Potty Publishing Presents




To the Top of DIY Heaven


Dr. Harvey "Gizmo" Rosenberg

















The power of high end audio in the 1970s derived from the fact that it was subversive to mainstream thinking....we were the AURAL rebels. At the core of this movement’s power was the notion that, in spite of the almost universal acceptance of transistor in audio equipment, that tube circuits still reigned supreme. This was the FIRST WAVE of modern tube consciousness, and it was anti-modern long before this was fashionable.

In 1980s there was literally only one type of tube amplifier available in America and it was a Williamson-type push/pull EL 34 or 6550 pentodes with lots of feedback. In 1981 I created the first commercial OTL amplifier, based on the Julius Futterman circuit, and then there were two types of tube amplifiers available. By the mid 1980s WAVE TWO emerged and there were lots more "normal" super high horsepower push/pull pentodes with lots of feedback, and more OTLs, and then in the early 1990s, the THIRD WAVE emerged with the growing popularity of very low powered single-ended directly heated triode circuits....because Joe Roberts of Sound Practices Magazine showed the us what Japan was into. At that point there were three different "core" topologies, push/pull, single-ended and OTL, and many variations of each to choose from.

It is impossible to disconnect single-ended circuits from the directly heated triode renaissance with "new" tube models appearing almost monthly. Now everyone is tube savvy, with many different subcultures of tube maniacs. When you look at these two decades, from the Guildmeister’s of view, (where technology always follows imagination) what we see is an ascension of tube consciousness...the tube mind, horny devil that it is, is insatiable in its craving for more refined forms of beauty. This is why it has created a wider range of expression and a more subtle one...this is a mind that is ascending to greater refinement. This is the mind on the 4th Wave.

What is the FOURTH WAVE in this tube ascension? It is the natural evolution of our musical sensitivity demanding more refinement, more subtly, freedom of choice and most importantly...the ability to fine tune tube circuits so that our audio system perfectly reflects our inner music.

In this case, right here and now with this Plitron project I am addressing one of the most important, yet overlooked, element of tube is time for us to get higher in output transformer saviness.. OPTs are the soul of every tube amplifier and are, and should not be an unknown commodity to you. After we have traveled the long road we must return to the most basic, soulful, consideration...the single most important element in every tube amplifier....the output transformer.


Can any of you imagine the shame of NOT KNOWING THE BRAND OR TYPE OF TUBES YOU USE? Can you imagine not knowing the brand of speaker, phono cartridge or cables you use? Expand a can you know nothing about the most important element in your tube amp...the output transformer? (Don’t blame yourself or rack your soul with shame...we are all part of a dysfunctional audio culture. If you are guilt persists join one of my Transformer Sensitivity Workshops)

Do you now understand the Guildmeister’s meta-campaign? I want you all to start taking the most important, and ignored element, of your objet d’amour more seriously. Do you understand the transcendent transformer is the output transformer? It is time for musicmaniacs all over the world to RAISE YOUR OUTPUT TRANSFORMER CONSCIOUSNESS. If you don’t, soon all of the attractive women in your social circle will know that you are a transformer meathead...a dullard...a cad...the kind of guy that goes bowling in a satin shirt.



The obvious answer is only if you want to be. Nothing is more frightening than changing your realizing that tube amplifiers are more musically authentic than transistor amps. Then you began to consider that there really is a difference in the aural matrix created by push/pull and single-ended amps, and that pentodes do sound very different than directly heated triodes....and then the thought starts creeping into your head... maybe our Japanese audiomaniac brothers, who are into a serious head about output transformers, know something that we are finally ready to deal soul matters...and that means output transformer quality matters, and it is below your par in store bought amplifiers.......

LET ME REVIEW THIS STATEMENT: The output transformers is the single most important element in your tube amplifier and you know nothing about them, and everyone assumes you are not smart enough to know the difference in quality. Why is the OPT more important than your tubes?...think about this bros’....once you have installed your OPT you are not going to change are married to it for life...tubes, you can change in less than a minute....divorces are easy and painless, and polygamy encouraged.



But first none of this makes sense unless you believe that......


"A Man Has to Have a Dream"

Do you dream? When you put your head down on your pillow, or while you are waiting for a train, or while listening to music, do you dream the dream that thousands dream...the dream of your dream amplifier that will transport you to the highest regions of musical ecstasy? Join the club dude.

In the evolution of human consciousness we find, at its center, a dream of beauty. We find this dream in the Paleolithic caves of France, in ancient Egypt, Greece, and Rome, throughout all native cultures and in the development of modern European culture. It certainly is present in America, though American men are most reticent about admitting their need for beauty, except when it comes to cars and magazine center-folds. It is the responsibility of each generation to redefine this dream and make it meaningful, which is why the artist, who is intrinsically the rebel, is so important in the evolution of culture....he is our guide in the natural wilderness of our dreams.

Decades ago I reached the conclusion that of all the modern arts, the audio arts was the most relevant and least understood. Not in sculpture, not in basket weaving, not in macramé, but in the audio arts I, like you and thousands of others, are able to express our dream of beauty...and it is all about the expanding possibility of ecstasy within music.

This explains why I have consistently supported the audio artist, the rebel, who is shredding the boundary, because that is always where art is most vital.

The entire audio industry, all of the designers, all of the manufacturers, editors and agitators, like myself, exist to serve your search for beauty. My job is to convince you to expand your dreams and demand more musical beauty.

This project exist because Menno Van derveen and Howard Gladstone of Plitron Manufacturing had a dream and work together to bring it into reality, and when I experienced....their work inspired a dream in me......


Stop, and now read my articles about why you should learn how to build a tube amplifier

I assume that you have two left hands, have never soldered a wire in your life, and can’t read a schematic and are terrified of getting an electric shock. Perfect. If that is true then you are the perfect man to build an amplifier, because it is too expensive and time consuming for you to sail across the Pacific or climb Mt. Everest.

A man needs a challenge and there is nothing more rewarding that confronting the limits of our experience.... except in this case we are going to make it very easy because I am going to insist you hire a skilled guide...someone who will sit by your side and take you through the process.

If you choose a single-ended amp that uses a simple two stage 6SN7 for a voltage amp and driver and a 300B output tube we are talking about a circuit that probably has less than twenty parts. All of the hard work is already done..the chassis is punched.

Get on the Internet or advertise in your local newspaper that you want to hire a local radio/TV radio dude, who will be paid by the hour to take you through the steps of building your own amp and teaching you own to solder, use a volt meter, and the simple techniques used NOT to get a shock.

What are the benefits besides the enormous pride of achievement and owning a state of the art amp and saving tons of money? Your experience of music will have been altered me on this one. The reason should be obvious and there are articles on the Triode Guild web site which goes into greater detail on how the creative process expands our experiential boundaries....YOU HAVE NOTHING TO LOOSE.


