Refinements of a Certain Stage – Low Frequency Decoupling Dampers

A german text version follows the end of the english text.

JBL 075 tweeter, modified with LignoLab bronze horn, decoupled from the low frequency enclosure underneath with special version LignoLab Niederfrequenzdämpfer DQ148 with support element.

Hello to everybody,

with this post I would like to introduce a new category "with rhyme or reason" into my blog. Here I will report about audio products in irregular sequence, which are made with intelligence, innovation and sense in mind. Such products are getting rare in a world made on top of a chinese workbench.

Today I would like to deal with a tiresome subject that is adequately known to every lover of high-quality audio reproduction – the influence of resonances to decrease the aural abilities within audio components. Too well such influences are treated with "sacred stones", decoupled cable beds foremost finished with massive CNC lathe machined anodised surfaces to be representative relicts in stores for "audio make worse trades", just to be lush money transformers. With profit margins reminiscent of dental technology, consumer products are thereby brought closer to guarantee always one thing: to mark a tremendous listenable difference as selling argument. All these products will have listenable effects, but will not substantially resolve the basic problem of decoupling down to the lowest oscillation frequencies below 10 hz, they just shift the resonances into another register of influence. All depends on the physical operational depth, its effect of insertion will have different effects with speakers in wooden enclosures electronic components or, at the most delicate place, within the pick up process of a analogue record player tonearm. This means the potpourrie of commercial offers is rich, sometimes reduced to simple home made recipes, voodoo and manly fashionable products from a audio boutique, but rarely based on solid physical principles, solutions and applications to master the problem. Naturally, the influence of such resonances in the analogous components of an audio chain is here greatest. Especially when evaluating a record player, where comparatively microphysical factors can produce enormous changes naturally the problem is fatal.

It was not until relatively late in the history of the analog palpation process realized that resonances in turntables have a large influence in this sort of sensitive application. Different it can not be explained why in particular the first division of brands for studio equipment turntables, namely EMT, Garrard, Thorens and Platine Clemént, but as well numerous refrigerator sized units from overseas with arm thick sized driving shafts, driven by bucket sized motor drives, have been mounted completely solid coupled to their studio consoles (the only exception proving the rule was the swing frame for the EMT 930, which was made to decouple the entire unit with a simple spring suspension frame, at least a first attempt in 1956). It started to be issue in 1959 with the first sub chassis player made by Acoustic Research, followed by Era 1962, Thorens in 1965 and later the well-known British players like the subscription project Sondek LP12 from the 1970s, managed to raise awareness of this problem.
These were and yet are still far away from a sustainable solution of the general problem. In order to visualize it in more detail, one must understand the physical preferences with delicate low (arm- / pick up-) mass of less than 50-100g and cantilever compliances from 5 to 25x10-6cm dyn. so that the oscillation frequency is below 10 Hz, better below 3 Hz. This value must be achieved so that the resonant frequency does not adversely affect the sensitive pick up process. This fact shows why a classic light weight sub chassis player of the above named types has a much higher resonance frequency due to the lack of damping properties for the spring suspension, resonances can be much easier develop from the input, decaying lack of mass and weight. This explains also equally sound wise their typical lack of colorrange and expression in the low frequeny response, even if they are well enabled to present all fine resolution within the middle and high frequency range as a benefit of their spring decoupling sub chassis designs.

Cuisine Française

Jean Constant Verdier, who died last autumn, was the unique design engineer of the turntable simply called  "Platine Verdier", which has written history in the past forty years in this regard and solved the topic of this article as much as possible.

Last but not least J.C. Verdiers early work with the company Era has led to a thorough analysis of the advantages and disadvantages of these light weight sub chassis constructions and have thus largely determined the structure and design of his unique first mass player to solve the problem. 

In the context of the French Maison de la L'Audiophile some developers have been in research between 1978 and 1988 about the conditions of the pick up process and around the player technology in general (P. Lurne). They tried extended analysis works with several main topic interests, since the turntable was still the foremost signal source for the audiophile in these years.

J.C. Verdier realized already in his first draft of his legendary turntable Platine Verdier (L'Audiophile, No 13, December 1979), the necessity not only of a precisely measured spring suspension, but also their pneumatic motion damping, so that this feet were damped down for maximum benefit to an oscillation frequency of 1-2 Hz. 

One would think the air damped suspension is a French specialty, because it was a similar pattern for the suspension of a French car maker Citroen (in the 1950s the Citroen 15CV was equipped with pneumatic damped suspension first time at one axis). Here with the Platine Verdier feet too, the combination of a loaded spring damped by a controlled air chamber for decoupling from typical vibrations was the innovation. In many other technical designs hence the more stronger made gas damper with higher frequency damping is used. In some vehicles even a simple torsion or leaf spring system were installed without any damping effect. The comparison may imagine a beautiful picture, where vehicles without damped suspension systems are just bumping over the road ... ?!

Drawing showing the first air damped spring suspended feet design from J.C. Verdier published
in L'Audiophile No. 13, Dec.1979

Together with the unique magnetic bearing design and the mass of 47 Kg for the complete turntable a incomparable "unit to play vinyl records" was invented by Verdier, at least in drawn theory published within three issued articles of the french audio magazine. Its realization is another completely different posting within this blog to follow later on some time. 

As we know today the Platine Verdier is a unique turntable, which did combine unmatched properties to a higher degree of interaction and led finally to a exceptional package of aural properties, which are even by todays standards almost 35 years after its first appearance, are still a milestone to pass. The Platine Verdier is the turntable that is still setting the pace for the today generation of all heavy mass players, oil rig inspired designs and ocean liner dashboard players (namely the ability of keeping the dynamic and musical content in a authentic flow of natural expression), combined to a higher degree with the typical known benefits from the best light weight sub chassis players (namely the finest resolution of micro dynamic harmonies), both welded together with an incomparable tranquility and homogeneity (by the magnetic bearing) in the finalized expression. No less and no more, and studied to date his master.
Unfortunately, this incomparable record players wide recognition success was denied in limited Iinternational scale, due to its heavy and bulky transport weight. In general, at overseas locations far outside central Europe, especially in Korea and Japan within the "audio gourmands" of the first hour, have been remained largely unknown about this design. Well, one can't have always the best...

Three different models are already designed to match almost any realistic mass in audio systems,
from left: Niederfrequenzdämpfer D172, D136 and SQ148, dedicated support element back in the middle.

