F.A.Q

Table of Contents

1. General

• 1.1. Why did you choose to have a F.A.Q. to introduce your company?
• 1.2. Why do you give greater importance to the amplifier in the systems that you recommend? Aren't you looking after your own interests?
• 1.3. You put forward the «naturalness», the « veracity of sound and music», and never «perfection» so much praised by your competitors. Is there a reason for it?
• 1.4. Do you intend producing tube amplifiers?
• 1.5. Are the amplifiers that you propose intended to be changed as soon as the new version appears ?
• 1.6. On all amplifiers currently marketed, appears a «CE Marking». Does this have a connection with the sound qualities of the device?
• 1.7. Couldn't you design more powerful amplifiers?
• 1.8. Do you intend producing acoustic loudspeakers?
• 1.9. What about after-sales service? Wouldn't I be well advised to turn to a well-known brand?
• 1.10. Aren't mass-market audio-equipment manufacturers better placed than a small company like yours to create high-quality devices?

2. Listening

• 2.1. When I listen to folk or country music on my system with Invocation 01 (02, or 03) amplifier, the singer has a nasal twang; I did not hear that on my previous amplifier.
• 2.2. I think that my system lacks of balance with your amplifier. I used to have much more bass.
• 2.3. How can we talk of natural sound when it concerns amplified or synthesized music?
• 2.4. Isn't the treble of your devices too metallic?
• 2.5. Why didn't the other brands launch into the manufacturing of devices similar to yours as far as sound is concerned?
• 2.6. What is the category of listeners who appreciate the most your devices?
• 2.7. Mos-fets have the reputation of having a rather warm and sweet treble sound, a dull bass, and a good midrange. What do you think of it?
• 2.8. Aren't the figures concerning distortion the most important?
• 2.9. It is alleged that some devices better bring out the rhythm and tempo of music than other devices. Is it true?
• 2.10. We speak of «intellectualized listening» to describe some devices. What does it mean?

3. Technical

• 3.1. Your devices are quite bare: no bass or treble controls, no balance. For what reason?
• 3.2. The sound of your electronics being more distinct and clearer than the one of other marketed devices, isn't there a risk of «listening fatigue» in the end?
• 3.3. Your devices are presented with the same technical specifications, whatever their position in the range. How do you explain this?
• 3.4. Your devices have a cottage industry aspect. Couldn't you have an industrial type finish?
• 3.5. Would a power of 40W into 8 Ohms (the one presented by Invocation range) be sufficient on my system?
• 3.6. Is it necessary to have a special room, carefully studied and equipped to properly operate your devices, possibly with sources and loudspeakers that you recommend?
• 3.7. Are your amplifiers able to supply any type of acoustic loudspeakers?
• 3.8. What is the benefit of pin-to-pin assembly on a card without copper track compared to standard assemblies?
• 3.9. Why do you use wood as a manufacturing material for the frame of your devices?
• 3.10. Your devices include a few components coated in silicone. Isn't there a risk for them to catch fire?
• 3.11. What is the life span of your devices?
• 3.12. What do you think of the passband criterion? Isn't it a major data to judge the quality of a system?
• 3.13. Why did you give preference to mos-fet transistors as power components of your devices? Are they necessarily superior to bipolars?
• 3.14. Do you think that one can design a device musically perfect by making it perfect to measurements?
• 3.15. According to you, what is the best type of acoustic loudspeakers? Rather conventional (electrodynamic), and in that case with what system of acoustic load: close, bass-reflex, transmission line, or rather electrostatic or other ?
• 3.16. Why don't the other manufacturers create simple devices, if this brings about advantages? Some of them do. The question is then: do they really get the most out of advantages obtained?
• 3.17. Some amplifier manufacturers put forward the size of supply capacities and their total value, to praise the qualities of their product and the energy it has at disposal. Is it important?
• 3.18. Aren't class A amplifiers the best by definition. (Since they are «First Class» devices!)?
• 3.19. What does a class A amplifier technically correspond to?
• 3.20. Since amplifiers have an operating mode designated by a letter, how can a class «AB» exist?
• 3.21. Is an amplifier in class A or not, or is there a gradation?
• 3.22. What is a class AB amplifier?
• 3.23. We sometimes hear that class A amplifiers are the most effective. Is it true?
• 3.24. Is it true that a class A amplifier generates less distortion than a class AB amplifier?
• 3.25. Class D amplifiers (or digital amplifiers) are tremendously in vogue. Do they present a real interest?
• 3.26. Do class B amplifiers have an interest concerning sound reproduction?
• 3.27. What do you think of the use of 5.1 (or 6.1 or 7.1) format for musical restitution?
• 3.28. Isn't the central speaker - generally placed under the screen - essential to the Home Cinema ?

