1. PARTS STOCK
One of the most important considerations when selecting professional audio equipment is the long-term reliability of the product. An inspection of details such as the standard of craftsmanship, the quality of components used, the quality of the solder joints, the wiring, its current and voltage capability, contact materials etc., will already give clues as to the potential long-term performance capabilities of the product. Of equal importance is the standard of pre- and final as well as in- production testing that the units undergo prior to shipment.
To guarantee that failures are reduced to an absolute minimum, a vast number of involved specific dedicated procedures and quality optimisations have been developed at FM ACOUSTICS: with the exception of metal film resistors (which have extremely low failure rate of 1 out of 4`000`000 pieces), each and every part is individually inspected. Every single building block, P.C. board and part assembly goes through an extensive list of tests during the manufacturing process (e.g., comprehensive components pre-selection, visual and electronic board checks, multiple pre-tests etc.). This way every single component is tested between 3 and 7 times. Thereafter each stage of the product is individually hand-calibrated and fine-tuned with high accuracy, purpose-built testing machine.
FM ACOUSTICS maintains a huge and costly parts stock (over half a million components!) to guarantee the continuous supply of parts. For every product service and parts availability is guaranteed for a minimum of ten years. During these ten years 99.8% of all parts can be delivered immediately, a tremendous investment in parts. FM ACOUSTICS products do not become obsolete. Even 28 years old units can still be serviced and are guaranteed to perform as good - or in most cases - better than originally!
Many of the precision components used in FM ACOUSTICS products are not readily available as they are specially manufactured for FM ACOUSTICS or non-standard parts that must fulfil special specifications (such as e.g. MIL spec).
2. STOCK CONTROL
Proprietary software tracks the stock, production flow, supply, rejects of components and much more. However, there is no blind belief in computers as a computer cannot prevent humans entering errors, so continuous checks and verifications of the many thousand individual parts are performed.
To a large extent the long-term reliability of a product depends on the quality of the parts used which is why all components used in FM ACOUSTICS equipment are of the highest quality, higher than those used in consumer, computer or communication products. Practically all of these components fulfil IEC, DIN and MIL standards.
Every single piece of every incoming part order is inspected. Not only quality and appearance are checked, but each individual capacitor, transistor, diode etc. is individually analysed for various FM ACOUSTICS-specific parameters. Most of these components have to be selected by hand on specially-built testing machines: for instance, each and every transistor goes through a beta selection and is thereafter completely analysed on high-power curve tracers. Five different measurements as well as a complex dynamic analysis (unique to FM ACOUSTICS) is performed on every transistor. Every capacitor is tested and selected for tolerance up to an accuracy of 0.1% (the tolerance of capacitors in typical "high-end" audio is ±10% to ±20%)! Other parts are subjected to further tests and selections. There really is no comparison between the way other manufactures are producing and what is done at FM ACOUSTICS.
3. PRODUCTION ROOM
To guarantee efficient, disturbance-free environment, it is vital to keep the production room clean and quiet. Working conditions exert a major influence on the quality standards attained. FM ACOUSTICS is located in calm surroundings in a non-industrial area directly on the shores of Lake Zurich. The well-being of our staff is of high importance: Maintaining positive relations, keeping a constant motivation to achieve the absolute best and assuring a comfortable work atmosphere are ingredients to creating the non-plus-ultra.
To guarantee optimal quality standards, there is absolutely no time pressure in the production, selection and test/calibration departments. Each craftsman/woman works at a pace in which he/she feels comfortable. There is no time limit in manufacturing or in testing. Humans have their stronger and weaker days so to exert pressure on weaker days would lead to errors. What counts at FM ACOUSTICS is only the quality standard, not what some just call "productivity". This is the basis for the unequalled standard of our products.
Freedom from time pressure also enhances employee long-term loyalty to the company and increases individual motivation and well being of the staff. Most of the staff has been with FM ACOUSTICS for more than 10 years, some for 30 years.
4. POWER SUPPLY ASSEMBLY
In audio electronics, especially with power amplifiers, the importance of a true low-impedance, wide-frequency power supply is generally underrated. Here every mOhm (one thousand's of one Ohm) counts. The connection between the large electrolytic capacitors (which also acts as the central ground for the amplifier's circuitry) is made with a massive bar of specially coated high-purity copper. Instead of standard flat washers, specially corrugated washers are used: these dig deep into the copper and guarantee an even lower contact resistance.