I take great pride in being the most critical audio journalist in the entire universe, and often awake from my sleep screaming, "Why Me Lord? Why Me?" It also clear to me, as ex-US Army soldier, and lover of G.I Joe action figures, that I have a patriotic duty to all freedom loving Americans to help close the "TUBE AMPLIFIER GAP" which exists on three levels: (1) the enormous difference between the true state of the art, custom made hot-rod, tube amplifiers you see on DIYers/audio artisans web sites and the tube amplifiers you can buy in stores, and (2) the enormous gap in creativity between American and Japan, Italy, and England all of whom are ahead of us in tube amplifier design. (3) Why should a state of the art tube amplifier cost as much as Harley-Davidson Electro-Glide? How many normal dickheads, like you and I, can afford such expensive transportation to higher dimensions of musical reality? Nothing is more important to me than creating for YOU the opportunity to experience what is normally beyond your budget.

I have raged against American tube amplifier and speaker manufacturers on my Triode Guild web site, and have suggested over and over again that, like all revolutions, the dynamo of change will come, not from the center, which is creatively petrified, but from the rebel....the audio artist on the fringe....YOU.




Of course this implies that you are ready to jump from the third wave to the 4th Wave..meaning you have reached a higher level of artistic refinement and you know the difference between the personality of EL34 vs. 6550 vs. 300Bs, or push/pull vs. single-ended.

Let me put this another way: There are two groups of tube amplifier customers: (1) Those who want the ease of walking into a store and buying a known brand...and don’t want to be confused by choices, and are not bothered by compromises (2) The higher IQ, more musically sensitive man who is no longer impressed with the highly compromised tube amplifiers that are designed to satisfy Mr. Normal, and is ready to have an amplifier created to satisfy his own unique vision. Of course, because this man is more knowledgeable he recognizes that what he needs may not be available in a highly refined push/pull forty watt per channel 300B or 6550 amplifier. Or what about the man who wants a 15 watt one tube single ended triode of ultimate refinement? There are none available in America. Or let’s get more basic...what about a single-ended 300B amplifier of ultimate refinement...and affordable? Not available in America.

YOU know that great tube circuits are simple, and that once you decide on a power rating, circuit configuration (push/pull or single-ended), output tube types (directly heated triodes or pentodes) that building the circuitry is not only relatively simple, but, if he so chooses, can be changed to a different configuration very easily when he gets bored.

Don’t like the carburetors or cam shafts in your hot rod motor? What do you do? Buy a new motor or just change the parts? Which explains why I own lots of different brands of tubes and own lots of different types of is much easier to change tubes and circuits than carburetors.




My nose knows. When, once upon a time long ago I was a textile designer, my clients used to say I had a great nose for design, meaning that I knew from among hundreds of designs which would was purely intuitive.

I have the same nose for audio circuits and I took one whiff of Menno’s new revolutionary design and I knew I was beholding something major....especially when I compared it to the gaggle of other "normal" transformers I have.

Most of you are unaware of toroid transformers which use a round hollow core, as opposed to the E/I core which use a bobbin in flat laminates. Toroids and E/I transformers, because of their very different physical design, create very different type of magnetics and that is why they operate differently and sound so different.

In the last twenty years toroid power transformers have gone from obscurity to commonality. There are so many advantages to toroid designs that they have rapidly replaced "normal" transformers. Plitron’s major business is toroid power transformers. I don’t know a high quality transistor amplifier that doesn’t use them. Of course Plitron’s major customers are not audio manufacturers. Though toroid power transformers offer superior performance few tube amplifier manufacturers use them in America (they are popular in Japan) because they don’t match the shape of the EI core ( square) output transformer. But my point here is that designing a state of the art toroid power transformer is a piece of cake compared to designing a state of the art toroid output transformer. There are hundreds of companies that make toroid power transformers and only one that makes toroid OPTs.

In the truest sense...Menno made the breakthrough, and I look at him in the same way I look at Julius Futterman...a true pioneer of the audio arts. This genius emerged from decades of dedication to Menno’s dream of creating an output transformer that permitted higher levels of musical ecstasy...Menno’s dream of higher states of musical union is the dynamo of his creative efforts.

Now that you have finished reading Menno’s books and all of the technical articles that are available on the Plitron web site you understand that his toroid output transformers have very different electrical characteristics than "normal E/I" output transformers and you are beginning to understand the relationship, though it is mystical, between their unique design and their unique aural matrix. You will note that Japanese audiomaniacs are groking these transformers...and they are the most sensitive to transformer aroma.

When I met with Menno at the Oct, 99 AES convention, to discuss his toroid pilgrimage, I immediately knew that he was a Zen monk in a previous lifetime, who probably crafted music bells. Passionate, introverted, philosophical and totally dedicated to exploring the shadows of musical ecstasy is an accurate description of the only man who "broke the single-ended toroid barrier". I am not diminishing his achievement in designing such high quality push/pull toroid OPTS, (which in their own right will soon cause a major revolution in the push/pull religion) but designing a single-ended toroid is like climbing Mt. Everest in a bathing suit. He deserves an award for this, and I gave it to him.

In 1999 Menno gave me a sneak preview of his upcoming single-ended design and I emailed my fellow tube savants all over the world and asked them what they thought of this concept. Most couldn’t even imagine it. Those who were familiar with the technical problems normally associated with toroid output transformers said it was a very bad idea and would sound terrible. I even asked my friend Ulrich Poulsen, of AlphaCore, who manufacturers toroid power transformers, and he said it couldn’t possibly work right. One heavy-duty old timer audio engineer blurted out..."Nonsense". Then I called Christopher Columbus and Orville Wright and asked them what they thought of Menno’s revolutionary concept.

By this time I received a large stack of yet unpublished technical papers from Menno which went into (way over my head) technical detail on how he solved the problems normally associated with toroid output transformers. This is a technical tour de force, and a significant technical and artistic achievement and I am very comfortable to state, with the boldest confidence, that any previous critical opinions about toroid output transformers, that are based on NOT Menno’s design, are irrelevant. Let me say that another way: Until you come to understand and experience Menno’s technical and artistic achievement your notions about toroid output transformers are obsolete.

It was obvious that Menno suffered for many years on the path of perfecting these designs, and I am certain that his artistic achievement/engineering skills indicate a sublime balance between music passion and engineering...very rare indeed. As you will soon discover from reading his book, his music passion created his passion for tube amplifier design and that birthed his passion for creating a new family of toroid OPTs that would expand our envelop of musical ecstasy.

And that is the difference between power transformer designers and OPT designers. OPT design is an art. An OPT is a magical device, and like all audio devices it electrical characteristic is only a meager insight into its potential. The electrical characteristic of an output transformer are extremely important because we want them to operate properly, but the only way to know their artistic capacity is listen to them in various circuits. Want a good map of Menno’s journey? Read his book ( I am not getting a commission on book sales).

Before I close this section let me make this point: I believe we are on the verge of a new genre of push/pull amplifiers...I feel it and I see it...all across the thermionic horizon...lower power, much greater refinement...very stiff regulated power supplies...and the key to maximizing this new push/pull aural matrix is to get very far down into the unique design of Menno’s push/pull designs.