4. Home cinema

• 4.1. Doesn't the restitution of movie soundtrack - the home cinema - require specially elaborated devices?
• 4.2. When I watch «2001: A Space Odyssey», I can't hear the noise of the spaceship. Is it normal?
• 4.3. Isn't it better to have a Home Cinema amplifier with an integrated 5.1 (or 6.1, or 7.1) decoder rather than a separated decoder system or integrated into the DVD player?
• 4.4. Isn't it better to have a 7.1 installation rather than a 5.1? (or a 6.1 rather than a 5.1)?
• 4.5. Isn't the presence of the subwoofer imperative in a Home Cinema system?
• 4.6. Will the monophonic units that you intend to realize be «specific to Home Cinema» concerning their sound or their technical specifications?

1. General

1.1. Why did you choose to have a F.A.Q. to introduce your company?

Today, the F.A.Q. is a product which has become standard practice for INTERNET users. This documentation method allows the presentation of products in a lively and interactive way. It allows the writer of the document, as well as the readers, to supply and/or discover information that they need according to their centre of interest.

We have divided the F.A.Q. into four major parts:

• General: All questions concerning the company, High-Fidelity, etc...
• Listening: All questions that you can have concerning the sound of our amplifiers.
• Technical: Our devices have an extraordinary sound, it is logical to try to know why...
• Home Cinema: Our systems bring a true solution for home cinema. If you have any questions...

1.2. Why do you give greater importance to the amplifier in the systems that you recommend? Aren't you looking after your own interests?

First of all, we give greater importance to the amplifier for entry level systems only. For these systems, the objective is to reach a good quality level while taking into account budget constraints. If we considered that the degree of musical and sound fidelity obtained was inadequate, we would recommend more expensive loudspeakers and sources. This is the case for vinyl turntable, where we think that an investment superior to the CD player is necessary - for the respect of music as well as for the records': a turntable not properly designed can very quickly damage LPs which are sometimes irreplaceable. It turns out that a well-designed phono system can be more expensive to manufacture than a CD player.

As far as loudspeakers are concerned, experience has proved that our amplifiers can magnify - properly designed - entry level loudspeakers, while being able to do much better on more advanced models.

1.3. You put forward the «naturalness», the « veracity of sound and music», and never «perfection» so much praised by your competitors. Is there a reason for it?

As a general rule, we consider perfection for what it is and for what it must remain: a philosophical idea. If perfection existed in matter of sound restitution, we could restitute the Berlin Philharmonic Orchestra, or a rock concert, in life-size and full volume, in an apartment or in a telephone booth... And this is not the case yet. Besides, if perfection is reached, why would we regularly create new product ranges? We prefer to try and approach truth rather than delude ourselves. If we modify a device, or create a new one, it is just because we consider - and that enough listeners have considered - that this new device will go in that direction.

1.4. Do you intend producing tube amplifiers?

This is one of our medium-term objectives. As a matter of fact, transistor technology (with, in particular, the use of power mos-fets, as it is the case with our amplifiers) authorizes good results. It is also the case with tubes, but we will propose devices requiring this specific technology when we think that they are rightfully well placed - when our test models will be sufficiently accomplished to be in a good position in our range.

Those amplifiers should bring other qualities regarding transistors. We will still have to consider their overall performances.

1.5. Are the amplifiers that you propose intended to be changed as soon as the new version appears ?

We carry out, on request, the updating of our amplifiers, thus ensuring the continuity of your investment. When a new version is available, you can ask for the change of amplification modules. This change, carried out in our workshop, and at a fraction of the cost of a new device, allows you to benefit from the performances of the new range without having to change your amplifier.

1.6. On all amplifiers currently marketed, appears a «CE Marking». Does this have a connection with the sound qualities of the device?

There is actually a connection, but it is not intentional. The CE marking concerns - (non exhaustive list) - electric safety, fire safety, potential electromagnetic interference..., but not sound quality level.

On the other hand, there is no doubt that, for various technical reasons, the conformity procedure applied on devices can have an effect on sound quality. Our amplifiers comply with standards, but we have corrected this effect on quality. On the other hand, many manufacturers opted for self-certification: in other words, they have decided to append their signature on a document where they declare that their device comply with standards. This procedure is authorized by law. But it is not bound to any objective guarantee regarding the conformity of devices. For them, the benefit of this practice is triple: they save themselves expensive testing carried out by specialized laboratories. They can ignore the standard constraints if they want to : thus, they save up again by avoiding modifications. Finally, the listening characteristics of their devices are not modified.

As far as we are concerned, we do not make any concessions, either on safety, or on other issues: our devices are certified by an independent laboratory. As mentioned above, they absolutely comply with standards. However, it is out of the question that the conformity procedure is done to the detriment of the restitution qualities of our amplifiers. Therefore, we have compared the measurements and listening characteristics of conforming devices with test amplifiers, realized before the conformity procedure. Then, we worked on the conforming versions, in order that their sound quality level was at least equal to test amplifiers.
They were finally examined again by the laboratory to assess their conformity. It is a constraining process, but it bore fruit...

