Revisiting my Favourite Sounds again

Hi everybody,

today I come back to an installation that I last discussed in 2017. Having described this chain as exemplary and outstanding several years earlier, it was at this time that its owner began attempting this set more linear qualities to educate. I would like to remind you once again that a classic analog tube amplified Shindo chain with a typical Monbrison tube preamp, a pair of the early legendary 300B single-ended power amps and analog three-way crossover with historical components such as oil-paper capacitors and auto transformer in combination with the LineMagnetic 22A/597A and WE7331A speakers. In these days changing from smaller dipole housings each equipped with Pushpull Klangfilm KL405 14'' basses had ensured outstanding results. I have described this chain in detail and also looked up for its variants in other places for comparison, everything is well documented in this blog within the past years.

In this last stage of expansion at that time, dipole bass enclosures got exchanged to larger and more solid made enclosures 100% comparable to the vintage originals from Western Electric in terms of material and design here manufactured and additionally fitted with LineMagnetic 14'' field coil drivers. In this last article, I did describe in 2017 that the original quality and restrained sound structure with the new, much more powerful and heavier paper cone bass speakers was no longer able to deliver the homogeneity and natural unobtrusiveness, that I value so much in favor of a more typical PA tuning.

New Location and first step towards a new set up, still LineMagnetic 22A, but equipped with ribbon tweeters.

A lot has happened in the meanwhile of five years, especially in all of our lives. We are now familiar with numerous corona virus variants as with their medically correct names, for a few months we have been able to correctly decline all weapon systems of the German military and their NATO partners and we are happy that as a result of all this the inflation values ​​​​in our country measure our quality of life in the low double-digit range. 

But also in this audio set up numerous stages of evolution were declined. First, the entire tube electronics were replaced in favor of a fully active DSP-supported digital amplification terminal. So it brought the possibility to switch from three to four and five-way systems. The LineMagnic midrange and tweeter horn systems were also exchanged for larger, similar horn system. Instead of the 22A snail horn, a Susuma Sato interpretation by a friend, LignoLab owner Norbert Gütte, was used. This means a completely double-walled construction with a resonance-reducing quartz sand filling. 

Norbert Gütte offers both curled necks and straight necks of different lengths for the sato-typical square meter opening. So it makes sense to evaluate different sized and different driver systems. From the classic 3/4'' pressure chamber driver to the 6.5'' paper cone driver, everything can be adapted to a dedicated straight horn throat in a mechanically optimized length. One after the other, modified Atlas/Klipsch drivers from Dietmar Hampel, JBL / Selenium 405, Celestion AXI 2050 were used. Modern PA drivers like the latter are of course no longer made with Alnico magnetic materials, but ceramic materials are used to achieve optimum efficiency in the PA dedication. With the 3/4'' version, the straight horn neck extends backwards over a distance of 2.40m and has to carry a solid weight. This requires a support system made from 12 meters for each side from typical Bosch/Rexroth structural aluminum profiles 40x40mm. The entire unit, consisting of the 7331 dipole bass enclosure, Satohorn and Mundorf AMT 197PP27R-740-452-CDH tweeter horn built into it from the Pro Series, is reinforced with these profiles and movably mounted on castors. One unit therefore easily reaches 1.00x1.72x1.80-2.40m (WxHxD) variable in depths by the preference of the middle tone driver size and a weight of 150 kg.

Sato with long straight neck, adapted with extension neck to match D. Hampels modified 3/4'' Atlas Sound driver

Sato with 6'' driver and recessed neck

After many attempts with different bass drivers, such as the Altec 416B/A, the Sonido 12'' driver is now being used in the dipole bass enclosure as final solution. The comparatively small 12" cone only works satisfactorily in combination with a SW Becker B1000 subwoofer with 18" bass drivers per channel, which are actively used below 80 Hz.

In this chain, the loudspeakers described with active crossover (Xilica XP4080) are used with DSP support. The crossover frequencies are therefore:

Subwoofer 28 < 80Hz; Bass / Sato > 180, or 200; Sato / AMT < 900 to 1000 Hz

Actual set up, three ways plus stereo subwoofers

Initially, a Butterworth filter characteristic was used, but in the meantime it has been switched almost exclusively to a Linkwitz Riley characteristic with 48dB/octave. This not insignificantly complex structure is controlled by the STA-800D or STA-400D power amps, depending on the power consumption required. The settings of the DSP have been subtly integrated to counteract the typical room modes. In this way, undistorted levels of at least 110 dB can be reproduced. At medium levels, the distortion factors are around 0.1 percent, and at high levels it is still below 1%.

