Tube sound - myths and facts. The best tube amplifier: characteristics and reviews Tube sound myths and reality

Conversations about which is better, transistors or tubes, have been going on since time immemorial. The dominant opinion of about twenty-five years smoothly and, accordingly, imperceptibly changes to the opposite. And if in the early seventies the number of transistors on which this device was made was indicated on transistor receivers (it was assumed that the relationship between quantity and quality was direct), then in the late nineties holes were drilled in the front panels of the equipment so that we could see the sacred fire of the lamp or lamps inside ultra-modern pre-amplifiers or sound processors, and tremble just from this alone. A thrill of this kind, in general, is not a bad thing - the emotion is rather positive. But for it it is proposed to pay additional money and, as a rule, considerable money. Manufacturers of lamp equipment, naturally, are trying to strengthen our confidence that if the device is lamp-based, it means it is certainly good. They have always tried to do this, but this time, due to the fact that the evolutionary spiral has almost completed a full revolution, they seem to be succeeding, and at present we are in the first stage of the tube boom. This is also confirmed by the fact that the question “Why is it so expensive?” The answer has become the norm - “What do you want, it’s a tube one.” It is advisable to meet the boom fully armed - with a sober head and a clear understanding of what you need. It is not simple. If it is quite difficult for a sound engineer with many years of experience in his specialty, who has heard a large amount of both tube and transistor equipment, to hang his head around it, then it is easier to confuse a semi-professional or amateur musician, of whom the majority are. The ability to compare the sound of different equipment is very limited. Information received from sellers of musical equipment, flavored with rumors (often inspired by manufacturing companies), fashion and pathos that accompany fashion, is far from the best platform for choosing equipment.

First of all, you need to understand how tube sound differs from transistor sound and why. It seems to me beautiful, laconic and, moreover, almost sufficient, the following explanation: well, in fact, in a transistor the sound is born in a crystal, and in a lamp - in a vacuum. It is difficult to imagine environments more dissimilar. So how can the sounds not be different? Ice and fire! Here I am not original, since articles devoted to this topic in foreign magazines are often published under headings like: “Warm and Cool”, “Hot or Cold”, etc.

In one of these articles, in which the author quite convincingly proves the superiority of a tube over a transistor in all respects (however, for some reason it does not mention such an important sound indicator as noise), an interesting explanation is given for the attractiveness of tube sound using the example of use in seventies classic condenser microphones with tube preamps. The fact is that these microphones have a very high signal level (up to 1.5 V) and the preamplifiers are forced to almost constantly work with overload. When the tube is overloaded, firstly, natural compression of the sound occurs, as a result of which it is perceived as more “dense”. Secondly, the sound is distorted, as a result of which it is enriched in harmonics. In tube technology, the location of these harmonics in volume practically coincides with the overtone series, that is, the second (octave), third (fifth), fourth, fifth, etc. harmonics are added, which is subjectively perceived as a pleasant, “musical” sound. A similar principle of enriching the original signal with harmonics is used, for example, in a device such as an exciter.

When transistor technology is overloaded, the sound is also distorted, but the signal is saturated mainly with odd harmonics, that is, the third, fifth, seventh, ninth, etc. Of these, the seventh and ninth harmonics are dissonant, which, to put it mildly, is not pleasing to the ear and is perceived exactly as it is - as a distortion.

Since the sound of transistors and tubes is seriously different from each other, it is obvious that the options for using equipment built on such dissimilar components must be different. Apparently, in some cases a lamp is preferable, and in others a transistor is preferable. To answer the question - why is it better to use both, it is necessary to give general sound characteristics of both tube and semiconductor sound devices. The latter are usually called “solid state” in non-CIS countries.

So, the lamp.
Pros: it sounds warm, and when overloaded it gives the sound additional “musicality”.
Disadvantages: noise (as a result of the difficulty with high-quality amplification of low-level signals), bulkiness, short service life (some guitarists are forced to change the tubes in their amplifiers every month), do not tolerate transportation well, low efficiency (most of the energy consumed by tube equipment is spent on heating the room , which can only be welcomed in winter, and even then only when the heating is not working).