If you don’t believe just check just check issue 12/summer 1999 of Vacuum Tube Valley Magazine...Kevin Kennedy’s 30 watt push/pull amplifier with two different types of tube regulation!


When you take the whole shebang and wrap it up into one ball of music wax; when you put it all into one big pot and stir it up this is the stew we are in:

The only reason that justifies a new form of audio technology is that it creates an expanded aural matrix...something that is easily recognized as being more mysterious and musically beautiful..Something that has the capacity too more deeply affect our primitive physical sense of music. Being a "new and better" circuit doesn’t matter a rat’s ass if we are not deeply moved by the music created.

There is no doubt, in my mind, that Menno’s new output transformers designs create a unique expanded aural matrix, (TRANSLATION: EXPANDED MUSICAL BEAUTY) and it must be because they are toroids, because when I take my "tube amplifier module" and plug "normal" transformers (which I can do in five minutes) the magic goes away..There is a shrinking of the aural matrix..It becomes narrower...there is less openess..the air is gone..the dynamics are limited...the harmonic whole-osity is diminished...what more can I is that obvious.

For those who love single-ended circuits and have accepted their well known limitations because they are so musically magical in other respects, I want to suggest that with Menno’s toroid design those limitations are very much less limited and you will rethink your notions about single-ended circuits.... and what we love...there is more of it. Those of you who have not explored single-ended circuits because you observe their lack of tight bass and top end extension...wake more complaints...and if you are looking for high powered single-ended circuits...this is the path.

I am not being flip when I say that it will take a long time indeed to fathom the full glory of these round gizmos because these demand much more sophisticated circuits....and America is just learning the art of sophisticated tube amplifier it existed in the 1930s...and exists today in Japan.

Let me say this another way...with the Plitron toroids the limits of possibility have been pushed out to the point where circuit designers are now going to have to catch up.... And I suggest you check out the Japanese articles on the Plitron web site to understand what I mean.






What is so impressive about the Plitron effort is the vast array of articles, technical information, and books by Menno, that are available to give you an excellent education in the art of tube amplifier design. This is the right way to treat customers in the world of the Internet.

We have all entered a New World of HI-IQ audio, and I believe Plitron is setting the right example for everyone, and I want to take this effort even higher. Yes I am very demanding...I demand and I will help you get very deep down into your dream amplifier creation process...and that means reading and studying all of Menno’s books...Plitron articles...and surfing around the web...

Let’s face it dudes, why would the Guildmeister want to associate with anyone other than the best and brightest?...makes no sense.... and the sense is... have the ego strength to know that across the ocean is a more refined audio culture that we should be pain, no gain...


Like I said, the reason I am such a Zen gizmologist is because I haven’t invented anything new here. I am just using the Internet to stimulate the development of the Japanese audiomaniac culture outside of Japan, Those of us who religiously read MJ and Stereo Sound, on the potty, and swoon over all those ultra-cool custom made amplifiers know this truth: In Japan the hot rod tube amplifier market exists so that the enormous community of skilled audiomaniacs (who know how to solder and read schematics) can build their dream amplifier. This is the path for the Japanese music connoisseur who wants ultimate performance.

Hey there Mr. America, Mr. South America, Mr. Europe, Mr. Madagascar, you deserve ultimate tube amplifier coolosity, so you have no choice but to go the custom made hot-rod route, because you have no choice. Isn’t that why you have all your suits made on Savile Row in London? I apologize in advance for all the beatings I will bring down on your head but just remember this analogy: autos are to America as audio is to Japan...the really cool gizmos of life can’t be store bought, you have to go the custom made route...My article on the Triode Guild web site about the amazing $5,000 Sun Audio of Japan amplifier kits are a good example of the type of companies supplying the connoisseur’s need for the best quality.

Because of the Internet you now know that the tube amplifiers available in stores, "off the shelf", are not where the state of the art can be found. Those store bought amplifiers are filled with too many compromises and too expensive for YOU, the community of gifted, sensitive music maniacs, who quite frankly demand a higher level of tube coolosity.....YOU KNOW TOO MUCH NOW TO SETTLE FOR LESS.

OBSERVATION: We surf to tube web sites and see really cool custom-made tube amplifiers. We look in the pages of Glass Audio, Sound Practices, Vacuum Tube Valley and see really cool circuits from all over the world. And what else do we notice? Chassises that look like they came from Toys R Us...flimsy, ugly and poorly fitted...and our dreams get limp because we want a beautiful circuit to be contained within a beautiful chassis. Would you buy an amplifier, no matter how cool its circuit, if it were mounted in one of those ugly toy chassis? Get my point?



Can we talk about the reality of being a Wholey dude?

Tube amplifier lovers are facing the same crisis that Hawg owners were facing. Thirty years ago when I bought my first Harley-Davidson I was member of an exclusive club. Today everyone rides a Harley, which is why custom Hawg shops are on every corner..sensitive dudes like us need unique totems that express our unique artistic personality. The same is true with tube amplifiers. The Internet has shown us that there is a heretofore-unknown world of custom hot rod high performance amplifiers...and music fires are burning in our loins...rightly so.

Life is short and who wants to look at life from the bottom of the mountain when the view from the top is so thrilling? (This wisdom also applies to (1) military strategies, i.e.: always fight from the high ground, and (2) for short people, like me). This wisdom applies to our most important passions. If smoking cigars is what makes your loins smoke then, go for it, and smoke the greatest work of cigar art, so you can experience the highest of cigar highs. What are you waiting for? Or, is the climb to the top of the mountain too expensive for you?

Of course, we live in a world where the music mountain keeps on growing wider and wider with more and more "low quality" music making the base. On the other hand, there are ever expanding possibilities of new forms of musical ecstasy, and they are at the top of the mountain and American Express can’t take you must climb and get off the beaten must demand more and give more of yourself if you want the ultimate music, or any other activity.

I guess I am asking you to ask yourself the most fundamental question: Where do you belong on the hierarchy of musical beauty?

Which brings me to the economics of ascension. The reason so many passionate musicmaniacs are not surfing the crest of the music wave is because it normally takes a BOATLOAD OF MOOLA....GIGANTIC GELT.....HEAVY GOLD BARS.....and that is what this revolution is all about....drastic reduction in the cost of surfing to the top of the mountain.


I can not find ONE transformer coupled tube amplifier that is manufactured for distribution through stores that meets my standards for "serious", which is why you should now go a check out my VERY SERIOUS TUBE AMPLIFIER CHECK LIST WHICH YOU WILL FIND IN SECTION THREE. Now that is a pretty outrageous claim and I am sure it will get many upset..tough on the chickens when the fox gets in...I didn’t make the revolution, I am only enjoying surfing it. This is a great business opportunity.

