WHY AND HOW DR. GIZMO CREATED
THE FIRST HYBRID TUBE/SOLID STATE AMPLIFIERS
SPECULATIONS ON THE DYSFUNCTIONAL
TONE OF SOLID STATE AMPLIFIERS
DREAMS HAVE POWER:
A NYAL BREAKTHROUGH
NOTE: Those of you who have read my two thrilling books, Understanding Tube Electronics, and The Search for Musical Ecstasy, know the whole Moscode ball of wax, and have read their critical praise .but there is much rumbling in chat rooms about them so here goes..
One of my most common emails are questions about the Moscode amps and preamps that my company New York Audio Labs manufactured between 1983 and 1987. It appears that Moscodes have become classics .just try to buy one. The Moscode amplifiers appear to very rare commodities on the used market because owners don't want to give them up and for good reason. Here is the true tale of how these, the first true hybrid tube/solid circuits came to be created.
In 1984 New York Audio Laboratories was the first company to introduce the first hybrid tube/fet tube amplifiers and preamps, and we called them Moscodes; a name that was a combination of Mosfets and cascodes. Cascodes is the name of the configuration of tubes we used for gain stages. The products range included the $169 Super IT phono/preamp, Minuet in A, a full featured phono/preamp, and the stereo Moscode 150, 300 and 600 amplifiers .respectively 75, 150, and 300 watts per channel into eight ohm.
The famous custom made Moscode Black Hole Amplifier, which is a legendary achievement, is the first amplifier that could reproduce the Voice of God, in the denomination of your choice, stands six stories high, can produce one million watts into 0 ohms, and cost $267 million .. can be viewed under the section of this site entitled TRIODE GUILD MUSEUM OF ART. This amplifier established me as KING OF THE HORSEPOWER RACE in 1984.
DREAMS HAVE POWER
Moscode amplifiers began, in the truest sense, with Julius Futterman's dream. The reason that Julius was so excited about the new NYAL Futterman amplifiers, that we were developing, was so that he would have time to devote to an old dream. He wanted to take his OTL circuit and modify it so that it would have a Mosfet output stage for four very good reasons: (1) he wouldn't have to go through the trouble of testing and matching output tubes, and (2) such an amplifier could be used with the prevailing, low impedance, power hungry "transistor" speakers, which an OTL amp couldn't drive properly and survive (3) the output tubes would never have to be replaced, (4) there was no limit on the amount of power the amp could produce..within reason.
This made lots of sense because the Futterman OTL was a very narrowly focused amplifier, as are all "normal" OTLs, and at this time more and more speakers were boasting "2 ohms" because solid state amplifiers would boast "1000 ohms into 2 ohms" one of the dumbest ideas in the history of the audio business. Of course the other consideration was that the Futterman amplifier had to an expensive product because of the time and effort that was needed to make each.
When, in 1982, NYAL established a joint venture with AFP Imaging, a manufacturer of medical electronics, this meant that we now had sophisticated, and, to a great extent, automated, electronics manufacturing available to us. The right way to exploit this manufacturing capability was to return to Julius's idea of a hybrid tube/fet amplifier.
This also seemed like a reasonable way to fulfill my dream of bring the quality of tube audio to the music masses.
The problem with ... Mosfet output stages is how difficult it is drive the gate of the Mosfet , which paradoxically was not a comfortable task for a small signal transistor which explains why most Mosfet amplifiers became extinct almost. But we were on a different path.
What is required is a very low output impedance driver stage with real balls very high current capability. Over the last decades I have asserted that the most critical stage of every amplifier is the first stage, and if this stage doesn't get "tone" right..then what you are doing is amplifying a unmusical signal and I have never heard a small signal transistor circuit that can match a tube/triode circuit for getting natural harmonics which explains why tube microphone preamps, line stages, and phono preamps are so popular.
The article by Eric Barbour, posted on this site, examines the difference in tonal quality between transistors and tubes and once again, what we have known for four decades .transistors produce a family of odd order, high order harmonics that are, relative to music, unnatural.
Fortuitously, primarily due to the research that Jon Syder did, with White Cascode Followers using a 6FQ7 (which were developed by Bell Laboratories for telephone transmission) for NYAL phono preamps .which was already being used in our NB1, and NCP II phono preamps), we had the right driver stage. George Kaye, who was in charge of the Moscode project, used the White Cascode Follower as the driver for the Mosfet output stage and it worked superbly and we were amazed. It seemed so simple and easy to get the Mosfets to work properly using the right tube as a driver. This was the first step in our breakthrough.
