یکی از کسانی که متفاوت فکر میکنه مثل آرتور و رومی و مایک و جین و لین اولسون و … آقای گیزمو هست. مقالات ایشون رو تو آدرس زیر میتونید بخونید:

 http://www.meta-gizmo.net/Tri/index-1.html

 بنظر من دکتر نوشته های جالبی داره و یکی از قوانینش اینه کیفیت صدای آمپلی فایر رابطه معکوسی با توان اون آمپلی فایر داره. R=1/P

این دکتر در مبحث ترایود ها مطالب جالبی نوشته و همونطور که میدونید طراحان این سیستمها مثل ریچرت Herb Reichert، کوندوسان Kondosan ، شیشیدو Nobu Shishido ، ساکوما Susumu Sakuma هر کدوم نظری برای کوپلینگ بین طبقات و طبقه آخر دارند. گیزمو  (Inverted Interstage Transformer coupled) شیشیدو رو دوست داره (به اختصار IT-coupled) و البته از سیستم جدید دیوید برنینگ هم خیلی خوشش میاد. دیوید راهی کاملا متفاوت رو طی کرده ، بعضی ها بدون ترانس هستند OTL بعضی ها با ترانس و دیوید برنینگ اومده از سیستم جدیدی استفاده کرده که هم OTL نیست و هم ترانس نداره تو خروجی.

در مورد دیوید و کارش بخونید :

Established in 1974, The David Berning Company manufactures vacuum tube audio amplifiers based on an unique Impedance Converter that replaces the traditional audio power output transformer and greatly extends and improves amplifier performance. We call our technology “ZOTL” for Zero-Hysteresis Output Transformerless.Operating at a fixed high-frequency without traditional audio output transformers, the ZOTL Impedance Converter eliminates the frequency-dependent performance limitations inherent in all transformer coupled tube amps.Berning amplifiers using the ZOTL technology exceed the performance of traditional OTL tube amplifiers by properly matching the tube impedance to that of the speaker. Berning amplifiers depart from traditional OTL amplifiers in that they do not require a large number of hot power tubes to supply adequate current for driving speakers.Berning amplifiers convey the musical transparency of tubes without the limitations imposed at the frequency extremes by audio output transformers. This limitation at the frequency extremes is a major contributing factor to what some negatively call “tube sound”. ZOTL extends the desirable musical transparency of tubes to the frequency extremes and provides the quickness of the high and low frequencies that are cherished by those who prefer solid-state amplifiers.

لیست زیر کسانی هستند که کارهای جالبی در رابطه با طراحی مدارات انجام دادند، در ادامه لیست برندهایی رو میبینید که از IT کوپل استفاده کردند، اون لینک ها رو دنبال کنید مطالب جالبی نوشته.

Nobu Shishido
Susumu Sakuma
David Berning
Anzaï Zaïka
Jean Hiraga
Herb Reichert
JC Morrison
Arthur Loesch
Hiroyasu Kondo
Ken Shindo,
Mr. Atarashi
Don Garber
Noriyasu Komuro (Nori Komuro)

 http://www.6moons.com/audioreviews/trafomatic2/sidebar1.html

 To map out a terrain familiar to me solely on hearsay, I identified the following, currently available commercial single-ended IT-coupled 300Bs :

Mike Morrow’s Morrow Audio 300B1S monos – $6,500/pr;
Hans-Jürg Dorn’s Althea Musica Royale 300B Concept Mono;
Sun Audio’s SV-300BSM – ¥810,000;
SAC Thailand’s custom-order WE 300B monos;
WAVAC’s EC-300B, MD-300B and MD-300Bm – from $8,500 to £16,500;
Promitheus Audio 300B monos – $1,500;
Audio Note UK Kegon – $49,000;
and the Border Patrols with outboard power supplies – €10,600 for the paralleled Model S20.
Allnic from South Korea
TruLife Audio from Greece, €1000 per watt, interstage transformer bandwidth beyond 2MHz
For kits or published DIY circuits with interstage transformers, reference AudioNote UK kits and Lynn Olson’s Nutshell HiFi Karna (6H30 or 5687/7044/7119 input, 45 driver). For further ‘open’ circuits, Nobu Shishido’s IT-coupled 300 SE Topology was published in Glass Audio in 1994. For perhaps the most generic non-IT 300B SET circuit, think 3-stage affair running 6SN7 dual-triode input/drivers. Much present Chinese offerings seem to fall into that category. Other designers don’t see the need for two voltage amplification stages with their higher complexity and cancellation of harmonics. They favor less stages. The earliest 2-stage circuits used pentode drivers like Western Electric’s legendary movie house amps. Shishido used 6L6s. Gordon Rankin’s 2-stage Wavelength Cardinal sports a shunt-regulated push-pull stage (SRPP) to drive its power triode. Other 2-stage topologies use single rather than dual triode drivers. Japanese audiomaniacs seem fond of the classic Western Electric 417A/437A drivers when transformer-coupled to the power triode, championed particularly by Shishido and Sakuma. SAC too adopted this recipe for its current flagship monos. Then there’s direct-coupling and the Loftin-White approach.

ژاپنی ها همونطور که قبلا گفتم ماسفت و ترازیستور های آئودیویی که میسازند به نسبت بهتر از آمریکایی هاست مثل توشیبا که ASR ازش استفاده میکنه و Sanken که ویتوس باهاش کار میکنه و تو ترانس هم قضیه دقیقا همینطوره و ترانس های ساخت ژاپن (مثل تامورا) در مجموع بهتر از بقیه ترانس هاست و حتی تو موضوع شماتیک مدارات هم پیشرو هستند مثل همین شماتیک شیشیدو که خیلی ها از روی اون مدار میسازند. ژاپنی ها تو انتخاب نوع ترانس هم از بقیه جلوترند و اونها زمانی که آمریکایی ها از ترانس های حلقه ای توروید استفاده میکردند ژاپنی ها بیشتر به C Core و EI Core و UI Core علاقه داشتند.

تو کل سازندگان غربی (البته بین ترانزیستوری ها و تا اونجایی که من میدونم) فقط  Vitus و ASR و Howland و Ypsilon از توروید استفاده نمیکنند و بقیه برند های ترانزیستوری از توروید استفاده میکنند.

برگردیم به نگاه دکتر گیزمو که مقالات جالبی نوشته مثل http://www.meta-gizmo.net/Tri/mag/KINGTONE.html که نگاهش رو بیان میکنه. مطلب زیر رو دکتر در مورد کار دیوید برنینگ نوشته :

First and foremost an output transformer, or any transformer for that matter, is an impedance-matching device. Impedance matching is used to transfer a source of power to a load so that both the power source and the load are operating under optimum conditions for maximum efficiency. What other kinds of impedance matching devices are there? Some such mechanical devices include an automobile transmission, bicycle gears, and a simple lever. Besides the transformer, a dc-to-dc power converter is an electrical type of impedance matching device. The dc-to-dc converter can convert a high voltage at low current into a low voltage at high current, or vice versa. Dc-to-dc converters form the basis of the switching power supply, but usually contain added complexity for regulated power supply applications. In its simplest form, the output voltage or current of the dc-to-dc converter is always related to its input by a proportionality constant which is just like the turns ratio in a transformer. Like the transformer, impedance matching goes as the square of this constant.

All current Berning amplifiers use the dc-to-dc converter to form the basis for impedance matching between the tubes and the speaker. The patent for this technology is US patent 5612646 (March ’97), and is reprinted on the Berning web site at http://www.davidberning.com This patent describes the many advantages of this amplifier over the transformer-coupled amplifier, so this will not be repeated here. Unless the reader is well versed in switching power supply design, it is unlikely that he or she will understand exactly how it works, and it is too complicated to try to explain it here. Perhaps the best explanation to read is the one given by Chuck Hansen in his technical review of the ZH270 that appeared in Glass Audio, vol. 12, issues 1&2, 2000. This is also reprinted on the Berning web site. In his review, Mr. Hansen reaffirms the success that this new technology has with preserving the tube’s transfer characteristics at the speaker.