At this point of the article I would like to focus on to Norbert Gütte, who was a long-time companion of Keith Aschenbrenner at Auditorium 23 from the start, not only as a carpenter of wide developed solutions for their speaker cabinets final realizations, but even as a "l'audiophile confessor". He has devoted all kinds of problems both supportive, as well with the adverse effects of resonances in the audio field extensively. Numerous speakers became addressed to the properties of musical instruments for taking advantage of harmonic skills from wood to be used with speaker enclosures. But also with reversed terms of the full scale avoiding the inherent resonant effects speakers have been designed and realized by Norbert Gütte, like the known component support rack called "Die Bank". This aim was achieved with subtle and complex unconventional material and joining technologies, still aimed to support the positive harmonious qualities in its stored audio components. So it is not surprising that Gütte began to examine the properties of Verdiers damped pneumatic spring principle at the turntable feet, since the Verdier turntable was distributed by Auditorium 23 from its beginning. The component rack "Die Bank" is typically a heavy mass unit, built with complex structures and joints, expanded in 2001 and equipped with Güttes first designed suspension damping feet series D172 for perfect decoupling of the total weight with more than 200 kg. The suspension of the rack can be adjusted to different weight support in order to match the important lowest resonance of 3 hz oscillation frequency. On top almost any record player can be positioned with all benefits known from this suspension/damping principle, additionally all other stored components like cd-players, amplifiers or recorders can profit from such a integrated completeness of decoupling.

The equipment rack Die Bank (100 kg) shown with centered three-feet damping system and security feet at the edges, the LignoLab preferred most efficient system. As well available with four D172 dampers in traditional edged position

Sectional cut through the side wall and carrying tray of Die Bank, shown with one D172 damper edge mounted in order to show the complex inner structure and the tonal best compound wood material for audio furniture, northern coniferous plywood.

Anybody who was not lucky enough to obtain a out sourced decoupling table from a physical research institute at a yard sale will get with "Die Bank" an sound key product for his high-quality audio components with incomparable attitudes to any other component decoupling system known. This is to be assumed in effective depth at least equal value of a exceptional audio component, – and it tops it with length for a fraction of costs. Here not only a extremely prone turntable can benefit, but this furniture also offers enough space much for the rest of the chain, such as pre- and power amps to be decoupled in one unit. The low frequency damper D178 can be equipped with different strong springs and can expand with further two or three dampers to a resonance system interconnected to the weights between 100 kg and 250 kg, decoupled precisely down 3 hz with different sized springs. Such a rack is a lifetime investment, which electronic components can do so?
As a logical consequence resulted from these dampers the complex built turntable bench TT100 (100 kg) is designed, since such a high mass optimizes the physical effect of a air damped spring suspended system. This table enables analog devices, so-called mass turntables perfectly to get into non resonant stage. Thus, these units can now get one of the unique features of the original Platine Verdier, namely their air damped suspension system, which is to my knowledge and experience may be even more important than the magnet bearing, been decisive for the remarkable sound quality of the Platine Verdier. Norbert Güttes TT100 can be impressively seen in action in a little Youtube video. Totally amazing, the entire unit can be irritated to several centimeters in vibration, without any sort of affection to the pick up process.

But amazement alone can not be a selling point, certainly when so little representation factor is associated with a product and since the feet purely functional appearance, then already sufficiently convincing properties have to play the role of desire. It can not be completely described with words, how a analog turntable can profit sound wise from such circumferentially decoupling. Very few have probably a assessed idea of ​​the actual aural signification to the skills of a high-end mass player. But if you follow the theoretical idea of a complete resonance elimination and to its sense of a system with low frequency isolation introduced and alternatively not in comparison the most will be more than surprised by the result and the depth of the effect. With a profoundness that goes far beyond completely different tone arm / pick up- / step up transformer sets, such a player wins exorbitant fine dynamic resolution, dynamic capabilities and allows the natural flow of music to follow a lot more with natural ease. Immediately one no longer recognizes his player back and actually begins now extensively to learn just as you have probably never heard it before. Norbert Gütte has varied the use of the D172 damper within a quartet or within an equilateral triangle as a triplet underneath "Die Bank" and with his newer turntable-bench TT100. Actually this first damper model is extended with two more smaller damper variants for lighter weighted components. The D136 can also be used in different versions with different inserted springs to match a range of three weights between 14 kg to 60 kg and is suitable to be mounted directly underneath a turntable, with built in weight adjustment and balancing option.

Laufwerktisch TT100 with Platine Verdier on top

Norbert Gütte takes the trouble to precisely tare the actually searched weight to adjust the usable range with the help of sample structures from brick stones to ensure a one hundred percent effective product. Thiese dampers can be placed directly under a component and are therefore also suitable for direct isolation of todays typical massive weight turntables. In addition, for lighter designs with plinth like the Thorens TD124, Garrard 301 u. 401, as well all other representatives of the typical idler wheel section, there is the low-frequency damper DQ148 of being able to balance weights between 4 to 25 kg. This damper type was originally designed for the decoupling of tweeters and midrange drivers in critical resonance mounting positions of loudspeaker enclosures, in order to protect these from the influence from heavy low frequency resonance insertion. Originally made for the JBL ring radiator 075 or 2402 may be provided with his own bronze horn, but these dampers can also decouple heavier drivers to the influence of powerful bass drivers in the same physical enclosure set for perfectly resonant freeness. I was not able to test this dedication within my own set up, but I know about such delicate decoupling issues from my own enclosures very well.

The only final word can be, that the decoupling effect and its profound values of refinement are second to none. Once installed nobody will reject such a system after personal evaluation, I swear. The remarkable profit in resolution and dynamic abilties is exceptional and exceeds the known dimension of change between two world class components in a given system by far, even not being cheap such a system can be counted as long term investment at the lower cost side of  the audio world. If you're wondering whether you really will need such a system, please answer the question: Whether you can do without a spring damper system in your car?The LignoLab dampers are the only universal available solution with such technical and audible efficiency and profit worldwide. Additionally all products from Norbert Gütte are produced in small series as pure manufacturing pieces, but deny any manual ductus of the emergence in absolute perfection in its execution, workmanship and finish. As to be typical for any LignoLab product.

For further informations about the LignolLab products you will find at the end of the German text all necessary addresses and links.

Evaluation to match perfectly the given weight of a customer with
3 hz oscillation frequency (here 46 kg).