Amplifier and crossover/DSP rack

It's all hard core technical and well complicated. Such complex and expansive installations in the past have repeatedly shown very similar soundstages, very dynamic, tonally very complex with clearly noticeable properties. In the past few years I have often had the opportunity to listen to such large horn installations. The tonal properties were usually extremely different. They mostly impressed with an extremely present and fanned-out midrange reproduction, so one believed to hear details that other sound transducer principles are not able to reproduce, including electrostatic transducers.

In addition, the space-consuming structure with its physically extremely large distances between the individual sound transducers and the clear expansion length of the respective sound generation is hardly manageable in the sense of a point source. This effect additionally supports the interpretation of a tremendously extended reproduction of the stage space. It is not uncommon for this sensation to become the originated problem after a short time of listening. The first thing that strikes you is the typical fatigue of our sensory perception. Later, one also notices that the supposed sensation is a result of typical inhomogeneities of such large three-, four- and five-way systems and turns the underlying sensation into its exact opposite, namely making listening increasingly an emotional stress.

It was exactly the same in 2017 in my report, when in the more solid and larger WE7331A replicas, 14'' field coil-driven LineMagnetic woofers supplemented the setup at that time. The originally extremely refined homogeneity, which was achieved in the bass section with two 14'' Klangfilm KL405 in push-pull operation, became so noticeable due to the significantly stronger cone structure that it suddenly got in the way of effortless, natural listening.

Intermediate installation with mixed amplifying devices, here still rolling tubes

Other Sato horn installations or similarly large horn systems that also work four-way with large passive or partially active bass systems sometimes also involve four-segment midrange horns, like the original installations in the 1970ties by Susuma Sato. In these days it was supposed to improve the linearity of the overall frequency response in the upper mids, but examples I did listen to, do play so little homogeneous that it seems possible for the experienced ear to identify all drivers as single sources at the same time, like a large orchestra to be heard separately with insane runtime differences. 

The experience trail shown here is also about tracing the complex path of the various ways that such a structure enables. Here the effort was increased to the extreme that is feasible, as many variants in the pictures impressively are shown. And this complex path of various tests has really paid off for an exclusive refinement at all.

With the usual scepticism about such overexpenditure and also about the technology used here, I did listen to this installation calmly and impartially. Despite a four-way structure (HT-MT-TT-SW), it has been possible to achieve a completely seamless and extremely homogeneous sound pattern with the finest tonal reproduction quality. Over the entire tonal spectrum, i.e. between about 40 Hz up to the limit of my hearing ability in the high-frequency range, an extremely dynamic but never conspicuous sound spectrum is projected into the room with unbelievable ease, which with such cogency I have never heard of such a large-scale installation. One is able to recall approximately a live performance, or to put it another way, the playback is incredibly close to the characteristics of a very good pair of open space headphones, such as the AKG K1000 with near field equalization. Especially with extremely difficult tutti passages of large orchestra recordings, i.e. music that can hardly be reproduced realistically via normal loudspeakers, the set impresses with a huge stage that makes an exact spatial staggering comprehensible, but above all the most important thing of such a reproduction, the unbelievable amount of moving air makes playfully realistically tangible. Other challenges such as smaller jazz ensembles, chamber music or voices, on the other hand, are almost a side exercise. One can enjoy listening to music for long passages without any signs of fatigue, and after all, that's exactly what we should all be aiming for. Even if this is often lost in pointless technical debates, here it shows that it will be possible with almost contradictive conceptions of audio response.

Half of the actual set up, 2022

This chain consciously relies on currently produced technology for the large-scale public address use, so it is completely free from the usual hifi terminations of a "beautiful sound", like exalted tube technology, "certain rare old components without which the earth would not continue to turn". Go then...

So if you are striving for something similar, in words a "walkable headphone", you might want to take advantage of the moment. The actual savings discussions might set your mind to convert existing inhouse swimming pools, indoor squash courts or the like in the generally sense. With a room area of less than 50 square meters it becomes difficult, the integration of such an installation into normal family life will probably inevitably lead to opulent maintenance payments. And if you were equipped in younger age with a pronounced play instinct addiction, which might have in your earlier life led to basement-sized H0 model railway installations, you can certainly think about a similar way of presenting such amounts of fun with music reproduction into your life.

Read on soon, Volker

Back to stage – a PSU for a known singing bird

Hello everybody,

in loose sequence I am posting articles about vintage audio equipment. In the last couple of month I have spend my time more with listening to music and with the support rearing of songbirds, in particular of black birds,  than with building audio equipment. To listen to the very different sound of birds is as well a exceptional training for the educated ear...