رومی خیلی اوقات مخالف بازی درمیاره که این موضوع به جذابیت اش کمک میکنه اما من معتقدم همونطور که خود دکتر میگه نباید ما به یک نفر تکیه کنیم و فقط ببینیم اون چی میگه ، بنظرم همونطور که دکتر میگه تو این مسیر آئودیو نباید دنبال بودا بگردیم و فقط و فقط ملاک تجربه شنیداری ما باید باشه.

Kill All Audio Reviewers Including Me

THE HIGHEST WISDOM ABOUT THE AUDIO ARTS IS YOUR COLLECTIVE WISDOM..AND NOW IT IS YOUR TRIBAL RESPONSIBILITY TO INSPIRE YOUR BROS’.

باز هم در مورد دکتر مینویسم …

http://www.positive-feedback.com/pfbackissues/0706/rosenberg.sun.7n6.html

The Sun Rises in America©
Reinventing Push/Pull: Some Dancing Advice from a 300B Maniac
by Harvey “The Wiz of a Giz” Rosenberg

During my short tenure as PF’s Techno-Shaman of Coolosity I have suggested that you, while artifying your harmonic/space/time continuum in your expanded aural matrix, consider singleended triode amplifiers with tube regulated power supplies, Nobu Shishido’s Inverted Interstage Transformer coupled SET amplifiers, David Berning’s ZOTL, and now the Sun Audio’s transformer phase splitter 300B transformer coupled push/pull amplifiers … all directly heated triode amplifiers, all unique high expressions of the outer edge of the thermionic arts. This is truly a golden age of thermionic creativity, and I am honored to take you to these exotic places of beauty.

A LITTLE BROWN MAN WITH BIG WHITE KNOBBY KNEES DELIVERS POETRY

The little brown man with big white knobby knees at my door was not an alien from Music HyperSpace, but the UPS delivery man, who was delivering to me thermionic works of art from a still alien culture to readers of PF.

In about fifteen minutes the amplifiers from over the harmonic horizon were unpacked, connected it to my Manley 300B line stage and I was listening to Samuel Barber’s Adagio, and I almost instantly began to slide into an oblivion of beauty; my entire body started to quake and tears filled my eyes … I was so overcome with emotion that I ran to my CD player and asked Puff Daddy’s score for Godzilla to rescue me from this totally unexpected emotional piercing. Then to bring sheen back to my funk I danced to Erykha Baduh’s Tyrone. To bring coherence to this emotional aural expansion I drove to the beach, near my home, mid taking a full breath of the sea’s musical aroma I wrote this poem, dedicated to you, the gifted listeners of PF:

Black Greasy Fingernails

I love men in their old leather jackets,

Which speak of long roads traveled by moonlight.

I love men with black greasy fingernails,

Muscle tugging at bolts building beautiful cars.

I love men who hunt beasts,

Pray and eat their hot dead hearts in thanks.

I love men who look into the sky,

And build monuments to fill their empty space.

I love men who pick up soldering irons and dance in Music HyperSpace

I love men who bend their fingers around instruments and play their scars away.

We are One Soul on Fire.

Do you understand how moved I am by the Sun Audio SV-300B MKII mono transformer phase splitter push/pull amplifiers from Japan? Can you vibe how blessed I am, once again, to experience audio art that compels poetry, dance and celebration? Do you remember my Rimbaud- (not Rambo) like exaltation over Nobu Shishido’s amplifiers? Does anyone have the mettle to stand up to me on this assertion: great audio art is a can opener of the soul, in exactly the same way as Van Gogh’s paintings?

Like the David Berning 300B ZOTL amplifier I arn now introducing you to another “classic” and “revolutionary” amplifier that demands our attention. I consider this the beginning of the next wave in push/pull transformer amplifiers, and any audio dealer that doesn’t sell it is either stupid, deaf or just doesn’t get it. Members of the legion of artistically sensitive men who love their pentode push/pull amplifiers gather your courage and audition this amplifier. Don’t forget there are three great peaks in Triodville……. Mt. Single-Ended, Mt. Push/Pull and Mt. OTL, and I love looking out from each peak because each has it own unique beauty. This is a very popular product in Japan, and for good reason.

THE THERMIONIC TIDES

We are all swimming in the tides of the audio arts; they are deep, powerful and they flow from continent to continent, rich with new life, feeding on the leviathans that are no longer. We swim with these tides, and we struggle against them, but we are only bubbling on the surface of these unfathomable depths. Standing on the beach, the smallest waves lapping on our feet are connected to the storrn in the wide Sargasso Sea, and yes, that tugging is pulling us into the darkness, tugging us back to the eternal music cradle.

Pay no attention to the topless nubile nymphet sprawled on the blanket. Listen instead, listen to the cawing of the gulls, the winds brooming the sand, listen to the harmonics from over the horizon. The next thermionic wave has left Japan’s shore and is squiding to our shore. Push and pull, tug and twist all you want…. its time has come …. the Sun is rising in America.

THE TRUTH IS POWERFUL

The American single-ended revolution has come to a temporary halt in the same way there is quiet after the storm. Before it can take its next leap forward (1) The American Priests of the Temple of Monkey Coffins must recover from the collapse of The Solid State, which reigned temporarily for the last two decades, (2) Much more consideration must be given to, meaning higher quality, power supplies and output transformers.

On the other hand, single-ended amplifiers have Hoovered up all of the attention of the vanguard of the thermionic revolution, and now it is time to re-stimulate attention on this next Wave… reinventing push/pull circuits… which have exhausted themselves, like the Cold War superpowers, in the horsepower race of brutish pentode complexity and astronomic cost. Let us not forget America’s dominant aesthetics are Wretched Excess and The World Federation of Wrestling.

In the same way I have suggested that there are artistic boundaries to single-ended circuit, I am also suggesting there are artistic limits to push/pull circuits … of course this is true in all art forms. But there is no limit to the horsepower race if you are ready to deal with the heat, the electricity bills and the inherent instability and unreliability of these multi-tube behemoths that glow in the dark. Let me say this another way: tubes are to transistors, as triodes are to pentodes. Pop a Prozac and just give this piece a chance.

The tides are shifting and we are returning to a time, the 1970s, when a 60 watt push/pull amplifier was consider humongous. I refer you to my first book, Understanding Tube Electronics, A Study in Natural Harnionics Audio, in which I stated that, after listening to almost every tube amplifier that money could buy, the most authentic were the smaller ones (see Triode Guild web site for pictures of my 1979 ultra-tweaked push/pull amps). I believe that this Sun amplifier, like the classics of that period — the Marantz 9 and 8b and the MacIntosh series — defines goodness and virtue in their genre.

All things being equal, a lower powered, simple push/pull amplifier using directly heated triodes, made with high quality parts, with a well regulated power supply, and with the right way of achieving symmetry will be more musically satisfying than a large complicated pentode amplifier …. if used with the right speakers. Have you got a clue of how difficult it is to get four, six, eight, ten or sixteen tubes to be perfectly balanced? It is impossible, and I am not talking about static bias and balance measurements, which mean very little.

In Japan, where audiomaniacs study the literature (and from the beginning of audio time), the literature is quite clear that the most daunting task is designing a symmetrical phase splitter. There are hundreds of ways of splitting the signal, each with its advantages and disadvantages (order back issues of Glass Audio, Vol 6, #4, Vol 7, #3), but none of these are equal to the precision and finesse of using a very high quality “transformer phase splitter.” Fritz, the 500 year old audiomaniac vampire, insisted that I put some schematics of amplifiers from the 1930s on The Triode Guild web site ( www.positive-feedback.com/triode/triodehome.html ) to demonstrate, once again, The Ancient Wise Ones’ wisdom. Just check a schematic of any Audio Research amplifier and you will see the enormous complexity Bill Johnson has put forth to keep everything symmetrical, and then compare that to the stark simplicity of this amplifier’s front end!