German Version:

Heute möchte ich mich mit einem leidigen Thema beschäftigen, das jeder Liebhaber hochwertiger Audiowiedergabe hinlänglich kennt, dem Einfluss von Resonanzen in Audiokomponenten und deren wirksamer Isolation. Nur zu gut wird seit Jahr und Tag im repräsentativen Reliquienhandel für Audioverschlimmbesserungsprodukte der Einfluss geweihter Steine, gebetteter Kabel und dies alles vor allem mit massiver CNC-Dreh- und Eloxaloberflächentechnik optisch wirksam geltend gemacht bzw. zu sattem Geld transformiert. Mit Gewinnspannen die an zahnmedizinische Technik erinnern, werden dem Verbraucher dabei Produkte näher gebracht, die eines auf jeden Fall fast immer garantieren, nämlich einen gewaltigen klanglichen Einfluss zu markieren. Häufig werden dazu dehnfähige Polymere, in einfacher oder komplexer Verbundtechnik als Allheilmittel mit wirkfördernder Namensgebung eingesetzt.
Inhärente Resonanzen in ihren unterschiedlichsten Ausprägungen beeinflussen den Klang von Audiokomponenten in gravierender Weise, sie können diesen sogar umfänglich verändern. Jedoch selten gelingt es mit solcherart Boutique-Produkten, den Hebel an die Ursache oder Wirkungsweise und -tiefe anzulegen und die gezielte Beseitigung des Problems zu bewerkstelligen. Häufig verändern diese Produkte die resonanten Eigenschaften oder verschieben die sie in ein anderes Register, in den wenigsten Fällen werden sie minimiert oder gar beseitigt. Dabei ist das Potpourri mehr als reichhaltig, nicht nur einfache Hausrezepte, Voodoo und zahlreiche Mode-Produkte aus der Audioboutique werden eingesetzt, sondern auch auf physikalische Grundlagen beruhende solide Anwendungen und Lösungen versuchen den Problemen Herr zu werden. Naturgemäss ist der Einfluss solcher Resonanzen gerade bei sensiblen analogen Wandlern wie Plattenspieler oder Lautsprecher einer Audiokette sehr deutlich erfahrbar. Beim Abtastvorgang eines Tonabnehmers, wo vergleichsweise mikrophysikalische Einflussgrößen ungeheuere Veränderungen durch die darauf folgende riesige Verstärkung von fast 100 dB erzeugen können, ist naturgemäss das Problemfeld der Resonanzanregung besonders fatal.

Norbert Gütte uses his Niederfrequenzdämpfer within his Sato-Horn installations, in order to
decouple the sensitive wide range horn from the sand filled Double-Onken-type cabinet.

Erst relativ spät in der Geschichte der analogen Tonabtastung hatte man erkannt, dass Resonanzen in Abspielgeräten einen großen Einfluss an dieser sensiblen Stelle nehmen. Anders lässt sich eigentlich nicht erklären, warum insbesondere die Erstligisten der Studioausstattung, nämlich EMT, Garrard, Thorens, Platine Clement und zahlreiche kühlschrankgrosse Studioprodukte aus Übersee (wie Fairchild, RCA und Gates mit armdicken Antriebswellen und eimergrossen Motoren) noch in den sechziger Jahren ihre Tonarme massiv mit den Antriebskonstruktionen verschraubten. Selbst im Verbund als Einbaugerät für Studiokonsolen wurden die Laufwerke weitestgehend steif angekoppelt. Eine effektive Entkopplung fand bestensfalls mit gefederten Einbautrahmen für die Gesamtkonstruktion nur unzureichend statt (Der Schwingrahmen des EMT 930 sollte das gesamte Laufwerk mit eine Federaufhängung entkoppeln, zumindest ein erster Versuch in 1956). Erst mit den sogenannten Subchassisspielern für den Heimaudiomarkt der ersten Generationen wie Acoustic Research 1959, Era 1962, Thorens 1965 und später die bekannten britischen Abonnementkonzepte wie der Sondek LP12 (wird seit Erscheinen in den 1970er Jahren fortwährend mit den gefühlt 56sten Upgrade verbessert), schafften ein Bewusstsein für dieses komplexe Problemfeld. Sie waren und sind aber von einer nachhaltigen Lösung immer noch weit entfernt. Um sich das Problem etwas genauer zu vergegenwärtigen, ist zu verstehen, dass der Einfluss beim sensiblen Abtastvorgang mit relativ geringen (Arm-/Abtaster-)Massen von weniger als 50-100g und Nadelnachgiebigkeiten von 5 bis 25x10-6cm dyn. gravierend ist. Dementsprechend ebenso plausibel, daß die Schwingfrequenz unter 10 Hz, besser unter 3 Hz zu liegen hat. Dieser niedrige Wert muss erreicht werden damit die Anregung sich nicht nachteilig auf den Abtastvorgang auswirkt. Ein klassischer Subchassisspieler der genannten Typen liegt aufgrund mangelnder Bedämpfung des Ein- und Ausschwingvorgangs, aber auch mangelnder Masse sehr viel höher und damit noch sehr deutlich im Hörspektrum. Dies erklärt auch gleichermassen derer Mangel an durchgezeichneter Farbigkeit und komplexer Ausdrucksfähigkeit in der Wiedergabe des Grundtonbereichs, obschon sie allesamt in den mittleren und höheren Frequenzen die Vorzüge einer solchen Entkopplung vorteilhaft zu präsentieren wissen. In diesen Frequenzbereichen funktionieren die weitestgehend ungedämpften Entkopplungsmethoden nachhaltig gut.

Viele vermuten bei Entkoppelungsmaßnahmen vor allen Dingen positive Effekte bei der Trittschallentkopplung von Plattenspielern, diese wird zwar auch wirkungsvoll mit diesen hier vorgestellten Dämpfern erreicht, jedoch geht es in diesem Artikel um weit umfänglichere Einflüsse, vor allem sollen die weitaus weniger wahrnehmbaren geräteinternen Resonanzanregungen beleuchtet werden, die durch feinste mechanische Schwingungskopplungen entstehen und sich unkontrolliert ausbreiten.

Cuisine Française

Jean Constant Verdier, der im vergangenen Herbst verstorbene Konstrukteur einzigartiger Laufwerke, schlicht „Platine Verdier“ genannt, haben in den zurückliegenden vierzig Jahren Geschichte in dieser Hinsicht geschrieben und hatten das angesprochene Problem bereits damals weitestgehend gelöst. 

Nicht zuletzt seine Tätigkeit bei der Firma Era hat Verdier genaue Erkenntnisse über Vor- und Nachteile der leichten Subchassiskosntruktionen verliehen und diese Erkenntnisse haben somit massgeblich die Konstruktion seines legendären ersten Masselaufwerks zur Lösung vorbestimmt. 

Im Umfeld vom französischen Maison de la L’Audiophile waren in den Jahren 1978 bis 1988 einige Entwickler mit Fragestellungen um die damals wichtigste Signalquelle Plattenspieler befasst (P. Lurne) und bemühten sich mit erheblichem Aufwand, Versuchen und physikalischen Messungen den ungelösten Problemen der Schallplattenabtastung beizukommen.

