The Legacy of Tube Preamplifier Designs – The Driving Output Stage I

Hello to everybody,

a last posting for this year is made with the intention to bring credit to the leavings of important figures which did die within the year, in the early beginning Ken Shindo and in autum Jean Constant Verdier. Ken Shindo is one of the few in the western hemisphere known japanese designers who did design a wide range of exceptional balanced and elaborated sounding tube amplifiers. As the most people might know, in Japan the evaluation of historic western tube equipment was paragon. They started to inspect, research. refine and outperform the classic examples made for the early professional broadcast or cinematographic use like WE. RCA, Altec, Klangfilm and others, while the western world got flooded with their cheap commercial electronic mass products from Pioneer, Sansui and others in the 1970ties years for home entertainment. Their particular asian appropriation of mastership thinking, their diligence and finally their conscientiousness made at the other end unique products possible, which collect more experiences in that field of expertise and are far ahead of other made product in the world of tube audio.

This article will be some sort of summery to my evaluations which I made within the last weeks in order find out about some basic influences of particular design topologies important with tube amplified output stages. It came into close inspection by a typical side accident which happened in November. I had a chance to listen to a original Kaneda preamplifier in a very elaborated audio chain, where a Line Magnetic LM22A/555W/597 horn system was driven by a Shindo power amplifier and a Monbrison preamplifier. It happened that we were talking about Kaneda preamps and it came to the point that I instantly got offered the chance to listen to a sample. Me was told that the (japanese) transistors inside normally love a long warmup time, – in every day use they never will be switched off… The Kaneda preamplifiers got popular in Europe through Jean Hiraga and the parisian Maison de L'Audiophile in the late 1970ties and early 1980ties, who brought this design topology from Japan. In these days the preamps got mostly sold as kits and have been highly praised as perfect alternatives to high priced tube amps mainly coming from the US in these days.

In order to get the Kaneda warmed up to best performance, we did wait for some hour before we switched over from the Monbrison. As we did before we did listen to digital streamed music material. This means we did listen to a fraction of both amplifiers, so only the output stage (line) and the power supply from each unit have been involved. During the warming up we did listen to the Shindo with a variety of program material, before we switched to the Kaneda unit.
To be honest, I would not have believed before what happened. The difference between both units was tremendous wide, more than that. Coming from the Shindo, the music was natural in a flow with all dynamic attributes right in place and loads of micro dynamic information (commonly named as air). With the Kaneda the music flow was stiff, almost grey and grainy, without any particular micro dynamic detail. It might be have been the temperature of the Kaneda, but even with a imaginable top condition it would not be assumable to difference out to a natural completeness shown by Shindos Monbrison. I was staggering and noticed that only one tube with its PSU was able to outperform and boost the Class A battery supplied Kaneda into a different world. Again a perfect example that Shindo did better than perfect know what he realizes. And in difference to the most other tube amplifier designers, he knows exactly how it has sound finally. His superiority was not alone the knowledge and experience with parts, components and topologies, it was mainly his aim to get the right decisions into order for a precisely aimed audible result, always having a perfect dynamic natural performance in mind.

After that unforeseen demonstration of superiority I went home deeply impressed how well Shindo implemented his output stage in his design. The most here reading, do know that I am into the merits of directly heated triodes in small signal stages since a decade. My long term approved preamplifier uses the Aa Weitverkehrsröhren, a design with some little restrictions (high output impedance) but so far best audible general performance I have used. I have been at a point were I did not want to question this design again. But this experience did do. It pointed out to the most questionable part, the output impedance of the driving line amp is tremendous important part of the complete sonic result. OK, thank you Ken Shindo for your advice, I will take another lecture as homework about this topic.

A typical professional US broadcast preamplifier as made by several companies like IPC, RCA, Pultec or similar with high mu input  stage 12AX7/ECC83 and paralleled 12AU7/ECC82 transformer coupled output stage in order to archive low impedance output (600 ohm or lower).