Why don’t more audio designers use transformer phase splitters? For good reason: they haven’t been available in America since the 1970s because the art died here (but that is changing), and most importantly … high cost. A high quality/wide bandwidth transformer phase splitter can cost as much ($200-300) or more than an output transformer, while a conventional tube phase splitter cost what a few tubes, resistors and capacitors cost. Of course in Japan the master transformer winders, such as Tango and Tamura, have kept this art alive and taken it to new heights, because the Japanese are ready to embrace the “ancient” wisdom…. because it creates the greatest beauty … it works best. There is no reason why our top tier tube manufacturers can’t use and boast that they use a Japanese manufactured transformer phase splitter. This is a no-brainer for the ego secure. Check both Glass Audio and Sound Practices for suppliers of interstage transformers.

THE MANLEY RETRO 300B PUSH/PULL RELIGHTS MY FIRE

You know I love the Manley Retro 300B amp because it is the perfect polygamous amplifier … it is single-ended and or push/pull, and I can adjust the feedback with a knob. It stoked my push/pull fires again, and for many good reasons:

(1) It uses 300Bs, which have a superior tone compared to pentodes. We have an expanding cornucopia of 300B brands to use, and I can twiddle with different brands of input tubes, and rectifiers. The combination of 300Bs and octal driver tubes is a very different taste and aroma than pentodes driven by miniature triodes. It is obvious to me that 300Bs in push/pull have the capacity for very low distortion, superior transient response, and superior tone.

(2) It has adjustable feedback, which means I can “tune” the amplifier to the speakers and individual music, and this is an extremely important feature, especially because I can choose “no feedback”. Personally, most of the time, I gladly pay the price for no feedback.

(3) It is enormously powerful at 40 watts … compared to 5-7 watts of 300B single-ended power, which means I can listen to a very wide range of loudspeakers that are 85 dB and up efficient. I will be badgering you over and over again that TWO (maybe four) tubes are the optimum configuration for push/pull circuits if you are seeking mystery. That means two, or maybe four 300Bs. While there is legitimacy in designing with 2A3, 845 or 811 family of tubes (there are virtues in each), all I can say is that the 300B is still the most perfectly balanced tube for me … but remember I am a 300B maniac (Check the Triode Guild web site for “The Return of King Tone”).

(4) Push/Pull amplifiers are more dynamically coherent than single-ended amplifiers, and if you love rock and roll and orchestral music this matters. This will also matter to those who have not taken a vow of celibacy, like yours truly, and are interested in making love while listening to music. If you want to experience the rich primal juice of music, then push/pull is the way to go, and you are hearing that from one of the primary promoters of single-ended circuits.

(5) And let me emphasize again the unabashed real-worldosity of push/pull circuits …. (again) which means that single-ended circuits must be connected to high impedance/high efficiency speakers of uniform impedance, and there are as many of those in America as there are Presidents who didn’t have sex in the White House. In other words (pay attention to Scott Frankland’s comments — see Positive Feedback, Vol. 7, No. 4) with “normal” high end speakers you should use push/pull amplifiers.

In summary, the brilliant Manley Retro 300B amps in Push/Pull mode reintroduced me to the unrealized artistic possibilities of 300B push/pull amplifiers, and stimulated me to reach out to Sun Audio in Japan. I have been waiting for these amplifiers for two years, and it has been worth the wait.

THE CULTURE OF TONE

“In a digital world nothing is more important than tone.”

I can spend two or three thousand pages explaining the Japanese audiomaniac’s advanced aptitude at creating audio devices of extraordinary tone, or, you can go to your local museum and spend a fine day grocking Japanese art. Their audio art emerges from their unique artistic tradition. Check out the porcelains, the lacquers, the silk paintings or silk costumes, or the Samurai armor. Pay careful attention to the finish, the texture and sheen in their art. Here the phrase “glowing with inner light” applies grandly. The Metropolitan Museum of Art in New York City has a fine Japanese art collection worthy of your attention. On the other hand if you are living in an igloo on the North Pole, go to your local library and get some books on Japanese art. Spend some time doing this before you read on so you will grasp what I mean about “tonal sheen”. Music pedagogues call this “burnished tone”. Those who play Stradivarius violins, or a Steinway Concert Grand needn’t bother because you eat tonal sheen for breakfast. This is the difference between Pablo Casal’s burnished tone and Yo Yo Ma’s tone.

Those of you who are connoisseurs of Japanese cooking know the taste of this tonal subtly. And this also explains why this is the land of the Alnico magnet speaker. Who are the consumers who used their dollars to force the renaissance of directly heated triodes?

In my articles about the now eternal Nobu Shishido, I asserted that his audio art emerged from the Japanese culture and their artistic priorities, and they are very different than ours. You, the elite gifted listeners in America, are evolving and learning about subtle tonality, in the same way the Japanese are growing and learning about the transcendent beauty of Harley-Davidson motorcycles which are also fine musical instruments. This international artistic convergence is the new revolution! Big is to America, as subtlety is to Japan, and remember this paradox: Japan taught us about the beauty of our Western Electric tubes.

And if all of the above artistic exploration doesn’t fit into your busy schedule just read Chapter 7 of Music, Physics and Engineering by Harry Olsen, in which the Godfather of the audio arts discusses the primacy of tone in audio systems. So it is not by accident that Mr. Uchida, the owner of Sun Audio, repeats the word “tone” over and over again in his catalog, and it is not by accident that this same word is used over and over again in the Tamura catalog, and it is not by accident that Mr. Uchida once worked for Tamura.

MUCH COOLER THAN A ROLEX

In my conversation with Nobu about the design goals of the WAVAC amplifiers he was clear in explaining his goal of integration between their physical beauty and their aural beauty, and this artistic wholeness is the aesthetic platform of Japanese art. So let me be plain about these amplifiers: they are works of art. They have a unique “classic” beauty both physically and tonally. To my trained eye they are an “ideal” transformer-coupled push/pull tube amplifier. There is a chunky symmetrical perfection to them; a cross between a fine piece of military electronics and a fine lacquered box. They are a deep charcoal gray, and I love their deep matte enamel finish. But it is the sculptured beauty of the Tamura transformers that define their thermionic totemic beauty, rightfully so. When these amplifiers speak, they proudly boast … TAMURA TRANSFORMERS. These mono amps are not large, and they remind me of the kind of chunky design self- confidence that we see in the MacIntosh 275, which means you can, and should, show them off, and never have to worry about cluttering your room or getting a divorce. Consider putting these amplifiers on a pedestal, or speaker stands … that is how superb they are as tube art.

Why is the Guildmeister of Triode Guild, the man who is America’s most aggressive promoter of OTL amplifiers, so impressed by these transformer phase splitter/transformer output amplifiers … that’s a lot of iron? The answer is the quality, quality, quality of the iron makes the difference, and it is (again) safe to say that 99.999999% of American audiomaniacs have not experienced the level of transformer quality in the Sun and the WAVAC amplifiers, but when you do, you will understand what you have been missing. Those of you who read Glass Audio are aware of Nobu Shishido’s emphasis on the importance of transformer quality. It is also possible to order these amplifiers with the highest quality Tamura output transformers for an additional charge.

My only criticism here is that the knob on the input pot should a 1940’s design, and the speaker binding posts should be of higher quality, but this is an easy retro-fit, especially if you buy these amplifiers in kit form….but hold on, I will deal with this later on.

My suggestion for Mr. Rich Guy is to buy a dozen pairs of these amplifiers and put them in your boat, your office, your garage, your bedroom, living room and den … they have they kind of masculine beauty we associate with Rolex watches … if you get my point about testicular beaudacity?

IS A TUBE A STRADIVARIUS VIOLIN?

What a silly question. Of course a tube is a fine hand-made musical instrument, which is why we love figuring out which combination creates the tone we prefer. This statement explains the artistic transcendence of tubes in audio circuits which always must be tuned for optimum pleasure. The musical dread of transistor and digital audio is that they have so little tuneability.