A short while ago this would have been an outrageous claim, but the Internet has elevated your perception of tube amplifiers, because every night, seeking your dreams, you surf to those audio artist’s web sites and drool over that really cool custom hot rod audio gear. Who can blame your male DNA for wanting the concrescence of coolosity? The days of believing that what audio reviewer is drooling over is absolutely the coolest audio gear is over...for ever.




I love men who passionately argue about beauty...especially musical beauty and that is what the debate is all about when it comes to push/pull versus single-ended circuits. Of course the good news is that, unlike transistor amps, you have lots of choices and this is not about right or wrong, but about which aural matrix triggers musical ecstasy in your soul.

Now that you read everything on the Triode Guild web site, you understand my position about both...neither single-ended or push/pull have been developed to a high degree of sophistication in America. If you have been comparing the relative value of each, your comparison is based on comparing less than optimal circuits. Does that mean when you compare the proper implementation of each that the differences disappear or get larger? The answer is definitely YES.

How should you decide which to choose? To a great extent the answer is dependent on your speakers, because the lower powered single-ended circuits require speakers of very high efficiency...though I remind you again that all tube amplifiers will sound better with high efficiency speakers.

My cycle of three decades of thermionic evolution flowed this way...push/pull pentode to OTL to single-ended/directly heated triodes, push/pull with directly heated triodes, and now I am ready to experiment again with push/pull pentodes...each is a unique form of beauty...and only you know what is right for you, my dear Dr. Frankenstein.



My goal here is to de-mystify the tube amplifier design/creation process, and convince you that creating your own dream amplifier, whether it is single-ended or push/pull, is no different than creating your own dream home, dream car, dream motorcycle, dream rifle, or dream barbecue grill. I was playing with the idea of using the "Lego" toy model as an example, where you can snap different basic components together...but that was too simple...yet in a sense it is true. My "Lap-Top Amplifier" article on the Triode Web site describes this project.

If you had in your library, all of the books and pamphlets I ever published...going back into the late 1970s, all the way back to "TUBE GOD", you would notice that everything I am recommending here, I recommended twenty five years ago, and when you surf to the really cool tube web sites, the same advice is being given today, and it is all much more advanced than what you read in audio magazines.

But remember my meta-agenda...this is just the beginning of the 4th wave where you are becoming much more sensitive and aware of your SOUL..the quality of your output transformer...which I believe is the weak link in American amplifiers.

This Dr. Frankenstein model is an effective, yet imperfect, analogy and takes all the romance and mystique out of tube amplifier design, and I hope it stimulates your imagination:

Here is a bold claim from Dr. Gizmo: This Triode Guild project is delivering to you the highest quality heart, soul, muscle and bones you can obtain America. All you have to do is figure out what brain you want....and... you can change your mind next year...if you get bored...and this is a surprise you will soon learn about...

You have two basic options: (1) If you are skilled builder you will assemble your own amplifier, or (2) You will hire some audio artisan to build your dream amplifier for you, and together you will decide the implementation of your dream.... and there is a growing list of these artisans on the Triode Guild/Plitron web site.

Now let me offer you my most profound personal advice:


Which is my core philosophy about tube amplifier circuits. Use simple high quality circuits with very stiff power supplies. Personally, I find complicated circuits sound complicated, they tend to be less reliable, and often exist, NOT in the service of musical ecstasy, but to satisfy the audio designer’s ego; so that the designer can claim that he has created something "new and different".

Designers of complicated tube circuits claim that their unique circuit point of view eliminates different forms of distortion, which may be true, but complicated circuits also add their own form of distortion, which I describe as a loss of tonal purity. I am not criticizing any specific circuit, and mention this credo as a general guide.

Let run through your artistic decision making process:

  1. Decide how much power you need
  2. Decide if you prefer the push/pull or single ended aural matrix
  3. Decide which output tubes you want to use
  4. Decide which output transformer you want to use
  5. Decide how "stiff" you want you power supply to be.
  6. Decide how refined you want your circuit to be
  7. Decide what input/driver circuit and "output configuration" you want
  8. Decide what aesthetics you want in your chassis design

That’s not so mysterious, and this is the process that every tube amplifier designer goes through. The implication of the above is obvious: Each feature or path you choose represents the crafting of your unique aural matrix. Push/pull pentodes create a different aural matrix than single-ended/ directly heated triodes...different input circuits sound different and different configurations of power supply sound different. For the novice this freedom can be confusing, and that is understandable, which is why the TRIODE GUILD chat room is there to help. For the tube savant this is literally a dream come true. With this project, for the first time, you are not given any can ascend as high as you want.....and now for a quick concrete example:

Everyone in America who makes 300 B single-ended amps uses either a 2.5K or 3.5K OPT because this impedance gives the greatest power, yet there is a well developed community of triode maniacs in Japan who believe, and they are right, that the 5K OPT gives a more refined sound, at the price of lower power...about 5 glorious watts. So I use 5K Plitron SE-OPTs because I made the choice that I preferred refinement to power...a choice not available to me in any store bought amplifier. And of course amplifiers with the quality of the Plitron transformers are completely unavailable at your local hi-fi emporium. I believe, as does Howard and Menno, in freedom of choice....for those who are refined and secure enough to demand and enjoy it.


But no matter your religious preference the existential reality is that the single most important commandment is: THOU SHALT USE THE HIGHEST QUALITY OUTPUT TRANSFORMER... the quality and personality of the output transformer you use is the artistic foundation of your dream is the soul of every transformer-coupled amplifier, and there is great deal of difference here in quality. Think on this for one moment: You can change your tubes very easily. It is easy to change your input/driver stage, but once you pick your OPT, your are married for life.

Which brings me to my pet bitch about the quality of output transformers used in American amplifiers, and I made this complaint long before I discovered Menno’s toroid OPT. It is shocking that the tube amplifiers the audio press considers state of the art have such mediocre output transformers...but there is a good reason for this. The OPT is the most expensive single component in any tube amplifier and this is where there is the greatest cost compromise, especially when you consider the universal cost/multiplier: every $100 of cost gets translated into $4-500 added on to the retail price. Use two high quality OPT that cost, at the very least $300 each. and you have added at least $2,500 to the retail price.

Let’s review this cost/multiplier that I knew well at New York Audio Labs. Let say an amplifier cost is $200 in parts and $100 in labor, equaling total cost of $300 which has to multiplied by at least two so that we make a profit, making the wholesale cost to the retailer $600, which makes the retail price for you $1,200 so the store can make a profit.

Now do you understand why it is impossible for American tube manufacturers to use the best quality output transformers? This cost multiplier also explains why the "custom-hot rod" Japanese tube amplifier market is based on customers wanting the highest quality OPTs that they know are never available in store bought amplifiers.

In Japan output transformer connoisseurship has reached such a high level of refinement that there are many custom output transformer makers that will gladly make you your own designs at a cost of between $1,000 to $2,000 each. Are you ready to spend $2,000 just for your OPTs?

