Monday, 28 July 2014

Incredible close to music VI – A Evaluation of Foreign References


to all interested reading on about further experiences with Line Magnetic and Shindo amplified set ups. Today I want to make a short report about a visit in Frankfurt some days ago, where a very advanced and experienced audio chain with Shindo amplifying devices and Line Magnetic components is in use. The owner Claus is a long term follower of advanced audio concepts with triode and horn amplification. He started his interest into audio during the early beginning of the european triode movement in France with Jean Hiraga at Maison L'Audiophile as initial. It is obsolete to mention that Claus has owned already a tremendous amount of equipment during that time of 30 years. He always stayed or sold back his components convicted to find paths behind the curtain of the typical superficial audio presentation into a more harmonic and natural representation of music. One example might show his behavior quite well, the shown Shindo 300B Mono amplifiers in my article: Incredible close to Music I – The System Matching.  Exactly this pair has been part of Claus installation til the early 1990ties, when he did sell them presumably with his typical words: "I don't need them anymore". This quote shows a rare attitude: the ability to concentrate to the essential qualities, where a lot of us others would stay with components as proud ownership in mind he gets rid of for him anymore useless components. After one more owner these amps harvested 15 years ago at Mikes set up, just to close the circle.

A listening room were walls are covered with shelves containing recordslots of records (may be 2000), books and CD's. The positive benefits of such surfaces and their physical masses for room acoustics are known and a lot of audio enthusiasts use their record collections for that sort of effect as well. But this time it was the first time, that there was not anymore a dedicated record player?! As I could hear he had a Platine Verdier player (what else?) and EMT turntables for years, now he uses streamed digital data, deliberated from a pure audio computer into a Line Magnetic dac. ("I don't need them anymore".)

Claus Line Magnetic horn set of LM22/597 is extended for low frequency support with dipole enclosures. Customized made from solid german oak, the enclosures are made similar in design to the "755" speaker from Auditorium 23. Inside he uses a fantastic delicacy, a pair of Microtecnica 15'' field coil speaker units. These are the most beautiful made low frequency drivers I have ever seen. They have been manufactured in Torino in the 1940ties by a company which concentrated to different precisely manufactured micro mechanic product lines, one line covered several products for the cinema industry like complete installations of projectors and sound equipment. Originally these wonderful speakers might have been used some time ago in a Italian cinema, presumably installed very similar to the well known Siemens Klangfilm Bionor sets, assembled with a front loaded integrated horn funnel in a huge wooden baffle board, together with high frequency multi cell horn dispersion on top.
Italian products of this particular time mostly show up with a typical exceptional attitude, where the finalized form follows highest ingenious standards in combination to a exceptional aesthetic expansion. This attitude has been rarely cultivated with mechanical produced components in other countries at this time. In the post Bauhaus era of the 1930ties other values did decide in wide parts of northern Europe about the form finding process in industrialized productions. "La bella macina", the underlying philosophical principle behind typical northern Italian (Piemont and Lombardy) industrial designs before war, was as well a cooperation between swiss immigrants of advanced technical expertise searching work in the most industrialized region of their culture. The term states the perfect combination of functionality, crafts and form. Exceptional motor designs, like made by Alfa Romeo or Gilera, with espresso machines by Faema, typewriters from Olivetti or bicycles made by Bianchi in these days, might remember of what I am talking about, even if a typical German arrogant purely ingenious based understanding of machines, neglects these facts persistently.

15'' Microtecnica Field Coil cinema loudspeaker in solid wood dipole enclosure

The Shindo 64B PP-Mono amps on top, left beneath the Mag-Amp beside at right the DBX active crossover. In Foreground the Shindo line preamp on top of the Line Magnetic DAC.

In difference to Mikes set, Claus positions his LM22 horns at the stereo base close to the center with the low frequency dipole enclosures mirrored to the outer sides. He uses a pair Shindo 64B push pull amplifiers in combination with a Mag-Amp by Lundahl for the active low frequency support. Each sides signal get devided by the use of a active Dbx 24dB filter unit, since the LM 22 and the LM 597 are cut off with a passive network. A rare and expensive paper capacitor from Western Electric supports the performance for the wide tone spectrum of the medium and high frequencies to a higher degree of refinement supplied to the field energy of both speakers.