In the same way Americans know how to make great tasting hamburgers, there is an tube gourmet orthodoxy in Japan which has now migrated to America … 6SN7 /voltage amp driver, 300B output tube, and 5U4G tube rectifier … stray too far from this gourmet combo and the aroma and taste of music, the tonal sheen, will falter. And while this may seem an artifact of culture, the 300B is a much more linear, lower distortion tube (and it is from 1936) than your typical modern 6550, meaning it needs little or no feedback, and the 6SN7 is superior to a miniature triode of the 12AX7 kind.

But let me go further … if you want to fully fathom the tonal glory of these extremely serious amplifiers, you must use the best possible tubes which means: (1) hunting for NOS pre-1960 6SN7, especially the Western Electric brand made by Sylvania. Buy lots of different brands and gladly pay for the best, because nothing is more important and more fun, than fine-tuning the tone of your amp with the first tube. (2) picking the 300B brand that pushes your ecstatic button, and today your choices are very great indeed (note: there are no bias and balance controls here, so you must use matched pairs of tubes), and (3) buy a NOS RCA or equivalent tube rectifier. If you can’t afford this combo, buy the best tubes you can afford and then save up and trade up.

I don’t understand why so many American’s use solid state rectification in small tube amplifiers when it is a guarantee of tonal deterioration. I remind you of my experience with two versions of the Manley Retro amps (solid state and tube rectification), and hands down chose the tube rectifier model. The price you pay for tonal sheen … some tightness in the bass. The tonal quality of your power supply matters!

On the Triode Guild web site is a schematic of this amp, and I will make some brief comments about it here. You immediately note how simple this circuit is: no coupling caps, a 6SN7 input tube connected to a transformer phase splitter which drivers the output stage. The power supply has a choke, which is rare in America, and there is no feedback. That is about as simple as you can get in a push/pull amplifier. “Less is More” also applies to push/pull circuits.

One very interesting feature of the Sun amp is that the 300B’s B+ voltage is only 320V, which is substantially less than the “normal” 400-450 Volts. This operating point is probably chosen because it creates the tone that Mr. Uchida prefers. This is only a 20 watt amplifier (the Manley is 40 watts) which means you will get maximum tube life. It is possible to let twice the horsepower out of the same air of tubes, but you pay the price in longevity.

THE IRON HEART OF SUN

Now we get the heart of these amps…(the soul are the tubes), and it is the Tamura transformers. The Japanese audiomaniac is very transformer savvy, and Japanese audio publications spend a great deal of time analyzing and reviewing output transformers because of the artistic intensity and curiosity of home tube amplifier builder. The Japanese audiomaniac knows it makes sense to save and buy the best transformers possible because, once you own them, you can use them as the basis of building any number of custom circuits. Ten years from now you can build a new single-ended or push/pull circuit with the same quality “classic” iron. The same high standards are also applied to the tonal quality of power transformers and chokes, which is a consideration that Americans don’t yet understand.

My triode bro’ Fabio Camaroni, who may be the current incarnation of Michaelangelo, the editor of the Italian audio magazine, Cositruire, lives and breathes Tamura transformers, which doesn’t mean he doesn’t also love OTLs.

I just received my first copy of Charles Kittleson’s Vacuum Tube Valley magazine, (Phone: 650-631-6550; www.vacuumtube.com) and did a swan dive into my birdbath I was so excited. It has taken twenty years, but America’s West Coat thermionic techno-shamans are setting the pace in doing what our Japanese bros’ do for fun … comparing the sound of different brands of output transformers. Check the Triode Guild web site for a reprint of VTV’s 300B/single ended transformer evaluation. This is an extremely important activity, because the force that drives up the quality of American tube amplifiers is your sophistication … you only get what you deserve!

Arthur Loesch, one of America’s most revered up-state New York thermionic techno-sharnans, is absolutely right in his assertion that the missing element here, the one that releases the nascent magic of directly heated triode is power, output, and phase splitter transformers of the Tamura/Tango quality. While this will cause many of you anxiety (it is a small price to pay for expanded thermionic consciousness) I insist, as your beloved Guildmeister, that you (I will not stop rny insistence) pick up the phone and call the Sun importer and get a copy of the Tamura transformer catalog, or go to the Sun Audio Web site at www.2.big.or.jp/~sunaudio.

These high quality transformers are not yet available in American “store bought” tube amplifiers, and I can’t emphasize too strongly what a difference this makes in tonal sheen, transient response and clarity. When you peruse the Tamura transformer catalog you are looking at a technically sophisticated company that makes a wide range of industrial transformers. With their audio transformers this clearly is a case of science serving art, because winding audio transformers, at this level of quality is an art, and their customers demand it, and so should you.

Steve Berger of AprilSound imports a number of ultra-high quality Japanese transformer brands, including Tango, and you should get his catalog ((212) 242-9515), and check his web site: http://home.earthlink.net/~aprilsound/to get a better understanding of the choices our Japanese bros’ have and we don’t. Steve’s site has a high slew of really interesting, edge of the art, directly heated triode amps and schematics that you should also check out.

How many times have I ranted that “normal” aluminum electrolytic power supply capacitors are tonal arsenic, which is why I use oil capacitors, which require chassis yardage to use? But there is a tonally cool power supply capacitor; it is a Elna brand Cerafine capacitor (check Michael Percey’s catalog for these type of capacitors), which has a unique construction …. The Sun sheens because of the quality of its components, which is rare in America …. you can’t fool Mr. Japanese Audiomaniac.

I have also included on The Triode Guild web site an illustration of the “inside” construction of these amplifiers because these are available as a kit, and are only slightly more complicated than assembling single-ended amplifiers, which is as easy as it gets. This illustration is important for another reason: It illustrates that there are no circuit boards here. This is all hard-wired, and for a good reason: hardwiring gives maximum tonal sheen. You notice the classic beauty of 1940s type military wiring, and it should not surprise you how much attention is put into the “beauty” of the wiring layout.

If I were building the kit I would use all solid silver wire, or solid copper wire with cotton insulation, and better quality input and output connects. Edison Price pure beryllium copper speaker binding posts available from Eminent Technology (904-575-5655) is a highly recommended addition. Anyone who has built any of the Cary Audio, AudioNote, or Welborne kits are more than qualified to take on this challenge … and this is the real McCoy. This is my suggestion when assembling: sip the finest Saki, wear a silk kimono, and listen to Kodo music …. make the connection to our Japanese audiomaniac brothers.

CAN YOU BEAT THIS, MY FELLOW 300B MANIAC?

I got up early in the morning and ate a bowl of breakfast cereal in the shape of 300Bs with milk from cows that listened to the music of Tammy Wynette playing on a 300B/Alnico barn sound system while they were being milked. Then I took a shower with a bar of directly heated soap in the shape of a 300B, put on my 300B T-shirt, turned on my Manley preamp that has a 300B output stage and turned on the Sun amps …. can anyone top that 300B mania? You know my email address. (drgizmo3@earthlink.net for those who don’t.)

One of my high traffic email questions is about which brand of 300B I recommend. Because of these amps’ refinement they are perfect for “The Directly Heated Karma Sutra Part 1: World’s First X-Rated 300B Evaluation”, which will shortly appear on the Triode Guild web site — be prepared for some big surprises. But now let me point out that every tube maker is getting higher on their 300B learning/quality curve, which means that with the increasing demand for 300Bs, quality and consistency is better across the board, and there are new 300B “variants” that are woodifying.

HOW DOES THE SUN SOUND?

Those who need more than 7-10 watts, yearn for that directly heated single-ended magic, and want the dynamic coherence and full frequency response you can only get from a push/pull amplifiers with real world speakers, have now had their dreams answered. Those who want that single-ended refinement and are thinking about getting a powerful single-ended amplifier (15-20 watts) such as an 845, 211 or 811 stop, and check these amplifiers out. Let me remind you that these amplifier still need a relatively high efficiency speaker … 85dB+/NOT 4 ohm, but there oodles of this sort available.