Verdier gebührt deshalb auch die Ehre, das Prinzip der aufwendig bedämpften Federwirkung, hier pneumatisch realisiert, für Plattenspieler eingeführt zu haben. Man sollte meinen die pneumatische Dämpfung ist eine französische Spezialität, denn sie wurde auch ähnlich funktionierend für die Federung eines französischen Automobils entwickelt (die erste hydropneumatischer Federung wurde im 15CV der der 1950er Jahre von Citroen verbaut, zunächst nur auf einer Achse). Auch hier bewirkt die Kombination von belasteter Feder und einer kontrolliert eingesetzten Luftkammer als Dämpfungseinheit den erwünschten Grad der Entkopplung von tiefstfrequenten Schwingungen. In vielen anderen technischen Bauformen wird deshalb der einfacher zu verbauende und härtere Gas-/Öldruckdämpfer mit höherfrequenter Dämpfung eingesetzt. In manch einfachen Fahrzeugen sind oder sogar noch Torsions- oder Blattfedersysteme ohne Dämpfung verbaut. Der Vergleich mag eine schönes Bild entwickeln, Fahrzeuge ohne bedämpfte Federsysteme springen über die Strasse…?!

Niedrigfreqeunzdämpfer D172 set as used with Laufwerktisch TT100 and Die Bank for perfect central alignement of masses

Verdier realisierte bereits bei seinem ersten Entwurf zu seiner Platine Verdier (L’Audiophile, No13. Dezember 1979) deshalb nicht nur eine präzise bemessene Federung sondern auch deren pneumatische Bewegungsdämpfung, so dass diese Einheit nach eigenen Aussagen bis hinab zu einer Schwingungsfrequenz von 1-2 Hz optimal wirken konnte. Zusammen mit der Magnetlagerkonstruktion und der Masse von 47 Kg war ein bis heute unvergleichliches Laufwerk zum „Abspielen von Schallplatten" zumindest theoretisch erfunden worden, dass es dann zu einer Realisierung kam ist eine weitere ganz andere Geschichte, die ich an dieser Stelle sicherlich auch noch vorstellen werde. Wie man eben inzwischen umfänglich erkannt hat, ist erst durch diese Kombination ein Zusammenspiel möglich geworden, welches unerreichte Eigenschaften in sich vereint. Die Platine Verdier ist das Laufwerk, welches die Eigenschaften sämtlicher Masselaufwerke (nämlich die Fähigkeit auch dynamische Musikpassagen mit authentischer Kraft, Ausdruck und Farbigkeit wiederzugeben im Stande ist) mit den typischen Eigenschaften der besten subchassisentkopplten Laufwerke kombiniert (nämlich mit feinster Auflösung mikrodynamischer Harmonien) und beides zusammen mit einer unvergleichlichen Ruhe und einem Fluss (Magnetlager) in der Musikdarstellung verbindet. Nicht weniger aber auch nicht mehr, und das sucht bis heute seinen Meister. Leider ist diesem unvergleichlichen Laufwerk der ganz grosse Anerkennungserfolg im internationalen Masstab aufgrund seines mächtigen Transportgewichts versagt geblieben. In Übersee generell, vor allem bei koreanischen und japanischen „Audio-Gourmants“ der ersten Stunde ist dieses Laufwerk weitestgehend unbekannt geblieben. Naja, man kann ja nicht immer nur das Beste haben....

Component base realized with heavy sand filled platform and three DQ148 Niederfrequenzdämpfer in triangle order for lighter weighted turntables and amplifiers, seen from underneath.

An dieser Stelle möchte ich auf Norbert Gütte zu sprechen kommen, der als langjähriger Weggefährte von Keith Aschenbrenner im Auditorium 23 von Beginn an nicht nur als gelernter Tischler vielfältige Lösungen für Lautsprechergehäuse mitentwickelt und realisiert hat, sondern selbst als l’audiophil Bekennender sich bereits früh für allen möglichen Fragestellungen sowohl der unterstützenden, wie auch der unerwünschten Wirkungen von Resonanzen im Audiobereich ausgiebig gewidmet hat. Dabei entstanden zahlreiche Lautsprecher die die Eigenschaften von Musikinstrumenten zur Vorteilsnahme harmonischer Fähigkeiten nutzen. Aber auch mit umgekehrter Zielsetzung, nämlich zur Absorbierung unerwünschter Resonanzen wurde z.B. das Komponentenrack „Die Bank“ entwickelt. Diese erreicht mit subtil und aufwendig umgesetzter Material- und Verarbeitungstechnik ebenfalls eine Unterstützung der harmonischen positiven Eigenschaften der ihm anvertrauten Komponenten. So ist es nicht verwunderlich, dass Gütte das pneumatische bedämpfte Feder-Prinzip der Füsse Verdiers auf universellere Wirkzusammenhänge hinreichend zu untersuchen begann, war doch das Auditorium 23 von Beginn an der Vertrieb für das Verdier Laufwerk. Gütte hat das Prinzip der bedämpften Federfüße schon seit längerem weiterentwickelt. Die bewusst schwer gebaute "Bank“ wurde dann seit 2001 mit der ersten Niederfrequenzdämpfer-Serie D172 um eine perfekte tieffrequente Entkopplung erweitert. Wer nicht zufällig in den Besitz eines ausgemusterten Kopplungstisches einer physikalischen Versuchsanstalt gelangt ist, bekommt mit der „Bank“ eine unvergleichliches klangentscheidendes Produkt zur Steigerung seiner hochwertigen Audiokomponenten an die Hand, das diesen in Wirkungstiefe mindestens als gleichwertig zu bemessen ist. Hier können nicht nur die generell extrem anfälligen Laufwerke profitieren, sondern dieses Möbel bietet auch noch Platz einen Großteil der restlichen Kette unterzubringen, so können Vor- und Endverstärker gleich mit entkoppelt werden. Der Niederfrequenzdämpfer D172 kann mit verschiedenen Federn ausgerüstet werden und kann somit im Verbund mit weiteren zwei oder drei Dämpfern zu einem resonanzfreien System ausgebaut werden. Mit individuell nach Kundenwunsch bemessenen Federn können dann Gewichte zwischen 100 kg und 250 kg präzise bis hinab 3 hz entkoppelt werden. Als logische Konsequenz daraus ergab sich dann mit diesen Erfahrungen der aufwendig gebaute Laufwerkstisch TT100 (100 kg Eigengewicht zur Masseoptimierung der Dämpfung). Mit diesem Tisch können schwere Analoglaufwerke, sogenannte Masselaufwerke perfekt entkoppelt werden. Somit können auch andere Laufwerke sich eines der beiden entscheidend wichtigen Alleinstellungsmerkmale der Platine Verdier, nämlich ihre Dämpferfüsse nun nachträglich als Vorteil zu eigen machen. Norbert Gütte führt auf seiner Homepage eindrucksvoll in einem kleinen Youtube-Video die nachhaltige Funktionsweise der Einheit vor. Völlig verblüffend kann diese im laufenden Betrieb um mehrere Zentimeter in Schwingung versetzt werden, ohne das der Abtastvorgang davon im geringsten beeinträchtigt wird. 