Let me also point out a unique feature of the Japanese audiomaniac culture and it, again, resembles our hot rod auto culture: the wisdom is to buy absolutely the highest quality speaker drivers and output transformers because they will never go out of style, but will appreciate in value. Buy a very high quality motor and it will never go out of just rebuild it. Get tired of your speaker system? Just change the configuration of the drivers (still using the same drivers); change the cabinet and crossover. Getting tired of your amplifier? Just change the input circuit, but never change the output transformer. Makes sense to HI-IQ types. I am suggesting you adopt this Japanese attitude.

To return to the Plitron toroid revolution:

  1. I do not know any better transformer than Menno’s OPT designs unless you are ready to spend $1,500 each on the custom Japanese models. They are my favorite transformers until something better comes along, and they totally satisfy my artistic standards and my campaign to get you into taking your output transformers more seriously.
  2. The quality of Menno’s toroid design means that you are assured of creating a tube amplifier with transformers that are truly state of the art, which if they were available in a store bought amplifier would be affordable only by Mr. Rich Guy.
  3. Dreams Have Power: It is time for you to make your dream amplifier a reality.


Now that I have convinced you to take your output transformers much more seriously, we can move on to a subject that I have been exploring for more than twenty years; a subject which I spent considerable time discussing in my first book Understanding Tube Electronics.

Do the Plitron toroid power transformers scare you because of their large size? You are immediately struck by how much larger they are than the power transformers used in your amplifier. Size matters and they are intentionally designed to be over-rated and flexible and what that means is superior performance and enormous flexibility now and in the future. If you want a very stiff power supply you must use a very over rated power transformer...and that means bigger and more expensive. Here for the first time are power transformers that encourages you to go wild and crazy with your designs. There are enough different voltage "taps" to support a wide range of circuits, and these transformers can be used with every AC input so it doesn’t matter if your wall socket is in Katmandu or Tokyo. This is all coupled with the inherent advantages of toroid power transformers, which I must comment on in terms of the refinement imperative....but first get out your stethoscope and put it on the power transformer of your amplifier and listen to its hum. The advantage of toroid power transformers is that they are very very quiet and they do not have the inherent mechanical vibration of normal transformers which can be transmitted into the input stage of an amplifier and cloud the sound.

Those of you who have read my articles in Positive Feedback Magazine are also aware of my campaign to upgrade the quality of tube amplifier power supplies. The expression associated with power supply quality is "stiffness" which means that the power supply B+ voltage doesn’t vary with the "music load". When an amplifier starts producing dynamic power its power supply voltage starts to sag and that is not a good thing. The best strategy for the ultimate power supply quality is to use active tube regulation, and this very old idea is finally coming back into popularity. I can’t recommend too strongly the exploration of this option.

The next best way, and the way used by 99% of serious tube amplifier designers, but almost completely absent in store bought American tube amplifiers, is to use chokes, which are inductors, which look like small transformers.

These are absolutely essential in every serious tube amplifier design, and as you will discover I suggest them on every DC voltage rail in your amplifier and that includes output, input, bias, and filaments (if they are DC and if you are really insane)). Why are they so important? The better the quality of your output transformer, the more important is the sonic signature of your power supply. Plitron OPTs demands the best quality power supplies because they will reveal the sonic weakness of "soft" supplies. Stiff power supplies are needed here, and that means very robust and over rated power transformers that are well filtered with chokes or regulated. Chokes also "filter out" all of the high frequency hash that can appear at the output of solid state rectifiers either because of their own inherent noise quality or high frequency noise contamination from the AC wall sock. But most importantly the electrical characteristics of chokes "smooth" out most of the residual AC ripple that is inherent in all rectifiers, both tube and solid state, and "stiffens" the power supply.

Let me translate choke filtration to sonic benefits: the first thing that is most noticeable with Plitron’s toroid OPTS, because it is most obvious, is the improved dynamic quality and clarity of the bass response. I will stand by this statement: without chokes, or active regulation, it is impossible to achieve high quality bass response in any tube amplifier. End of argument. So if you want to fully realize the improved bass quality of these OPTs use a stiff power supply.

But in the long run it is the higher degree of refinement in tone, and the expanded aural matrix, that really matters, and you can especially experience that in the midrange. In this area which is always the strong suit of tube amplifiers choke filtration makes the great, glorious. By eliminating the ever present AC noise contamination and by diminishing power supply AC ripple the midrange becomes must clearer, more radiant and subtle, and the benefits are not subtle. In other words the taste of the midrange becomes strictly gourmet.

As you will discover I suggest, if you are seeking ultimate refinement, use, at the very least, a completely independent and choke filtered power supply for the input circuit, which completely decouples it from the output stage power supply. I know of no American store bought amplifier that uses a separate power supply for the front end, or (obviously) one that is choke filtered. Yet, when you look at the true state of the art DIY tube amplifiers in Italy and Japan it is common practice! Are now ready for one of my favorite taunts? You will also notice that this was standard practice in the 1930s...just check out the old schematics! The future is the past. Wake up America!

Consider this point: chokes are passive devices that are completely reliable so they do not change the reliability of your amplifier. Only the Triode Guild chassis is big enough to accommodate them. It is possible that you may use as many as FIVE chokes for each mono chassis or SEVEN in a stereo amplifier. Count the number of chokes in your average $10-15,000 store bought amplifier! IT IS USUALLY ZERO!

Let me mention this trick to anyone who is contemplating a stereo amplifier, one that uses one power supply for both channels: use a choke for each output and input stage (four), thereby giving you maximum power supply separation possible in a stereo design. Fortunately the Plitron chassis is big enough to accommodate this.

The type of power supply capacitor you use is also an important consideration and I am antagonistic to "normal" electrolytic capacitors power supply capacitors because of their grungy sound. In my own custom made amplifiers I only use industrial oil capacitors in the power supply.... but NO store bought amplifiers have them because they are so large. The only large value power "lytic" supply capacitor you should use, if you want ultimate refinement, is the Cerafine brand...and they are expensive.

There is a hierarchy of rectifier righteousness and at its bottom is the universally used cheap 25 cent silicon diode which produces horrendous high frequency hash which is toxic to tonal righteousness, and must be avoided at all cost. If you must use solid state diodes you must use Hexfreds and they must be filtered with chokes. Why use solid state rectification? It is cheap, convenient, and may give better bass response...and if you are building a tube amp that needs a very high current power supply it may be impractical to use a large higher current tube rectifier. Everyone will want to use Hexfred rectifiers if you need DC on your filaments, (but again it must be filtered with a choke, or regulated when used on directly heated triodes if you want ultimate refinement)

Now having said all of that, the only way to achieve maximum refinement is by the use of tube rectification, and again I suggest a separate tube rectified power supply for the both the input stages, output stage and bias supply in single-ended triodes. Tube rectifiers produce a higher quality tone because they don’t produce the "hard" harmonics of solid state rectifiers. There is an obvious sonic difference between solid state and tube rectification and tube rectifiers win by a long shot.