Transistors and other semiconductors.
Pros: correctness, uncolored sound, low noise, compact semiconductor devices, low energy consumption.
Cons: dry sound, sharply deteriorating when overloaded.

As we see, the characteristics are diametrically opposite - what is good for lamps is bad for transistors, and vice versa. Particularly successful is the use of lamps in overload mode, that is, where it is necessary to change or color the original signal. In this case, tube equipment (be it a microphone preamp, compressor or guitar amp) becomes like processing, the simplest (but, as it turned out, far from the worst) effects processor. A striking example of the use of lamps as sound insulation is the TL Audio Valve Interface device - an eight-channel device that has eight inputs, eight outputs and a power switch. Not a single adjustment. And inside there are lamps that can simultaneously insulate something eight-channel, for example, ADAT. Transistor technology is best used where uncolored sound, low noise and distortion levels are especially important.

In general, it seems to me that it is quite possible to apply the theory of gender to the “characters” of transistors and lamps and take this into account when selecting equipment. The lamp is clearly a lady. Its sound is smooth and comfortable, it tolerates overload well (transforming unfavorable circumstances into favorable results) and can make your inexpensive dynamic microphone sound like a large diaphragm condenser microphone (women tend to exaggerate). Tubes have a clear advantage over transistors in guitar equipment. It must be said that guitarists in general are a very conservative people and, in essence, did not switch from tubes to transistors, or, in any case, always preferred tube sound. But as studio control equipment, tube technology, apparently, should not be used - what is needed here is an uncompromising, minimally colored, non-misleading sound of transistors. He will not wishful thinking - you can rely on him. In a word, the sound is masculine.

A completely logical question arises: is it really not possible, with the modern development of electronics, to make the sound of a transistor device warm, and a tube device reliable? Of course you can! And such a technique exists. It costs a lot, though. For example, the Tube-Tech PA 6 studio reference tube headphone amplifier, which produces uncolored sound, costs US$1,999. So I propose not to use special women as bodyguards and no less special men as office assistants. But if exotic lovers want to pay, then, naturally, no one can prevent them from doing so...

Now about the prices. Semiconductor and tube devices that are similar in class should have comparable prices. Yes, the tubes themselves are more expensive than transistors, but tube devices are much simpler and contain an order of magnitude fewer parts (this is also why tube adherents today explain the amazing sound quality of their sponsored devices). However, historically, tube equipment is still somewhat more expensive (there are pleasant exceptions: for example, the very decent ART Tube MP microphone preamplifier costs $199). Somewhat, but not many times, I ask you to keep this in mind when, at the height of the lamp fashion, they will offer you for crazy money everything that has at least something glowing in it. In general, today only Ilyich’s light bulbs or devices that replace them (for example, kerosene or oil lamps) can be considered absolutely necessary.

Some professional audio companies are making tube-semiconductor combinations, trying to combine the best qualities of tubes and transistors, thereby proving that the horse and the quivering doe can be used as draft power if done wisely. An example is the Aphex Tubessence 107, a solid-state tube mic preamp that won the 1995 TEC Accessory Award. The English company TL Audio has also achieved some success, making preamplifiers, compressors and equalizers, in which semiconductor input stages are based on low-noise microcircuits, and the stages directly responsible for compression or frequency regulation are made using tubes. As a result, the signal to the lamps is already amplified, which makes it possible to obtain an overall decent signal-to-noise ratio. Thus, semiconductors provide low noise, and tubes do exactly what they are good at: compressing and insulating sound. Idyll, and nothing more.

I really want to believe that a path to a compromise has been found and that the future lies in combined technology, in which, like in a happy family, the heroes of this article will live, complementing each other, delighting you and me and rejoicing themselves. Moreover, today the reviews about the combined equipment are very encouraging.