Power freaks stop reading now and go to the notable Brad Meyer’s web site “How Much Power Do You Need” at www.smr-home-theatre.org/Power/index.html, and check out the loudness/efficiency/power table and you will discover that with an 87dB+ speaker you can cause ear damage with 20 watts. With 99dB efficiency is only takes 1.3 watts to cause the same damage.

The dynamic quality of these amps is totally dependent on your speakers … with the Sunlight Engineering 308s they are equal to Pratt and Whitney jet engines.

May I be bold and vain? I only write about significant audio art. These amplifiers are significant for an extremely important reason … the debate about single-ended versus push1pull has now moved to a much higher ground. What we have found artistically crude about push/pull amplifiers is not an inherent quality of push/pull circuits, but the way we execute this principal in America. I am asserting there — and it is proved by the Sun amplifiers — that the disdain we feel for the tonal discombobularity, lack of refinement, midrange choppiness, and aural flatulence of push/pull amplifiers is not a design imperative. The Tamura tramformerphasesplitter is a way big deal. The Sun amplifiers has proved to me that, when done right, push/pull is much more than we imagined. This the first time I have absolutely no trouble not listening to my single-ended 300Bs … let me say that differently …. my SETs haven’t been used in weeks!

Another highly respected thermionic techno-shaman, and fellow editor of PF, Lynn Olson, also believes that the next wave is transformer phase splitter/directly heated triodes, and for the last year has been perfecting his own extremely refined version of this concept using Lundahl transformers.

Go to www.teleport.com/~lynn/ABC.html to check out his truly innovative design and schematic. Note the tube regulation!

Do you need more validation?: When discussing this article with the loftiest of lofty, Eric Barbour of Svetlana, he too agreed that a high quality transformer phase splitter was optimal for push/pull circuits … and directly heated triodes pushed the boundary of push/pull possibilities.

Does the Sun amp have the sublime subtle midrange coherence and juice of my best single-ended 300B amps? No, but SET amps are, in effect, midrange amplifiers and do not have the ability to play with most speakers … how many of you own 100 dB + Tannoy horns or the Sunlight Engineering 308s? The bigggg difference here is that the Suns can create a coherent musical wavefront, from top to bottom, that no single-ended circuit can. There are very few “store bought” tube amplifiers (because they are pentode) that have this tonal rightness and I have explained why.

There are two groups of music lovers I wish to address: jazz and chamber music maniacs, two genres where the priority of tone is obvious. You must experience this type of music with a 300B amplifier.

I am aware of how desperate brainy analytical audio professors are (those still stumbling around in the dark dank basement of the disintegrated “accuracy metaphor”) for me to describe these amplifier’s individual attributes, and compare them to my other amplifiers. Well, I guess you missed the whole point of this article. I don’t analyze … I integrate, and I don’t compare Van Gogh to Picasso. A wholey man’s job is integration. Go back to the top and re-read it … these amplifiers made me write poetry, cry and dance, and that is about as wholey as I can get when it comes to an audio gizmo. Will the Sun amps make you cry and dance and write poetry? Only you can discover that. Do you have the same type of brain damage as I do?

TOP SECRET: Because you know me well, you know I will not be able to resist connecting some of my industrial tube regulated power supplies to these amplifiers to discover their effect…but you will have to go to the Triode Guild web site to get the results of my experiments ( www.positive-feedback.com/triode/triodehome.html ).

A pair of these mono amps cost $6, 250 without tubes. The kits cost $5,000, which should give you an indication of just how serious the DIY market is in Japan. I do not know of anything in America that equals this extreme quality in the category of 300B push/pull amplifiers. Are there any? Like the WAVAC amplifiers these amplifiers can never become obsolete. These are classics.

You will find the Sun Audio catalog a trip to an exotic land. Those who are in love with single-ended amplifiers will be thrilled by Sun’s single-ended amps, and there are a many other push/pull amplifiers and some exotic phono preamps and line stages … all express the same passion for tone.

Some advice for audio dealers: these are the real McCoy and a great way to get curious gifted listeners into your audio space. Strike up the band and let’s start dancing to our favorite tune … Less is More.

Wake up American tube amplifier designers, the next wave is building … surf it, don’t be drowned by it … start designing your high quality 300B push/pull/transformer phase splitter amplifiers … this is a very juicy wave, and worth surfing. And my fellow gifted listeners — can we be certain that the American Priests of the Temple of Monkey Coffins have the intellectual heft to get their high efficiency act together ?

Now that was really good for me. Was it good for you?

Celebrating your wholey dudeness, and reminding you that you are music, I remain,

Dr. Gizmo: drgizmo3@earthlink.net

Triode Guild Web Site: www.positive-feedback.com/triode/triodehome.html

تو این شبهای تهران زیر برف و باران شدید زندگی چه حال و هوایی داره …

رابرت هارلی میگه کسی نمیدونه چرا تکنولوژی 100 سال پیش بهتر از الان تو صدا جواب میده من میگم فقط 100 سال پیش صدا بهتر نبود خیلی چیزها بعد از دوره تولد یک دوره اوج دارند و بعدش اوضاع تغییر میکنه. موسیقی ، نویسندگی با موضوعی خاص ، روحیات آدمها طی یک دوره تمدن و خیلی چیزهای دیگه تو نقطه ای به اوج میرسند و بعدش وضعیت فرق میکنه.

های فای هم مستثنی نیست و به اعتقاد من دید آبجکتیو و کاهش دیستورشن مسیر رو اشتباه کرد، رابرت هارلی نوشته بخونید :

http://www.theabsolutesound.com/articles/a-survey-of-amplifier-types-tas-217-1/

A Survey Of Amplifier Types by Robert Harley

Most power amplifiers, and the amplifier sections within integrated amplifiers, are strikingly similar in operation. These so-called “Class A/B, push-pull” amplifiers have been around for decades and are the staple technology of nearly every amplifier manufacturer. I’ll explain how Class A/B amplifiers work later in this excerpt, but first I’d like to introduce you to some alternatives to the classic Class A/B amplifier. These include the single-ended triode amplifier, the single-ended solid-state amplifier, the switching power amplifier, and the digital amplifier.

Single-Ended Triode Amplifiers

One of the most interesting trends in high-end audio over the past 25 years has been the return of the single-ended triode power amplifier. The single-ended triode (SET) amplifier was the first audio amplifier ever developed, dating back to Lee De Forest’s patent of the triode vacuum tube in 1907 and his triode amplifier patent of 1912. SET amplifiers generally deliver very low power, sometimes just a few watts per channel.

You heard right: Large numbers of audiophiles are flocking to replace their modern power amplifiers with amplifiers based on 100-year-old technology. Have the past 100 years of amplifier development been a complete waste of time? A surprising number of music lovers and audio designers think so.

The movement back to SET amplifiers began in Japan in the 1970s, specifically with designer Nobu Shishido, who combined SET amplifiers with high-sensitivity horn-loaded loudspeakers. Many who heard SET amplifiers were startled by their goosebump-raising musical immediacy and ability to make the music “jump” out of the loudspeakers. Thus began the rage for SET amplifiers in Japan, which was about 10 years ahead of the SET trend in the United States. You can’t open a high-end
audio magazine today without seeing ads for very-low-powered single-ended triode amplifiers. The SET enthusiast’s mantra, coined by reviewer Dick Olsher, is, “If the first watt of amplifier power doesn’t sound good, why would you want 199 more of them?”

One early audio-amplifier triode tube, the Western Electric 300B, was suddenly in such demand that audiophiles were paying as much as $500 apiece for it. This shocking fact prompted Western Electric to start producing the 300B again. If you’d told Western Electric executives of the 1980s that in 1997 they would put the 300B back into production, they’d have thought you were crazy. (A single-ended triode power amplifier using the 300B output tube is shown in Fig.1 The 300B is the bulbous tube in the middle.)

The triode is the simplest of all vacuum tubes; its glass envelope encloses just three electrical elements rather than the five elements in the more common (and modern) pentode tube. Triodes have much less output power than pentodes, but more benign distortion characteristics. Virtually all modern tube amplifiers before the SET-comeback used pentodes.