1.7. Couldn't you design more powerful amplifiers?

Our amplifiers have generally more than enough power for musical restitution and for home-cinema in most cases. When more power is required, it is possible in the case of bi or tri-wiring loudspeakers, to use multi-amplification devices - which increases a lot the power available. Moreover, we intend to market shortly, «bridged» power units delivering an efficient power of 120 Watts into 8 Ohms, which will be suitable for professional use, such as a studio. Nothing technically prevents us from thinking of a superior power, but this will be only useful for specific applications - for example, a home-cinema installed in a very large room, a nightclub, or to supply loudspeakers having a very low electric output. Those devices are being studied, and could be launched in the more or less long-term. They will be able to support bridged operating mode, which will lead to amplifiers of one kilowatt and more. Do not forget that they are very underestimated powers compared to the real dynamic margin of our devices.

1.8. Do you intend producing acoustic loudspeakers?

It is possible. We have carried out research into this subject. We will propose them to music lovers and home cinema lovers when we think that they really bring an improvement compared to existing models. This is also true for CD/DVD players.

1.9. What about after-sales service? Wouldn't I be well advised to turn to a well-known brand?

Our after-sales service is based on the principle of rapidity and efficiency. But we deserve no credit for that, apart from having designed devices voluntarily simple, where the number of components is minimized - which enables to increase very significantly the quality and thus, sound quality and reliability: potential repairs are thus very simple, and much fewer than with complex products. Some devices contain several hundred cheap components. This is not the case with ours ...

1.10. Aren't mass-market audio-equipment manufacturers better placed than a small company like yours to create high-quality devices?

Of course, most leading audio-equipment manufacturers have at their disposal, armies of engineers and designers. We do not question their skills. It turns out that our objective is not the same. Their aim is to market devices which produce a maximum commercial margin, which do not go off the beaten track, and have more or less the same sound. Their sound - according to us and we are not the only one to say that - is very far from natural sound. Their main selling points are aesthetical, and more often, supposedly technical. A few measurement figures are not enough to assess the degree of likelihood of sound restitution, but this is what we could believe by reading their documentations. We chose a more arduous way, but more satisfying in many respects: «It is not the way which is difficult: it is the difficult which is the way».

2. Listening

2.1. When I listen to folk or country music on my system with Invocation 01 (02, or 03) amplifier, the singer has a nasal twang; I did not hear that on my previous amplifier.

It is normal: voices are accurately restituted by our devices, with their specificities. By the way, Texans (for example) rarely have a Ménilmontant* accent.... *(typical Paris quarter)

2.2. I think that my system lacks of balance with your amplifier. I used to have much more bass.

Do not let yourself influence by listening habits. Most acoustic instruments have less bass, but also a much «drier» and faster bass tone, than the one we hear on most systems.

However, If the lack was real, with respect to the instrument, it would be necessary to re-examine the position of acoustic loudspeakers: place them nearer to the back wall or the corners, by small movements, at 5 cm (2 inches) or so, even less. A non realistic and exaggerated bass can spoil the restitution, it removes its clearness and likelihood.

2.3. How can we talk of natural sound when it concerns amplified or synthesized music?

Music remains «a combination of sounds pleasant to the ear». Musicians chose their amplifiers according to their aesthetic wish. It is the same for synthesized sounds. To reproduce them accurately and naturally is to conform to the artist's wishes.

2.4. Isn't the treble of your devices too metallic?

If you often listen to acoustic instruments - or in very well equipped studio booth - you will notice that it is simply accurate. Of course, rock or jazz drums are percussive and metallic... For excellent reasons!

2.5. Why didn't the other brands launch into the manufacturing of devices similar to yours as far as sound is concerned?

Our manufacturing method is specific to obtain the quality level required: it is demanding and delicate. Many brands prefer easiness. And we also have our small secrets...

2.6. What is the category of listeners who appreciate the most your devices?

Music lovers used to concerts, and musicians, because they have more landmarks - are those who recognize our approach as being the closest to musical veracity. Many home cinema lovers too, mostly when they appreciate that their movies «sound true».
In the long run, any listener can appreciate our approach. Experience showed that it will be difficult for him or her to go backwards.

2.7. Mos-fets have the reputation of having a rather warm and sweet treble sound, a dull bass, and a good midrange. What do you think of it?

We think that this is not the point. The real question is: which device, as a whole, is the closest to sound veracity? A guitar, a piano, a violin are never described as having a warm treble sound, or a good midrange, etc... either the sounds of nature, or speech or street noises. If the naturalness of these sounds is well restituted, as well as the musical interpretation, then we have approached sound veracity... «and the rest is of trifling importance...».

2.8. Aren't the figures concerning distortion the most important?

No, they aren't. Unless they reach aberrant rates - and it would be good to come up with the question of measurement methods - which will be easily detected by the ear. If the measurement revealed a distortion, and if it was undetectable by the ear, why should we worry about it? It is a little like the old question: «If a tree falls and that nobody is there to hear it, does it make a noise?», which could be transposed in : «If a tree does not make a noise while falling, and that your only concern is noise, then where is the problem?»...