It is also necessary to mention the Hi-End equipment. This is where the use of lamps is absolutely justified, since this equipment serves exclusively to please the ear and should sound as beautiful as possible. Although the authors of audio magazines, in my opinion, have long ago completely confused two such concepts as the beauty of sound and its naturalness, and often equate these two, not always coinciding, concepts. In the high-end world, the tube sits unshakably on the throne and, since the intolerance of audiophiles is soon to become proverbial, the most relaxed of their descriptions of transistor technology is the maxim: “A good transistor amplifier is an unplugged transistor amplifier!”

In parting, I would like to repeat that you need to approach the choice of equipment calmly and carefully. Phrases like “only a lamp” or “transistor - definitely!” would be funny if it weren't so unpleasant to communicate with people who are prone to similar approaches. Where peremptory behavior begins, competence ends, and these people prefer swearing to arguing. So I advise you to doubt - listen - read - think. Good luck!

An interesting point of view from Pavel Makarov. The author’s presented arguments are very, very reasonable; there is quite a lot of common sense in the thoughts. That is why the information is provided on my website.

Vacuum tube enthusiasts often classify solid-state sound as "harsh" and "transparent", while they refer to tube sound as "warm". If we continue the analogy of a transparent window to the world, used by Robert Harley in his Encyclopedia of Hi-End Audio, to characterize undistorted sound reproduction, we can say that adherents of tube sound insert frosted pink glass into their window frames. A pleasant sound is not a measure of quality and reliability. Midrange instruments such as an electric guitar, when played through a tube amp with high second-order distortion, will sound convincing. However, if you try to reproduce the sound of a good concert grand piano through the same amplifier, it will become “wobbly” and lose all the nuances. And attempts of various kinds to “improve” a lamp UMZCH are as pointless as speeding up the operation of a mechanical adding machine: it will never be able to work faster and more accurately than a simple electronic calculator.

Now let's go through the shortcomings:

1. The reactive nature of the output transformer in tube amplifiers causes significant phase shifts in the audio signal, especially at the edges of the audio frequency range;

2. Since the transformer is a nonlinear element with distributed parameters, when the tube amplifier covers the general OOS, it turns into a modulating comb filter of audio frequencies;

3. Tube amplifiers do not adequately reproduce pulsed signals and transients (due to the reasons mentioned above);

4. In nature, there are no lamps of opposite conductivity, which makes it impossible to build completely symmetrical, “mirror” circuits, free from even harmonics;

5. The low slope of the current-voltage characteristic (CV) of lamps does not allow the implementation of amplification stages with a high gain and/or low output resistance, as well as high-quality transformerless amplifiers (with a small number of amplification stages);

6. Due to their large geometric dimensions, the lamps are inferior to modern transistors in terms of dynamic characteristics, which does not allow the implementation of a sufficiently broadband (even transformerless) tube amplifier;

7. The speaker impedance must be matched to the taps on the output transformer, and most tube amplifiers are not universal when driving a wide range of loads;

8. Tube amplifiers have very low efficiency due to the need to heat the filaments;

9. Tube amplifiers exhibit lower reliability than well-designed semiconductor devices and are more susceptible to component aging due to temperature cycling as well as emission loss;

In conclusion, there is an interesting observation mentioned by some authors. It's understandable that audio engineers in recording studios pay top dollar for the very best audio equipment, since their livelihoods depend on the highest quality audio achievable at any price. If tube amplifiers provided higher sound quality than transistor ones, then every recording studio in the world would be equipped with tube amplifiers. In fact, with the exception of a tube guitar amp, you will never see a tube amp in a decent recording studio.

Bravo! Pavel Makarov, there is no such thing as too much common sense.

You can try to formulate objections in accordance with the stated order of Pavel Makarov’s claims to the miracle lamp technology. I would like to make a reservation right away that the thoughts expressed should not be considered a confrontation with the respected author. For the most part, these are just amendments, corrections of inaccuracies and clarifications of substance, often justified claims. Personally, I have no prejudice against transistor technology, just as I have no fanatical adoration of tube monsters. I would like to think that I am closer to a balanced and reasonable assessment of the merits of all devices for sound reproduction, performed at a high professional level and with great responsibility for the result. I would like to always have this approach and call it the approach of common sense prevailing.