Tube rectification has the added advantage of giving you a slow turn on of your B+ voltage, which prevents your tubes from being zapped with high voltage before their filaments turn on. This extends the life of your tubes and over the long run will insure lower noise levels.

The only negative feature of tube rectification is that they may not have the best bass transient response compared to solid state rectification. But that limitation can be overcome with proper power supply "stiffness".

Which brings me to the power supply dilemma of high powered push/pull amplifiers whose power supply would need a very large tube rectifier or a "tube rectifier bridge" made from four tube rectifiers, which may become impractical. My suggestion in this case is use a tube rectifier for your input stage, Hexfreds for the output stage, but make sure you use choke filters. In this case be sure that you are able to turn on your filaments with a separate switch, so you can turn them on first, and warm up the tubes, before you turn on your B+ voltage.

OUTPUT TUBES: This is truly the golden age of tubes with an enormous variety of extremely high quality tubes available and that includes both pentodes and directly heated triodes, as well as miniature octal and twelve pin tubes. What is so glorious about this current "Neo-Classical" era is that for the first time in the modern audio arts we have choice between so many different brands of directly heated triodes, especially well as pentodes. Only a short while ago we had no new directly heated triodes to choose from, and pentodes were getting scarce.

It is a good thing that those who love push/pull amplifiers can now run through a menu of different brands and variations of their favorite pentodes: EL 34, 6L6, 6550s, and KT 88s. The other exciting development is the return of the push/pull amplifier that uses directly heated triodes of the 2A3 and 300B variety, which is a return to the glory of the late 1930s when these designs first appeared....and pentodes weren’t in vogue yet. Push/pullers can literally become faint with choices of output tubes.

The challenge here is to achieve maximum reliable power with the greatest possible refinement, and that is where the Plitron toroid OPTs, coupled with stiff power supplies will take you beyond the beyond...especially if you use the right input/phase splitter circuit.

On a personal note, because it is my prejudice...if you don’t need more than 60 watts I would like you explore the use of 300Bs in push/pull amplifiers. It is a unique and mysterious experience.

A comment about tube reliability: Tubes are as, or more, reliable as transistors when used properly. Both the US and Soviet Military still use tubes. Don’t design a circuit that uses the tubes at their maximum rated voltage. Tubes are voltage amplifying devices and if you use "tube killer" speakers, which are low efficiency, and below 8 ohms, you are inviting Dr. Kervorkian into your living room.

A concrete example: I use tube regulated power supplies that are over 30 years old, and they all have their original tubes, and they work perfectly because these were well designed and conservative circuits.

I don’t have to spend too much time here talking about your choices of directly heated triodes in single-ended amplifiers because the Triode Guild web site is filled with my discussions of the different brands. But there is one aspect that is worth mentioning because for the "custom hot rodder" this is important.

Recently because the titans of directly heated triodes, Riccardo Kron and Alesa Vaic, have invented a new category of high current directly heated triodes, the boundary of refined power has been significantly extended. It is now possible with a one-tube output stage to achieve from 15-30 watts of power. All that is required, in the case of the Plitron SE-OPTs is that you use a Plitron power transformer designed for this high current operation which means it has a rectified B+ of 590 volts and can produce 100-150 ma. of idle current. The important consideration here is that Menno’s OPT design can handle this higher current and power load, and that is not true for many other single-ended transformer designs.... I know I have tried it. BUT I want to suggest that these higher powered directly heated triodes be used conservatively...these are expensive my suggesting is stay within the 550 volt/90 ma range limit.

In my recent experiments with the above I can assure you that the Plitron toroid single-ended OPTs can handle the increased voltage and current and sound truly amazing at the higher power levels.

If you choose to go the high current single ended directly heated route, which more musicmaniac are choosing, be aware that you need to use a driver stage that is matched to these tubes, which will have to swing more voltage than driver stages designed for "normal" 300Bs.

Those who are blessed with super high efficiency speakers that are above 94 dB efficient are free to explore the ultimate mystery of 300Bs, 2A3s, and 45 with the Plitron 5K SE-OPT. Those of you who are into Lowtherosity pay attention: you need the refinement of the Plitron 5K SE-OPT!

SELECTING YOUR PLITRON OPT: Before I get into this subject let me point out something that you have been denied up until now. Have you ever seen the output transformer specification, like you see listed by Plitron, from any other transformer manufacturer or manufacturer of tube amplifiers? Do you want me to get really aggressive on this issue? What other OPT transformer winder makes available a design book as complete as Menno’s, or any for that that discusses all of the paradoxes and compromises of transformer design?

The answer is probably NOT, NO OTHER. I haven’t found another, which is why Howard and Menno flaunt their specifications and Menno’s book, which is quite extraordinary. What is the relationship between these electrical measurements and musical performance? While there is no scientific correlation between perceived music and distortion measurement, I can assure you that based on my own experience Menno’s toroid OPT are shredding the boundary of OPT performance. But you understand this because you have read his new book.

As I am writing this word started to leak out in the audio industry about this project and I began to get emails from other transformer winders and they were upset with me, in spite of the fact, that I have suggested this similar strategy to them a very long time ago, and they all refused saying it was too much trouble. I’ll bet you Cameron Diaz’s bicycle seat that other’s will soon follow the Triode Guild model...and that is good for everyone.


SINGLE-ENDED AMPLIFIERS: Chapter 9 of Menno’s book is one of the best explanations of the benefits and limitation of this topology, and by now you know that a majority of my articles on The Triode Guild web site are in praise of this circuit’s paradox.

There is only one way to connect a tube (directly heated triode) to a single ended output transformer ( I am not discussing pentode tubes used with single-ended transformers because they are not popular), except if there is the use of some variable feedback control, which is rare.

When you scan your single-ended OPT choices here you will note that you can choose a design from 1 watts up to 90 watts. You will note that certain models can easily handle the new high current directly heated "300B type" triodes by KR and VAIC, and there is a special model for using the Svetlana directly heated triodes, which creates a 90-watt single-ended amplifier. Yikes.

There really is only one issue for you to consider here. The question is should you use "fixed" bias, where you can adjust the bias current running through the output stage with a meter, or use self bias where the tube sets it own bias. I normally recommend self-bias, but there is a good reason to use fixed bias, and it is if you are going to "play" with lots of different brands of tubes. Also changing the bias current flowing through your tubes will change the way your amplifier sounds. You will also note that when you set the bias for 60 milliamps for a Western Electric 300B and change and then plug in a KR 300B this tube is not drawing 60 milliamps, and if you want this tube to operate at that point so you will have to adjust the bias.

You should be aware that many claim that self-bias sounds better. You should discuss this issue with the artisan who is building your amp.

PUSH/PULL: A TRIP TO P/P HEAVEN: Goodness gracious great balls of fire. There are so many choices here you may need a computer to list them all, and that is the fun of push/pull amplifiers.