2.9. It is alleged that some devices better bring out the rhythm and tempo of music than other devices. Is it true?

It is quite true. Just as some devices can give the impression that musicians play or do not play together, that all is «in place» or not...These are elements which contribute to the naturalness of the restitution, but they are not the only ones. For example, if rhythm and tempo are respected, but if instruments are not physically at their place, or the timbers of instruments are not natural, then the restitution cannot be convincing...

We prefer to envisage sound restitution as a whole that has to be rendered harmonious. This harmony allows us to approach musical and sound reality, which is our main aim in the design of devices.

2.10. We speak of «intellectualized listening» to describe some devices. What does it mean?

In general, it is rather pejorative - at least in the usual meaning. Most of the time, it indicates devices whose sound rendering is quite far from reality, lacking of life, of conviction. This does not apply to our amplifiers. If you watch an action movie with a realistic sound track and use our amplifiers on your home cinema, you will be surprised... If «intellectualized» means lack of energy, you will have as much as you wish - or rather, as much as planned by the film director. Now if «intellectualized» means that we have used our intellect (but neither more nor less than our sensitivity) to finalize our devices and approach sound veracity, then we claim it.

3. Technical

3.1. Your devices are quite bare: no bass or treble controls, no balance. For what reason?

It is a technical choice aiming at obtaining the best musicality. Controls, even left on neutral, are the cause of a loss of quality: the musical signal cannot cross cables, solders, contacts, components ... without being altered. The main objective of our electronics is to reduce these alterations as much as possible.

3.2. The sound of your electronics being more distinct and clearer than the one of other marketed devices, isn't there a risk of «listening fatigue» in the end?

It is exactly the contrary that happens: a bass which is exaggerated and bloated, and in general, a distorted restitution, are tiring for the ear... and for the brain.

Experience shows that our devices generate less fatigue when listened to for a long time than most marketed devices; our senses and mind are made to perceive natural information.

3.3. Your devices are presented with the same technical specifications, whatever their position in the range. How do you explain this?

The technical specifications that we give are for information only; they do not reflect (and cannot reflect) the essential point: the degree of respect of musical veracity brought by the device. You get closer to this musical veracity when you go up the range, thanks to technical means whose effects do not appear in conventional measurements, but are obvious when listening.

3.4. Your devices have a cottage industry aspect. Couldn't you have an industrial type finish?

Our devices are very much that of a cottage industry; let's take an example among others: the amplification cards are Teflon plates without copper, including exclusively discrete components, connected up by the component pins, or by carefully selected conducting wire. This type of assembly leads to a better respect of music and sound than conventional assembly, but to be out carried properly, it can only be realized by hand.

3.5. Would a power of 40W into 8 Ohms (the one presented by Invocation range) be sufficient on my system?

It depends: if you have mini-loudspeakers with low output, placed in a very large room, and that you favour loud listening levels...but these are not reasonable conditions. In most cases, the power of our devices is sufficient, as well as for home cinema applications. Besides, measurements here again are not enough: our devices turned out to be more powerful when listened to than amplifiers presented as being capable to deliver 200 W into 8 Ohms.

More powerful models should be launched shortly.

3.6. Is it necessary to have a special room, carefully studied and equipped to properly operate your devices, possibly with sources and loudspeakers that you recommend?

Certainly not. Most of our listenings - those of our customers and end-user listeners - is carried out in standard size rooms, furnished in a usual way.

Besides, is it essential to adapt the acoustic of your living room if you have to install a piano? If music is reproduced with enough truthfulness, it will manage to express itself where you live. Of course, extreme cases can arise: for example, a room entirely bare and empty, with large picture windows or large mirrors will hardly be favourable... not even for a musical instrument!

3.7. Are your amplifiers able to supply any type of acoustic loudspeakers?

As a rule, yes, they are. They have been tested on numerous models, standard loudspeakers (equipped with electrodynamic speakers), electrodynamic, orthodynamic, electrostatic flat-panels, ribbons...However, the wide range of products existing in this field does not allow us to be definite. In case of doubt, contact us, or make a test.

3.8. What is the benefit of pin-to-pin assembly on a card without copper track compared to standard assemblies?

Conventional assemblies are generally carried out on cards covered with a copper layer of 40 microns - exceptionally 80. Anyway, this layer is too thin to correctly conduct high intensities without widening the tracks. Even tracks intended for low intensities are in the end flat and wide. So we have a conductor which is far from being optimum: the signal will be altered in different ways. It is constituted of various frequencies, and thus may give rise to skin effects and capacitive effects...The proximity effect is neither unimportant. As a matter of fact, the ideal conductor would geometrically look like a component pin: with a cylindrical section, it would have a diameter of 0,5 to 0,7 mm. The other benefit is homogeneity: there is no brutal rupture of conduction between the conductor and the components: when listened to, the sound is more natural.