Disadvantage 1. The reactive nature of the output transformer in tube amplifiers causes significant phase shifts in the audio signal, especially at the edges of the audio frequency range.

Not fatal at all. The nature of the output transformer is truly reactive. There is quite a lot of passive reactance in any amplifier. And you shouldn't faint from this. There is a simple and ironclad argument in favor of a transformer. This passive element and it does not have a control function (unpredictable intervention) like active nonlinear amplifying elements. The transformer only transmits the signal, adapting it to the load with given operating parameters. And the benefits from the nature of the transformation phenomenon of the output transformer, in the sense of matching the resistance of the lamps and the loudspeaker, are much greater than the harm. The indisputable advantage of the tube amplifier itself can be considered the minimum number of nonlinear active amplification elements harmful to sound and the absence of transistor p-n junctions that are toxic to sound.

Disadvantage 2. Since the transformer is a nonlinear element with distributed parameters, when the tube amplifier covers the general OOS, it turns into a modulating comb filter of audio frequencies.

The description of the second drawback is incorrect. A mess of judgments.

Firstly a nonlinear transformer is used in the most linearized mode in a home-made amplifier, which is carefully tuned precisely in order to achieve the highest possible quality. The nonlinearity of its characteristics is significantly compensated by circuit solutions and operating restrictions, so that even at the edges of the frequency range it is possible to provide a level of nonlinear distortion, which creates a result that is practically inaccessible for a serial, poorly tuned transistor amplifier. Perhaps only a fanatic would set up a serial household transistor amplifier and select its components according to the required level of quality. People use ready-made products, often with shitty quality transistors. But lamp things are made in single samples and set up quite carefully, selecting lamps, of which there are only 3-4 pieces in the product, and not 30-40 transistors. In fairness, it must be said that all amplifiers need to be configured conscientiously and efficiently. But the reality is completely different. And this is an iron fact that you cannot argue against.

Secondly, it is absolutely incorrect to declare the output transformer of a tube amplifier as a device with distributed parameters. This is either deceit or incompetence. There is no point in going into the wave computational domain, creating calculated errors that are an order of magnitude larger than standard engineering methods. There is no need to declare a device with lumped parameters and a known equivalent circuit as a wave object, especially in the audio frequency range. But in fairness, I can note that I have come across “scientific” publications in which the wave object was considered to be leafy wooden poles of power lines at a frequency of 50 hertz. And also other similar crap. This is a mind game on the verge of schizophrenia. In connection with the above, I suggest that you remain of sound mind and sober memory and not wander into the darkness without understanding the concepts.

Third, the generalization that the transformer turns into a comb filter when using OOS requires specification, i.e. confirmation by calculation. We need specific values ​​of the system parameters and a set of conditions under which such a feature becomes possible. In electronics, nonlinearity is considered by numerical methods and only in conservative systems with lumped parameters. In radio engineering, nonlinearity is generally assessed approximately, and what the distributed parameters have to do with it is not clear. It is advisable to be more careful in terminology, otherwise you may end up with a “modulating” squirrel. No matter how much one would like to see a miracle, the transformer does not turn into anything, but remains a piece of iron.

Disadvantage 3.Tube amplifiers do not adequately reproduce pulsed signals and transients (due to the reasons mentioned above)

Not fatal at all. Well, there are spots in the sun, so what? There are limitations in transmitting a pulse signal through a lamp. The conversion is not entirely correct, the speed limit is obvious, the frequency band is narrow and there are quite a lot of accordions. But on the other hand, they are all relatively small in amplitude, and the tail is of limited length. Therefore, they are not at all evil, like semiconductor technology, for perception by the human ear. An ordinary transistor amplifier will make a “gift” that is much less accurate and incomparably less pleasant to the ear. The question of the measure of adequacy is important here. And this measure turns out to be quite sufficient with careful tuning of a tube amplifier created from a minimum number of elements.

Disadvantage 4.

