path inside amplifier, no dust).
Cooling
Orose® up to 16mm thick anodized aluminum external enclosure including steel controls and rose-gold.
Enclosure
482 wide (front panel) x 539 deep x 149 high mm including feet (19” wide x 21.5” deep x 5.9” high)
Dimensions (version G)
34 kg /pc (75 lbs /pc)
Net weight (version G)
Silver or Black anodizing
Finishes
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.