In a single-ended triode amplifier, the triode is configured so that it always amplifies the entire audio signal. That’s what “single-ended” means. Virtually all other power amplifiers are “push-pull,” meaning that opposing pairs of tubes (or transistors) alternately “push” and “pull” current through the loudspeaker. (Later in this excerpt we’ll look more closely at how this works.) SET proponents believe that because the triode amplifies the entire waveform, SET amplifiers offer the ultimate in sound quality and musicality. Moreover, SET amplifiers have no need for a circuit called a phase-splitter, making them even simpler. Note that a single-ended tube amplifier can use more than one output tube; what makes it single-ended is that the tubes are configured in such a way that they always conduct current throughout the entire musical waveform.

In addition, SET circuits are extremely simple and often use very little or no negative feedback. Negative feedback involves taking some of the amplifier’s output signal and feeding it back to the input. Such feedback lowers distortion, but many feel that any feedback is detrimental to amplifier musicality.

On the test bench, SET amplifiers have laughably bad technical performance. They typically produce fewer than 25Wpc of output power and have extremely high distortion—as much as 10% total harmonic distortion (THD) at the amplifier’s rated output. Although most SET amplifiers use a single triode output tube, additional triodes can be combined to produce more output power. Some SET amplifiers, however, put out just 3Wpc. In fact, there’s a kind of cult around SET amplifiers that strives for lower and lower output power. These SET enthusiasts believe that the lower the output power, the better the sound. One SET designer told a reviewer, in all seriousness, “If you liked my 9W amplifier, wait until you hear my 3W model.”

In addition to low output power and high distortion, SET amplifiers have a very high output impedance as amplifiers go: on the order of 1.5–3 ohms. This is contrasted with the 0.1 ohm output impedance (or less) of most solid-state amplifiers, and the 0.8 ohms of many push-pull tube designs. Because a loudspeaker’s impedance isn’t constant with frequency, the SET amplifier’s high output impedance reacts with the loudspeaker’s impedance variations to produce changes in frequency response. That is, the SET amplifier will have a different frequency response with every loudspeaker it drives. These variations can range from just 0.1dB with some loudspeakers that have a fairly constant impedance, to as much as 5dB with other loudspeakers. The SET amp’s sound will therefore be highly dependent on the loudspeaker with which it is matched.

Despite these technical drawbacks, my listening experience with SET amplifiers suggests that this ancient technology has many musical merits. SET amps have a certain presence and immediacy of musical communication that’s hard to describe. It’s as though the musicians aren’t as far removed from here-and-now reality as they are with push-pull amplifiers. SET amps also have a wonderful liquidity and purity of timbre that is completely devoid of grain, hardness, and other artifacts of push-pull amplifiers. When I listen to SET amplifiers (with the right loudspeakers), it’s as though the musicians have come alive and are playing in the listening room for me. There’s a directness of musical expression that’s impossible to put into words, but is immediately understood by anyone who has listened for himself. You must hear an SET firsthand to know what the fuss is about; no description can convey how it sounds.

When auditioning an SET amplifier, it’s easy to be seduced by the midrange. That’s because SET amplifiers work best in the midband, and less well at the frequency extremes of bass and treble. If the SET demo is being run for your benefit, be sure to listen to a wide variety of music, not just small-scale music or unaccompanied voice—both of which will accentuate the SET’s strengths and hide its weaknesses.

The importance of matching an SET amplifier to the right loudspeaker cannot be overemphasized. With a low-sensitivity speaker, the SET will produce very little sound, have soft bass, and reproduce almost no dynamic contrast. The ideal loudspeaker for an SET amplifier has high sensitivity (higher than 93dB/1W/1m), high impedance (nominal 8 ohms or higher), and no impedance dips (a minimum impedance of 6 ohms or higher). Such a speaker will produce lots of sound for a small amount of input power, and require very little current. There’s been a resurgence in high-sensitivity speakers that has paralleled the popularity of SET amplifiers. Some loudspeakers designed for SET amplifiers have sensitivities of more than 100dB, which enable them to produce satisfying listening levels with 5Wpc. SET amplifiers are often coupled with horn-loaded loudspeakers, which have extremely high sensitivity but, in my experience, can introduce unacceptable levels of coloration.

The popularity and unmistakable sound quality of SET amplifiers pose a serious dilemma: How can an amplifier that performs so poorly by every “objective” measure produce such an involving musical experience? How can 100-year-old technology eclipse, in many ways, amplifiers designed in the 21st century? What aren’t we measuring in SET amplifiers that would reflect their musical magic? Why do conventional measurements fail so dismally at quantifying what’s right in SET amplifiers? Do SET amplifiers sound so good because of their high distortion or despite it? As of yet, no one has the answers to these questions.

Single-Ended Solid-State Amplifiers

Single-ended amplifiers aren’t confined to those using ancient vacuum-tube technology. Transistors can also be configured to amplify the entire musical waveform. A solid-state, single-ended amplifier is shown in Fig.2. Note the large heatsinks required to dissipate the additional heat produced by single-ended operation.

Single-ended solid-state amplifiers have better technical performance than single-ended triode amps, with a lower output impedance, more power, and the ability to drive a wider range of loudspeakers. Still, they share many of the benefits of SET amps, particularly the very simple signal path, lack of crossover distortion, and greater linearity. Although single-ended solid-state amplifiers generally produce less power than their push-pull counterparts, they generally have much more output power than single-ended tube units. Nonetheless, it’s a mistake to equate single-ended solid-state with single-ended tube amplifiers: there are so many other design variables that single-ended solid-state and single-ended tube amplifiers should be considered completely different animals.

Switching (Class D) Power Amplifiers

If single-ended triode amplifiers represent a return to fundamental technology, the switching power amplifier may represent the future of audio amplification. Switching amplifiers, also called Class D amplifiers, have been gain-ing in popularity due to their small size, low weight, high efficiency, and low cost. You can hold some 250Wpc switching amplifiers in the palm of your hand. Many of them dissipate so little heat that they can be housed in an enclosed equipment cabinet—something you’d never do with a conventional amplifier (also called a linear amplifier). That’s because a linear amplifier is typically about 15% efficient, meaning that it converts only about 15% of the power it draws from the wall into the electrical signal that drives the loudspeakers. The other 85% is dissipated as heat. By contrast, a switching amplifier is as much as 90% efficient, converting just 10% of its power draw into heat. Fig.3 shows a switching power amplifier. This monoblock delivers 175W into 8 ohms and 335W into 4 ohms. It weighs just eight pounds and measures 8.5″ x 14″ x 1.8″.

Switching amplifiers are sometimes erroneously called “digital” amplifiers, but that appellation is reserved for a special type of switching amplifier described later in this excerpt.

At the low-end of the audio spectrum, switching amplifiers are ubiquitous in home-theater-in-a-box units and as integral subwoofer amplifiers. A home-theater-in-a-box may need to power six loudspeakers from a DVD-player-sized chassis—all for a few hundred dollars. Such a unit can output perhaps 300 watts (50Wpc x 6), yet run cool enough to be placed in a cabinet. In this application, the advantages of a switching amplifier are undeniable. But are switching amplifiers suitable for high-end systems?

Before tackling that question, let’s first look at how a switching amplifier works. In a conventional linear amplifier, the output transistors amplify an analog signal—the musical waveform. The current flow through the output transistors (or tubes) is continuously variable—a direct analog of the musical waveform. In a switching amplifier, the analog input signal is converted into a series of “on and off” pulses. These pulses are fed to the output transistors, which turn the transistors fully on or fully off. When the transistors are turned on, they conduct the DC supply voltage to the loudspeaker. When they’re turned off, no voltage is connected to the loudspeaker. The audio information is contained in the durations of these on-off cycles. The train of pulses amplified by the transistors is smoothed by a filter to recover the musical waveform and remove the switching noise. Because the signal amplitude is contained in the width of the pulses, switching amplifiers are also called pulse-width modulation (PWM) amplifiers. In fact, the Direct Stream Digital encoding system used in SACD is nearly identical to the pulse-width modulation scheme in Class D power amplifiers.