Absolutely fair statement, there are no lamps with the opposite type of conductivity. But this is not fatal either. But there is a vacuum, a completely neutral environment with respect to charge carriers. And it’s impossible to ensure complete symmetry, right. Is this fatal? Look in the mirror, is facial asymmetry really a fatal disease? I think no. Maybe we should add some common sense, literally a little? You need to try to apply rational circuit solutions for the double-stroke skeleton and not push the load mode to the limit. Most likely, luck will smile and you will get a very decent quality tube amplifier. After all, even on a clumsy, asymmetrical mug, some people manage to attach the crown of European monarchs and wear it for decades.

Disadvantage 5.

Has very little to do with tube amplifiers. And you don’t need a lot of steep characteristics. There are quite enough available in-lamp resources. Even without this, the direct sound path of the lamp lamp contains only 3 lamps. And at the same time, a full-scale high-quality audio amplifier is realized. Maybe I don’t understand something, but it’s difficult to create a sound amplifier with three transistors. But quality comparable to that of a lamp is impossible. As far as I know, it is the lamps that have a resistance - less than transistors in relation to the load. Transformerless amplifiers are not needed by ordinary people. Exoticism and various anomalies are generally the lot of select “special” people. chosen by God or Satan. I present my own position within the framework of the lifestyle of a community with a traditional orientation.

Disadvantage 6.

The disadvantage is not obvious, not at all obvious. What do they say in everyday life? And they say that size matters, and they say it with a plus. But in relation to a different subject. And with regard to the broadband of an audio device, a high level of quality, there is a standard. A strip wider than according to GOST is hardly necessary. And therefore, I consider the statement about disadvantage number 6 doubtful. This drawback is not obvious given reasonable restrictions on consumption. Well, marketing extremes and extremism are often observed in many ways.

Disadvantage 7.

Tube amps really aren't universal. like transistor ones. And that's not bad at all. The requirement of universality is redundant in relation to the subject of narrow specialization and high quality. It basically contradicts the purpose of a tube amplifier. It is unreasonable to demand versatility from a Rolls-Royce in order to carry potatoes on it. A specific tube amplifier is designed for a specific acoustic impedance with minor variations.

Disadvantage 8.

The low efficiency of a tube amplifier is an indisputable fact.. There is no escape from this, the heat consumes up to 50% of the electricity. But who does this hurt? And to what extent? You need to realize that these are microscopic losses, in comparison with even unnoticeable household losses of electricity in the form of one light bulb on, in the toilet of a forgetful TV viewer. Efficiency is not at all a determining factor in the quality of sound amplification. This indicator has nothing to do with the concept of sound reproduction quality.

Disadvantage 9.

It is true and undeniable, lamps are getting old. Man also has this shortcoming, he shoots. And this is a much more significant drawback, since it is irreversible. And the aging of tube amplifier components is an easily fixable problem. Moreover, this is a much less noticeable problem than frequently repairing a car on bad roads or regularly changing the engine oil. Once every few years, you can start replacing the vacuum tubes in the amplifier. This somewhat enlivens life and brings variety to it.

Disadvantage 10.

The output impedance of a transformer really cannot be reduced radically. And increasing the resistive resistance actually changes the nature of the oscillation somewhat. However, this is the lesser of the evils of connecting a tube amplifier with multi-band acoustics equipped with high-order crossover filters and compression speakers. Much worse is the decrease in the reliability of sound transmission due to a sharp increase in phase distortions at the interfaces between the bands. And that is why you should not use multi-band acoustics with crossover filters for a lamp. A tube amplifier requires broadband acoustics without filters. Well, this is ordinary objective reality. Everyone is accustomed to the fact that the wheels of a VAZ car and a Mercedes are different, and the wheels of a Belarus tractor are completely different. This is probably a drawback.

I'll add the rest later.

But the words spoken by Pavel at the end of his original article are rational and accurate, there is no point in even commenting. Indeed, studio amplification equipment is of an extremely high class, built on semiconductors and tuned to very high quality. But the price tag for such equipment is cosmic, which makes the described material objects inaccessible to all television viewers without exception. Yes, they don’t need that. There is simply nothing to argue about here. I always guessed that a well-tuned tube amplifier was quite accessible to the average TV viewer. But high-quality transistor sound from equally high-quality transistor equipment is fundamentally unavailable.