Such details, of which there are many hundreds, are what make the difference between an FM ACOUSTICS and other equipment.
A component of major importance are electrolytic capacitors. It is widely believed that it is the capacitance value that describes a capacitors' capability. This is not correct.
More important than capacitance per se are the loss factor, the Electric Series Resistance (ESR), the maximum ripple current that the capacitor can handle and other less known details, e.g. how the internal aluminium foil is connected to the terminals (the usual way this is done, crimping, results in considerable contact and wire resistance, which degrades the capacitor's peak and continuous current capability and increases heat and ESR).
FM ACOUSTICS uses proprietary technology in its high-grade capacitors, many of which are specially manufactured to FM ACOUSTICS' specifications. This results in a lower ESR and a much higher ripple current capability than found in standard capacitors. The capacitor's size can thus be minimized accordingly and the loss factors are much reduced (lower temperature = longer lifetime).
5. WIRING HARNESS
The higher the power of an amplifier, the more crucial the size, quality and routing of the cables inside the unit. FM ACOUSTICS precision power amplifiers are capable of delivering extremely high output currents at the same time as large output voltage - much higher than any other amplifier. Because of the huge currents, FM ACOUSTICS amplifiers require a very careful layout and assembly as well as elaborate interior shielding techniques in order to guarantee no negative influence on the low level stages.
All harnesses are wired and assembled entirely by hand. All contacts are pressed manually under no time pressure. The wiring harnesses are then tested on special contact-connection verification boards. Even the contacts used by FM ACOUSTICS are specially treated: a unique multiple coating (depending on the application, either gold or other materials that are optimal for their specific application, are used - gold is not necessarily the best material for high current/high power contacts). These special coatings have proven to be more reliable than standard materials. In the larger amplifiers the usual contacts cannot be used because of the immense currents involved (up to 400 A peak currents have been measured!). Therefore, all high power connections are hand-soldered to MIL standard with greatest care (no crimped connections like is done in other so-called "professional" or "high-end" products).
The above picture shows the specially manufactured cable rollers and wire guides which facilitate wiring harness production. As wood is the favourite material of the employee responsible for these harnesses it was decided to use a nice wood for this cable stand rather than much cheaper steel or aluminium. This conveyed to the employee that we do care about her and her work. Such details help to increase motivation.
6. TRANSISTOR SELECTION
The above picture shows the selection of specially made power transistors done on a high power curve-tracer. After the chips have passed the specific tests at the foundry every single semiconductor is first pre-selected and thereafter measured and analysed. This is done on the curve-tracers, testing five different parameters under static and - unique to FM ACOUSTICS - dynamic conditions. This transistor selection is far better than the typical "transistor matching" that simply put the transistor on a "Beta" meter where only a static single voltage and a single current value is measured. Transistor may have the same Beta at this one specific voltage and current, but they may be much different at other voltages and currents. If standard transistors that have undergone such a simple ''Beta'' test are used in an amplification stage, non-linearities are unavoidable; these non-linearities then have to be compensated with error correction circuitry, a unsatisfactory approach as such error correction circuitry invarably compounds various other negative effects on reproduction quality. Most of these errors are not measurable with the currently available instruments - which are only capable of analysing static signals. Music signals, however, are dynamic and cover a large frequency range, which means that measuring instruments (whilst useful for quality control) do not give an accurate representation of how a product will reproduce music.
FM ACOUSTICS takes a totally different approach. Every single transistor is tested with the utmost care and thereafter selected by hand over the entire voltage and current range. Using such specially selected transistors, distortion created in the positive and negative sides of the amplifier stage cancels out, resulting in a stage that is inherently distortion-free. Through cascading such distortion-free amplification stages, error correction circuitry can be avoided resulting in dramatically better performance. This proprietary technology assures that the usual effects - like instability, frequency-dependent feedback, increased distortion and other negative influences on the audio signal - cannot occur. Dynamic and transient behaviour is dramatically better.
These selection procedures are very time-consuming and a considerable percentage (anywhere from 40% to 95%) of the devices must be rejected because they do not attain the FM ACOUSTICS standards.