One major drawback of switching amplifiers is the need for an extremely clean power supply. Remember that the transistors switch the DC supply directly to the loudspeaker. Consequently, any noise or ripple (a small amount of AC on the DC voltage) will appear at the loudspeaker’s input terminals. Moreover, the output transistors may not turn on and off at precisely the right time, introducing distortion. Finally, switching amplifiers generate large amounts of switching noise that must be filtered by huge inductors and capacitors at the amplifier output. In practice, the sound quality of switching amplifiers seems to be highly dependant on the environment, the loudspeaker, and the loudspeaker cables. A switching amplifier that sounds reasonably good in one system might be unlistenable in another.

Nonetheless, some successful high-end amplifiers employ switching technology. The field is relatively new, and manufacturers are finding ways to get good sound from switching amplifiers. A few of the high-end switching amplifiers I’ve heard sounded excellent, suggesting that switching technology may have a future in products other than car stereos and home-theaters-in-a-box.

Digital Amplifiers

A related amplifier technology uses a switching output stage, but accepts digital, rather than analog, input signals. These “digital” amplifiers take in the pulse-code modulation (PCM) signal from a CD transport, music server, or other source and convert those audio data to a pulse-width modulated signal. This PWM signal drives the output transistors, just as in a switching amplifier. The difference between a switching amplifier and a digital amplifier is that the digital amplifier accepts digital data rather than analog signals.

This difference might not seem that great at first glance, but consider the signal path of a conventional playback chain with a digital source and a switching power amplifier. In your CD player, data read from the disc go through a digital filter and are converted to analog with a DAC; the DAC’s current output is converted to a voltage with a current-to-voltage converter; the signal is low-pass filtered and then amplified/buffered in the CD player’s analog output stage. This analog output signal travels down interconnects to a preamplifier with its several stages of amplification, volume control, and output buffer. The preamp’s output then travels down another pair of interconnects to the power amplifier, which typically employs an input stage, a driver stage, and the switching output stage. In addition to the D/A conversion, that’s typically six or seven active amplification stages before the signal gets to the power amplifier’s output stage.

To reiterate the contrast with a true digital amplifier, PCM data are converted by DSP into the pulse-width modulation signal that drives the output transistors. That’s it. There are no analog gain stages between the PCM data and your loudspeakers. The signal stays in the digital domain until the switching output stage, which, by its nature, acts as a digital-to-analog converter in concert with the output filter. The volume is adjusted in DSP. Digital amplifiers are usually not just power amplifiers, but also include inputs, source selection, and volume control, effectively giving them the functional capabilities of an integrated amplifier. Fig.4 shows a digital amplifier, and Fig.5 is a block diagram comparing the signal path of this amplifier with conventional system architecture.

Output Stage Topology and Class of Operation

We’ve seen that the output stage of a power amplifier can be configured either as single-ended or push-pull. To reiterate, in a singled-ended amplifier the output devices (tubes or transistors) always amplify the entire musical waveform. The single-ended amplifier cannot operate in any other way—that’s the very definition of “single-ended.” In a push-pull output stage, pairs of opposing devices are arranged so that they work alternately—one device “pushes” current through the loudspeaker and then other device “pulls” current through the loudspeaker. Multiple pairs of output devices can be grouped together to increase the power output, called parallel push-pull.

That’s a description of an amplifier’s output-stage topology—how the amplifying devices are configured. Now let’s look at a separate but related factor—the amplifier’s class of operation.

Class of operation refers to how a given output stage is driven. The two main classes of operation are Class A and Class B. In a Class A amplifier, the output stage (single-ended or push-pull) amplifies the entire musical waveform. In a Class B amplifier, opposing pairs of transistors (or tubes) are operated so that one transistor in the pair amplifies the positive half of the waveform and the opposing transistor amplifies the negative half of the waveform.

Class of operation is easily confused with single-ended and push-pull output-stage topologies. But there’s an important distinction. A single-ended amplifier always operates in Class A. But a push-pull amplifier can be operated in either Class A or Class B. It might seem like a push-pull Class A amplifier is a contradiction in terms, but it’s not. In a push-pull Class A amplifier, opposing pairs of transistors are driven in such a way that current flows through both transistors throughout the entire musical waveform. All the output devices participate in amplifying through the full cycle of the audio signal. One device pulls current through the loudspeaker and the other pushes current, but both are always turned on and conducting current.

By contrast, in a Class B push-pull output stage, one transistor amplifies the signal during the positive-going portion of the signal, and the other amplifies the negative-going signal half. When one is working, the other is turned off (and getting some needed cooling).

Once again, two key factors are the output-stage topology—how the output devices are configured—and class of operation—how those output devices are driven. To clarify the matter:

• Single-ended topology always operates in Class A
• Class A operation can be implemented in a single-ended or push-pull topology
• Push-pull topology can be operated in Class A or Class B
• Class B operation is only implemented by a push-pull topology

Let’s move on from these distinctions to the more practical aspects of amplifier class of operation.

Most power amplifiers are called Class A/B power amplifiers because they operate in Class A at very low power outputs, then default to Class B operation at higher power outputs. A 100Wpc amplifier may put out 5W of Class A power, and then switch to Class B above that level. Even the heftiest Class A/B amplifiers can put out only a small portion of their rated power in Class A. A typical value is about 1% or 2%. Although this may not sound like much, an amplifier may be running at just a couple of watts at low listening levels with high-sensitivity speakers.

How much of an amplifier’s power output is Class A is determined by the amount of bias applied to the output transistors. Bias is a DC current that flows through the output stage at idle. The higher the bias, the more current flows through the transistors when no signal is present. More bias results in more Class A output power. Class B operation has no bias current; Class A/B has moderate bias current; Class A has very high bias current. The designer can keep increasing the bias in a push-pull output stage until all of its output power capability is delivered in Class A mode. The amplifier’s power output rating would be the point at which the amplifier leaves Class A operation and begins operating in Class B. The limiting factors to increasing the bias current are the ability of the transistors to handle the greatly increased current flow through them, the power supply to keep up with the transistors’ current demands, and the heatsinking to dissipate the considerable heat caused by the high bias current.

To give you an idea of the demands placed on the output stage, power supply, and heatsinking by an output stage biased for Class A operation, let’s compare two products with identical output stages that are biased completely differently. The two products are the Pass Labs INT-150, a 150Wpc Class A/B integrated amplifier, and the Pass Labs INT-30A, a 30Wpc pure Class A integrated amplifier. The INT-150’s push-pull output stage is biased so that it produces 10Wpc of Class A power before switching into Class B to deliver its full rated output of 150Wpc. The amplifier can double its output power to 300Wpc into 4 ohms. The INT-30A is exactly the same amplifier, employing the same power supply, an identical number and type of output transistors, and the same heatsinks as the INT-150, but is rated at just 30Wpc. The difference is that the INT-30A’s 30Wpc are pure Class A watts. The amplifier biased into Class A delivers just one fifth the power output of its Class A/B counterpart.

As you can see, Class A operation is enormously inefficient. A Class A amplifier converts nearly all the power it draws from the wall outlet into heat, and consumes just as much power at idle as when it is operating at its maximum output power. Moreover, a Class A amplifier is much more expensive to build on a “watts per dollar” basis than its Class A/B counterpart.

So why would designers go to the trouble and expense of creating Class A amplifiers, and why would consumers pay such a huge premium for “Class A watts” over “Class A/B watts”?