Passive filter network for the medium and high frequencies, made up as flying installation with rare expensive paper capacitors from Western Electric (behind LM555W telephone).and some ordinary paper caps.

We did listen to a variety of Claus digitally stored music, with a concentration to contemporary jazz, but as well some large orchestral classical music. With good 30°C room temperature or more and high humidity it was not the perfect day to listen to tube amplified audio sets. Well, I didn't know at the beginning of the listening, – was it me, the climate or the set, I did hardly find into the music. For compensation I did drink a good liter of water during the first three tracks. The music did show all the signs, which are so typical for the projection of the wide frequency LM22 horn, but it was a good bit to dry for my taste and it was a bigger bit dryer than I do know the components already from Mikes or Hans sets. It was like with a exceptional wine, which was some years stored to long in the cellar. Like a Tignanello of 12 years age, of a well known year, it might take a good while to oxidate and open up, before its shows its exceptional complexity together with a refined harmony in the foreground. As well here, everything was there, it was just a bit to tight and dry… I do know these horns in the meanwhile very good and I know them better balanced. After a while Claus stopped the audition and asked: "Now I would like to change to a different power supply for the field coils of the Line Magnetic horns?"
It took a while to change all connections and we started to talk about several topics. I started as well to make some photographs of the set. A good hour later we came back again to listen to similar music and I thought: If I will be able in a foreign set up after a hour time to realize any difference of a power supply?
It did not take long, may be two minutes and I tried to evaluate, if we do listen with completely different settings, I had the feeling it was set with a lot higher volume level than before. But it was even more than volume settings, the whole soundstage had lost all the dryness and its shortness of breath. Instead the well known wide open dynamic soundstage performed with incredible detail, harmony and transparency. I did ask, is it true that there is only a different power supply for the field coils? And is it set to the same voltage? I could not believe the difference. I started to tweet my feet and started as well to like the music, which always points the major difference. Just a power supply, … for the field coils, unbelievable. There is not even some direct connection to the audio signal, it must be a foremost interaction between magnet and voice coil? Nobody can really explain this effect...

Now the chain had shown up with all the unique advantages the Line Magnetic horns are known for. For me it was really amazing to realize how small the differences of sets in the final performances are, even when whole parts of the chain can be different or the surrounding room is absolutely different, the general performance shows the absolute same advantages.
Here the only little difference in Claus set is the active 24db cut for the low frequency path. As a result the frequencies from 300 to 500 hz are less prominent, comparing it with Hans and Mikes set. Their 6 db passive filter brings a mild support in this particular frequency range. But these differences are far beyond qualities, they have to be seen with respect to different ideas and taste, performed harmonics and preferences of different owners.  As different power amps, like the Shindo 300b Mono blocks of Mikes set would have a influence to the presentation here, the Shindo 64b amps would do in reverse with Mikes set. At the end I could find completely back to what I already know about this speakers. As well here again the Line Magnetic set up confirmed my understanding to be one of the most transparent speakers for audio use. They are able to produce almost natural dynamics together with a refinement in harmonic detail, were other systems will be judged by. So they can offer the most advanced insight into well recorded music and can make the listener to forget about its origin. A pitty that the beloved Microtecnica speakers were on such a level of perfection, that I could not really hear them in the set, they just acted perfectly to be true invisible…

Later in the evening I had the chance to listen to the new A 23 loudspeaker "Hommage à Ken", made as a homage to the shortly faded away master Ken Shindo. Equipped with a totally new designed LM755 chassis, which in difference to the first LM version with field coil magnet, is exceptional close in all details to the rare an expensive WE755A. It incorporates as well a w-shaped alnico magnet like the original and a extremely similar made cone structure. Out there is a quite huge community relying to that first version to be the best full range speaker built ever. For me it was a first time to listen to such a alnico version, and it was the first time to evaluate such a speaker not to be operated in the classical baffle board.
Two things are remarkable from the first sight. This 8 inch cone can do real "full range" and it shows a exceptional refined resolution of musical harmonies together with all necessary dynamic abilities. Coming from Claus LM set, it was a very similar experience to find into its presentation. It is of course not a "full range horn", with all benefits of a little aluminum diaphragm, but it has a quite small cone and performs without any crossover on the other side. It brings out a similar tonality, so that the shallow listener would not see any argument to get such a complex system like the LM22/597 with LF-support, if a simple cone can do the same…?! Almost the same, to be honest….