First of all I did work out theoretically all possible tubes which might be superior within such a design (output transformer with 600 Z secondary). For the beginning I did look up what will be available from my shelves, – what will be necessary to get. I had several output transformers for that reason lying around (different types of Lundahl LL1660, LL1680, its original UTC LS27 and a pair of Tango permalloy core 20K:10K/600) and for practical reasons I started with tubes I already own. The most output transformers are limited at 10K to 20K primary impedance when set to a realistic 600 Z output with reasonable DC in primary (5-20mA). A rule of thumb says that you need to calculate three to five times the internal resistance of the tube to find the best working value of the output transformer (example a 3K Ri of a given tube will match a 12K transformer primary side). A variant of design is to incorporate a additional anode choke (getting the OPT transformer off dc in its primary, but reintroduces a coupling capacitor). For that variants I will have a selection of Lundahl LL1667 air gapped chokes for 5 to 25 mA DC by hand.

Other than a producer of commercial amounts of units I can set my interest to the best components available, I don't have to take questions of availability or single prices into account when I decide. All my tube amplified life I was a great fanatic of the RCA red base series of tubes (5691/6SL7GT, 5692/6SN/GT, 5693/6SJ7GT) which were originally made for the cruise missile control units and are extremely mechanically rugged versions with double heater consumption of the standard octal versions (600mA does not make them a universal replacement). Even their prices have always been literally skyrocketed and so you rarely will see any commercial made audio amp designed with them (Bruce Moores Luminiscence), but I believe they are some of the very best made tubes ever. In all these years these tubes have outperformed everything similar in all my preamplifiers, 12AY7, ECC82 or 802s, Telefunken, Mullard, – everything!
Here now the 5692 with internal impedance of 8K is a candidate for paralleling their two units to half their internal impedance. As well a true legend from the German Post, the C3g with 3K ripple in triode mode is a ideal contender for such implementation. Western Electrics 417A with 1.6K might be a true choice as some other space age tubes like 5687, 6463, 6386 have to be taken into account. But as well real power output tubes like 6F6G, EL84 and similar types will do the job. All named tubes are indirectly heated types, but there are a few DHTs as well which might outperform the late high-tech stuff? The Ce/Cas Weitverkehrsröhren with 4K ripple, the british pedants 3A/110-B and 3A/101-B and of course the Western Electric tennis ball battery tubes are matching perfectly, but you need to find them since they are exceptional rare. As there are little better known small power triodes like 801A, 2A3, etc., but they make output transformers necessary with higher DC capability in the primary winding or the use of the parafeed design together with a choke load.

To make such a comparison meaningful I know that the power supply might take an important part at the final result. So I arranged three different interchangeable power supplies within each setup.

First my standard PSU with AZ12 (mesh plates), all oil paper capacitors and several chokes in the HV rail and a selenium rectified LV supply with chokes is a complex and huge unit. All Transformers are hermetically sealed oil filled types. The anode supply is regulated and stabilized with two tubes as three active units.
Second a industrial type PSU with Selenium HV rectifier and highly regulated and stabilized with four tubes and AC low voltage supply is a alternative solution.
Third a standard supply without regulation and stabilization, just choke and capacitor filtered. LV selenium rectified and RC-filter rail is another option.

With all supplies I have the chance to adjust the anode supply widely, so that any tube from my range can be optimized with anode voltages between 150 to 230 volts. So I started to install identical connection plugs to each unit, which gives a flying change during evaluation a chance.

The results of my comparisons are nothing less than remarkable and expressive, they gave me a deep insight into the effects, requirements and influences of each topology. The optimal working point of the tube itself, the adaption and matching of the output transformer, the influence of different generated anode voltages and as well different filament supplies. And finally the tube itself and its character in the final soundstage. As little shortcut to the end it can be said, the tube itself has a highly overrated position to the final result.

