OPTIMAL SET DHT AURAL MATRIX
THE CURRENT DHT VERNACULAR
The DHT aural matrix is expanding at the speed of our demand to express our rapidly evolving musical consciousness, with new DHTs appearing every month, not every year, or decade. This explosion can be explained by looking at your local magazine rack, which has literally hundreds of magazine devoted to a mans favorite subject. Why are there so many when they all have the same old, same old, sprawled out on their centerfold? The answer is when it comes to pleasure, men love subtle variety, and never tire of variety.
Am I the one claimed that mens imagination is polygamous, and that is why the current DHT is so exciting? How many 300B wives do you need?
Now let me, for the newbies, once again focus on the paradoxes of the DHT revolution, it is a revival of the tubes that started to the whole electronics ages at the beginning of this century, and were popular until the late 1940s when higher powered pentodes replaced them.
A decade ago we discovered that our far more sophisticated bros in Japan were lusting for these ancient tubes, and for the first, rather than ridiculing this notion, we listened. You know the results.
Demand for DHTs was strong enough that savvy entrepreneurs made the significant investment to start producing DHTs again. Even after Western Electric went out of the 300B business, Charles Whitener, a great American hero, raised enough capital to restart production because of the Japanese demand.
We also discovered that the Chinese and ex-Soviet bloc DHT valve was open and flowing strongly. Then KR and AVVT created a new family of DHTs that never existed before.
Just check the catalog of KR and AVVT tubes to see how intense DHT creativity has become.
Paralleling the introduction of this new family of DHT is the availability of a new family of SET output transformers. And paralleling all of this is much more serious consideration about SET circuit design especially drive circuits. And power supplies. These parallel developments are understandable because you cant separate a tube from all of the components that surround it, and to explore the deepest dimension of these tubes we must become more demanding.
THE JUICE IMPERATIVE
The challenge facing us is NOT, "Which is the best tube"? The mature challenge is: HOW CAN I SQUEEZE THE MOST MUSICAL JUICE FROM THE TUBE I CHOSE?
The question is not "Is a burgundy better than a chablis"? But how to get the most pleasure from each unique variety.
While this sound, its implication are vast, and represent a rejection of THE OLD AUDIO TESTAMENT which is based on static amplifier design.
TWO TITANS OF THE DHT ARTS
As you know Count Kron and Alesa Vaic were once partners in the same company. I have a pair of tubes made by that company and when it was introduced it shaked the thermionic world because it was the first modern DHT.
Are you aware of the great "artistic arguments" that have occurred over the last five hundred years between artists who, in their passion for beauty, passionately disagree with another artist? Listening to the vast difference in the type of beauty created by the KR and VAIC tubes it is easy to understand how these two titans of the DHT arts wouldnt get along they are polar opposites.
This is a great boon for all of us because it offers us the opportunity to explore the polar opposites of our musical brain,
So let me make this point clear..again..especially in a context relative to pentodes. The question is not which is better, but HOW DO I EXPLOIT THE VAST RANGE OF CHOICES IN AURAL MATRICES THAT I CAN NOW CREATE WITH THESE DHT TOOLS that does not exist in the pentode cosmos?
ANSWER: DEVOTE A LIFE
"Which DHT and OPT do you recommend? This question often appears in chat rooms, and the answers are feeble because the answer is so complex .and indicates that we are STILL at the dawn of THE NEW AUDIO TESTAMENT .and this is very threatening to most because it is a challenge to our artistic commitment. The only answer that makes any sense for the HI-IQ is "The best tube is the one that you wrestle with to create your optimal aural matrix..and that process is constantly evolving and is a life long challenge. This means that there is only one authority on this subject: YOU.
My job? All that I can do is inspire you to get as high as possible on your path of discovery. WE ARE ALL CONNECTED IN A WEB OF INSPRIATION
MY JAPANESE INSPIRATION
Though it is lost in the fog of my audio memory I think I was reading this article in a Japanese audio magazine about ten years ago. Even though I cant read Japanese I knew the article was an attempt to answer the following question: What are the real differences in DHTs?