Today I am talking again about building a power supply for a British tube preamplifier with RIAA-equalizer stage. A familiar customer asked me a while ago if I will be able to make him a power supply for his Concordant Exelsior preamplifier. He pretended to have a schematic for it and as well the schematic of the amplifier itself. I said that it would not be to difficult to make one. Next he asked me if I will be able to make one with tube rectification and better components. I said I need to check, because some components are hard to find in the meanwhile and that I would need to check my stock of parts. The schematics turned out to belong to a completely different version of this preamp. As the most people might know mains transformers with split balanced HT-output and two different filament windings "don't grow anymore on trees" as it would be needed for this! A quick look in my storage gave me some overview to pulled transformers from old equipment, foremost from old radios, some were missing parts, others where winded for 4 volts filament, etc. I didn't find the right part to do it well. Next question is to find new parts, Lundahl might here the right solution, but nothing under 200 €, which was expected a lot to expensive. Next problem would be to find a matching case for all, matching in visual terms, but as well big enough to harbor all components. Not easy, but I decided to get forward with a black painted Hammond casted aluminum case of the same height and depths of the Concordant. My customer limited the cost range for all to 250 €, which is an almost impossible sporting competition to stay beyond. A rough calculation showed immediately that such amount will pay the needed parts but not the work making it. On the other hand this guy never had a chance to listen to this preamp before, since he bought it without power supply. This person normally listens to a Shindo Monbrison and other well priced and established products, so he does not know what he will become at the end, just to explain his tight money framing. To be honest with this limit a simple PSU with silicon rectification and simple filter stage for the anode rail and silicon 12 volt IC regulation will be the solution to bring the package back to life within such financial limitations. I told him about and he pleaded to get something better, smoother sounding. I told him, that there will be no guaranty that even a perfect made PSU will bring this preamp to the level he ideally might expect.

Ok, I started some research at the internet and opened the Concordant case with the result that I realized that this version is equipped with ECC82 in the output stage and ECC88 in the RIAA-filter stage. This means with ECC88 it needs a 6.3 volts filament supply – no way make a cheap silicon based regulation with penny parts only ugly rails of hated caps and resistors to drop the voltages. 

So it gets back to the start with tube rectification with EZ81, choke regulated loading and filter stage for the anode supply. I looked again into my storage list for mains transformers, where all transformers are listed, which are useful for power amplifiers with their exact output data. The most of the transformers are collected as pairs, I am always afraid to use one of them for a single project, so still a lot of them is untouched since years. So I found the right type with the right taps, just a little bit oversized for such a project, but otherwise perfect. I decided to use it because I am not getting younger and the future projects might get countable. Now I needed to order a Hammond 157G 30H/40mA smoothing choke and I found a supplier who offered a bunch of NOS double capacitors 2x100uF/400V of ideal physical size to match my selected case. The Concordant sports a luxury, a mirrored double filament support for each channel, so it says at the front plate double mono preamplifier. At the back it has two identical unusual German DIN three pole jacks for this reason. I found in my storage the matching plugs, otherwise nowdays hard to find. So I collected all necessary parts from my storage together, – switch, fuse holder, cables and wires, resistors, tubes, silicon rectifiers, oil caps, supports, screws, nuts, bolts and more. When I first time tested the size of the case with the real components, I realized that it will get tight, – exceptional tight. At the end there was not the space for one more resistor inside. I needed several times to regroup the components inside to make it work!

At the end of the day all parts were in place and the case could be closed without pressure. Before I needed to isolate delicate exposed contacts. For example the tip of the EZ81 just matched the close case because I drilled ventilation wholes into the cover, the middle whole takes the tip, underneath the octal socket I needed isolation, because there was only 1mm air left between HT contacts and the base plate!

When I connected the new preamp with PSU to my setup, I was really astonished. The sound was exceptional refined, with wide open smooth and liquid soundstage, exactly so I do like it a lot. Of course I don't have any comparison to the original version, but I must say this combination is very very good. Yes the PSU uses some basic ideas which have been established in my equipment for years. For example the push-pull choke for the filament, the low oil capacitance in the loading stage for the rectifier tube to make it fast and smooth. 

I am looking forward about the ruling of the owner when he does the compare it with his Shindo Monbrison. It might get difficult... This is definetly under all tube preamps which had a chance to listen to one of the rare singing birds.

And who is now going to pay my work? 

Revisiting own History – The classic Leak TL12+ amplifiers

As already widely shown in my earlier articles I collected in the early 1990ties during my London time a whole lot of classic Leak tube amplifiers. Foremostly I remember one visit in London in 1992 when I did buy an exceptional lot of amplifiers from London dealers. On the way back to Germany my car got stopped from French custom officers because of its obvious visible overweight in its trunk, the rear wheels already were deep hidden in the chassis with an extra 15º camber. I will never forget the officers face when I did show him the tight stacked amplifiers, he had no idea what he was looking at. I don't exactly remember, but it must have been around 6 to 8 pairs of this model TL12+ and several Stereo 20 and as well some pairs TL10.1  and TL12 point one's. I tried to explain that these are historic audio amplifiers, but he hardly could believe my words looking at a wall of golden chassis.