Read on soon, Volker

Monday, 14 July 2014

The Aa Line Preamplifier I – The Mechanical Construction of the Enclosure

Hello to everybody reading my blog,

now after the end of the soccer world championship it might be time to start a new series of entries about the building of a DHT preamplifier as central component of a future orientated system. Several times I have quoted my extremely positive experience from my Aa Line preamplifier, which I do use since 2004. This was my first realized preamplifier incorporating directly heated triode tubes in the small signal section of my chain, namely the line stage of my set up. When I realized this concept almost ten years ago, I did not expect to be so much convinced one day that such a preamp will go to be my final word in the line amplification stage.
At the beginning it formed a extremely well sounding approach towards refinement, but in 2004 my chain was not in that developed stage, where it is today. The first remarkable side effect came when I started to rediscover my digital signal sources again. For more then a decade my Meridian CD player was into storage. With my Platine Verdier Record Player and my time living in the US, created a concentration into vintage vinyl as foremost signal source. But around 2005 the digital storage of music attracted my attention. I did start to record my vinyl for digital storage at harddisks. The combination of "lossless" storage and Apples hard- and software (Airport Express w. digital out, lossless format to be supported), formes a easy access to digital systems within my analogue tube amplified audio set up. Together with my new Aa-line amp it created a extremely refined sounding system, with lots of merits I didn't know from my analogue arm. In these days I did use my audio mainly to listen to my analogue jazz record collection, from time to time I made some recordings from vinyl just for storage issues. I didn't take the digital side to serious, I was a lot more shaped by my early experiences from the 1990ties, when early digital recordings and cheaply made transcriptions from vinyl to CD created my worse experience with digital and formed the decision to leave it for the "consumer".

When I had to move my studio in 2010 I had to adapt new listening conditions. At the beginning I did start just to set up a digital streaming chain as first set, in order to have some music by hand. It came as is always happens, new room acoustics did create new courtesies, I started to like the digital arm of my set up quite well. Together with a new interest into actual and therefore newer recorded music, I realized a unknown conservated audible quality. It was very obvious that in the recording part of audio in the last decade a huge quality step was realized. Completely digitally recorded, mixed and finalized takes showed up with a remarkable close and accurate preserved soundstage, in a way of perfection I rarely didn't know from vintage vinyl. All the typical aural fingerprints, made by every analogue component in the recording chain, the microphone, its input transformer, the preamp, the mixer, the tape recorder, the amplifier and serveral other chained components seem now not any longer exist in a conspicuous way. Instead a much more homogenous and digitally corrected sound image seem to be the new standard of actual audio preservation today. A better focused staging with unknown lots of captured air is the typical side effect of modern well made recordings. All the former unavoidable phase shift effects seem to be gone with digital shaping, instead a wide, dynamic and refined window to lively recordings seem to be now some sort of standard. With the exceptional resolution of my line preamplifier, these qualities were the foremost sensual facts to be experienced, which I rarely did only know from a handful of my best analogue recordings. The DHT tubes combine a extreme musical coherence with absolute linear resolution in a way, indirect heated tubes don't show. The Aa Weitverkehrsröhren are exceptional top performers within the common known DHT's for small signal amplification. I did try other tubes as well like the widely used 26 tube ore the TM2 with similar success, as well with transformer coupling, but I will stay with the German Post Tube, since I like its extremely open, transparent and dynamic sound better than any other. They are made once for 10000 hour service in professional installed telephone relay systems and have some other mechanical advantages the most other DHT's don't show up with, because these typical US-american tubes once were made as consumer products for radio receivers in the 1930ties. The availability of German Post tubes is far better in my culture than any US-DHT and there is the variety of three different brands with different properties to find. The rare and expensive original early (from 1927 on) tube from Siemens (with tip and glass tree inside), the common Valvo type (globe type with mica spacers) and the last version made in the former East Germany by Neuhaus Röhrenwerke (with brass socket and coke bottled glass shape and ceramic spacers).