3.9. Why do you use wood as a manufacturing material for the frame of your devices?

As a matter of fact, - apart from the aesthetic advantage - wood is technically interesting: many components are sensitive to vibrations, and usual metallic frames do not help: they tend to resonate at rather high frequencies, to which the ear is very sensitive, moreover with resonance peaks registered at very specific frequency levels.

All this causes interference while listening, and part of these unpleasant effects are superimposed on music. Wood - and in particular the one used to make our frames - is much more neutral, its resonance is less punctual. As a result, listening is clearer. Besides, on our Invocation 01 high-end model, the supply capacities are assembled on a suspension system in order to minimize the vibration effects.

3.10. Your devices include a few components coated in silicone. Isn't there a risk for them to catch fire?

Our device comply with fire safety standards (included in the CE Marking) and has been checked by an independent laboratory. Besides, silicone is used to manufacture the seals of fire-proof doors...

3.11. What is the life span of your devices?

The theoretical life span of our devices is over tens of years. The first prototypes using our technology have now more than ten years and work without incident (and with the same musicality). As a matter of fact, the specific techniques used in our amplifiers are such that the life span of supply capacitors is considerably increased (usually, their life span in standard conditions does not exceed 5 years before the degradation of their auditory qualities).

3.12. What do you think of the passband criterion? Isn't it a major data to judge the quality of a system?

It is an element. But it is not necessarily significant - among other things, because of measurement methods. An examination of the impulsional response, for example, is often more convincing than the one of a simple sinusoid with variable frequency. But one has to realize that: all things considered, it is musical and sound listening which matters. Nothing can replace prolonged listening realized by numerous listeners.

3.13. Why did you give preference to mos-fet transistors as power components of your devices? Are they necessarily superior to bipolars?

In general, mos-fet transistors are interesting, because they go up very easily in frequency and are much easier to drive than bipolars. They also have other qualities, for example on the thermal level. Then, it all depends on techniques implemented. They allow us to obtain a clearer and truer restitution of sound and music. If it was not the case, we would use another technology. If our research would lead to better results with bipolar transistors, we would change without hesitation.

3.14. Do you think that one can design a device musically perfect by making it perfect to measurements?

No. What kind of measurements would it be? No measurement or series of measurements being really able to give an account of sound or musical result, it is absolutely illusory to envisage this. Regarding perfection, we can wait for it without fear of being disturbed...

3.15. According to you, what is the best type of acoustic loudspeakers? Rather conventional (electrodynamic), and in that case with what system of acoustic load: close, bass-reflex, transmission line, or rather electrostatic or other ?

Here as anywhere else, technique must be considered as a mean, not as an end in itself. If the sound restitution is clear and seems natural, then we are on the right track. It all depends - for a same technology - on means implemented, and those used for the realization. Good and less good results can be achieved with acoustic loudspeakers of all types. We can say that our devices will allow to get the most out of acoustic loudspeakers, whatever their operating mode. To know if «the most» will be enough for an appropriate sound restitution is another question. This is the reason why we prefer to recommend loudspeakers, when our customers do not have any or want to change them, or suggest to test our devices with their loudspeakers for those who are already equipped and do not want to purchase new ones.

3.16. Why don't the other manufacturers create simple devices, if this brings about advantages? Some of them do. The question is then: do they really get the most out of advantages obtained?

Simple circuits often turn out to be paradoxically more difficult to finalize than complex systems, where compensations are multiplied (which enables to have good results with measurements, but not when listening). Once you got over the finalization problem, which is elementary (if I may say so), the circuit still has to reveal its true sound and musical potential. This is what we modestly managed to do, with different means among which some are original, even exclusive to our devices. Finally, a simple circuit runs properly when it is assembled with high quality components, and that is what we do by selecting them by listening - it is much less expensive to multiply cheap components, without selection, in order to obtain good results with measurements. Of course, listening will be poor, but marketing claims will be there...

3.17. Some amplifier manufacturers put forward the size of supply capacities and their total value, to praise the qualities of their product and the energy it has at disposal. Is it important?

The size and total value of filtration capacities - which also constitute real energy storage tanks for the device - are certainly not insignificant. But these data are devoid of meaning if we do not know the size of the transformer, its technical characteristics, as well as those of the rectifier(s). Then all of this must be related to the characteristics of the amplification circuit. And this is getting complicated with a few additional subtleties which make things much more complex. In the end, it requires an harmonization with the complete structure of the device. In fact, to announce this kind of thing, is a little bit like giving the car tyre sizes. With this single element, it does not take us very far...It would be necessary to entirely describe the device, and even then, this would not be enough. Anyway, listening must decide as a final resort.

3.18. Aren't class A amplifiers the best by definition. (Since they are «First Class» devices!)?

In fact, (sorry for technicians who are already informed) class A does not mean «First Class device». Class A is the first operating mode invented for an amplifier hence this letter expressing a chronological order: it was then determined in class B, C, etc...

