Jewels Of Audio Art

Last month, in the first part of my review of FM Acoustics' Resolution Series 811 power amplifier and 244 preamplifier, I detailed some of the ultra-precision handcrafting, cost-no-object quality of parts, and proprietary devices and procedures which contribute so heavily to the truly extraordinary sonic accuracy and musicality of these gilt-edged components. The goal of Manuel Huber, the perfection-minded head of FM Acoustics, was to design and build an amp and preamp free from any constraints imposed by time and manufacturing costs. His intent was to redefine and go well beyond the previous state of the art. Many of his ideas and design philosophies fly in the face of conventional wisdom, and almost fanatical attention to every detail, from input to output, was needed to achieve this.

For example, the 811 features a special soft-start surge-protection circuit which limits the in-rush current known to make capacitors age faster. This circuit uses no relays or resistors, and it greatly extends the life of the capacitors. The capacitors used in the 811 are proprietary designs made exclusively for FM Acoustics. Many audiophiles seem to feel that capacitors which resemble 105-mm artillery shells 411/.001 are indicative of a high-quality power supply. Huber points out that the larger a capacitor is, the higher its inductance and resistance at high frequencies. In addition, a capacitor has a nonlinear electrical series resistance (ESR) with respect to frequency. The FM Acoustics capacitors reduce the ESR by a factor of about five as com pared to conventional capacitors.

Thus, their ripple current capacity is extremely high. This allows the use of smaller and fewer capacitors, making the ESR lower and far more linear over the entire frequency band.

The 811's, 2,900-VA transformer (described last month), proprietary capacitors, and matched pairs of power transistors (with their huge 46-sq.-mm chip area) mounted directly onto the cooling fins are part of the reason it can supply an immense output current. However, it is the 811's unique on board analog computer which really makes possible its virtually unlimited output current.

The computer measures peak and continuous output current, output volt age, rail voltage, bias, temperature, and other parameters 20 times per second and compares this data to optimum values stored internally. If you introduce, for example, a very dynamic signal (but not a short circuit), then the output voltage will on average be very high, while the average current will be reasonable-but the peak current will be huge, while the rail voltage remains stable. So here the output current re mains absolutely unlimited, producing as much dynamic current as is required by the load. This, of course, requires huge reserves (another reason for the cooling fan), and the amplifier will reproduce precisely what is fed to the input, limited only by what the a.c. power can supply.

If a short-circuit situation develops, peak current is high, continuous cur rent is shooting extremely high, and the rail voltage drops (because it collapses with such great amounts of cur rent). At that moment, the amplifier shuts off before the output stage can be damaged. There is no limiting, compression, or anything similar. The amplifier shuts down, and the front-panel display shows an error message. An other circuit is immediately activated to measure the load impedance 20 times per second. As soon as the short circuit is removed, the amplifier automatically resets and becomes operational. Thus, the amplifier either works perfectly--or shuts off. No negative influence on the audio signal is possible.

The computer also monitors other error conditions. For instance, the 811 is provided with separate positive and negative d.c. sensors on both outputs; if there is any d.c. above 1 V, the amplifier switches off and the display shows "DC Error." The computer keeps measuring (20 times per second), and as soon as the d.c. is re moved, the amp resumes operation.

The 811 has sensors for high-frequency oscillation that might occur be cause of ground loops or oscillating equipment. The sensors allow short bursts of high frequencies, like those from tape machine bias, to pass. How ever, with any continuous oscillation over 20 kHz, the amplifier instantly switches off. It should be noted that in the case of d.c. offset and high-frequency oscillation, the inputs and out puts of the 811 are switched off, as continuous very-high-frequency input into the 811 could destroy it. A proprietary relay with special contact material has 16 parallel contacts, each rated at 2,500 watts, to switch off the amplifier. This relay makes sure that the superb damping provided by the 811 actually gets through to the speakers.

Another feature of the 811 is that it has a star grounding system of super-low impedance, the type used in many professional recording studios. Star grounding is expensive. Every single amplification stage (there are seven in the 811)--every single active device, in fact-must be grounded by a separate wire or connector to the central grounding point. This method, free from ground modulation, guarantees proper grounding, very low impedance and resistance, and no influence of any stage on any other. This is one of the reasons FM Acoustics can make a single-chassis stereo amplifier that equals or surpasses the separation of monoblock amps.

Before it leaves the lab, the 811 goes through elaborate testing. FM Acoustics subjects the 811 to a wide variety of loads and to switchable short-circuit tests. Accurate voltage and current measurements are taken.

High-voltage insulation and accurate operating temperature are tested, and the protection circuitry is checked with a d.c. offset generator. Multiple burst measurements are also made. The 811 is run through 599 thermal cycles in a 100-hour burn-in and then subjected to violent vibration on a shaker table for an hour. After this abuse, the entire test procedure is repeated. While FM Acoustics uses many precision tools and devices, many of them proprietary, in the manufacture of the 811, I still have little doubt that there is more labor-intensive handcrafting on the 811 than on any other amplifier.