So I started after almost 20 years to buy again some CD's, giving me a new unknown listening pleasure on the first hand, but as well as streamed data beam digital sets a comfort and usability I never could establish with vintage vinyl recordings. Vintage vinyl is still unique in different fields, it wonderful large size covers, the printed informations and a typical liquidity in the timing of their sound, digital formats do not cary. Today I use both systems side by side with mating success, but the operability of streamed data sets the pace for the years to come. So the quality of the line stage is the key for that kind of use and needs to be of exceptional ability.

First  evaluation stage of my Aa-Line preamp in 2004, equipped with battery clips for the heaters and here showed with rare Siemens Aa tubes, identified by the tip.

Solid mechanical construction with complete relying at oil caps and solid silver wire for the signal path. On the left: the variacs for the lead batteries and a stepped attenuator for volume control.

But I will not conceal that there are some problems with the use of thoriated tungsten filament direct heated triodes, other tubes don't show. With directly heated triodes the cathode acts as heating element for the tube, which means the heater is part of the signal path. The most people know this problem from power tubes, where it creates sometimes hum problems, which can be solved quite easily, because of the higher signal to ground ratio. But at a lower signal levels and following further amplification, any little hum sign will be amplified up to solid levels. Here the problems needs to be solved completely. To get it work, it needs advanced solutions for the heater supply. In the beginning I did start with classic regulators (LM317), these bring a lot of radiated heat to the amp and don't sound very good. After burning my fingers at the chassis of my preamp I did decide to look for other solutions and ended up with a very uncomfortable solution, I did use lead batteries first. Now I had to charge every day my batteries in order to have enough energy for some hours of listening pleasure. I did try several different battery types, since the cheap Chinese lead batteries didn't last very long, after 100 loading cycles they lost  energy to be stored. So I switched to nimh-batteries. I got a quite good sound but only for two hours time with one set of batteries. So I had to buy several sets, which needed to be exchanged after a good year of use by charging them every day. I liked the sound qualities a lot, but hated the charging practice and the all around contact problems in practice. Always some hiss or hum happened needed some helping hand to fix the contact problems for further listening. Not comfortable.

In 2010 I switched to Rod Colemans CCS boards, which make life a lot easier. These constant current supplies are sounding as good as battery power and do not burn tremendous amounts of heat like other regulators do, when well implanted. These can be used with almost any DHT triode, independent of current amount with good success. So they are as well a good solution to be used with power amps.
Now after almost 10 years of use with this preamplifier and after final evaluation comparing it to other options with my new speakers, but as well in other chains, I decided to bing this concept into the next level and final stage. This will be accompanied with several blog entries.

It needs a well made mechanical design to find the long term usability. 

Now, in the final stage the line amp is going to be the switching center for all types of sources and needs several in- and output options. Only the best components are prefered for the job to be a final preamplifier, here with Lundahl iron, NOS Daven stepped attenuators and a Elma switch. Classic WE components are a good guide how to make a well organized amplifier.

For my new approach the Line amp becomes a central position in my chain. Beside the analogue system arm with my vinyl record player, the dac will feed the line stage with digitally streamed music using the comfort offered by wlan and with the iPad as a remote system, since all data are stored at the hard disk of my computer. For the future this is a important and foremost feature to be extended as main source? As well a recording option has to be kept be in mind, which will create other problems to be solved with tube amps.
I did try to listen again to some conventional line amps in the last couple of month. After this exceptional evaluation with very different amplifier concepts of advanced stage I was restless convinced about this preamplifier and therefore I did decide to bring it into a final state. For absolute perfection it needs a much lower output impedance to work flawless universal with every tube amp. With the high impedance of the Aa (30 K) it is almost impossible to match this preference, so some tube amps are not happy with the high load and connecting cables are getting a difficult choice. So, staying with the Aa tube and relying to its extreme unique sound qualities make a fundamental change of the implementation necessary. Cutting the internal resistance into half as a result of the doubled tubes into parallel mode, might be the way to get half of the output impedance. It should sound as good as before with much improved load into the most input stages of tube amplifiers.

Read on soon about the next steps, Volker