Now our goal was to create a family of amplifiers that, as close as possible sounded like a Futterman OTL 1 amplifier that would have lots of power and would be completely reliable because it had a solid state output stage. I am not suggesting that any solid state amplifier can sound exactly as a tube amplifier, because that is an electrical impossibility (transfer function rules) .but we were trying to create an affordable, high powered amplifier that had the most desirable qualities of OTLs..tone, dynamics, magical spatiality.
As you know, while test equipment is needed in the designing of any circuit, all conventional test measurements are useless is determining sound quality, which is why none of our designers paid attention to the dumber than dumb notion of "accuracy". Our advantage was having the OTL-1 as a meta-reference and a collection of electrostatic, planar speakers, which were considered state of the art at the time. It also helped that we had master tapes and tube tape recorders as source material.
A LITTLE BIT OF AUDIO HISTORY: This was the golden age of the mega-planar/electrostatic speakers (Acoustat, West Electrostatics, Magneplanar IC, Infinity, Apogee and various other ribbon speakers these gigantic, and low impedance speakers, needed lots of horsepower, and because of their clarity, owners were using 250 watt per channel pentode push/pull amps that would do the Kervorkian every sixty days because their tubes would fail. These speakers did not sound happy with big solid state amplifiers because they revealed the tonal dysfunctionality of solid state amps .the point being there was a need for a higher powered and, most importantly, reliable amps that had the aural aptitudes of tubes for this huge power hungry speakers.
Moscodes happened because they satisfied a need. Selling between $499 and $1600 the first hybrid amps became instant hits because they sounded so good again because we tuned them to sound the way we thought an amplifier should sound .which was as close to the Futterman OTL 1 as possible .and there was no way they could blow up driving difficult low impedance speaker loads in the way those high horsepower pentode push/pull amplifiers imploded.
And to demonstrate, , at one CES how reliable Moscode amplifiers were meaning their ability to drive the most complex difficult loads we fed a Moscode 600 with a 60HZ signal and connected an AC receptacle to the speaker outputs, and plugged a vacuum clean into it, and vacuumed the floor for audio dealers .to show them how they could "clean up" with them. Driving a AC motor is, in absolute terms, one of the most difficult loads, and any amplifier that can do that, can drive any speaker in the world. To demonstrate the high tonal quality of Moscode's liquid midrange we connected a blender to the AC receptacle and made Margaritas so dealers could take a real taste test of its liquidity. Dealers unanimously agreed that they had never tasted a better midrange.
AND WHAT ABOUT APARTMENT DWELLING AUDIOMANIACS AND MR. NOT RICH MUSIC MANIAC WHO WANT THE TASTE OF REAL BUTTER?
Even though all of the above was happening in the first golden age of high end audio..most of my friends and most music lovers in America weren't crazy or rich enough to own tube amplifiers and weren't ready to deal with their personal care and adjustment .but everyone of my friends who heard the real Futterman Mc Coy loved what they heard .and most of them lived in small New York City apartments .
In that sense Moscodes were an exciting business opportunity to deliver high quality sound of tube circuits in an affordable and reliable form. The Moscode 300 and 150 gave me real spiritual thrills knowing that so many could now experience the aural advantage of tubes in a carefree way that wouldn't make air conditioning useless in the summer..and dominate the room.
THE MOSCODE SECRETS REVEALED AND YOU DISCOVER THAT MY SERMON HASN'T CHANGED IN TWENTY YEARS.
My ranting about the importance of active regulation in tube circuits is decades old: All of the Moscode amplifiers featured completely independent and regulated power supplies for the tube front end. The Moscode 600 was quite special because it used tube regulated power supplies, for the front end of each channel featuring the same regulator tube used in the Futterman circuit. Not only were the Moscode amplifiers the first hybrid tube/fet amplifiers, this was the first time that tube regulation was used on a tube/mosfet amplifier. Again .This should remind you that I have been singing my "tube regulating tubes" song for at least twenty years now because this creates an elixir of harmonic ecstasy.
At this time there were many Mosfet amplifiers on the market, but none of them sounded like the Moscodes, even though they used the same output devices, and this can be explained, in large measure, to the benefits of circuit simplicity because (now remember my shower song LESS IS MORE) solid state input, driver and phase splitters always must be complicated and use lots of feedback. It is the stark simplicity of the Moscode circuits that creates their aural advantages.
Because I never wanted to fry a speaker there were more protection circuits built into these amplifiers than space ships, and over the last decades a number of "tweakers" including George Kaye, have offered a service which removes some of these safety features..to improve sound. Yes, they do improve the sound and yes you are more vulnerable to amplifier and speaker meltdown.