3.19. What does a class A amplifier technically correspond to?

This operating mode is characterized by the fact that active components (tubes or transistors) are continuously in conduction, and run through by a major quiescent current (which is a direct current).
Let's say that a device equipped with a class A output stage, with a power of 50 Watts, will continuously dissipate the double, i.e. 100 Watts (Per channel! i.e. 200 W dissipation for a 2x50 W). Which means a constant thermal dissipation, not always welcome, mostly in the summer, a bulky device equipped with huge radiators for transistor devices, and finally an electrical consumption not insignificant. Without forgetting the cost of the device itself: for the same power, a class A amplifier is much more expensive to manufacture - and thus much more expensive when put on sale. Those are not insignificant drawbacks. Besides, I must add this: owing to the major current required by a class A output stage, designers have to resort to a stabilized, even regulated supply, or to a filter inductor.
Failing which, the distortion and noise of their amplifier are going to increase, proportionally to the signal, when this one will decrease: the lower the music will be, the more distortion there will be; whereas natural sounds reflect exactly the contrary, this distortion is thus extremely unpleasant while listening. And a stabilized and regulated supply or with a filter inductor is delicate to finalize, if you want to preserve the speed and dynamic of the device. It is a little the quadrature of the circle...

Let's note here that many devices, even if they do not operate in class A concerning their output components, use it with entry transistors and/or other different amplification stages. Given the low power consumption of these stages, we can use them like this without any difficulty : it is a simple means in the principle, not in its application! - to maintain a low distortion while listening. To obtain the same quality level of the output stage, without using class A, is a bit more complicated. This is a difficulty that we have overcome.

3.20. Since amplifiers have an operating mode designated by a letter, how can a class «AB» exist?

In fact, class AB designation is an exception: it is not based on a chronological order (the invention order of an operating mode), but on the fact that it is technically intermediate. To explain this, after examining class A operating mode, it is necessary to explain class B operating mode.
Class B consists of this: the positive and negative alternations of the signal are managed by two output components (or two groups of output components) which assume the task in turn. Each output component (or group) is alternately shut off, or carrying out «its portion of the signal». The benefit of this operating mode is that it saves energy : the output transistor (or tube) is only used when necessary. Otherwise, its energy consumption is non-existent. Moreover, when it conducts the signal it is only crossed by this one, and does not have to be subjected, at the same time, to a quiescent current. The drawback, is that when passing to the neutral (in other word to the O Volt signal), there is, by definition, a component which shuts off while the other one turns on electrically. Since components are not perfect, there happens a «commutation peak» : distortion increases in a radical manner when crossing over this «border». This specific distortion is called crossover distortion. In order to minimize this problem, one applies a quiescent current: a continuous current which permanently crosses the transistors in order to avoid the commutation peaks, by always maintaining them in conduction. This current is however lower, by one or several orders of magnitude, than on a class A amplifier. We are thus in an intermediate system between class A and class B, hence the name class AB.

3.21. Is an amplifier in class A or not, or is there a gradation?

In fact, the rule - which indicates a dissipation equals to the double of the output power, if we speak of class A - is only a good approximation. Reality, as often, is a little more complex. Many factors can intervene: for example, the impedance of loudspeakers, but also marketing: it is tempting for some manufacturers to declare that their device operates in class A, even if it is only the case up to half, or even, a quarter or less of its maximal power. In the same way, there used to be and there are many assemblies which claim to be «pseudo» class A (a dozen names and may be more) which must supposedly be part of it ....without being part of it. This reminds me of a commercial for a soda! This is not our approach: our present devices operate in class AB.

3.22. What is a class AB amplifier?

An amplifier in class AB can be distinguished from a class A as follows: output components - although always «turned on», i.e. continuously conducting a current, as in class A, during the running of the device - have a very low quiescent current compared to class A, about 2 to 5 Watts for 50 Watts in output.

3.23. We sometimes hear that class A amplifiers are the most effective. Is it true?

According to us, it is not always true: you can have a very good sound reproduction with a class AB amplifier: it is the case with ours, backed up with listening test. So how is it really? Most of sound advantages supposedly linked to class A are dependent on factors which can be tackled differently: the influence of temperature on components («thermal distortion»), or problems linked to the reactivity of supplies in front of sudden and major current needs. We have mastered these aspects in our devices, with different technical means. However, if our research would lead us to obtain better results in certain aspects (or better in all its aspects) with class A, we would propose devices equipped with this operating mode. But they would be ineluctably more expensive to manufacture and to sell and would exist in parallel with our present range, which already operates better than most existing «class A».