Aber Verblüffung allein kann kein Verkaufsargument sein. Schon gar nicht wenn so wenig Repräsentationshabitus damit verbunden ist und das in einem Geschäftsbereich, der eigentlich heutzutage nichts anderes mehr als genau diesen verkauft. Dann müssen schon hinlänglich überzeugende Eigenschaften wirken und diese sind mit Worten kaum zu beschreiben. Die Wenigsten haben vermutlich eine Vorstellung davon die tatsächliche Wirktiefe der Niederfrequenzdämpfer auf die Fähigkeiten eines hochwertigen Laufwerks zu übertragen. Aber wenn man den schlüssig physikalisch abgeleiteten Erkenntnissen folgt, ist man immer noch mehr als überrascht über den realen Zugewinn. Die Tragweite ist eher mit einer möglichen Investition in eine höchstwertige Audiokomponente vergleichbar. Dabei gewinnt jedes wertige Laufwerk an feindynamischem Auflösungsvermögen, dynamischen Ausdrucksfähigkeiten und macht es möglich dem natürlichen Fluss des musikalischen Geschehens müheloser zu folgen. Man erkennt sein Laufwerk eigentlich nicht mehr wieder und beginnt damit es nun umfänglich komplett neu zu erfahren, genau so, wie man es vermutlich noch nicht zuvor gehört hat. Norbert Gütte hat inzwischen den Niederfrequezdämpfer D172, der im Quartett bei der Bank oder auch im von ihm präferierten gleichseitigen Dreieck als Triplett auch beim Laufwerkstisch TT100 eingesetzt wird, um zwei weitere kleinere Varianten nach unten erweitert. Der D136 kann auch mit geringeren Gewichten als sein größerer Bruder optimal eingesetzt werden. Er deckt in verschieden bestückten Ausführungen im Dreierset Gewichte von 14 kg bis 60 kg ab und ist somit geeignet direkt unter entsprechend schweren Laufwerken montiert zu werden. Hier kann Gütte vier Gewichtsvarianten anbieten. 

Er macht sich die Mühe das tatsächlich gesuchte Gewicht seiner Kunden mit Hilfe von Probeaufbauten exakt auszutarieren, um eine einhundertprozentige Wirkweise sicherzustellen. Zusätzlich für die noch leichter bauenden Zargenlaufwerke, wie den Thorens TD124, Gararrd 301 u. 401, sowie weitere typische Vertreter der Reibradtechnik, gibt es noch den kleinen quadratisch gebauten Niederfrequenzdämpfer DQ148, der in verschieden bestückten Versionen in der Lage ist Gewichte von 4 kg bis 25 kg zu entkoppeln. Dieser Dämpfer wurde ursprünglich entwickelt um Hoch- und Mitteltontreiber in resonanzkritischen Montagepositionen bei Lautsprechern (s. Bild am Beginn des engl. Teils) vom Einfluss der tieffrequenten Schallwandler zu schützen. Zu diesem Zweck kann man ihn mit einem veränderten Auflageaufbau ausrüsten, wie z. B. für den JBL-Ringradiator 075 oder 2402 der auch mit Norbert Güttes Bronzehorn aufgewertet werden kann. Aber auch schwerere Treiber lassen sich komplett vom Einfluss der kraftvollen Basstreiber im gleichen Gehäuseverbund perfekt resonanzfrei trennen.

Abschließend kann man zusammenfassen, die Wirktiefe einer pneumatisch bedämpften Federung ist in empfindlichen Einsatzpositionen von ungeheurer Bedeutung und ist sie einmal ausprobiert danach schnell auch unverzichtbar geworden. Das diese Dämpfer natürlich auch nachhaltig Trittschallprobleme auf schwingenden Fußböden absorbieren, ist eigentlich nach allem Gesagten selbstverständlich wie naheliegend. Wenn Sie sich jetzt fragen ob Sie ein solches System wirklich benötigen, beantworten Sie sich die Frage: Ob Sie in Ihrem Auto auf eine Federdämpfersystem verzichten könnten?

Erst recht bei analogen Laufwerken und auch bei hochfrequenten Hornlautsprechern (der Wirkungsgrad der Resonanzen und damit verbundenen Irritationen auf die feinsten übertragenen Frequenzen ist einem einem mechanischen Verstärkerprinzip wie einem Horn naturgemäss sehr hoch) ist der tatsächliche Gewinn an musikalischer Auflösungen als ein mehrfaches einer höchstwertigen Komponente jeweils anzusehen. Die Dämpfersysteme und -Möbel decken in allen Varianten fast jede denkbare Möglichkeit zur Entkopplung ab. Die LignoLab Niederfrequenzdämpfer sind das einzige universell adaptierbare Produkt ihrer Art, diese bieten eine einzigartige nachhaltige Lösung der Resonanzproblematik und dies mit absolutem Alleinstellungsmerkmal. Selbst das Original, die mit pneumatischen Dämpferfüssen ausgerüstete Platine Verdier kann bei schwinganfällgen Fußböden in Kombination mit Bank oder Laufwerkstisch durch das gesteigerte Gesamtgewicht noch einmal deutlich profitieren.
Sowohl die Bank, als auch der Laufwerkstisch und auch die Niederfrequenzdämpfer werden in Kleinserien als reine Manufakturarbeit hergestellt. In ihrer Ausführung, Verarbeitung und in ihrem Finish repräsentieren sie allesamt Güttes Auffassung hochwertigster Funktionalität verbunden mit einer konsequent von überflüssigem Habitus befreiten Ästhetik in jedem Detail. Die Dämpfersysteme und -Möbel sind wahrlich kein Sonderangebot, aber deren klanglicher Einfluss auf hochwertige Audiokomponenten ist im gleichen Maßstab derer Kosten als Sonderangebot zu werten und das auch noch mit Langzeitstabilität. So betrachtet bekommt eigentlich auch noch jeder "Geiz ist Geil"-Einwand seine unverdiente Belohnung.

Weiterführende Informationen zu den Produkten von LignoLab:

LignoLab
info (at) lignolab (dot) com
Norbert Gütte
Telefon: 02327 54 66 97
Fax: 02327 54 66 98
Mausegatt 59
44866 Bochum
Germany