7. POWER TRANSISTOR MOUNTING
The pre-tested and pre-selected power transistors are next mounted onto the cooling devices. Special washers are used for this purpose. The transistors are tension-adjusted to guarantee that no under- or over-tightening occurs. Under-tightening would result in a higher thermal resistance while over-tightening could shorten the expected lifetime of the transistor due to potential chip cracking. The power transistors are unique in that they can deliver extremely high currents and voltages (depending on type, up to 60A / 300V / 350W) at transfer speeds far higher than anything else available. Thanks to this only few tightly selected transistors can handle the full duty. This allows unique circuit solutions as in most other high power amplifiers a large number of often cheap semiconductors must be used to achieve a half-way acceptable drive capability - a capability which is far below that of FM ACOUSTICS power amplifiers and is often insufficient to handle the actual requirements of the more demanding modern speakers loads.
8. TRANSISTOR NOISE SELECTION
FM ACOUSTICS' employs an exclusive listening test selection of low level transistors. Measuring instruments alone are not sensitive enough to distinguish whether a transistor's noise performance is truly perfect for audio applications. Even if a transistor's noise level measures o.k. on test instruments - which is only a static/momentary measurement (!) - its noise may not be acceptable over a certain time period and its actual noise quality can negatively influence audio reproduction. This is audible at lower levels. In a true State-of-the-Art unit this is unacceptable. FM ACOUSTICS has developed a proprietary and unique listening evaluation process which every single low- and line-level transistor must go through. Only after it has passed all three selection processes is the transistor allowed to be used - in perfectly matched pairs.
A tremendous amount of work goes into each unit manufactured: e.g., a single monophonic FM 334 crossover requires 120 (one hundred twenty) perfectly matched, noise-selected line level transistors! This means, for example, that before a single FM 334 can be manufactured between 400 and 900 transistors (the actual quantity depends on the yield) must be selected and auditioned on specially-built testing machines. The most costly part is not the rejected 400 to 800 transistors but all the lost time for the selection of those transistors that cannot be used!
9. POTENTIOMETER SELECTION
At FM ACOUSTICS it's not just semiconductors that are selected. Each of the special multi-wiper potentiometers is carefully selected by hand for tracking accuracy. The test unit used to accomplish this task has been specially built by FM ACOUSTICS' engineers. Using a sample and hold function that displays an initial default value assists in analyses which is done manually by slowly moving through the whole range and watching for any potential tracking difference. If a tolerance higher than fractions of a dB are found, the potentiometer is rejected. Each selected potentiometer is therefore of high accuracy.
In the above photograph the test machine is hooked up to the oscilloscope. The two traces of an oscilloscope show the difference between the two potentiometer tracks (channels). This is an example of a Volume potentiometer that is tracking very poorly. Without additional selection procedures even costly high-quality parts like this potentiometer cannot meet the quality standard required at FM ACOUSTICS.
Rather than switched (stepped) attenuators, VCA circuits, digital Volume controls, optical encoders or a relay matrix, in FM ACOUSTICS products laser- trimmed and hand-selected precision potentiometers are used.
With stepped attenuators the limit of resolution is determined by the individual steps. Music levels, however, do not come in steps but rather must be finely tuneable to achieve the most realistic reproduction. Therefore, they must be continuously variable. VCA's (Voltage Controlled Amplifiers) and the circuitry of optical encoders are known to be detrimental to audio quality and therefore must be avoided in order to attain optimal results. Multiple switched relays have the same limitations as stepped attenuators, in addition to having less long-term reliability (partly due to a massive additional electro-mechanical component count).
While not "fancy", finely selected precision potentiometers, as used in the FM ACOUSTICS range, give better results all around. They are the optimal choice.
10. HAND SOLDERING
At FM ACOUSTICS every board and every single connection is soldered by hand. Automatic wave soldering is not acceptable as the quality of such soldering does not reach FM ACOUSTICS standards. Furthermore, the boards are not soldered in the standard manner which leaves an open cut that, over the long run, can result in oxidization of solder joints. In time, such oxidized joints can become very troublesome and adversely affect the performance and reliability of the product.