You will also note that all of the Moscode products were a modular design so that they could be easily manufactured, tested and repaired all benefits of having AFP Imaging manufacturing expertise working for us.
There was also a MAXI version of the amplifier which had big polypropylene capacitors in parallel with the two big computer grade power supplies capacitors, to tame some of these capacitor's inherent tonal roughness.
WHY I INCLUDED AN AUDIO PAMPER IN EVERY
MOSCODE AMPLIFIER..AND BECAME FAMOUS..
I quote from a 1986 Stereophile review of the Moscode 60O by Anthony Cordesman..
"If all amplifiers sounded alike, then Harvey Rosenberg doesn't exist. His raison d'etre is that his New York Audio Laboratory amplifiers simply do not sound like other amplifiers, nor are they intended to. This comes across even in NYAL promotional literature, which rivals that of even high priced turntable manufactures in the ability to obscure functional with baroque form.
A few examples in point. The amplifier comes with a diaper so the sonic excitement generated by its use will not embarrass you with "losing control of some private functions (A little more genital and a little less anal hyperbole would be welcome Harv, baby). You are warned not to jump out of the window when you play Prokofiev. You are promised that you will jump for "joy, jiving, diving, twirling and quivering. If this isn't upchucking good fun suitable for a Linn or SOTA turntable, I don't know what is "
Even before the Internet "brain viruses" happened soon everyone in the audio business was talking about the NYAL Audio Pamper and wanting one. At the next CES show I gave dealers signed limited edition copies.
Again, again, and again .Because the first stages of an amplifier the voltage amplifier is the key to ultimate tonal quality which is why I spend so much time discussing this subject relative to single ended triode amps .f you screw up tone in the first stage with a meany transistor, nothing you do down the audio pike can correct this tonal corruption. My articles about TONE explore in greater detail why small signal transistors, and their power supplies, corrupt tone. Using a 6DJ8 tube voltage amp/phase splitter, which, at the time, was very radical because almost everyone was using 12AX7s, meant that we started off totally righteous, and with the simplicity of the circuitry, and the low impedance 6FQ7 driver stage, we achieved what no conventional solid state amplifier that used a transistor front end could achieve NATURAL TONE which is why the subtitle of my first book, UNDERSTANDING TUBE ELECTRONICS, is A Study in Natural Harmonics Audio.
Moscodes soon became the darling of the electrostatic/ribbon/planar speaker users because they were the only amplifiers that had the power/reliability of solid state amplifiers, and didn't sound like solid state amplifiers
Let me make this plain this was not just an intellectual challenge for me . because NYAL owned both the huge West Electrostatic speakers, and Apogee Ribbon Speakers and listening to earth shaking rock and roll on these speakers with Moscode amplifiers was a unique, and thrilling jogulation of my music metacontext. As you know . at the opposite music polarity was my Quad/Futterman OTL combination, which was more refined, but never able to create the dynamic excitement of the big speakers.
NO GAIN, NO PAIN
Let me give you the briefest over of the challenge of designing phono preamps/line stages, and it is all about the immutable laws of audio design .NO GAIN, NO PAIN or to put it another way whenever we create gain, we create distortion
Actually it is worse than that because there doesn't have to be any gain in a circuit for harmonic corruption to go down a signal can just be flowing through an inert piece of wire, or a resistor or a capacitor for distortion to occur .because every active and non-active component in an audio circuits alters the signal in some form .but active circuits like a tube, transformer, or transistor does it on a grand scale
And this becomes a critical consideration in a world of low output/low impedance moving coil cartridges that need very large gain/low noise which was much easier to achieve with transistors but they didn't sound any good so tube savant wrestled with how to achieve high gain/low noise at the lowest possible level of signal distortion.
HISTORICAL NOTE: NYAL was the first company to market a Nuvistor tube
(a tiny metal tube) head amp for moving coil cartridges for about six months and we stopped making the unit because it was too problematic .
The choices a designer faces is using many tube stages of moderate gain to create the overall gain need added complexity, or using few tube stages of higher gain with the problems of noise and instability.
And again..remember my MOSCODE challenge high performance tube circuits, that were affordable and reliable. The NYAL NCP II megabuck phono preamp/line stage with HTMPS tube regulated power supply was our design standard.
The design team of Ted Hammond and George Kaye, I believe, made a significant breakthrough one that we considered patenting..at the time..