To answer this question the editors built a very interesting "modular" amplifier that had a bunch of gauges and dials so they could adjust voltage and current on each tube, and the ability to quickly change OPTs. This amplifier obviously had adjustable regulated power supplies. The group of editors was sitting in front of this machine. While they listened to the music they adjusted/tuned the amplifier until they agreed that each tube was operating at its "optimal beauty" point. This meant they fine tuned this amplifier and chose the best OPT.
I remind you once again of my dialogs and articles with Nobu Shishido and his message about his Japanese audiomaniac bros: the transcendent pursuit is beauty and engineering is subjugated to that Lord and Master.
Because none of the new DHTs, that we are now enjoying, existed at that time they were testing different brands NOS DHTs including WE 300Bs, 300A, classic American 2A3s, 45s, and some of the classic European DHTs. All of these tubes were made before 1950.
This process is what I call THERMIONIC JUSTICE because it compares each type of tube at its best operating point, with the best OPT. Dont DHTs deserve this level of respect? What do we learn from this ultra serious test procedure?
The implication of this article had a profound effect on Dr. Gizmos thinking about DHTs challenge.
AN AMPLIFIER IS A MUSICAL INSTRUMENT
The implication of this article was obvious: an amplifier is a musical instrument and must be tuned just like every other musical instrument. As you know there are, in effect, two levels of tuning: The First Stage is getting all of the harmonic/dynamic elements of the scales in balance, and The Second Stage is very personal because it is the subtle level of tuning. Though a Gibson and Fender guitar five string guitar are tuned the same way, they are not only very different sounding, each guitar player tunes his instrument so that he can express the most subtle level of his aural matrix.
This truth applies to amplifiers, but unfortunately the prevailing OLD TESTAMENT/STATIC orthodoxy doesnt permit this level of tuning, and thereby limits our ability to "tune into" our SET amplifiers.
4TH WAVE MODALITY: DR. GIZMO GLOMS
The emergence of my 4th Wave Modality concept that a modern amplifier must be tunable because of the well-known ancient truth EVERY AMPLIFIER IS A MUSICAL INSTRUMENT, and therefore it must be tunable for maximum performance IS A GLOMATION FROM JAPAN. How new is this notion? Probably five thousand years old or one hundred and fifty thousand years old. This truth is one of the most heretical to the Priest of the Old Testament.
A TABOO SUBJECT
Julius Futterman compelled me to consider the true nature of audio output transformer distortion. Then David Berning went further and published some interesting papers about how tubes and output transformers interact. Then I read Menno van der veen's papers about how his new torroid output transformers solved many of the traditional transformer problems. This is a very complex subject, with every OPT being an artistic balancing act which is why they are so much fun.
A subject that is taboo is the interaction of the output tube and the OPT, and then the interaction of the OPT with speaker. They are ONE ELECTRICAL CIRCUIT and no audio circuit is completely stable. But let us just deal with the output tube and OPT for one moment. Consider a matrix of interacting electrical characteristics that are so complex you need a supercomputer to grasp it. On the other hand if you are a gifted listener all you need is your golden ears and the courage to throw away conventional wisdom.
Why should we throw away conventional wisdom about the interface between a tube and the OPT? Conventional wisdom is all about achieving maximum power, at a low distortion level, not achieving maximum beauty at a low distortion level. DO YOU WANT TO TUNE FOR MAXIMUM POWER OR MAXIMUM BEAUTY? Maybe you want both. Perhaps some tubes, like the type used on your woofers should be tuned for max power; the DHTs used on your tweeters should be tuned for maximum beauty.
Which brings me back to my original point: to get the bestest and mostest music juice out of the new family of DHTs an amplifier must be tunable in terms of its power supplys voltage/current so that you can tune by ear for what sounds best for you.
The other "non-normal" investigation of the heart and soul of DHTs was using David Bernings SET ZOTL, which uses no audio output transformer, and therefore offers a completely unique insight into the aroma of these new DHTs. I view Davids amplifier as a DHT master class because of all that it teaches.
4th Wave Modality Affirmation: My ability to instantly switch between 300Bs and the KR 2A3 in SET ZOTL solidified my notion of just how cool it is to have one amplifier that lets us use many different types of DHTs. Using Davids amplifier also clarified for me the unique, and non-optimal personality of the WE 300B when it is used at 425 volts/60 ma.