The Tannoy 15'' Enclosure for the Enthusiast Revisited – The First Birthday

Hello to everybody interested

reading further about my 15'-Tannoy enclosure loudspeaker design. A bit more than a year time has passed since the dipole based front loaded enclosure has been finished in its final form and did set place in my everyday audio setup. Today, after that time, I can say this was one of my most important steps in my whole audio life towards a refined, smooth and absolute natural audio response. Since last February these speakers have given me so far the rare present of hundreds hours of inspired musical listening pleasure, were the technical aspects of its origin did step into a background role.
In the former 30 years I have owned several different original Tannoy speakers/enclosures with almost all types of drivers with alnico magnet. All these loudspeakers are quite well known and have several fans around the world. They all show up with similar audible characteristics and attitudes. Their very conspicuous presence of articulation, illusion of space and exceptional dynamic abilities, which are common similarities independent of size and enclosure principle, have made Tannoy to a classic in audio history. They perform in a well known robust tradition where other similar vintage makes from Altec, Jensen, Stephens, University and more are gathering, but were refinement and natural aspects do not play the foremost attitude, instead their typical common habits are more or less similar cheeky frequency ends. The Tannoy typical reflex/vented port cabinet designs (like Canterbury, Lancaster, Mansfield, Cheviot, Arden, Devon and their similar designed predecessors), but as well the highly favored back loaded horn designs (like Autograph, GRF, Corner Canterbury or even both Westminsters) are good examples for more than prominent low frequency response (but unbeatable excellent all-time favorite selling arguments). The latter group extend this spectacular attitude into the region of lower mids as a result of the to short and to small opened backing horns, mixing up with a cocktail of unwanted wooden resonances as a result of large interior surfaces of the horn development.
Excuse me, these classic speakers might be able to fulfill the claims with typical attitudes of electrical amplified performed rock music, but for lovers of naturally performed and articulated music with delicate dynamic structures such designs are are of no use, unable to represent a full spectrum of micro dynamic information. For audio gourmets these classic designs need a lot of work to be a final choice.

A loudspeaker is one of the most important components in a audio set up. As the final transducer of  electrical signals into acoustical waves it has a important function. If it is unable to transform the signals without harmonic relevance and dynamic finesse, other components will not be able to catch up the loss.

My enclosures did lead my long term relationship with Tannoy Dual Concentric alnico drivers into a complete new adventure of unknown land. My listening experience with such "full range" horn installations from Linemagnetic LM22A/LM555/LM597 with TA7331 inspired the dipole woofer idea for my enclosure, as the LM22A did inspire the front loaded funnel for the medium frequencies (to be honest since the middle 1990ties I did plan to add such funnels to a typical Tannoy enclosure, but I never realized this idea before 2014). Within several articles I have honored the "best audio set ups I personally have listend to" and I am still in hope to extend this experience one day with a larger wooden horn like WE15A in a similar refined set up.

My own unique way to follow such exceptional sets uses a Tannoy Dual Concentric speaker in combination of dipole enclosure, where the purposed half is formed to act like a front loaded horn development and the backing part acts like a traditional open chamber. Such a front horn helps to overcome the most difficult fault of the large 15'' paper cone. The medium frequencies response between 500 and 1500 hz will be mechanically amplified and supported, a tonal spectrum where a cone speaker of such mass and size is physically limited in its ability of resolution finer harmonic details. In the same time the funnel does act as a extension of the cone, who itself is already a seamless extension for the high frequency driver. So the horn is enabled to conduct lower frequencies with its wider and longer opening development. Not only to my personal taste the Tannoy high frequency horn is known to be one of the best two or three horn tweeters built ever. It shows up with a exceptional rare attitude, its seems to be unlimited extended in its higher frequency performance, since it is at the same time completely acoustically invisible, as any for hf-horns typical superficially is at the same time completely absent.

Horn development as seen from the mouse, the funnel extends the cone, who itself seamless extends
the hf-horn. Additionally the funnel enables the cone to conduct a larger air mass.

The dipole principle for low frequencies was a early simple invention to obtain fast and naturally sounding low frequency response in early cinemas of the 1930 to 1950 years. Together with the open baffle principle, which is physically seen as a similar design, it was in these days preferred over any closed or ported cabinet design. These came into account when the amplifiers started to be powerful enough to drive small enclosure types to allow complex filter units for massive corrections of low frequency radiation.
The dipole shows some advantages comparing it to other designs, like the fastness of the transients, the completely uncompressed tonal expansion and the non-existence of any wooden resonances, which are typical for all cabinet priniciples. Open baffles mostly fail any acceptance in living room surroundings because of their space consumption (a square meter plus wings is a minimum to obtain some LF below 100 hz). The folded baffle into a such dipole design ends up with a quite room friendly size of typical classic speaker enclosures (here my speaker dimensions are 90 x 55 x 45 cm, HxWxD).

But the backward radiated energy makes a delicate room positioning necessary. The speaker radiates wide parts of the frequency spectrum in anti phase mode, a effect which makes a minimum distance to the backing walls necessary to avoid problems. Anything closer will result in typical phase erasure and adding effects, both can degrade the tremendous abilities of the speaker. I have positioned mine with a distance of 60cm from the backing walls. On the other hand the funnel helps to direct and disperse the forward radiated energy, which is a another welcome advantage, this helps to keep the vagabond room reflections in almost perfect control and limits further room treatment to a minimum.
If you can set up the speakers with such space, you will be rewarded is one of the most dynamic and expressive loudspeakers available, together with a rare freeness of resonances and a exceptional refinement of finest micro detailed harmonies, most other speakers of that league cannot compete with.

My speakers show up with the typical grill cloth at the back opening of the enclosures.

Detail of the backside, the former installed sliding mechanism is completely redundant. So I have removed the rails and fixed the inside enclosure, the shown felt seals are not any longer useful. The former planned blinds to adjust the backward
radiated energy are as well completely redundant.

One of the two best 15'' Dual concentric speakers of the Tannoy line: Here the reconed
Monitor Red with specially designed crossover to complete the enclosure design with front
loading. Later versions show up with higher paper cone weights and less optimal impedances
for low power tube amplifiers. No other duplex speaker design in history makes such a seamless
integration of high to low frequency with front loaded funnel possible.

I am now extremely happy about the behavior of this a phantastic speaker, a result which I didn't expect when I started to built up that concept. More than this the speakers are able to work in a highest possible stage of harmonic audio response with a almost invisible holographic dynamic soundstage other speakers of that size do not follow.
This speaker works so refined that it made possible to detect several limiting aspects in my chain, which in former times I was not able to detect and resolve.

I hope that such design will find some more interest in the coming future,
Volker

Restored and Ready Converted SME Tonearms to MK1 Standard

Hello to everybody

interested into the conversion to the legendary MK1 version with a heavy stainless steel armwand.

Beside the sale of a conversion kit for do-it-yourself I will offer completely converted SME 3012 arms as I will offer commissioned conversions on customer requests. This process includes a complete restoration of the classic vintage SME armparts from the 3009/12/II/(R)-series together with all necessary refurbishments to bring out the technical advancements together with extraordinary aesthetical wonderfull vintage look for the unsurpassed use of low compliance cartridges. (The R series is not really recommended for such conversions)

From now on I will extend my offerings of the well established kit with a separate offer for completely refurbished and rebuilt SME 3012 tonearms to like new condition were the kit has been used. This offer has been set up after several requests and is dedicated to customers who want a perfectly refurbished like new arm, combined with the merits of the more rigid heavy arm mass known only from the rare first version. Beside ready arms I will offer commissioned conversions of customer owned arms for people who don't have the confidence to process the conversion theirselves. Common attributes of the converted arms are are the heavy stainless steel armwand, steel knife edge bearings and adequately customized weights to match perfectly the different cartridge/headshell masses. With pure silk isolated 4N-solid silver wires of 0.1mm thickness the internal wires are matching the highest possible standard to be used (Ikeda is the only brand selling the same wire at 499$ for the 12 inch set). The refurbishment will include a polishing of the v-shaped counter bearing part of the saddle, as well a cleaning and adjustment of the wo vertical ball bearings inside the main shaft. Both acts end in a play free, frictionless adjustment of the vertical and horizontal movements.
These finalized arms will be fitted with a new designed contact terminal equipped with rhodium plated RCA-sockets and a extra earth wire connector/plug for improved integration of the shielding into the component earthing.