Class A has many theoretical and practical advantages. For starters, Class B and A/B amplifiers suffer from crossover distortion, a discontinuity at the zero-crossing point where one transistor in the opposing pair “hands off” the signal to the other transistor in the pair. A waveform discontinuity can occur at this transition, and is lessened as bias current is introduced and increased in value. Crossover distortion can’t occur in Class A operation because each transistor amplifies the entire audio waveform, not just half of it. Second, the large thermal hardware capacity required by Class A has the advantage of keeping the output transistors in better thermal stability (a more constant temperature). This makes their operating characteristics more uniform, and less subject to changes resulting from the signal characteristics the transistors are amplifying. For example, if the transistors have just delivered a surge of current to the loudspeakers, they won’t behave differently—and thus sound different—immediately afterward because they are momentarily hotter. Third, increasing the bias current so that an amplifier produces more

Class A power not only reduces harmonic distortion, but more importantly, changes the nature of the harmonic distortion. As the bias is increased, the upper-order harmonics (everything above the third harmonic) that are most sonically harmful are most dramatically reduced in amplitude, leaving the predominant distortion component the more sonically benign second and third harmonics. Class A power amplifiers can sound extremely good, with a sweetness and liquidity that set them apart from Class A/B amps. In my experience (I recently lived with a pair of 100W Class A monoblocks for 18 months), Class A amplifiers have many of the virtues of a tube amplifier but without the tube amp’s technical limitations. This isn’t to say that a Class A amplifier mimics the sonic character of tubes, but rather that Class A avoids many of the characteristic nonlinear distortions of Class A/B solid-state amplifiers.

شاید شما هم آلبوم راجر واترز رو شنیدید که تو اون وقتی هاپوهه واق واق میکنه صدا از جایی بیرون دو تا بلندگو میاد. این آلبوم تو سال 1992 از تکنولوژی پردازش دیجیتال کیو ساند استفاده کرده بود.

http://en.wikipedia.org/wiki/Q-Sound

About QSound Audio Technology

QSound Labs’ full suite of three-dimensional (3D) audio algorithms extend the ability of a given number of audio output transducers (headphone elements or speakers) to convincingly position sound in arbitrary locations in space. Specific QSound Labs processes address the unique requirements of each situation according to:

• the number of input signals and the number of output channels
• nature of content: interactive vs passive

3D Positional Audio

Process Function

A basic 3D positional audio processor accepts a monophonic audio input signal, and produces two or more output signals as required to match the number and type (headphone, speaker) of output transducers in the playback system. The algorithm “positions” the sound for the listener at a specific apparent location. The specific signal manipulations and output distribution methods are necessarily specific to the output configuration.

Strictly speaking, simple stereo and multi-channel surround “panning” are themselves crude positioning algorithms. Simple panning uses only the relative level of the input signal sent to each output to provide a sense of direction, and has significant limitations. True 3D positional audio algorithms are an extension of this panning (panoramic) concept.

Applications

Because of the one-to-one mapping of input signal to specific spatial location, 3D positional audio has the following general areas of application:

• To create apparent or “virtual” speakers in place of physical ones, in order to render multi-channel surround content effectively with fewer physical speakers. (See Virtual Surround.)
• In the mixing phase of any multi-input audio production. Here a number of input signals, typically each representing an individual sound source (whether musical instrument, voice or sound effect) are positioned independently and mixed together to produce a music recording, TV or film soundtrack. This is referred to as pre-processing of passive content, since 3D is applied in the production environment and the end recipient simply sits passively to experience the prepackaged presentation with its built-in 3D audio effects.
• In a positioning and mixing application which has many similarities with “pro audio” production as described above: controlling multiple independent sounds for a virtual reality simulator or video game. Unlike the case of pre-processed passive content, this processing and mixing happens in real time on the end-user device, milliseconds before it is heard, according to the logic designed into the simulator or game engine, and dynamic user input. Hence this is classed as a real-time interactive application.

Presently, the most significant application for 3D positional audio is enabling of realistic audio environments for electronic gaming, whether in personal computers or handheld portable devices. QSound Labs addresses this market with its Q3D™ process.

Enhancement of Home Entertainment Audio

Mono & Stereo-to-3D

Stereo-to-3D enhancement, as provided by QSound Labs QXpander™, creates a more realistic and thus more enjoyable listening experience from existing source material by increasing the width, immersiveness—and thus realism—of the perceived audio image.

Stereo-to-3D has applications in computer and handheld audio as well as consumer entertainment electronics. Because enhancement can be applied to arbitrary source material (radio and television broadcast, recorded music, video, multi-media, games, etc.) and does not rely on special production techniques, it is suited to virtually any consumer audio product.

A special case of enhancement, mono-to-3D creates an ‘omnidirectional’ 3D stereo image. This is useful for improving mono recordings, broadcasts, or mono surround channels.

QXpander is available as a stand-alone algorithm, and as a feature of QHD, microQ, and mQFX.

Mono & Stereo-to-Surround

The completely unique QSound Multi-Speaker (QMSS™) algorithm creates 3, 4, 5, 5.1 or 7.1-channel output from plain mono or stereo input. Well suited to multi-channel PC audio systems, home theatre, compact surround systems and car audio, the QMSS process makes the input signal seem as though it were produced in multi-channel surround. Considering that most available content is still in mono or stereo formats, QMSS adds significant value to multi-speaker system.

Since QMSS can also be used to resynthesize multi-channel output from decoded and down-mixed surround content, it can serve as an economical alternative to the high licensing costs associated with full multi-channel decoding and output. If implemented using one of the company’s analog integrated circuits, D/A cost reductions can also be realized.

Virtual Surround Sound

The goal of virtual surround sound (e.g. QSound Labs QSurround® process) is to render fully decoded multi-channel formats such as Dolby Digital effectively on headphones or using as few as two speakers. Multiple 3D audio processes are applied to the decoded surround channels in order to create virtual surround sound speakers (using positional 3D, or mono-to-3D, for stereo and mono surround signals respectively) and to improve the apparent separation of the front channels (stereo expansion). The individual processes outputs are then down- mixed, typically to two channels. Primary applications are home theater (See QSurround), desktop computers, and Mobile TV (See QSurround Mobile).

Surround Enhancement

Surround enhancement is akin to stereo enhancement in a multi-speaker setting. 3D can be usefully employed to “fill in” areas that are traditionally weak in the surround sound stage (especially the sonic gap that tends to exist between front and surround speakers) resulting in a more continuous and immersive experience. (See QSurround).

اینم لیست 30 آلبوم برتر از دید یکی :

Top 30 Best Album :

01 – Amused to Death – Roger Waters (1992)
02 – Touch – Yello (2009)
03 – Acoustic Live – Nils Lofgren (1997)
04 – Metallica – Metallica (Black Album) (1991)
05 – The Last Resort – Trentemøller (2006)
06 – Dark Side of The Moon – Pink Floyd (1973)
07 – The Colour of Spring – Talk Talk (1986)
08 – We`re Here Because We`re.. – Anathema (2010)
09 – Sir John Alot – John Renbourn (1968)
10 – Kilo – The Nits (1983)
11 – Jazz at the Pawnshop – Diverse artiesten (1977)
12 – Wish You Were Here – Pink Floyd (1975)
13 – Cafe Blue – Patricia Barber (1994)
14 – Live in Paris – Diana Krall (2002)
15 – Beste van Twee Meter Sessies (1987-2009) – V.A. (2009)
16 – Live at Carnegie Hall – Harry Belafonte (1989)
17 – Moon Safari – Air (1998)
18 – The Girl in the Other Room – Diana Krall (2004)
19 – Gone To Earth – David Sylvian (1986)
20 – Sgt. Pepper’s Lonely Hearts Club Band – The Beatles (1967)
21 – Deadwing – Porcupine Tree (2005)
22 – Frances The Mute – The Mars Volta (2005)
23 – Heartbreaker – Ryan Adams (2000)
24 – Kind of Blue – Miles Davis (1959)
25 – Dear John – Ilse DeLange (1999)
26 – The Big Gundown – Ennio Morricone (1966)
27 – Architecture & Morality – Orchestral Manoeuvres in the Dark (1981)
28 – Seldom Seen Kid – Elbow (2008)
29 – Montgolfieres- Gianmaria Testa (2003)
30 – My One and Only Thrill – Melody Gardot (2010)