The FM Acoustics 244 preamplifier, the companion unit for the 811 power amplifier, is built to' the same uncompromising level of quality as the 811.

The 244 has absolutely zero feedback or feedforward in its circuitry. The proprietary signal-amplification circuitry is encapsulated in plug-in modules, which have discrete Class-A circuitry.

As in the 811, all transistors are hand-selected and matched on a curve-tracing instrument. (Around 400 transistors must be checked to find enough matching pairs for one Model 244!) The front panel has push-button switches to select a phono input and three high-level inputs. There is a tape loop, mono/stereo switch, headphone jack, and balance and volume controls. The headphone jack doesn't have the usual IC headphone amp but uses a discrete Class-A amplifier. Balance and volume controls are sealed, conductive-plastic, multi-wiper potentiometers which are checked to ensure that they do not deviate by more than 1 dB over a 55-dB range. Another feature of the balance and volume controls is that they are isolated from the gain stages by pure Class-A buffers.

The 244 is available in Version A for moving-coil cartridges, Version B for moving-magnet cartridges, and Version C for purely high-level operation.

In Version A, mini switches on the back panel allow for selecting resistance and capacitance for various MC cartridges. As in the 811, the 244 uses a star grounding system, and on the back panel is a ground-lift switch which can be used to check for ground-loop problems.

The bandwidth of the 244 is extremely wide, extending from 2 Hz to 2 MHz! There is said to be no phase shift from 20 Hz to 20 kHz. The output impedance is a very low 10 ohms, al lowing the unit to drive several hundred feet of cable without attenuation.

Rated distortion on line is an impressive 0.025% THD and on MC phono is 0.03%. Rise- and fall-time is 0.2 uS, with no overshoot. On line, hum, and noise are 90 dB below 0 dBV.

The straightforward specifications of these units are impressive, but al though the numbers should be indicative of good sound, in no manner can they prepare you for the stunning musical verisimilitude provided by this gear. After months of intensive auditioning with the most demanding mu sic, there is no doubt in my mind that a new pinnacle of musical performance has been achieved.

No amplification equipment should have a sonic "signature," but many do.

Total neutrality, with no euphonious embellishment, is the ideal. The 811 and 244 reproduce exactly what is re corded on the source. If distortion and noise are in the recording, they are as faithfully presented as the music. Like wise, there is no alteration to the ambience of the original recording hall or any glamorizing or romanticizing of the musical instruments.

The 811 and 244 are incontestably the best I have ever heard in what I call dynamic expression, the ability to fully reproduce the wide dynamic range of the best CDs with absolute accuracy and to do so without the slightest hint of compression, all throughout the musical spectrum. I heard things on familiar recordings which I had not previously perceived.

On a CD featuring Mitsuko Uchida's monumental performance of Debussy's "Etudes for Piano" (Philips 422212-2), the piano is reproduced as if it were in your listening room, at live playback levels! The dynamics of Uchida's great fortissimo bass chords never sound strained or harsh but simply resound with huge, resonant authority. Her quicksilver runs and trills are totally accurate. Every note is completely articulated, and there's never a trace of transient blunting.

On a disc of Shostakovich's Eighth Symphony, with Neeme Jarvi and the Scottish National Orchestra (Chandos 8757), the most thrilling music of the third movement-with its relentlessly rapid unison string passages punctuated by high-level tympani strokes, brass fanfares, and snare-drum rolls is reproduced with stunning accuracy.

The unfettered dynamics give the music an exhilarating panache.

John Eargle's landmark recording of Respighi's "Feste Romane" (Delos DCD-3070) is simply unbelievable. The tumultuous outpourings of brass, huge bass drum explosions and accenting tam-tam, fierce high-register strings, and thunderous organ-pedal counter point are reproduced by the FM Acoustics components with simply overwhelming sonority. The demands of dynamic expression on this recording are probably as great as you'll find on any CD and will severely tax even the best audio systems. If your speakers can handle this musical onslaught at realistic levels, the 811 will flawlessly provide the requisite dynamics.

On his dmp label, Tom Jung has produced some of the cleanest, most explosive and demanding recordings on CD. On his Heat of the Moment (dmp CD-468), track 5 has just about the most tremendously sonorous piano you'll ever hear. It is deliberately larger than life, for Tom coupled the mike pickup on the piano through a MIDI to a synthesizer, recording subterranean bass frequencies along with huge bass chords from Warren Bernhardt's piano. For the vast, rumbling, ultra-powerful bass, the 811 has the immense reserves of output current needed to reproduce it cleanly.

At $27,000 for the FM Acoustics 811 power amp and $6,000 for the 244 preamp, few people are likely to own these simply incomparable jewels of the audio art. But I can tell you that listening to great music through them is on the same level as driving fast cars or indulging in other thrills. So now I've got to fill out my lottery tickets.

(adapted from Audio magazine, Dec. 1990; Bert Whyte)

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