Here you can look at actual converted arms which are offered for sale right now:

Both alternative weights, left the 220 g weight and the 160 g weight mounted.

New RCA-socket terminal with earthing wire and dedicated contact

These tonearms are the perfect partner for the classic idler wheel turntables like Garrard 301 and 401, Thorens TD124s, Rek-O-Kuts, Commonwealths, Connoisseurs, Lencos, Fairchilds and similar types. Together with the all time favorite low compliance cartridges like the Ortofon SPU's, the Denon DL103's  (specially with the LignoLab bronze housing), the Ikeda's, the Fidelity Research's and the Koetsu's, the arms improve the dynamic attitude of these sets in a unknown way. Together with the legendary Platine Verdier players (both Versions) it is getting a perfectly matching unsurpassed dream team. Read what customers say with their own experience with such converted arms. In difference to the vintage classic SME 3009/12/SII/R arms, I do not supply a antiskating option. As with the original first MK1 version, the weight of the armwand is double mass of any later version, it does not need a skating compensation, in particular not with heavy cartridges like the SPU and therefore applied weights of 3 pond or more. Of course the necessesary parts can be delivered on special order.

Polished pillow bearing for the knife edged saddle by using 1200 grade sand paper with oil.

Optional parts for the antiscating assembly

Silk isolated solid 4N silver wire of 0.1 mm

According to the increase of prices for vintage SME 3009 and 3012 arms, which is a typical market reaction to the dwindlingly disappearance of originals, the prices will fastly climb in future. I did observe the prices of vintage SME arms for the last twenty years, it was obvious that the prices have hardly risen within the last two years. In the same time the former permanent presence of used 3009/SII's has been changed into disapearance in massive numbers. This means it will get hard to find good acceptable originals for high quality conversions or even for normal use within sophisticated audio implementations.


The current price for a such like new improved SME 3012 tonearm is actually set to 1499,00 EUR. The price will be adjusted to movements of the market prices for vintage similar arms and that means it is definitely not static, it will climb. Take your chance to get one.

Commissioned arm conversion on special request: Several additional work is necessary to match the different sizes of the late R ams (headshell and extension tube connector, knife edge, armwand length  here shown at a SME 3012/R in order to create the best SME tonearm of all times combining the mass an rigidness of the MK1 type combined with the luxury and ease of use of the late R-types for use with low compliance cartridges:

Customized cinch socket terminal with special made shielding can

Here you will see some examples of classic series two arms which I have converted and refurbished during the past two years:

The New Conversion Kit for SME 3000-Series Tonearms

I don't offer any longer such complete kits or commissioned conversions! I only can offer some single parts like stainless steel armwands, 220g balancing weights and a few lateral weights, all other parts are gone!

Hello

to everybody interested into the conversion process of classic SME tonearms of the early 3000-series. Several complete kits have been sold or installed since late 2012, when I started to offer it at Ebay. After all the experience with customers from almost all continents and desperately permanently changes with Ebay as main platform for the publishing and sale of the kit, I change the terms and policy. In future a complete kit as already known will not be anymore available, instead I offer a more or less complete armwand as kit (it is coming without the typical headshell socket known from the SME3009/12 Series II tonearms). I am reacting to a broad market request, where there seems to be more interest to find a cheap solution instead of perfectly customized one.

The new kit is dedicated for the solely armwand conversion with a heavy stainless steel tube in order to increase the arm mass for perfect matching of low compliance cartridges. It is still aimed to improve the tracking ability with such cartridges like the Denon DL103 or the all-time favorite Ortofon SPU. This offer is a low cost alternative to the former complete kit and will not include any further support or any sort of customizing option. Price is 299,00 EUR plus shipping and handling fee, depending on the destination.

The new kit.

The new kit with stainless steel armwand. It is the same quality and material selection as before, with all proved advantages from earlier kits, only reduced in parts and price.

The built quality

Instead I decided to offer complete conversions as commission with all necessary weights, internal wirement and a refurbishing process for all used vintage parts like pillow bearing polishing and further adjustments of all ball bearings. This sort of commission will be based on personal inquiry through mail. Beside customer missioned conversions I will offer complete like new refurbished converted tonearms here and with Ebay for 1499,00 EUR.

Please check the compatibility for your tonearm before inquiery!

A converted SME 3012

A converted SME 3012 MKI

A commissioned conversion on the base of a complete customer existing SME 3009/12/SII will cost around 650 to 800 EURO including all parts for the armwand, wires and one set of three weights (main weight, end cap and lateral weight), but a precise calculation will be necessary for each admission. The final costs for such conversion are determined by missing parts and extra services. My aim is to bring a almost like new arm out for the customer able to outperform any vintage SME with the right cartridge. It has been established that a short communication via mail or telephone will be the perfect base for such admission.

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

Hello to everybody interested to read on,

today I want to report about my unexpected experiences which I made through my evaluations with inductive coupled stages within preamplifiers. As I said at the beginning of these series of articles, the red based RCA tubes have alway played in my tube amplified life a exceptional role of superiority. I came across to them by an article in Sound Practice Magazine in the early 1990ties. Shortly after that event I did find a handful used red tubes at a hamfest in these days in Germany.
The RCA Red Based Tubes 5690, 5691, 5692, 5693 are a set of specially made octal tubes as highly  mechanically rugged design variants (three mica spacers, three ss supports, strengthened and volume reduced glass envelope) of the common 5AR4, 6SL7GT, 6SN7GT and  6J7GT tubes made by several brands. From my experience these tubes are by far the inferior best sounding indirect heated small signal tubes made ever. The high mu triodes 5691 and the medium mu variant 5692 have been incorporated into my phono and line stages since I have used them the first time. They impressed me from the beginning with exceptional audible superiority and I never found something close to them. Their built quality and their exclusive metal materials are chosen without any restriction to form the perfect operating devices for the us cruise missiles with a shock resistance preference of 500 g and long life service of 10000 hours. I know in theory there are a lot of other tubes matching these specifications written down to paper, but in real I never found other tubes able to compete in all aspects of comparable applications as audio tubes, by far.