When you read Menno’s book you will discover that this man has shredded the push/pull transformer design envelope. CHECK OUT THE SPECIALIST RANGE. THIS IS TRULY ONE OF THE MOST EXOTIC TRANSFORMER MENUS AVAILABLE...for all the classic pentodes, directly heated triodes including Class A RF, including the Svetlanas, and Russian "regulator" triodes.

Grand good news is that Menno has literally invented a new type of push/pull output transformer, which permits you to create a SUPER TRIODE© or SUPER PENTODE© configuration of extra-ordinary performance. These are, again, described in Menno’s technical papers which you can download.

During the 1970s when I was a push/pull addict I had three "mule" amplifiers, A Dynaco MK VI, Dynaco 70, and a Harmon Kardon Citation, and if I had a dollar for every time I rebuilt the output stage and tried a different configuration I would be a millionaire today...which is why Plitron’s SPECIALISTS RANGE of push/pull amplifiers gives you so many and advanced ways to configure the output stage.

Pentodes create unlimited possibilities in the way they can connected to their output transformers (if the transformers have the taps) , and each has their advocates. With Menno’s toroid push/pull OPTs you have the choice of using the various types of "screen taps" or not. Do you want to use screen grid winding technique, cathode feedback or unity coupling? You have all the options and I don’t know any other brand of OPTs that offer these options, and certainly none of them have the unique qualities of Plitron toroids.

On the other hand, directly heated triode tubes used in push/pull don’t require or permit all the output stage "screen" variations possible with pentodes because they don’t have the extra tube elements that are present in pentode tubes that can be used to optimize OPT connection. Adherents of the directly heated triode push/pull school (like myself) claim that they don’t need them, or feedback, because these tubes are more linear than the more modern

(higher powered and less linear) pentodes.

Now is the time to inflame your imagination: There are no ultra-refined low powered (30 watt) EL-34 amplifiers in America; an amplifier that takes the Marantz 8B aesthetic and extends it. Menno’s new Super Pentode and Super Triode are calling and as soon as I have time this is a project I am going to undertake for myself, and am suggesting that you consider it because this is the first time that we can create this genre that exploits Menno’s feedback options. Menno is rightly a big fan of the EL-34 and has designed a circuit board so you can quickly experiment with his concepts. You will also note how much development work he has done with this tube, and has literally re-invented its possibilities.

What I am trying to explain is the fun of push/pull amplifiers, and remember you can always change the configuration of your screen problemo.

If you are using a multi-tube output stage, both halves have to work in perfect push/pull sync for quality performance. The issue of how these multiple output tubes are biased becomes critical, and explains why so many designers pick fixed bias where each tube can, and must, be individually calibrated for the right bias. (This is explained in detail in Menno’s book) If you have eight output tubes, they should all be drawing exactly the same bias current, and you will periodically have to adjust the bias of each..... so that they are all drawing exactly the same current. I suggest that it is important to be able to adjust each tube individually. If your dream push/pull amplifier only uses two tubes then by all means buy matched pairs and use self-bias.


This usually refers to the combination of the voltage amplifier and the driver stage, which in a push/pull amplifier is the phase splitter. There are encyclopedias written on this subject, and you will note all the different web sites noted where you can check out all of the different points of view, so rather than getting bogged down in a micro-discussion let me offer you a meta-view:

I am encouraging polygamy, just like it was practiced in the Old Testament....check out what follows this section....

Chill out: If you change your mind about your input circuit, no sweat. After trying one input/driver stage and you get bored, and become curious, try another. This is the beauty of this The Triode Guild project made possible by the extremely flexible power supply and a chassis that can accommodate any input circuit...including transformer phase splitters or drivers.

Want to get really far out and use a combination of a 6SN7 as a voltage amplifier and an EL 34 to drive your 300B single ended problemo...plenty of options are yours.

Want to change the driver/phase splitter on your EL 34 push/pull problemo.

You will note that in the mono chassis design the "INPUT PLATE" (or circuit board) which will be punched for the tubes you use in your input circuit is 5"x5" which large enough to contain the most sophisticated multi-tube circuit plug regulator tubes...or what ever. The stereo amplifier uses a 5x7 INPUT PLATE, again, more than enough room for your exotic or simple circuit.


Based on my own experience over the last twenty years I concluded that there was a "beauty wall" in transformer coupled tube amplifiers because once you went past 100 watts per channel, you needed such a large transformer that there was a rapidly diminishing sense of musical magic. Personally, I don’t like the idea of a high powered tube amplifier because to go beyond 100 watts a channel requires a very high degree of circuit complexity and so many output tubes that it is very difficult to keep the "push and the pull" in balance. More power can mean more aural confusion. The need for amplifier power is directly related to speaker efficiency and an optimal approach with all amplifiers, and especially tubes amplifiers, is use high efficiency speakers. This is a very classical notion: high efficiency speakers, low powered/high quality amplifiers, and it is still the best guide for maximum musical ecstasy.

You may find it hard to believe, but in my own reference system, my Plitron SE-OPT 300 amplifier produces about 5 watts of potentially paint peeling power...because my speakers, Tannoy Westminster Royals, are 99 dB efficient. A friend of my attempts to get the same dynamic quality and he isn’t successful and he is using four 1,000 watt solid state amplifiers and very inefficient loudspeakers.



You are dealing are now dealing with not only the Guildmeister of the Triode Guild, but one of the oldest audio hound dogs (with a connoisseur’s nose) and a man with a bat ear transplant who has been exploring edge of the tube amplifier art for three when it comes to serious...I know what serious means...and I have also been around the block a few times as far as tube amplifier manufacturer are my nose knows.

So let’s put the beef on the table...if you want to experience the full potential of a tube amplifiers capacity for creating musical beauty you have to do some serious thinking...ponder your choices....get yourself crazy for a while...just like you were making the decision to get married...only this is much more important. This may be difficult for many who are not accustomed to having no limitation on their imagination...insecurities can pop follow me.....

The meaning of very serious, when it comes to tube amplifiers, is quite simply your ability to incorporate into your dream amplifier every single feature that advances an amplifier’s refinement...all of which we have known about for at least six decades, and features that are regularly featured in the most refined custom made Japanese and Italian amplifiers...again..... ABSOLUTELY NOTHING NEW INVENTED HERE.

To start, we must start with the soul of the tube amplifier, the output transformer. It must be of the highest quality, and that means you should at the very least know all of the relevant specifications. Like every machine there is a balancing act here, and you must decide what characteristics are important to you. The very fact that you can choose your OPT from the Plitron menu immediately separates you from the masses.

And again I insist that before you proceed with this project that you buy Menno’s new book....and don’t worry about any of the technical stuff you don’t understand...learn as much as you can so you can make the best decisions possible. Your custom builder will also help you pick the right toroid OPT...and it is great having choices.