MY GONZO INVESTIGATING PROCEDURE
This investigation occurred over a period of at least one-year.
These are my artistic judgements which may not be worth much. Their ultimate value is to inspire you to take the creation of your aural matrix much more seriously. Remember I love short hairy women, so what good are my value judgements.
Using my hot rod Tannoy horns I used these speakers with both:
- Marchand Tube crossover: This gave me the ability to tune a tube to a dedicated frequency range. But its greatest value is eliminating the masking/distortion effects of all passive crossovers, which eliminate at least 30% of the music juice we love. The difference in the aural matrix of these tubes when they are liberated from passive crossovers is so significant it is taboo for the audio low roaders, who are afraid of discussing this subject which means: How can we improve passive crossover design?
- My Hot Rod Passive Crossovers: Consists of the new "Jensen Tobias "Toast" oil capacitors, and a combination of AlphaCore pure silver foil inductors and Jensen Tobias wax/paper copper foil inductors.
MICRO-ZOT SET: This amplifier operates at 425 volts DC, but because David made a "filament adapter" for me can be used with both 300Bs and the KR 2A3 which can tolerate this high voltage.
OPTS: I used the new Plitron torroid OPTs in both 3.5K and 5K primaries.
IRON LOADING AND COUPLING: My voltage amp/driver stages used various combination and models of Lundahl grid chokes, plate chokes, and interstage transformers.
VOLTAGE AMP/DRIVER CIRCUITS: I used three but will only describe two now. Remember that I used independent adjustable tube regulated power supplies for the front end of my SET amplifiers so I can tune them. Like you I believe it is essential to have a very robust drive circuit..that can swing voltage/current and has a low output impedance/
For the low powered DHTs I use a 6SN7 with one triode being the voltage amplifier that used grid choke instead of 100K grid resistor, and a plate choke instead of a plate resistors. Why? Because it creates a very creamacious aural matrix. Yes there is aural contamination from resistors that is very different than the aural contamination from "magnetic loading". This stage is directly coupled to the driver stage, the other half of the 6SN7, is connected to an interstage transformer with drives the grid of the DHT output tube. PAY ATTENTION: This combination of "magnetic loading" and tube regulated power supplies is very unnusual..so unusual in fact that I know of no other who is using this combination.
For the higher-powered DHT I use the same basic configuration except I use NOS RCA 6EM7 which is a video octal tube with some unusual electrical characteristics. While this tube does not have the harmonic refinement of the 6SN7, it does have very large balls. It is like a combination of a 12AX7 because of the high gain of one half, and the other half is like a small amplifier with very high current/low impedance capability. The second half has one of the lowest output impedance of any small signal tube and can produce ten times the current of a 6SN7. This means I must use a different Lundahl IT for this tube than I use for the 6SN7. This combination of high current/low impedance connected to an interstage transformer, that is connected to a tube regulated power supply, creates the type of drive circuit that liberates high-powered DHTs testicularity. This is the key to liberating their huge aural matrix.
I will not now comment on the use of the new AVVT DHT driver tubes.
Let me now comment on another aspect of these driver stages: their sensitivity to "supporting" components. The type of resistors, and capacitors used makes a big difference. According to the theory one of the primary benefits of "magnetic loading" is that it isolates the tube from power supply ripple..like a regulated power supply. Yet, by changing from one type of tube regulated power supply to another I can create a significant aural difference. The aroma/personality of your front-end power supply should be very different than your output stage power supply, and this has not yet been taken seriously.
It is also important to note that all of my regulated power supplies have oil capacitors on their outputs. The big thrill is using the Jensen Tobias oil power supply capacitors, but if you cant afford them get some other brand of oil power supply capacitors to decouple your front end.
WHAT IS IN A NUMBER?
Is a KR 300, or an Electro Harmonix 300 a 300B? Yes, and no. What is so confusing about the number designation of the new generation of DHTs is that these numbers were created long before we were born and there can be an assumption that these new tubes, that share the numbers designation with the classics, sound the same THEY DONT, CANT, and NEVER WILL.. On the other hand a 1938 amplifier designed for a 2A3 can use any modern 2A3 because the voltage/current rating of the old tubes and new tubes are in the same ball park..ALMOST. For example: You can operate the KR 2A3 at the classic "1930s" 250 volts, or more modern post WW II 350 volts, or as high as 425 volts something that would be fatal for a classic 2A3.
