FM ACOUSTICS Resolution Series FM 411-MKII


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It is with great joy that FM ACOUSTICS announces the "MK-II" version of the FM 411. The original winner of the coveted
"Component Of The Year" award,
the FM 411 was somewhat expected to find admirers but who would have thought that it would stay such a success over its 12 years of continuous production?
Perfected so carefully that it never required a single modification or correction in all these years, it is FM ACOUSTICS most successful power amplifier - not least because it provides an unmatched price/performance ratio.

Recently, new parts have become available that - together with advanced insights from continuous research - allow the first amelioration since 1994.
With such a background, the refinements can, of course, not be "tremendous". They result in some smaller refinements but also some more substantial improvements - as described below.

Every little detail matters...

Every little detail matters...

Superb hand-craftsmanship even where it is not visible (here a detail of the underside of the internal chassis). The quality of each hand-pressed connector is carefully inspected before assembly. The outstanding standard of hand-soldering (important for long-term reliability) is apparent.
The more massive power supply of the MKII is helped by cooled dual rectifiers featuring high speed at the same time as very high current capacity.

Long-life level controls

New sealed long-life level controls use a conductive plastic track rather than the usual carbon or cermet track. In addition to much longer life expectancy this provides better resolution and guarantees no noise.

HR" modules

The new "HR" modules are used on the inputs. They help to achieve an astounding 100dB (!!!) of rejection of Common Mode signals (such as interference, hum, noise etc. which must be cancelled out before the amplification stages). They rend the FM 411-MKII immune against interference. This CMRR rejection is achieved not with cheap op amps but with individually fine-tuned discrete Class A circuits guaranteeing the ultimate resolution FM ACOUSTICS products are esteemed for.

Light bulb

Light bulb changes are a thing of the past.
FM ACOUSTICS' new frontpanel display provides a more even light distribution and uses high reliability LED's instead of incandescent light bulbs.
These LED's have a theoretical lifetime in excess of 100'000 hours (we could not really test them for that long so let's hope the specifications are realistic...).

Longer lifetime

Another small detail: left the new ultra-bright bulb now used for the mains power switch illumination. The cost is 3000% higher than the good old "long life" light bulb on the right (which needs replacement after a while - depending on quality of mains power). The new lamp uses dozens of LED's encased in its housing achieving higher brightness and much longer lifetime.
It is compatible and can also be used in the MKI version of the amplifier upon request (although not free of charge - for the above reason).

Resonance-eliminator support

To avoid negative influence from spurious resonance and guarantee positive coupling the 411-MKII employs FM ACOUSTICS unique resonance-eliminator supports. These isolate the unit from potential resonances making the unit immune to parasitic resonances.

A number of ameliorations are not visible but help the performance, amongst them:

  • The new FM 411-MKII employs circuit technology that is pioneered in the FM 115 (the winner of the prestigious "Grand Prix"). Total absence of any form of distortion - be it dynamic or static and even at the lowest signal levels - betters other designs by magnitudes.
  • New higher capacity power supply results in absolute linearity and even higher output power into low impedances
  • An even better interchannel crosstalk suppression results in total separation of the channels - important in a stereo amplifier and when used in "vertical" bi-amplification mode.
  • Multiple layout refinements achieve some slight and some more noticeable improvements
  • Absolute interference rejection thanks to phenomenal Common Mode Rejection on input stage
  • New high reliability components help to further increase lifetime expectancy
  • Several power supply refinements etc.
  • With these improvements and its unique original characteristics chances are good that the FM 411-MKII may be uncontested for many years to come.
    Today, the FM 411-MKII can guarantee:
  • Music reproduction to dream of
  • Proprietary discrete circuitry using special curve-tracer analysed and hand selected semiconductors
  • Superb balanced discrete Class A input stage. Sensors automatically recognize the connection standard and perfectly balance both unbalanced and pseudo-balanced signals sources right at input
  • Tremendous headroom and reserves
  • Superb rejection of noise, hum or interference thanks to perfectly balanced inputs (interference rejection is 100-1000 times better than other so-called "balanced" equipment)
  • Multi-protection systems for amplifier and speakers trigger the output and reset automatically when the error disappears.
  • No signal compression, limiting nor any other negative influence on the audio signal is possible. The protection circuits are totally separate from all audio stages.
  • 5000V mains spike suppressors
  • Outputs drive any speaker load perfectly, even very low impedance - or high capacitance transducers
  • Unique dynamic damping of speakers results in perfect impulse response and no overhang
  • Proprietary enhanced Class A circuitry provide unmatched musicality
  • Precision low noise level controls avoid the often experienced change in tonal characteristics when changing volume level
  • Ultra low-loss FORCEPLUG 200 output connectors.
  • Tremendous output current capability as peak output current is not limited
  • Mechanical resonance elimination with the new isolation supports
  • Internal transformer is shielded. Special techniques prevent stray fields
  • Lowest impedance power supply for unlimited dynamics
  • Hand-selected and perfectly matched components of DIN, IEC & MIL standard
  • Each unit is handcrafted and calibrated in Switzerland to absolute performance standards


Minimum Power Output:
320 W peak into 8 Ohms
600 W peak into 4 Ohms
1000 W peak into 2 Ohms

160 W RMS into 8 Ohms
300 W RMS into 4 Ohms
500 W RMS into 2 Ohms

Max. Output Voltage: 110 V pp.

Max. Output Current:
Unlimited repetitive peak output current. More than 20 A continuous per channel. No output or DC fuses, absolutely no form of current-, voltage- or any other kind of limiting.

Distortion: Average distortion: 0,005% THD

Bandwidth including Input Filter:
Less than 1 Hz to 60 kHz;
if required, internally settable to any frequency between 1 kHz and 60 kHz (Low-Pass) and
1 Hz to 1 kHz (High-Pass).

Risetime at Full Power: 3 us

Hum and Noise:
Below full power typically -110dB
Minimal unweighted:
better than -100 dB

Proprietary electronically balanced discrete enhanced class A circuitry, floating ground, non- inverting or inverting mode. Optimal performance with either balanced or unbalanced (single-ended) sources. Unbalanced sources are automatically balanced right at the input of the FM 411.


Input Sensitivity:
1,6 V RMS for full output


Input Impedance:
At all level settings from balanced and unbalanced sources: 40 kOhms

Input Stage Common Mode Rejection:
100 dB typically, better than 90 dB at 50 Hz, even better at other frequencies.

Load Impedance:
No minimum impedance. The amplifier is designed for 1 Ohm to 10'000 Ohm systems. It can drive any speaker impedance (even below 1 Ohm) with dynamic (music) signals without any limiting, compression or other negative effects on the audio signal. Despite this, the amplifier is fully protected against short circuits, open circuits and all other adverse conditions via a unique onboard computer that continuously surveys all important parameters.

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