3.24. Is it true that a class A amplifier generates less distortion than a class AB amplifier?

The two main types of distortion against which class A is supposed to immune an amplifier are crossover distortion and thermal distortion. As far as thermal distortion is concerned, the case is relatively clear: the fact that output components are continuously maintained at a high temperature avoids them from being subject to strong variations of their characteristics, according to the musical signal. This is specially true for tubes, given the temperatures reached. Nevertheless, we have our own techniques to overcome this type of problem on a class AB amplifier. For crossover distortion, we can envisage two scenarios: if it is an amplifier operating with a push-pull output stage, i.e. where two components or series of components manage in turn the positive and negative alternations of the signal, the high polarization current is supposed to avoid this type of problem. Concerning single-ended devices, where a single output component or group of components manages the totality of the signal wave, the crossover distortion is absent by definition. To conclude that single-ended class A is the only good amplifier, it is a step that we will not take: those devices have other drawbacks.
However that may be, we consider having overcome the crossover distortion on our class AB devices. Anyway, listening remains a must. This is the preponderant element which allows us to think that our approach is good.

3.25. Class D amplifiers (or digital amplifiers) are tremendously in vogue. Do they present a real interest?

For us, digital amplifiers are mostly remarkable owing to their very high efficiency (some claim 90% efficient and more). This efficiency has as a consequence, proportionally to the output power, a low electric consumption, and thus a low and light power mains supply, as well as a low emission of heat, hence small size radiators. If you want a machine capable of supplying 400 Watts per channel for a weight of hardly 10 kilos, stop looking for it. On the other hand, the quality restituted by these devices seems questionable to us. It has been said that a digital amplifier (for example, operating in class A or AB, as opposed to digital devices) was not perfect, owing to some distortions. Well, we could add that the digital amplifier is perfect, except for other distortions...

It seems that these distortions, not very obvious to show by standard measurements, are, on the other hand, easily characterizable when listening. Moreover, we must not forget this fundamental element concerning digital operating: the more the signal level decreases, the more the distortion increases. This distortion increase corresponds to the making of harmonics, undesirable harmonics in this case. Natural sounds, whether it is a voice, a bird singing or a musical instrument behave just the opposite: the more the sound level increases, the more the sound is enriched with harmonics. Digital systems have thus a behaviour in this domain which goes against the functioning and education of our nervous system. Which receives its information from the inner ear, where the chain of mechanical transmission of the sound up to the auditory nerve leads exactly to the same type of phenomenon: the generation of harmonics increasing the sound volume and that our brain is trained to ignore. So it is not surprising that formats like DVD-Audio or SACD can present an interest: they are supposed to improve the listening performances with respect to the CD. This one had to be perfect, we know now how it really was. The definition of these new formats is, in theory, more than sufficient, but everything leads to think that in practice, it would be barely sufficient...

3.26. Do class B amplifiers have an interest concerning sound reproduction?

No, they don't. The actual principle of class B leads to such a spectacular distortion (i.e. crossover distortion) when listening that these applications are excluded. On the other hand, it happened to have a marketing use: at the beginning of the eighties, a well known brand showed in a leaflet the advantage of its «pseudo class A» circuits, by comparing the photo of a sinusoid stemming from their device against a class B amplifier. It was unanswerable: in class B, the commutation peaks were nearly as high as the sinusoid, whereas their device did not show the slightest defect in output. The leaflet was very careful not to specify that any device in class A or AB, even a very basic one would do the same, whereas the class B signal, acting as a foil, was the one of a circuit used as a control system of automatisms.

Moreover, if a simple sinusoid was enough to prove the qualities of an amplifier, the perfect device would have existed long ago...

3.27. What do you think of the use of 5.1 (or 6.1 or 7.1) format for musical restitution?

We tend to prefer a listening in 4.0, i.e. with 2 front loudspeakers and 2 rear speakers, if possible identical, or at least with the same timbre characteristics (thus belonging to a same range) and capable of restituting the bass without adding a subwoofer.

To go further, the approach of Mr David CHESKY, (Mr CHESKY is a musician, runs his record company called «Chesky Records», and is an expert in sound recording) who recommends 6.0 (i.e. 2 front channels, 2 rear ones, and 2 located on the side at 55° in front of the listener) seems very interesting. We expect to test this type of installation shortly.

3.28. Isn't the central speaker - generally placed under the screen - essential to the Home Cinema ?

The central speaker is sometimes a necessary evil. Its main function is to bring the feeling that dialogues come from the screen, even if you watch the movie from a decentred position on the left or on the right with respect to the screen. It will prevent from the feeling of having the actors' voice coming from the right or left front speaker. On the other hand, the central speaker will destroy all or part of the stereophonic effects in the front. The voices will all come from the same point or almost, instead of coming from the actors' positions, and this, even for a person ideally placed in the centre or next to it.

In a movie theater, where the financial constraints require to propose a maximum of seats to the audience, the central speaker is almost essential. In your home cinema room, if the audience sits in the same zone where they could take advantage of a musical listening with a correct sound image, then the show will be better - more realistic - by turning the central speaker off.