Let me make this clear: the modern DHTs do not sound like the NOS classics and that includes the WE 300B for a very good reason. They are made with different materials, and or, they are different mechanical design and construction. The new DHT tubes have a higher vacuum/TORR and their glass is usually heavier, and this affects their aroma.
There is no doubt that the NOS classic DHTs have their unique beauty that no modern DHT can create. On the other hand, the new family of DHT can do things that the classics cant..and they are available, reliable and are creating creative possibilities that never existed before.
ASCEND TO MICRO-POWER
META-CONTINUUM OF BEAUDACITY
You cant achieve both refinement and power if you are working within the Old Audio Testament. If you are using one amplifier full range, you must choose. You must figure out where you want to be on the refinement/power continuum. The lower powered DHT are more refined.
AT THE END OF THIS SECTION I DEAL WITH THE BIG MUTHA TRIODES..
But why not use each type of DHT where they are able to do their job best? That is what the optimal aural matrix strategy is all about.
LETS GET DHT NITTY GRITTY DOWN
WESTERN ELECTRIC 300B: The mother of us all. Using this tube with a 5K OPT at 340 Volts at 80 ma. creates at completely different aural matrix than using it with a 3.5K OPT at 425 volts at 60 ma. It is sweeter, more three dimensional and clearer. It is a wondrous experience into the deepest mystery of DHT to experience this tube without any passive crossovers to muck up mysterious the power of its midrange. I often use the combination of WE 300Bs (the woofer tubes run at 425/60 ma with 3.5K OPTs and the tweeter tubes run at 340V/80ma with 5k OPTs) just to experience one of the most profound midrange presentation on this earth. This is the standard for midrange righteousness BUT WE 300Bs do not have the extended lower or higher frequency ranges of other DHTs, and not the subtle harmonics of the lower powered DHTs. Consider this tube a classic Indian or Harley Davidson motorcycle. This the classic against which all other DHT are to be judged.
I have seen Charles Whiteners slide presentation of the assembly procedures at the WE factory, and I believe his assertion that these tubes are made at a higher quality than the originals. That doesnt mean that these new WE 300Bs sound indentical to the originals.
SVETLANA 300B: A very good/cost effective attempt to create a WE 300B aroma. This is an excellent "classic" tube and what I have described about the WE 300B applies here in terms of "midrange" emphasis. Does not have the tonal refinement of the WE tubes. This tube makes push/pull 300B sensible.
SOVTEK 300B: Another good/cost effective attempt to create a WE 300Bs aroma. Lower cost/performance than the SVET. Consider this your starter 300B, and there is nothing to be ashamed of.
JJ TESLA/ELECTRO HARMONIX 300B: They look very similar and they sound very similar and they do not sound like classic 300Bs, and I like what I hear. These tubes are more aurally robust, dynamic and go deeper and wider than the classics. Both of these tubes remind me of the first VAIC 300B I heard six years ago. This is the first rung on the "modern" 300B ladder. Not the WE midrange wholosity.
CHINESE ARTS 300B: The tube I have uses a carbon anode like the type used in the much larger Class A RF triodes, which means it is very rugged, and can dissipate more current than the classic 300Bs. The price paid is the loss of subtle harmonics. There is a thickness to the sound, but run at higher voltages and current you create a higher level of bass slam. NOT the midrange magic of other 300Bs
GOLDEN DRAGON 300BS: Probably the best "classic" Chinese 300Bs
Again: dont be confused by the number designation. These work in a "normal" 300B amplifier that was designed for "normal" operation voltages/current, but "normal" usually limits their performance.
KR 300BXL: I have two different version of this tube. This tube when operated at its max voltage/current rating opens the door to a form of rock and ecstasy that I never knew existed when used on the woofers. Now we are into the deepest regions of the DHT New Audio Testament .revolution. Can you buy an amplifier that fully exploits this tube? NO. You have to make one. Here is the fun: as I am listening to this tube I adjust the voltage/current from its " normal 425 V" range up to its 500V+ range and listen to the transformation of the aural matrix..how it becomes deeper, more dynamic and reaches a level of sweet/slam that is completely unique. The combination of this tube on my woofer and a lower powered/more refined DHT on my tweeter is my ultimate SET rock and roll space probe.