Read on soon, Volker

Natural vs. Analogue vs. Digital vs. Fraunhofer Algorithm processed Music IV

Hello to everybody at the christmas holidays,

I will try now to finalize my series of articles about different recording and storage methods of audio information. So far I have tried to describe the holy religious believe into the audible improved qualities of analog mediums like vinyl records or reel tape. As well I did start to describe my experiences with digital stored information and tried as well to difference out a variety of different sampling and word length formats. I did try to describe arguments of availability for different stored formats, the massive influence of hardware to the performance and their comfort of use. Today I want to find final arguments about these topics, since some sort of serious discussion will not start throughout this blog, even when I did try find provocative thesis's and arguments for one or another strategy.

As I did describe before, I have a huge collection of vintage vinyl. I did concentrate my collecting to first releases of recordings in the fields of Jazz, Blues and some classical chamber music. I did collect with a general interest into a diverse range of interprets in different fields of practice. Just to give some examples, I did collect saxophone performed music and did try to complete the original recordings (only EP and LP) from the most well known musicians of this genre. So I got a range from Coleman Hawkins to Archie Shepp, from 1948 to today with 30 and more records of lets say the 20 best saxophone players of all time each. Next to a whole lot of dedicated jazz music as well with female voices, I did collect music with Cello as main instrumentation. (No wonder cello, sax and human voices cover the same tonal range) So I got the Pablo Casals work complete and continued to collect over lots of other interprets like Jaqueline du Pré to Sol Garbetta today. Just this three genres might explain how I do collect music. So it came that I got a still quite small collection of vintage vinyl, maybe 1500 records, but with the most of them of exceptional rareness. As stated in the earlier articles, I was driven from the believe, that only the first pressing will contain the "richest" and most complete transcript of the original recording. And sometimes when I had some later pressing before I found the first release, I could confirm my believe.

Variety of first releases of "Miles Davis - Kind of Blue" in mono and stereo, a exceptional example where the first pressing is a incredible lot better comparing any later reissue, even the the 50th anniversary edition from 2009 of the most important jazz album of the 20th century.

The captured quality between first and later releases hardly depend on the handling of recording companies with their masterings for later planned reissues. Some of them did store the original master away as some sort of untouched back up and others made copies for their further use. This practice will degrade every later release with a typical increase of dynamic attitudes normal with every reproduction step. Others seem have handled this question different, Verve for example seemed to be a company where even later releases are able to store the same quality known from their first pressings. Some companies had better or sometimes even lower quality levels within vinyl production, several companies have been sold during a quite short time. So the production parameters changed a lot permanently. Another aspect is the distribution aspect of the first released records worldwide. So the most recordings have distributed foreign cousins of the same time. RCA for example did held for the German market a joint venture with Teldec, a german vinyl production brand from Telefunken and Decca, another european joint venture. As we see there was a lot of money in these days markets and like always, when profit attracts analysts, quality is not anymore the foremost argument. Was it ever?

Vinyl is rich. ...and tasty!

Today the most of a younger generation have audio playback reduced to smartphones for storage and don't see arguments for specialized audio hardware anymore. The basis to such handling are compressed audio files, a development made possible by the invention of the Fraunhofer algorithm for MP3 compression. In 1982 this compression standard was invented there, right two years before Phillips/Sony introduced the Compact Disc as a second digital format (after crash with the laser disc). With the invention of compression the digital distribution of audio technology started its crusade through all media components.
In the former separated audio world the first arguments for the compression have been found in the necessary reduction for the increased bandwidth of 5.1 surround sound audio – do you remember? Creativity in capitalism is never forced to find better qualities for the same amount of money, rule is to find almost the same quality for half the production price as only effective argument. Staircase to hell...
So it made possible that you might be able to carry my whole vinyl library of 1500 vinyl recordings and the additional 500 CDs at my smartphone, just compressed to MP3 standard? – Progress. Yes for the markets …