At FM ACOUSTICS, all soldering complies with highest military standards. After the pre-selected components are hand placed on the boards, each component wire is individually cut and each joint is then hand-soldered carefully. This technique guarantees that the wire cut is totally covered with solder and that it can no longer oxidize.
Another important aspect is the type of board material. Of course, flame retardant P.C. boards are used. While most high-class electronics use FR4 grade boards, the material FM ACOUSTICS employs has some major differences:
a) All the racks that carry high current are extremely wide and
b) High-current boards using special, three times larger copper layers are used.
c) The boards are then finished with an additional special plating process.
These differences result in much lower resistance, better conductivity, less heat generation and clearly better overall performance.
11. CALIBRATION AND PRETEST
Here we see an assembled pre-amplifier being calibrated and tested. At this point each individual amplification stage is carefully fine tuned for optimum performance. Then all stages of the amplifier are calibrated. The behaviour of the amplifier is analysed and then optimized for performance. Power amplifiers are checked at all power levels and with various loads.
Amongst the multitude of checks, calibration procedures and measurements, the action, speed and performance of the protection systems are examined under various conditions. Many pages of measurements are taken and a test report is written out for each unit documenting in detail the amplifiers capability and characteristics.
12. BURN-IN
The custom-built testing machines at FM ACOUSTICS meet every possible demand. Besides standard tests such as distortion analyses, noise measurements frequency response etc. other special tests and measurements performed by these machines include the following:
* A wide variety of switch-selectable loads
* Accurate voltage and current measurements
* High voltage insulation tests
* Wave from tests
* phase linearity tests
* Attenuation accuracy tests
* Thermal tracking and operation measurements
* Thermal overload tests
* Multiple specific error generation for checks of protection circuitry
* D.C. offset tests and calibration
* Ultra-accurate CMRR measurements
* Transient behaviour tests
* Multiple burst measurements
* Short-circuit tests
* Precision RIAA and de-emphasis
* Precision filter measurements
* And more...
After each product has been pre-tested and performs perfectly, and after all data have been recorded, the unit is then moved to the specially built burn-in room. There it is exposed to a long-term burn-in test running under the most severe test conditions, this for at least 200 hours in a thermal multi-cycling mode. These cycles are programmable from a few minutes up to several hours. The units consequently heat up and cool down repeatedly, going through between 1000 to 2000 full thermal cycles. In this manner worst-case test scenarios and heavy-duty burn-in (including the important pre-aging) are achieved and the possibility of later malfunctions and defects is virtually eliminated.
13. VIBRATION
After the aforementioned extensive tests, each and every product is placed on a heavy-duty shake-table where it is vibrated for a minimum of one hour (50000 vibration cycles). In these extreme tests anything that is not 100% firm or any soldering connection that is not 100% perfect will show up within minutes.
14. FINAL TEST
When the unit comes back from the vibration table the testing starts all over again. It is placed on another test bench and once again thoroughly analysed. All initially performed checks and measurements are repeated. After this, all measurements are compared (from the data before and after the burn-in and vibration tests). If all test results are perfect and identical, the product can be guaranteed to perform reliably in any practical application for many years.
However, if even the smallest deviation of a single parameter is found, the cause of this discrepancy is analysed and the unit is moved back to the burn-in room to once again undergo another full burn-in test and vibration test cycle.
Copies of all data and measurements are kept in FM ACOUSTICS' files so they can be used for later reference. In this manner true long-term performance of all products can be verified. Due to these extensive procedures, the average final testing time is twenty to fifty times longer than with other makers.
15. IN-HOUSE RESEARCH, DEVELOPMENT AND DESIGN
At FM ACOUSTICS all research, development and construction are done in-house. Contrary to popular management methods, "in-sourcing" is the way to go, not "out-sourcing". Only by having every detail under constant control and supervision can accuracy and true quality be guaranteed.
Furthermore, practical experience gained under real-world conditions can be efficiently incorporated into the designs as all parties are able to communicate instantly and in person.
Every year FM ACOUSTICS invests a minimum of 20% of its total turnover in advanced research and development. This is an extremely high figure (compare this to the average research budget in the audio field, usually between 0.4% and 3% of annual turnover).
It is such unparalleled commitment to perfection that explains both the unique performance of FM ACOUSTICS products and why they remain the true State-of-the-Art for sometimes decades.