Count Kron creates DHT that have a harmonically rich, aurally wide and dynamically deep aural matrix. This tube, like all of the KR tubes, has a big voice that can shiver your timbers, make your eye blink and for the rock and roller duplicate the sensation of being in one of my favorite gizmos The Orgasmatron. This tube is "baaaaaad?. Does not have the midrange refinement of the WE 300B, nor speed and "space between the notes of AVVT".
AVVT 300B SL: Is it possible to worship the funk of Grand Funk Railroad and the shadows of Wanda Landowskas soul hidden in the keys of her harpsichord? What a stupid question. The answer YES, and each of these unique trips into our inner aural matrix requires different tools. Blessed is Alesa Vaic for creating the type of DHT aural telescopes that permit our imagination to leap out to the frontiers of harmonic intelligence. This tube is at the opposite polarity of the KR. This tube passes the most difficult test for any DHT: there is a silence between the notes that makes each an every note shine with a clarity that I have only previously experienced on my last trip to Triode Heaven. This tube doesnt have the dynamics and low frequency extension of the KR tubes, but it does have a midrange clarity, transient response, and high frequency righteousness that the KR doesnt have. Want to try some interesting DHT genetic engineering? Use the KR 300BXL on woofer and use the AVVVT 300B on midrange/tweeter. I tune this tube for maximum sweetness, not power, because in a digital world, it brings us up against the PARADOX OF CLARITY.
This tube, like all AVVT tubes, is angelic
Again, again, again: To fully exploit this new generation of DHT the Old Audio Testament of static amplifiers must be overthrown for the New Audio Testament, the 4th Wave Modality of tunable amplifiers.
AVVT 302: What do angels do when they are not being watched over by God because She is shopping for some new shoes? Angels get down with rock and roll and they use the AVVT 302, which is the baaaadest angelic tube I have in my collection for listening to rock and roll. This is the higher voltage/current version of the AVVT 300B, and it doesnt have the refinement of this tube, but it does have an angelic testicularity that is completely unique but again these tubes demand the highest quality input because of their unparalleled clarity. I cant sleep at night trying to imagine what a refined push/pull amplifier with these tubes would sound like.
SOVTEK 2A3: The award I gave Mike Mathews for this tube says it all. A mind zapping bargain, and the key to creating 2A3 push/pull amplifiers. Because the new audio coolosity is exploring the notion of ASCEND TO MICRO POWER, which is exactly the opposite of the American wretched excess orthodoxy, this tube is the first step for most, on this ladder. Take this tube very seriously, and tune it for maximum beauty, and that could be somewhere between 250-350 volts. This tube tries to get close to the classic 2A3 aural matrix.
KR 2A3: This is not really a classic 2A3 sound, but something much different and from my point of view better because when it is used at 400-425 volts it has a power/beauty that no 300B has. It does not have the low frequency slamosity of any of the 300Bs but it brings a dynamism and tonal refinement to the midrange that makes rock, rock in a way that will make your socks sing. Use this tube at much lower voltage and higher current and it is much sweeter. Are you a rock voice freak? This is the ticket for making those digital recordings sound human. The combo of this tube with the 300BXL is, as I said before, equal to a rock and roll Orgasmatron.
AVVT 2A3: If you love the electric guitar this tube will reveal a truth about this instrument that no other DHT can. This is the tube that Ry Cooders guardian angel plays. The mesh plate technology in this tube translates into an aural matrix that does sound like a classic 2A3 because none of these tubes have the speed, agility and delicacy of this tube. It is also dangerous, because it shows no mercy for circuit crudity. Want to hear the obvious difference between types of resistors? Want to the hear the difference that plus/minus ten volts can make in a tubes cream? This tube is an electronic harmonic microscope, and if you have the right stuff, it will change your mind about the DHT revolution. Though this tube can operate at 300B voltages I tune it at much lower voltage/higher current to keep it in its sweetest spot. Want to experience a really weird drug?: KR 2A3 on woofers/AVVT 2A3 on tweeters.