The Moscode preamps were quite unique in 1984 because they incorporated a hybrid cascode consisting of a fet/tube which gave us a great deal of gain, great linearity and very low noise. This was important because with a simple circuit we were able to achieve 74 db of gain, which meant a moving coil cartridge could be used without additional gain stages that would have added to the cost and complexity. By using a fet, a solid state device, as load on the 6DJ8 voltage amplifier we achieved our goal. Granted an all tube cascode sounded more refined, but was impossible to achieve at $599 or $169 IT.
The $269 Super It, phono/preamp, (the more expensive version of the $169 IT) has become a classic and I original intended it to be high quality phono stage that could be plugged into a solid state receiver to take place of the very mediocre internal one. In a world that had not yet gone digital the Super It made a huge difference in sound quality in "normal" sound systems that were still all vinyl. If used with a moving magnet cartridge the Super IT could be plugged directly into an amplifier because it had 62 db of gain. The very smart use of hybrid solid state/tube components made this little wondrous mutha possible at a selling price everyone could afford.
I have also discover that the SuperIT has become a cult item, with its own group of aficionados who are tweaking it.
THE MOUSE/ELEPHANT EFFECT:
WHY HASN'T ANY OTHER AUDIO COMPANY
CREATED HYBRID AMPLIFIERS?
In fact right, after NYAL introduced our amplifiers, Counterpoint Electronics (which is no longer in business), introduced a line of hybrid tube/solid amps that didn't sound as good as our and soon disappeared from the market.
Lux of Japan, introduced a hybrid receiver that didn't last very long .. a good idea, not properly executed.
Yet, in an audio world almost completely populated by "transistor/low impedance/power hungry" speakers, hybrid amplifiers still make lots of sense so what gives?
I think the answer can be found in the male ego or I should say the ego of the audio design which tend to be very tightly focuses "I design tube gear", or "I design solid state gear". Have you noticed just one solid state designer that also designs tube gear also? On the other hand tube designers, like Bill Johnson of Audio Research and Lew Johnson of Conrad Johnson have created solid state products with little success. Bill Johnson once created amplifiers with transistor front ends and tube output stages and they quickly failed in the market place.
Of course, we can't discount the MOUSE/ELEPHANT EFFECT so well portrayed in Walt Disney's classic DUMBO. Why are elephants terrified of tiny mice and why are so many audio elephants terrified of Dr. Gizmo? Could it be that there is a pervasive fear that anyone who designs a hybrid amplifier will receive my wrath because I jealously guard this innovation?
Recently I had some experience with the Lamm Hybrid amplifier .and here is where designer's ego and taste comes into play to me, this amplifier still sounds like a solid state amplifier and doesn't have the musical juice of tube amplifiers and this is not a criticism because I think the designer's goal were achieved.
THE FUTURE OF HYBRID AMPLIFIERS
A common email I receive is:
Dr. Gizmo..why don't you make Moscodes again?
Desperately Seeking a High Powered Amplifier That Sounds Good
Many of my friends use Moscode amplifiers, and I have compared them to my current reference SET DT "brain damage" reference system and I always get a smile because using a Moscode 600 with my speakers that need..to peel paint .about five watts means that the amplifier is never doing any work, and is operating in its "sweet spot".
Of course I am very biased the Moscode 600 is still the best sounding high powered amplifier and I obviously hear its virtues and limitations. Its dynamics on some of my Mickey Hart CDs are awesome. It is a push/pull amplifier and I can hear it's phase splitter pushing and pulling, and it does not and can not have the aural wholosity of a low powered phase/splitter free SET. It doesnt have the tonal quality of directly heated triode amplifiers .and my thermionic imagination started to kick into gear
If I were going to design a hybrid amplifier I would take a different path the path that would exploit everything I have learned in the fifteen years since the Moscodes first appeared. My goal would be to give the amplifier a higher degree of tonal refinement improve the quality push/pullness, and now I would use the aural aptitudes of the single-ended directly heated triode amps as a design standard in the same way I used a Futterman OTL twenty years ago and you know what that means ..It means a very high standard indeed. I would use a different compliment of tubes, a different driver stage, different regulators, and I might not use MOSFETs in the output stage because I would explore development in power transistors that have occurred in the last decade..
But this is pure fantasy now it is just a dream.
And there is potential new customers for these amplifiers .
Hybrid amplifiers may be the righteous path for achieving high quality sound in home theater .and in recording studios which use solid state amplifiers that should come with EAR SICKNESS BAGS.
And I remind you that the MOSCODE BLACK HOLE is the only amplifier that can reproduce the full dynamic range of a volcanic eruption in your living room, which appears to be the highest artistic aspiration of home theater at the moment.
Over and out from the Nth Dimension of Music Hyperspace.