The classic late 1959 Leak TL12+, here already with RCA-socket and input pot.

The shown pair is one set of this batch. I did restore all of them to my highest possible standard these days. In particular this pair got the best care because of the rather rare color "champaign" and with the aim to keep them for my own collection. As regular treatment I replaced the electrolytic filter caps to oil caps. Here the old electrolytic content needed to get emptied in order to reuse their cans for originality and color with new caps glued in. Generally all coupling caps where replaced to oil caps, a expensive step these days because the only modern source for such was Audio Note, who cared about the distribution of Jensens Audio Caps, a good 20£ investment for each value which added alone to 200£ for a set. All carbon composition resistors got exchanged to new German Beyschlag 2 watts carbon composition types, each around 2 € only available in 10er belts these days. The cathode bypass capacitors generally got changed to bipolar tone frequency caps, which mainly where used as crossover parts in speakers. The religion in these days was the use of triodes in all stages, so I always changed the input stage from EF86 pentodes to ECC83 triodes in order to refine the soundstage and to reduce the input amplification factor, which is with all Leaks extremely sensitive. I brought generally the power stages of these push-pull designs to semi triode operation of the EL84 tubes. All these steps were introduced in order to achieve with this little amps a much more sophisticated and smoother operation, in contrast to the impressive, but a bit too cheaky performance of the original version. The reduction of output power from 12 watts to hardly 4 watts in pseudo triode operation emotionally perceived with efficient speakers (better than 96db) as to be a even better drivability. 

Close up of input stage in foreground, in background whole lot of modifications at the filter stage with smoothing choke (at left) and fuse holder, switch (at right) and power cord.

As some might expect the days weren't far that I decided, with almost every Leak model in daily use, the most of them in several versions, to get rid of some doublets to save space and money. Some friends of mine got within this years involved into my passion and became interested as well to use tube amplification in combination with Tannoy speakers. So I sold some amps from my collection to them. As reported in my last entry a Leak Stereo 60 of my early collection revisited me unexpected end of last year. This example found a caring new home in the meanwhile. Shortly before New Years Eve another friend visited me and brought another former pair into service, which acted for 30 years a long term companion to his Tannoy Lancasters with 15'' Monitor Golds for him. When I started to inspect this pair, I realized what 30 years of rough use with several house moves and more or less permanent plugging and unplugging can do. They were completely rocked down. Loose contacts, open wires, leaking capacitors, wax dripping from transformers, tubes run down to 20%, in one an almost black ashed rectifier tube showed the remnants of an unexpected firework, – he had treated them almost to unusable wracks. My friend decided to spend good money for another life and a total revision. At my first restoration in 1992 these amps were already 35 years old, now added on to another 30 years. I will try my best to give them another third life for the next 30 years. Maybe these little wonders will find one day when I already will be passed away the next owner who might bring them into a fourth period of living  –  this is what I will call sustainability – not the highly acclaimed class G digital amps to be so.

View of the complete mainboard, just at top edge underside of pot and the filament symmetry element

For this reason to open up for a new future I decided to change some principles I had 30 years ago. I always took extremely care to keep mechanical originality of the amplifiers, which was meant not to drill wholes or remove unused components, like the octal sockets for chaining further Leak- or other components. Today or even better tomorrow nobody really will use a Troughline tuner or a Varislope preamp, so contemporary preferences for practical use are getting more important instead of originality. A better control of the input signal, in particular with modern high output components (min. 2V or more) like preamplifiers, computers or digital streaming clients, – more or less hum- and hiss free operation and of course still the smooth and dynamic soundstage are relevant for the aficionado.

So I needed to find mechanically and electrically matching filter capacitors as paper-in oil types, not an easy job even with eBay within such sizes. Pots, switches and simple things like fuse holders are more and more difficult to be found in well known high quality, foremost made for military use in the 1970ties.

Knob inlay made from real embossed calf leather matching luxury expectations...

The Leaks got now smoothing chokes (8H/100mA) in the filter stage, NOS mil spec input potentiometers, perfect RCA-sockets, switches, optimized AC-cords and of course a set of best possible NOS tubes in every stage. So equipped this little pair will do a perfect job in the coming years and play now in the same league where best handmade tube amplifiers like Shindo, Thomas Mayer or others are bought for in difference to modern chrome monsters made to match Asian expectations. 

60 years of technological time shift to play music

Now this little amps are ready for the time which is already there, a time were music streaming has overtaken the music market and digital components are feeding their playlists into such ultra analog audio chains. After 10 years of wireless music stream into my own chain from my notebook as to be the 'jack of alle trades'. I did spend at the start of 2022 myself an actual iPad with 1Tb storage to be solely my comfortable music juke box to play from cloud services as well from my own digital collection at a finger touch. 

Stay healthy, it might find an end sooner or later, Volker