AVVT 8: While this tube was originally designed a new breed of DHT driver tube, it can be used as an output tube. This tube takes the core Vaic aesthetic to an even subtler place. Call this tube the King of DHT Angels in terms of delicacy, clarity and ethereal space/time. Very low powered, not big or dynamic, but who cares? Shall I call this tube the ultimate tweeter DHT?
KR-PX 38: I suggest that the new and very exotic KR PX-25, which is named after a European DHT which, existed between 1920 and 1940 was mislabeled on purpose. It should have been labeled the P-38 after WW IIs most thrilling twin engine fighter. Why wouldnt Count Kron want us to know the truth about this tube? Why am I so certain of this? Every day after school I used to get into my P-38 and fly up into the clouds, belly roll, dive, and loop, and that seven year old boy-pilot is still in me and can still feel those physical thrills so I know this tube is doing exactly the same thing to me. No other tube opens the door to my P-38 aural matrix.
This tube is as different from any 300B as it is from any 2A3, and that is why I love it so much, and why I have put so much effort into exploring the nano-harmonics of its juice. The one feature that separates this tube from all other DHTs is its 4-volt filament, as opposed to the 2A3/2,5 volt filament, and the 300B/5 volt filament. This is good news, bad news and a great opportunity. It is good news because anyone who uses a P-38 amplifier has satisfied an important male need: exclusivity.
I am so excited about this tube I have asked Mike Le Fevre, American Zen Audio Output Transformer Artists to make one of his unique para-feed OPTs for the P-38 so I can build one of my typical Formula One Gonzo SET amplifiers to exploit this combo.
BIG MUTHA TRIODES
Of Course Size Matters
845, 211, 805, 838, 833, Kronzilla, WE 212/308,
INTRODUCTION: MIKES WOODY
Mike Le Fevre, the man behind Magnequest Transformers called me with the type of exuberance men usually express when they have scored in a major way..and he did. Jim Dowdy Lama just sent him a pair of the huge WE 212s which were originally created in the 1930s to used as the output tubes in aircraft carrier PA systems that could play loud enough so that commands could be hear above the roar of fighter planes engines. These tubes are twelve inches long and about four inches wide, and as far as I know they are the only tubes that can give Johnny Wad a run for his money. Now you know why Mike was so excited.
Of course you want one of those amplifiers that uses those HUGE totally phallactic directly heated triodes. History is ample proof that when men create art and culture we create monuments that celebrate our favorite tool of ecstasy. I have now explained why we keep on building taller and taller skyscrapers because it is important to have the biggest one .because size matters to puny defenseless apes living on the ground that are the favorite meal for big, powerful, fast hungry predators.
Check out this affirmation:
It is now time to explore another one of those delicious dialectical delicatessens of the audio arts the polarity to the Triode Guild Mantra ASCEND TO MICRO-POWER.
Let me start this delicious journey by once again pointing out that it is our more sophisticated and refined Japanese brothers who are responsible for this woodifying aesthetic, because none of the tubes in the "Big Mutha Triode" category were originally intended to be used in home audio systems. All of these tubes were intended, when they were originally invented, before1940, to be used in industrial applications. Most were designed for AM radio broadcasts. Many had application in the military.
Before I continue let me suggest you buy Nobu Shishido's definitive "How To" book on using these type of Class A and B RF tubes in audio applications. In spite of the fact that it written in Japanese it has great pictures, and all of the schematics are insights into the challenges of using these tubes for a purpose that they were never designed for. For Nobu's birthday I gave him an original 1938 RCA tube manual of these industrial tubes and he was thrilled
I can't blame you. You are a real man and you want a tube amp with those big totally woodifying Class A or B RF directly heated triodes like the 211, 845, 805, 833, or 838 or those super expensive Kronzilla, or WE 212. You have seen pictures of the Audio Note (Japan) Ongaku, or the Cary 805, or the magnificent WAVAC amplifiers all big bucks all heavy weight. And what about the amplifiers that exploit the KR 1610, "Kronzilla", or the new Western Electric 308?
Again I will take you back to the time when I was the first, in American, to be honored with auditioning the WAVAC amplifiers which featured the 433 and 805. This was while Nobu Shishido was alive and we spent a great deal of time talking on the phone between American and Japan talking about his designs. At that time there was only one high powered single ended amp in America, and that was the Cary 805 which used the 211.