Prepared a note based on the publication materials

Evgeny Bortnik, Krasnoyarsk, Russia, June 2016

Having acquired some practical experience in constructing ULFs using tubes, and having read a significant amount of literature and forum discussions, I allow myself to note that, as around any practically important and at the same time difficult to strictly scientific analysis issue, the ground arises for the emergence of various kinds of myths, and tube sound is no exception. True, I honestly admit that due to the inevitable degree of subjectivity in the perception of sound, this article should be taken only as my personal opinion, IMHO.

Myth one. The larger the Raa (or Ra) of the output transformer, the higher the sound quality. This myth has a simple basis - the higher Ra, the lower the harmonic coefficient (however, this is only true for a triode). But as has long been established, tube amplifiers are inferior in terms of harmonic distortion to transistor amplifiers, but this does not make them sound worse, quite the contrary. My experience is that as Ra increases, the sound of the amplifier becomes analytical, flat (the width and depth of the stage narrows) and emotionally unexpressive - this is especially felt for triodes - although it remains very clean tonally and accurately detailed. In the general case, the most optimal is the ratio, well known from theory, Ra = (2 – 3) Ri for a triode and Ra = 0.1 Ri for a pentode, although practically for different lamps and transformers this ratio can vary within certain limits. There are also known exceptions to the rule - 6S41S and 6S19P, and other lamps with high transconductance for power supply devices - for them Ra = 5 - 8 Ri is the norm.

Myth three. The sound of the ULF improves if the output impedance of the preceding stage (preamplifier, phono stage, tuner, etc.) is as small as possible, and the input impedance of the ULF or subsequent stage is as high as possible (this myth partly echoes the first one mentioned above). This myth, like the previous two, also comes from theory. It is clear that this reduces losses, minimizes harmonics, and facilitates the operation of the output stage on the line (if there are interconnect cables). But this is theoretically correct for a mono sine wave signal. But music is not a mono signal. And not a mechanical sum of mono frequencies. This is a very complex wave system that is difficult to accurately analyze mathematically. I would say this is a stream of sinusoids of various frequencies, amplitudes, phases, which, like all wave systems, is capable of interference (intermodulation) and diffraction. And the task of the ULF is to convey this flow (more precisely, its structure) from beginning to end unchanged. But significant impedance differences disrupt the structure of this flow. Therefore, for example, you should not install a 6N30P cathode follower at the end of the phono stage if you have an ULF input impedance of 100 kilo-ohms. The use of a cathode follower (100% OOS) in combination with its very high input impedance has a particularly bad effect on the transfer of volume of sound images. One of the few elements that can preserve the structure of the sound flow with a significant difference in impedance is a transformer - this is why the Japanese pay so much attention to the design of these devices, and successfully use them not only at the output of tube ULFs, but also as an interstage one. As a result, a high-quality ULF circuit capable of conveying all the nuances to the listener, including such concepts as volume, depth and width of the stage, image detail, should not have significant impedance differences between stages. Deep OOS can also disrupt the structure of the musical flow, but this is a separate discussion.

Myth four. OOC kills sound. The reason for the appearance of this myth is not entirely clear, but perhaps it lies in what in philosophy is called the negation of negation, or, more simply, a hangover after the craze for ULF with OOS at the end of the last century. In the 80s and 90s, in Radio magazine it was difficult to find a ULF circuit in which the authors would not present the presence of deep and/or multi-loop feedback as a means of improving the quality of the amplifier. Time passed, and now, when it became clear that everything was not as good with OOS as it seemed, now high-end apologists have gone to the other extreme - no OOS at all! Of course, this is much simpler - you don’t have to calculate phase shifts and fight self-excitation - you just don’t have to do OOS and that’s it! Here, I would compare some of the creators of false high-end on triodes without OOS to an unlucky cook who claims that the most delicious soup comes only from pure potatoes - and no tomatoes, cabbage, and God forbid, spices! It seems to me that a small (shallow) OOS, especially in powerful (and as a result, multi-stage) ULFs, is very useful for reducing distortion and increasing the stability of the amplifier. And it does not at all disrupt the sound flow mentioned above, but on the contrary, sometimes it introduces a small but very useful “reverberation” into this flow. The introduction of OOS has another advantage - the amplifier becomes less sensitive to the selection of components - it already plays like a complete circuit with its own style, and not as a set of isolated parts or cascades, on the selection of which you can spend a fortune and a lot of time - and never achieve conclusion, what influences what here and what the final result depends on... And it’s better not to talk about the reproducibility of the results at all.

