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FM 411-MKIII

It is with great joy that FM ACOUSTICS announces the "MK-III" 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 24 years of continuous production?

Perfected so that it never required modifications or corrections  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 a major amelioration. No superlatives needed from us. These are provided by the owners of this marvel. The improvements of the MKIII version result in some smaller refinements but also some substantial performance increase - as described below.

Every little detail matters...

Superb hand-craftsmanship is evident 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 visually and electrically before assembly. The outstanding standard of hand-soldering (important for long-term reliability) is apparent. At FM ACOUSTICS no cheap wave-soldering is acceptable.


The more massive power supply of the FM 411-MKIII is helped by multiple precision rectifiers featuring high speed at the same time as very high current capacity - and some "special treatments"....

Long-life level controls

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 freedom of noise. In the FM tradition each and every control is hand-selected and coded.

HR" modules

The new "HR" modules are used on the inputs. They help to achieve an astounding 100dB (!!!) of interference (hum, noise etc). rejection. Such non-musical signals must be rejected/removed before the audio signal enters the amplification stages). The 411-MKIII is therefore immune against interferences. This rejection is achieved by highly selected components (to 0.25% tolerance - where others are happy with 10%...). Individually fine-tuned discrete Class A circuits guarantee the ultimate resolution FM ACOUSTICS products are esteemed for.

Display

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

MKIII resonance-eliminators

To avoid negative influence from spurious resonance and guarantee positive coupling new resonance-eliminators are employed. Initially introduced in the MKII series, the new MKIII isolators have increased isolation making the unit immune to parasitic resonances.

A number of amelioration's are not visible but help the performance, amongst them:

  • The new FM 411-MKIII employs circuit technology that is pioneered in the FM 1811 and the FM 115.
    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 impedance
     

  • An even better inter-channel cross-talk suppression results in total separation of the channels - important in a stereo amplifier and very important when used in "vertical" bi-amplification mode.
     

  • Multiple refinements achieve some slight and some more noticeable improvements
     

  • Absolute interference rejection. No hum, RF, noise etc.
     

  • Hand selected high reliability components help to further increase lifetime expectancy
     

  • Several important power supply refinements etc.

    With these improvements and its unique original characteristics the FM 411-MKIII will be uncontested for many years to come.    The FM 411-MKIII guarantees:
     

  • Music reproduction to dream of
     

  • Proprietary discrete circuitry using special curve-tracer analysed and hand selected semiconductors throughout.
     

  • 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, activate an alert 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.
     

  • 5000 V mains spike suppression
     

  • 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 unlimited
     

  • Mechanical resonance elimination with new isolation supports
     

  • Internal transformer is shielded. Special techniques prevent stray fields
     

  • Hand-selected and perfectly matched components of DIN, IEC & MIL standard
     

  • Each unit is hand-crafted and calibrated in Switzerland to uncontested performance standard

Some Specifications

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: better than 0,005% THD

Bandwidth including Input Filter:
Less than 1 Hz to 60 kHz;

Risetime at Full Power: 3 us

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

Input:
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-MKIII.

 

Chassis Resonance Damping:
New chassis design effectively isolates sensitive electronic and mechanical components from potential negative influences such as induced resonances. Mechanical resonance damping on panels is employed. Specific purpose-designed anti-resonance technology is employed.

 

Input Sensitivity:
1,6 V RMS for full output

 

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

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 on-board computer that continuously surveys all important parameters.