THE SINGLE-ENDED WALL
CAN WE GET OVER IT?
The problem that every high powered single-ended amp faces is the limitation of single-ended output transformer design, that must have a DC bias current running through it. Inherent in the design of a single-ended output transformer is an air gap. The smaller this gap, the better..BUT..the more current that is running through the OPT, the larger the gap must be. The larger the tube, the more bias current, (at higher voltage) must pass through the output transformer and this means the gap must be correspondingly larger and very soon there are a host of electrical problems . aggravated by the fact that most of these tubes have very high plate impedance which means the "turns ratio", between the primary and secondary of the output transformer, must be higher higher than the smaller directly heated triode tubes. This means that all of the electrical problems endemic to all single-ended output transformers are larger . which means slower rise time, higher inductance, higher capacitance .all of the electrical problems that diminish sound quality.
When I compared the sound quality of the three different WAVAC amplifiers the 433 (Class B RF), the 300B, and 805 (Class B RF) it was obvious that the 300B, the lowest powered of the lot was the most musically authentic. The 805 model, which produced a huge 50 watts, was extremely powerful below 400 Hz, but lost the nuances and tone of the 300B amplifier. The 433 amplifier was quite amazing in the midrange/upper frequencies but did not have the natural balance of the 300B amp and Nobu agreed.
Why was Nobu so thrilled about creating this new class of higher-powered SET?
Nobu was thrilled for all the reason that mountain climbers are thrilled Nobu was, and continued to, until his death, scaling the SET peaks that no other audio artist had scaled in terms of getting power from SETS. His "833 cookie jar" amplifier is an outstanding work of art..in terms of the technical achievement of being the first 100 Watt per channel SET, It is also one of the most beautiful amplifiers ever created, and Nobu was very excited about this accomplishment. Just think of the thrill .One hundred watts of single-ended power was a historic achievement.
On the other hand I am suggesting that we are seeing, once again, the typical male impulse that drove pentode push/pull amplifiers into wretched excess. Of course if 5 watts of beauty is so alluring we want 50 watts of the same NOT possible because there is a price to pay for more power, and it is less refinement and I didn't make this up. If I could pick on amp it would be the 433.
Recently John Atkinson of Stereophile tested the new Cary Audio's amplifier that used the Kronzilla tube. John had previously tested a KR amplifier that used one of Count Kron's new "high powered" directly heated triodes. The test results for these two amplifiers were disastrous. Many thought that there was something wrong with these new tubes. How could such expensive amplifiers test so badly?
My suggestion is that the type of testing that John was doing was producing maximum current through the single-ended output transformers, which was causing their electrical field to collapse..which is called "core saturation". With core saturation, the OPT literally stop "transforming". Others will claim that under real world conditions this saturation effect is not present, because rarely is maximum current flowing through a SET OPT. But that begs the question. If you decide to run into the wall, your head is going to get slammed.
You might be wondering why more companies aren't using the 845 or 211 Class
A RF tube in single-ended amplifiers; tubes that were originally used in AM
The paradox is that these tubes are now readily available from China and are a bargain compared to 300Bs. There are a number of reasons:
WHAT HAPPENS AFTER THE ROMANCE IS OVER?
Over the years through email and direct contact with musicmaniacs I have encountered the typical male experience: a romance doesn't make a long term marriage, and the common complaint is that after a romantic interlude with these very impressive amplifiers something is missing compared to the smaller DHT amps and this is right.
Recently I was in an audiomaniacs house, and he was excited about playing his system for me, which was a Lowther and 2A3 amp. In the corner was a Cary 805, which he told me he no longer used, but loved looking at.
USE MY OPTIMAL TUBE AURAL MATRIX STRATEGY:
Consider biamping using a tube crossover, with a 300B or 2A3 on midrange/tweeter and use one of these big mutha triode amps on the woofers use each where it is best suited bada bing, bada boom.
I will be spending more time very soon discussing this strategy. If you need the woofer juice, use these big mutha amps for their juice, and then use the smaller and more refined amplifiers for the midrange juice.
e-mail Dr. Harvey "Gizmo" Rosenberg: firstname.lastname@example.org
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