When operated within high quality audio components it is clearly audible that a and in particular a higher compression of MP3 shrinks out almost any fine and micro dynamic content and reduces the remnant to a rough torso of soulless blunt music images. The compression rate defines how much micro detail will be captured in order to find space for storage. Within high resoluting audio components the later invented algorithm of "lossless"-compression is the only acceptable audio format to capture the audible content of the original "red book"-standard known from CD.
Since the turn of the century "higher resolution" digital formats (96kHz/24bit) have become standard within any sort of audio distribution. So all recordings have been made nowadays with this new industry standard. But as well all mixing, shaping and mastering happens completely in digital form. This has a tremendous impact to the finalized and kept quality, since almost all interventions happen without trace. All the former well noticeable "fingerprints" in analog productions left from each step of and each component is rejected for a general highly refined audible result. For a lot of people this progression into refinement, better phase correction and a truly better balanced and wider sound stage, will be called "analytical"or "artificial" and are connoted to them as "digital sound".
As already stated in my last article, I do appreciate the extra apparent nivelling attitudes of modern digital recordings made within the last decade. Here the general difference between a poor and a well made digital recording hardly can be assumed as a 10% tolerance, where analog vinyl can be proud to capture 50% tolerances at its best. Some people call it "rich and colorful". For me and my vintage record collection it is getting harder and harder to accept both features as positive arguments when comparing vinyl with modern digital records. The most vintage records are not really easy to listen to, they create a high degree of attention with sometimes sparkling energies and superficial dynamics, mostly a bundle of overwhelming attracting attributes. The modern digital recordings at the other side give me more chance to get into the music flow and let me forget about the electronics equipment involved.

Conclusion

End of November I went to a life concert of Cassandra Wilson. When I booked the tickets I had several values with different price tag. I needed three tickets and wondered that very close to the stage at the right side three related seat were bookable. At the performance I realized that just in 90° angle to the stage the view was very close and fantastic with 8 meters distance, but the sound was really terrible poor. All speaker columns where installed high above the stage with direction to the main hall, in my position only the stage monitors have been audible and the reflecting sound from the opposite walls, ending in a really vague, queasy and inaccurate sound. My friend and I agreed about the perfect view of the event, but the sound was amazingly better known from home with a good audio set up. So finally I was happy to capture a colorful live image of her to be assembled with better sound at home. Apart from that I did find curious that a world class singer performs today almost a complete set of songs from an album released 22 years before in 1992, "Blue light 'til dawn" her first album with Blue Note. This album did exist for almost twenty years only as CD release, the vinyl version is quite actual. As I said earlier I did buy vinyl albums believing that the vinyl is richer and better in every respect, since I did own the CD for almost twenty years. Everybody who knows this album, knows it is a really well made recording, with perfect dynamics and well resulted harmonics and perfect micro detailing, in a way exceptional for its time.
Writing at these articles and infected from the poor life event sound, I did pull out my vinyl record and my digital version of that album in order to make some comparison. I did take perfect care about both loudness levels to be perfectly identical. Before I was absolutely sure that vinyl will be more dynamic and the digital version might show up with better resolution of mids? I did try the test for a whole side of the vinyl record, perfectly pitched into the same groove/track.
I did switch from one source than to the other, I did switch back, –  again and again. I could not believe what I did hear. It was absolutely the same. Not even a small difference, after five times switching I did loose the source, what is actually playing? Platine Verdier with SME 3012 and SPU or the streamed digital file using WiFi into my preamp? Nothing no difference at all. Exactly the same. I was completely irritated. AAD, analog recording, analog mixing and digital release vs. AAA with analog release as a vinyl record. Believing and blindtest, – religion and reality…