Half-myths. For example, that fixed offset sounds better than automatic. Perhaps for some lamps, other things being equal, this is true. But under equal conditions. But how to comply with them? Open any reference book on lamps. Let's take 300V for example. It says in black and white that the maximum resistance of the grid resistor with automatic bias is 250 K, and with fixed bias - 50 K. The difference is five times. Well, how can you “improve” the sound of classic 300V ULFs with automatic bias? After all, it is necessary to reduce the resistance of the grid resistor! But then off we go - accordingly, we need to increase the capacity of the interstage capacitor five times - that's one, reduce the output resistance of the previous stage... - two, and install a separate power supply circuit of negative polarity - three..... After such an “improvement”, which is more correct Call it a major overhaul, it's unlikely your amplifier will sound any better. At a minimum, you will be faced with the fact that the sensitivity of your “improvement” has become lower, and a preamplifier is already needed... Or then you will have to design a new one, with a different, cooler lamp in the swing... So much for an improvement. Or maybe it’s still easier to buy a good electrolyte for the cathode resistor and still leave it automatic? Think! By the way, let me remind those who like to work with triodes that they are more sensitive to overestimation of the grid resistor (I suspect that this is why one of the filament halves often burns at 300V); in this regard, pentodes work more stable. So this is an additional argument in favor of using pentodes in the final stage with a fixed bias.

Another half-myth. The larger the output transformer, the better. The reason for this myth probably lies in the same place as the reason why so many people prefer to drive around the city in jeeps (or drive alone in minibuses), or why “size matters.” Yes, there is no doubt that a transformer of significant size will produce deeper bass, but this is where the list of its advantages ends. Even if we don’t talk about the price or the high costs of materials and effort for its manufacture, such a transformer will not be able to provide an acceptable bandwidth at higher frequencies, and the likelihood of mechanical resonances in the windings and core is very high. In addition, if we take into account the magnetic losses in the core, which inevitably increase with increasing weight of the iron (even if you work with a slightly lower value of magnetic induction), then it follows that an increase in losses will lead to a decrease in detail in the transmission of nuances. Below is a picture of the dependence of losses in the core depending on the magnitude of magnetic induction. And this is for one of the best brands of transformer iron - M6, it is clear that with OSM, TS, etc. iron available on the market, the situation is even worse. Additionally, on this topic, I would like to quote a passage from the publication www.gendocs.ru/v4971/?download=3

Energy losses during magnetization reversal

This is an irreversible loss of electrical energy, which is released in the material in the form of heat.

Losses due to magnetization reversal of a magnetic material consist of losses due to hysteresis and dynamic losses.

Hysteresis losses are created during the process of displacement of domain walls at the initial stage of magnetization. Due to the heterogeneity of the structure of the magnetic material, magnetic energy is expended to move the domain walls.

Energy loss due to hysteresis

Рг = a*f

Where A– coefficient depending on the properties and volume of the material; f– current frequency, Hz.

Dynamic losses R Tue caused in part by eddy currents that arise when the direction and strength of the magnetic field changes; they also dissipate energy:

Pw = b*f*f

Where b – coefficient depending on the electrical resistivity, volume and geometric dimensions of the sample.

Eddy current losses, due to their quadratic dependence on field frequency, exceed hysteresis losses at high frequencies.

Dynamic losses also include aftereffect losses. R p, which are associated with a residual change in the magnetic state after a change in the magnetic field strength. They depend on the composition and heat treatment of the magnetic material and appear at high frequencies. Aftereffect losses (magnetic viscosity) must be taken into account when using ferromagnets in a pulsed mode.