A equivalent to the white Alba truffles with tubes are the red RCA's: Here the RCA 5691 und 5692 with typical black plates and extra strong ss-columns and triple mica spacers with typical red octal sockets made and stamped by RCA. The same tubes are sold by GE, other brands made them with brown base and different mechanical design.

Within this evaluation I did use several indirect heated tubes with perfect theoretical preferences for the planned implantation as output tube with transformer coupling. I did test the famous and once exceptional expensive german government tube for telephony, the C3g, a highly praised contender strapped down to triode use it will show up with theoretical perfect internal resistance for transformer coupling. But in practice with Lundahl LL660/18mA it could not convince me with a above average performance. May be a problem that it is a penthode and not a real triode, but it could not follow on the better real triodes.  Further I did use the 6SN7GT/5692 as single system (8.5 K) with choke load, as I did test them with their loctal variant 7N7 in parallel with OPT and in single implementation with choke. Both designs are as well tested with 5687 and with ECL85, tested as two step amplifier with the pentode system strapped as triode with 3.5-4 k as partner for the output transformer coupling. I did listen for a couple of days to each set up before I changed the design for the next value of tubes. The C3g showed up with the worst performance, maybe a result as being not real triode, together with the 7N7, which showed the typical spills known from several brands of 6SN7 tubes.

My evaluation enclosure to test different set ups. here seen with Lundal Ll1667 plate chokes and german post sockets serving as stand up contacts for the adapter boards mounted on the top cover. 

It ended completely (if it ever will end once) different than expected and it is a good sign of such open ended research. I made a complete new bundle of experiences (thank you Sakuma San and again Ken Shindo), which are a lot more detailed, contradictory and expressive than I expected before. I am almost unable to describe here the complete evaluation process and its results. These comparisons brought me a complete new lesson about the role of impedances between tube stages and their effect to audible frequencies. Their physical hand over improves when low enough, comparable with a supported sort transport of natural energies and resolving finest textures of harmonics. Just pure ease.

The Ease of Listening

In general it can be said (again) that inductive loads bring a general refinement and linearity into each tubes performance, which is a tremendous advancement comparing it with classical rc-coupling designs. In 99% of commercially made tube preamplifier stages tubes are rc-coupled or show up with with SRPP designs, inductive coupling seems to be to expensive for profitable ventures. Almost 99% of all small signal tubes have a higher internal impedance than 4k, which means without transformer it is impossible to get it under the 1k output impedance line, this means all here described benefits will not be available within the most of all tube amplifiers. Tubes with high current heaters systems (RCA Reds pl: 600mA/20mA, 5687: 900mA/18mA) and relatively high internal current are better sounding than their lc counterparts.
The aimed low output impedance of less than 1 k acts as a perfect server for the dynamic and energetic attributes of the audio signal without destroying the tender micro informations and keep the harmonic structure in a natural balance. Both achievements reassemble a tonal and dynamic completeness of a audio performance as sort of ease, which hardly can be obtained with other design issues.

Any of the named tubes matches more or less in a almost perfect way the preferences for such implementation with a Lundahl LL1660 output transformer. Alternatively all these tubes have been used with a plate load choke LL1667 coupled with a pio capacitor. Both choke and OPT have been used with different air gaps to provide optimal induction before saturation (I used them in variants between 5mA to 20mA).

My evaluation enclosure with adapter board for two octal tubes, here shown with two RCA 5692 in parallel mode and choke load.

The by far best combination till now (actually only indirectly heated small signal tubes have been compared) are the choke loaded paralleled 5692's in pure class a mode. It was a instructive lesson when I did parallel the internal systems, because I did use each side of the tubes for separate channels before with OPT. Originally each half of the tube will show up with 8 k Ri, a bit to high for transformer coupling. To get it made I did parallel the internal systems in order to half the resistance and to match the transformers preferences ideally. But again with LL1660/20mA I was not really impressed comparing the audible performance with the single half tube version in choke mode. In choke mode the tube seem to have a much better linear performance and improved coherent tonal harmony. Before I did use the 5687 with 4 k Ri at the OPT with a quite good results (as described in my last article), this gave me the push to try the 5692 in parallel in a almost identical set up as well. The 5692 were different, but still some sort of limited, a bit repressed, not the pure wide open natural performance I was looking for. So I did use this design with chokes. It took my breath away how much the soundstage improved. It did not even remind me a little to the OPT version and improved against the single half tube in a way I did not expect. Here now it was a perfect example to show how right low impedances are supporting audio frequencies and its physical character of delivery.

Everybody knows this effect from coupling speakers to a power amp. If the preferences of speakers are ideally matched by the driving ability of a power amp, the sound starts to shine with dynamic completeness and with liquid naturalness. This process is often compared with the physical parameters of a car, were the weight and its power are arguments, but can have different formations with two or eight cylinder engines, either with small or big cubic capacity. A perfect match of amp speaker/combination shows up with exceptional driveability, comparing it with the high torque of a big high power pump loaded diesel engine…

As well other tube stages will show the same importance of their deliver ability to prevent any losses of finest energy, liquidity and tonal structures to hand over from a source. In terms of a audio chain there are several transfer stations, were signals can loose a tremendous part of their completeness through wrong coupled impedances. It starts with the cartridge, as moving coil it might have to match the first stage, a step up transformer (a quite well known critical match were you can loose almost 70% of the cartridges signal), as next the step up transformer needs to match the grid of the voltage amplifier of the first stage of the RIAA-equalizer. If the the phono stage is a stand alone unit, its output stage will be the next critical point. Otherwise the commonly highly underrated line stage is the next critical step. For the most people the line stage is less important, because it does not make any high amplification, it's role is just to balance different levels of sources and to bring their output impedances to a lowest possible level, that the following amplifier can take the signal without any loss. (From my todays point of view with this new experiences this are nice little words for a exceptional important function).

My RIAA-equalizer with two 5691 in the voltage amplification stage and two 5692 choke loaded (Lundahl LL1667/20mA) under (stainless cover) for the output stage.

After the experience with the paralleled choke loaded 5692 and its superior drivability I did introduce this design into my RIAA-equalizer as output stage. As well here the coupling improved in a exceptional unforeseen way the audible informations. Together with my line stage it forms a train of musical informations realized never before. Both output stages are now high current low impedance mode in pure class a. Exceptional refinements without any hardening or compression effects, carried with a dynamic performance of pure liquidity and natural finesse. A completely new impression about ease of listenability. This system will be back upped for further evaluation.

As preview to one of the next articles about preamps and direct heated tubes I show here a rare delicacy, the Philips made TS20 eqv. of the STC4021A or the WE104D. A ideal low (1.8K) impedance triode from the 1930's from the telephone era shown with typical Johnson 210 bayonet sockets (like 300B).

In the next article I will try to find arguments for the use of the parafeed coupling. I am awaiting a well combination of benefits from choke loaded designs combined with even lower impedance figures, we will see.
Read on soon if interested, Volker