If you sit next to a speaker - the left rear for example - it is mostly this one that you will hear. So you might as well stay in a «reasonable» use zone of the system.

4. Home cinema

4.1. Doesn't the restitution of movie soundtrack - the home cinema - require specially elaborated devices?

If you want to faithfully reconstitute the atmosphere and the noises, correctly hear the dialogues with all their subtleties, approach as much as possible what the director wanted, then our devices are the better placed to do that. Amplifiers dedicated to home cinema are most often studied to appear flattering, by exaggerating the effects. The atmosphere is not natural; the bass tone is too present - often omnipresent, treble is softened - or exaggerated, which is not better. Here as in music, we prefer to look for veracity rather than easiness. Moreover, our devices, owing to their design, allow to obtain an exceptional intelligibility, even when a very powerful sound is associated with very thin or even tiny sounds: everything «remains in place», everything is natural and clear.

4.2. When I watch «2001: A Space Odyssey», I can't hear the noise of the spaceship. Is it normal?

Yes, it is. The space void cannot convey sounds... but for production needs, one can decide that it is capable of doing so, as it is the case in many other science fiction movies. We could call this a poetic licence...

4.3. Isn't it better to have a Home Cinema amplifier with an integrated 5.1 (or 6.1, or 7.1) decoder rather than a separated decoder system or integrated into the DVD player?

The proximity of the amplifier and of the decoder, both contained in the same frame should be an asset for amplifiers with an integrated decoder; as a matter of fact, it is the opposite that happens. In order that a decoder integrated into the amplifier operates better, the supplies should be first of all separated - because they have different requirements and operating modes: the supply of the power amplification section requires a lot of energy, it is highly solicited by major power calls. The supply of the decoder, much less greedy in power, requires stability and - at a high level - subtlety. In practice, on a device with an integrated decoder, it is secondarily supplied in relation to the power section. We are a long way short of the target: the reciprocal influences between the power amplification part and the decoding part are inevitably significant. We can say reciprocal since a major need in energy on the power section will influence the decoding, which will pass on this problem to the power output by supplying it with a distorted signal, and so on.

The situation is, in principle, better for a decoder integrated into a player, if the supplies of the player and of the decoder sections are sufficiently independent: the power needs of a player, although not insignificant, are not of the same order than those of a high volume power amplifier.

Of course, considering what has been said so far, the ideal is to have a decoder situated in an independent frame, equipped with its own supply - which also enables to minimize influences by radiation.

In fact, we can see here again the situation which prevailed for digital input amplifiers - i.e. with an integrated digital/analogical converter - which were put forward by leading manufacturers about fifteen years ago: the idea seemed good, but the results were disappointing. Players with integrated converter - the majority on the market - are more effective when listening. Finally, most of the time, the best results are obtained with separated converters: it is the same logic.

4.4. Isn't it better to have a 7.1 installation rather than a 5.1? (or a 6.1 rather than a 5.1)?

We are not in favour of channel multiplication for the sake of it. In fact, backed up with tests and demonstrations, our devices already operate better in 4.0 (2 front loudspeakers, 2 rear loudspeakers, nothing more!) than most 5.1, 6.1, 7.1 systems of the market. Additional channels must be used according to real need, with discernment.

4.5. Isn't the presence of the subwoofer imperative in a Home Cinema system?

According to us, .1 (in other words, the subwoofer in a 4.1, 5.1 system) is only useful if the main and rear speakers have already a lack of extreme bass in the room concerned. Moreover, to do things properly, we should pass in .2 : there should be a subwoofer per front loudspeaker, judiciously positioned...The ideal solution being to place the subwoofer under the loudspeaker! Failing which, the sound image tends to vanish (you can then hear each loudspeaker instead of an homogeneous unit) or to «polarize» towards the subwoofer. Anyway, if during decades, the loudspeaker systems called «triphonic» remained relatively marginal with music lovers, there are some reasons. These are linked to live wire questions - the bass below 100 Hz is of course omnidirectional, but the question of its synchronization with the rest of the signal is not insignificant. With 2 loudspeakers, it is already delicate, so with 4, 5 and more! - but also to harmonic problems. Even if you only leave the lower frequencies (30 Hz for example) to the subwoofer, it will inevitably generate harmonics, thus multiple frequencies from those reproduced, in a more or less large quantity, according to its adjustment level, to the material used, and many other factors. These harmonics can rise high in frequency, and inevitably indicate the presence of the subwoofer - mostly if it is placed away from the loudspeakers, for example for aesthetical reasons.

4.6. Will the monophonic units that you intend to realize be «specific to Home Cinema» concerning their sound or their technical specifications?

For us, it is groundless. A properly designed amplifier must be able to deal with any type of modulation. What would «more natural than natural» mean? These devices will be capable of reproducing music as well as a movie soundtrack. The fact of having a power unit per speaker - with each channel equipped with it own supply - can make the choice of a home cinema lover, but also a music lover.