Total losses in magnetic material

P = Pg + Pvt + Pn

…….”

Please note that all loss formulas include a quantity such as volume, which is directly related to mass (through density). Moreover, the formulas also include frequency, sometimes to the second power, which suggests additional losses of information in the high-frequency range.

An example of myth-busting is a great-sounding American push-pull stereo (two channels of 35 watts each) DYNACO ST-70 amplifier on an EL34 pentode, which, by the way, also has shallow OOS. I bought it from the American audio enthusiast Bob Latino in the form of a whale, and while I was moving my workshop from Riga to Balgale, my friend Stanislav assembled it for me, for which I thank him very much. Unlike the classic device, it has an improved preamplifier. Here is the diagram (there is an error in it - capacitor C5, like C3, should have a value of 0.1):

So the sound of this amplifier is powerful, but at the same time voluminous, detailed and dynamic even at low volumes. You can listen to it even with one speaker - you get the full impression of a stage. Because it has OOS, it is not very sensitive to tube and capacitor changes. Selecting lamps, I managed to get simply magnificent, tonally balanced and at the same time surround sound with 6P3S-E lamps instead of EL34 (fortunately they have the same pinout). Fans of wide sound will like EL34 (or KT77) FROM JJ - they have elevated bass and treble. The 12AT7WC PhilipsJAN is very good as a bass reflex; on e-Wow they sell for 6 - 8 dollars per piece. In many ways, the volume of sound depends on the first tube; I currently have a 6201 Valvo installed, but I’m looking for a cheaper replacement. Interstage C7 and C8 - Mundorf MCap, 35 Euro for 4 pieces, but the K40U-9 also worked great - this is a rare case when replacing Soviet capacitors with Mundorf ones did not change anything in the sound. Kenotron – 5AR4 from China. The transparency of the amplifier's sound greatly benefited from connecting it to the network through a surge filter, apparently for the reason that there is no filtering of RF interference through the power supply at the amplifier input. Now I’m listening to this masterpiece with inexpensive Phonar three-way floorstanding speakers. To compensate for the RF weakness of the 6P3S, the amplifier is connected to the speakers with a silver-plated speaker cable from Qued: http://www.qed.co.uk/173/gb/product/speaker_cables/silver_anniversary-xt.htm. As a result, I inadvertently finally received a recipe for “how to cook 6P3S?” “-before I couldn’t make anything worthwhile out of it. But this is a separate topic.

March 6th, 2011 , 09:10 pm

TLZ. As if the devices show that transistor amplifiers are better. But audiophiles praise tube ones.

I once read in one forum that supposedly a large part of the TLZ feature is that tube amplifiers have a poor connection with the speakers in terms of voltage, and more so in terms of current. That, supposedly, if you take “tube” speakers and connect them to a transistor amplifier through a ballast of several ohms, you will get a good approximation of TLZ.

If the speaker is driven by current, the inside and outside of the speaker will be more acoustically coupled. In this case, external sounds will be able to resonate with the insides of the speaker, as if it were completely disconnected from the amplifier, but internal reflections will just as easily come out instead of accumulating.

It is clear that in reality there is something in between.

In general, speakers are usually designed on the basis that they will be controlled by voltage, not current. But, on the other hand, if we control the speakers with current, then, although we will get harmonic distortion on the electric filters and the dynamic head, we will reduce the influence of re-reflections, which, in theory, can greatly spoil the impulse response, and even add nonlinearities.

Has anyone looked into this issue? Have you tried driving the speakers with current? Or include a resistor in the circuit, as some advise? How does the sound change?

UPD: “Tube” speakers are speakers intended for use with tube amplifiers, they differ in the type of dependence of the complex electrical resistance on frequency, I don’t remember what exactly the difference is.

UPD2: I took a 3-way speaker and tried to tap the mid-range speaker with the circuit shorted and open. The sound is different. When the circuit is short-circuited, the sound is sharp and elastic, as if knocking on plastic or a tightly stretched rigid film. When open, the sound is also elastic, but soft and lubricated, as if knocking on a tight sofa or hanging carpet.