Remarkable test, if I would not have made it myself, I would not believe the results. For somebody like me, some would name me a hardcore quality enthusiast and refusal of the common "self-healing power of the market"- believe, it was a dry lesson. My understanding of audible perfection is grounded to experiences where older means mostly means better in general, deeper involved, longer lasting in terms of functionality and superior sounding in any audible aspect. When clearly today the first generation of speakers, horns and drivers made by Western Electric Co. in the 1930ties are able to outperform any following product in history in almost any term, such is a basic experience. If almost any audio product designed and engineered for professional use in the broadcast industry, betters any commercial made mass product for audio, it shows another side of the same coin. If product history of original superior products show a permanent decline in quality terms into mediocracy with every released product generation, i.e. like with products from Altec or Tannoy, it shows another problem of the tensile forces with common markets as third argument. Than it is difficult to accept that a solely commercial made product like the digital audio file will be on par or even superior to its analog predecessor, the analog master with the vinyl record. But was a vinyl record ever something different than a commercial placed product for consumers?


I would be happy to learn about other peoples experiences with that topic,
Volker

Natural vs. Analogue vs. Digital vs. Fraunhofer Algorithm processed Music III

Hello to everybody,

interested to follow on. In my last article I did end describing that my believe into the superiority of analog audio reproduction has had almost religious qualities, based on a deep believe, breaded by several "audio mullahs" of the orthodox conservative brotherhood of vinyl junkies.
I did believe for almost my whole life within audio components, that analog play back is superior to any digital technology. I spend 25 years of faithfulness, energy, money to find that believe confirmed by complex evaluations. To be honest, even with substantial input into my system (I did ignore for 15 years any digital source) I never reached a stage of perfection, where I would subscribe with real empiric experience this sort of "religious confirmation". I did always buy the vinyl record if there was any, even when I already had the CD. My long term experience from the early 1990 years with digital music had shown me a poor source, when evaluated with higher degrees of audio program. The mistake once I did made with this score can be cleared up today. The digital program material was mainly based to analog recorded, mixed and mastered material transcribed to CD. Music which had already all the fingerprints typically imprinted from loads of analog components within their production, but with a additional stage of influence, the remastering for digital, cannot sound any better than its original. Every step of reproduction leaves a clear finger print, but in these days digital stored music was the "jack of all trades", able to solve unknown problems – in theory.

It took a long time that my music taste changed to more contemporary performed music of younger generation musicians. Together with my interest to manage my small digital self recorded music library  from my computer, I started in 2005 to play music from there using an audio interface. It didn't take long, that I worked out that my "old school dac" (Meridian 263) did a good job to convert the digital stream into analog audio signals, a lot better than my interface was able to. And in detail after several evaluations with modern "high resolution" dacs, it showed up with the old truth that mainly the analog output stage converters make a audible difference, in particular with following tube preamplifiers and the their input impedance preferences. But as well a solid designed audio output stage made with single coupled transistors, or even better with tubes, bring the dramatic dynamic changes into view, it is not the dac topology in general. The always as standard implemented op-amps here for the analog amplification stage is the foremost achilles' heel and dramatically reduce the finalized output quality.

The album was Archie Shepp's On Green Dolphin Street, became the first digitally-recorded album in the history of jazz music  was made by Denon.

During experiences with my own digital recordings and first results with audio software for a computer based audio workflow from 2005 on, brought out several findings about digital influences to the final result. Different resolution options and compression settings showed me their inherent limiting issues, together with the effects of variated word length rates, the influence of general sampling rates higher than 44,1 kHz up into actual regions of 192 kHz have been tested for superiority.
To me the so called "high resolution"-audio formats (96, 192, 384 or more kHz with 16, 32, 64 and more bits word length), mainly introduced as argument to find new selling options within a shrinking market of downloaded or streamed music formats, are in a high resolution audio chain of completely negligible importance for the quality of audio performance (believing trust). While any sort of digitally introduced compression algorithm is clearly accompanied with a precisely defined loss of micro information, phasing, spacing and dynamic ability. I do not know one audio system where such values are able to determine audible qualities of any importance!
In the age of component less music consumption, relying to the smartphones as universal remote control for any question of todays life and here more or less as converting unit into the analog music signal, another belief takes ground, the religion of zero and one always to be the same figures...