INPUT/DRIVER/PHASE SPLITTER CIRCUITS: As an American, you should have the inalienable right to choose the type of input/driver circuit you prefer, and if you get bored or curious you should be able to change this circuit easily. The notion that you must be locked into one input circuit for the life of your amplifier is an obsolete idea, NOT SERIOUS.... and it is totally based on the ignorance of most musicmaniacs (not you) who believe that there is only one right way to create an input circuit for an amplifier. Each input circuit has its own personality, benefits and limitation...just like the humans who invented them. Be proud that you are an American, or a freedom loving human, and exercise your freedom of choices, and never let any tube amplifier designer put into the chains of bondage to one input circuit.

CHOICE OF COUPLING CAPACITORS: One of the commonly used input circuits is the RC coupled circuit, which employs capacitors in the signal path. Though capacitor coupling is subject to the limitations of the capacitor, this type of circuit has the benefit of extreme simplicity, and that matters. There are different schools of thought about types of optimal coupling capacitors, which you are, I am sure, are aware of. You should decide which you prefer, (oil, polypropylene, Teflon, air) and if you change your mind or are bored you should be able to change them easily. I like oil caps in my single-ended amplifiers and polystyrene caps in my push/pull...but am always ready to listen to a new brand that comes along. The different personality of these capacitors permits us to tune the tonality of our amplifiers and the ability to easily change these capacitors is an important consideration.

INDEPENDENT POWER SUPPLY FOR INPUT CIRCUIT: It is very desirable to use a separate power supply that it is completely independent and therefore decoupled from the output stage power supply. We do not want any interstage interaction here. This will make a big difference in the quality of your aural matrix in terms of clarity, openness, and will also have a big effect on the quality of bass response. I strongly recommend at the very least, a separate tube rectifier and choke filtration here and optimally tube regulation. Because the currents needed here is so small a very small tube rectifier and choke is needed. This also means that this stage can be regulated with a simple circuit employing a gas discharge regulator tube.

I don’t know any store bought amplifier that employs an independent power supply for the front end, but you should demand it. You deserve it and it is very simple to implement.

DC FILAMENT SUPPLY: For the lowest possible noise floor use DC on your tube filaments and use a regulator or choke to remove all the high frequency noise. You want absolutely the purest, cleanest voltages on your first stage, because any noise and garbage will pollute the music signal and be amplified at the output stage. The paradox of clarity applies here...a circuit of great clarity will reveal all of the garbage too. When you have a dead quiet power supply the silence between the notes is more distinct and the tonality quality of the music is vastly improved.

SOLID SILVER WIRING: Demand solid silver wire for your signal carrying wire. It doesn’t take much wire and makes a big difference. NO STRANDED WIRE FOR THE SIGNAL. Cost? Under $10 for both amps at the most.

DO NOT MOUNT YOUR ON OFF SWITCH ON THE FRONT OF THE AMPLIFIER: You do not want any form of AC voltage running up your amplifier near your output stage or input stage. Mount your on/off switch on the back of your amp right near the power transformer.

INPUT ATTENUATOR: If you decide to use an input attenuator use a stepped attenuator that employs individual resistors for maximum refinement.

POWER SUPPLY CAPACITORS: I don’t like the sound of aluminum electrolytic capacitors, even the computer grade ones. They sound grungy, they resonate and are tonal arsenic, but if you must use them only uses the highest quality the expensive types that are made in Japan just for tube amplifiers. I use very small values of these brands and then I use the largest amount of big oil capacitors that I can fit on my chassis. One of the main reasons that the Plitron chassises are so large is so that you can accommodate these oil store bought amplifiers uses these capacitors...

CHOKES: Like money, and hair, you can’t have too many chokes.... almost, and they are almost completely absent in store bought amplifiers because they take up extra room, and ad cost...and it is assumed you don’t know about their benefits. In today’s world, besides their primary job of "stiffening" the power supply they are great devices for removing much of the AC line contamination that can get into your signal on the power supply rails. Want to be really serious? Use double PI filters on your output stage B+ rail, and use a choke on the input stage, all your filaments and your bias supply. You will hear the difference as an aggregation of refinement. Chokes are passive devices so an increase in complexity here doesn’t alter the reliability quotient of your amplifier. Chokes come in different values and check the Plitron specs and catalogs.

PUSH/PULL OUTPUT TRANSFORMERS: Menno’s book is your best way to understand just how serious Plitron P/P OPTs are because of the choices they give you. There are some significant innovation here, and it is all about the fact that each different "OPT feedback tap" option creates a different aural matrix and you must choose which you prefer...and you can always change your mind and try a different connection, because the change-over takes no more than one hour. This is possible with pentode output tubes, but not with triodes. Do not confuse this with changing a pentode tube to "faux triode" operation, which is accomplished by connecting two of the pentode plates together with a resistor. Here we are taking about how the pentode tube is connected to the OPT, and I know of no store bought amplifier that gives you the ability to switch, which is giving you control over your tonal destiny. This is way cool.

POWER TRANSFORMER RATING: This is easy to explain..think about what happens when you start driving up a steep hill and you do not have enormous reserves of power in your engine..same thing is true for a power transformer, which is why (revealing the secret of all New York Audio Labs products) I have always used and demanded over rated power transformers that to many seems absurd...but we can hear the difference. This means that the power transformers have to be large and more expensive...and this is the weakest arena of design in America. You will note that all of the Plitron power transformers meet this condition and are extremely over-rated and large. The problem often encountered with large power transformers is that they have a mechanical hum, which contaminates the circuit. Not so with Plitron toroids.

You will also note that on the Plitron power transformers for single-ended amplifiers that the filament voltage taps are very over-rated. That is because of the wide range of current required by the new family of directly heated triodes.

Note that the current rating on the B+ for the input circuit on all transformers is large enough to feed the largest most complex circuits.

INPUT AND OUTPUT CONNECTIONS: I am suggesting that you mount your RCA input right on the INPUT PLATE so that there is the shortest possible wire between the input jack and the first tube. I also suggest that your speaker terminals be as close as possible to your OPTs. And now a few words about speaker terminals. My favorite are the Edison Price Beryllium Copper (unplated) posts available from Eminent Technology. I don’t like plated ones.

AC FILTER: One of the advantages of the larger chassis is that you can incorporate a transient filter to your AC receptacle. They are available from Mouser and Digi-Key and are a very good idea.

TUBE RECTIFICATION: Go for it if your circuit can tolerate their current ratings. Different brands and types can be used for a specific rating and they all have a different sonic signature just like your other tubes. The Western Electric 274 is legendary and it may be available again from VAIC soon. Many are now using TV Damper Diodes in audio amplifiers and these have some advantages. As I mentioned a separate small tube rectifier for the input or bias is also a good idea. The reason I am so insistent about tube rectifiers is because you are and should be questing for ultimate tonal refinement and this is the path of harmonic magic. This is the old fashioned and the right way.

AESTHETICS: Who picks out your clothes and dresses you in the morning? What could be more fun that designing your own amplifier...Do you want a nice thick anodized aluminum faceplate? Do you want your chassis painted or chrome plated. I feel silly explain how serious this is because I am sure you have designed your own home, or hot rod or you get it.



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