When I started to transcribe my own vinyl collection into digital, it was supported from the believe to preserve the better i.e. "richer" sound of analog vinyl on to digital. I tried with different methods and recording hardware (in "old school"-terms hardware has had always a tremendous influence to audible sound quality, believing again) to find the best possible sound quality for my recordings. So I did use the first Philips/Marantz professional CD-recorder (Marantz CDR600 with the built in legendary first laser burning mechanism with a unsurpassed burning depths for long term archival storage at golden CD-Rs Philips made). I did try with professional DAT tape recorders as well, as I did do HD- recording with stand alone machines and finally I did use my computer with audio interfaces and software to optimize my recordings. I spend a lot of time into that research with the result, that I could not rate any recording principle as to be superior in terms of audible qualities. Only the comfort of use, the spend input of energy and time, as the ease of storage, did finally determine my decision. I even pulled out my old Meridian CD-player to try another step to use hardware for playing digital stored music, but I stayed more or less with the computer and sold all specialized hardware, a step I did explain myself to set for future demands …

I still did believe into my analog system with a Platine Verdier turntable, SME 3012 tonearm, Ortofon SPU pick up and extremely complex tube amplified phono amplifier with inductive equalization to be state of the art. Vinyl is clearly listenable to be the "richer" format, specially when it comes to typical vintage vinyl and so it stated these arguments to be highly superior. The black box of digital data generation can always be seen in contrast as some sort of "diabolic mystic conviction" and with its inherent mathematical system as a true unnatural operating generator, it can be seen as a complete opposite of the musical instrumental origin.
Further religions: US Americans need firearms for better safety, earth warming is not affected by humans, German cars are best in the world and several other ideas withstanding any serious intelligent approvable investigation are of similar significance.

Using the computer for audio storage brings several other questions into account. As photographer and graphic designer I have learned my whole life to work with Macintosh hard- and operating software to optimize analog products. A obvious decision in the first move was to use iTunes for the organization and storage of my still not really seriously taken digital music library. And there is the question of the finalized format included, several compression formats are existing, as well the newer Fraunhofer variant of Mp3, the Lossless format can be a serious option, apple supports the most of them, others don't. And what are the formats in the coming future? The hall of fame of rejected data formats and carrying hardware has grown to a football field size hall of confuse within the digital age, if you just recall 5,25'' floppy disks or optical disks of different manufacture. Today we use clouds (not me) and hard disks for storage, what will be the technology in five years time? Do we need to own our music or will it change completely to cloud streaming with flat rates? It will depend as well on our relationship to our music. Since I don't need any shuffle playing option from my library, others prefer such a undirected support of all-time background music. On the other hand, when I have stopped once playing some of my albums, I hardly find back to them, so I might not need to own them for a lifetime period.
But what when it will happen like in 1995 again, when almost all new produced music sold as vinyl format disappeared for the CD, and today the CD as medium will disappear together without any option to get the same audio standard in other form, it might be getting difficult. My digital preference for my library requires "red book standard" as minimal resolution option, any lower option is not acceptable in audible terms!

Today all recordings are made with solely digital production parameters, where almost all steps of mixing, refinement, manipulation and mastering are introduced in the digital stage. Here now the typical fingerprint of each component and part known from former analog productions is almost invisible for a all around neutrality. This effect creates a much much better general audio quality as average result, comparing it with the early 1990ties. Modern digital recordings can be compared in quality terms within a range of deviation with maximum of 10% divergence, they differ mainly in terms of captured overall dynamics and lost of micro detail, values absolutely unknown from analog vinyl productions, where the captured quality differs to my estimation for more than 50%.

Read on soon, Volker



Reference to the shown miniature speakers was a japanese web page, I was unable to decipher a name of its author, I am sorry for that. I hope the shared attention will be welcome.