Uwe Kirbach

Image HiFi

“With his OTL/OCL-Line preamp Allnic L-10000, Kang Su Park has raised the bar for preamps a little bit further. For me, he has become one of the great developers of hi-fi history.”

“Then came the deep piano sounds: voluminous, contoured and powerful. The difference is so huge that any comparison is superfluous. The sound of the drums, too – I’ve certainly never heard a drum set even come close.”

The Breakthrough

I usually burn in new equipment in my second listening room. Since Thomas Kuehn’s version of the Jadis JA 80 is often running there with the OBX-RW3 from Living Voice (i.e. whenever other loudspeakers are in the large listening room for testing), it’s really good fun. Kevin Scott’s creations are tolerant of almost any- thing: virgin components so new that they still sound a bit dull or even aggressive; being placed somewhat too close to the wall; even the sound spat out by the Panasonic DMR BCT940 Blu-ray recorder. But the Living Voices reward you immediately and reliably as the burning-in process progresses and when really good components are introduced to the system. The exception being the Panasonic – its output never sounded any better than ‘de- cent’. In any case – it was certainly never built for audiophiles. And now I’ve a new preamplifier to try out: the Allnic L-10000 from Kang Su Park. A man who recently made a huge splash at image hifi with our Amré Ibrahim with the H-7000 phono stage. And a man for whom I’ve always had a soft spot, at least since the ’nineties, when I heard the big Silvaweld preamp he designed, which was for me one of the first really musical preamps.

But nothing could have prepared me for what happened after connecting up the L-10000. A recording of the 9th Birdland Radio Jazz Festival is announced on the radio. Before we get to Enrico Rava, there are some introductory words from the presenter. How full and direct his voice sounds, surrounded by the typical studio atmosphere, giving an unusually strong impression of being able to ‘see’ right into the speaker’s booth. The Panasonic has never been able to do this with digital cable programmes before, yet now it sounds more like the golden age, when live analogue radio signals fed a top-quality tuner. Then came the deep piano sounds: voluminous, contoured and powerful. Then, Ra- va’s flugelhorn, with its cornucopia of sound, and all the corresponding air noises, all of which appear much better presented in the listening room – completely free of the speakers – than ever before with the Blu-ray recorder. The difference is so huge that any comparison is superfluous. The sound of the drums, too – I’ve certainly never heard a drum set even come close via the Panasonic. With skins that vibrate and clearly move volumes of air.

And now again overtones from the piano, causing their typical ‘sizzling’ in the ears. And all this from this previously unremarkable source, to which I have listened in the past five years through so many pre-amps and with live jazz or classical music from the digital cable channels, only several levels worse? How can that be? It is certainly not down to a particularly outstanding recording, be- cause what I am hearing has never been remotely within the capabilities of the Blu-ray recorder. In fact, it is hard to believe how – a leap back in time – the orchestra plays Nino Rota in the live broadcast of the New Year’s Concert from Venice, how much finer the cymbals sound, yet at the same time more powerful and accentuated than ever before, the harp strews its warm garlands of sound and the strings extend into the room just as warmly and physically as the plucked bass. That the dynamic spectrum has suddenly increased, compared to all the previous preamps over the years, as if changing from a small MM pickup to a racy MC, is also con- firmed by the aria of rage from an outcast from Rigoletto – the baritone of Luca Salsi is not only full of expression, he’s also tangibly standing there in the stage panorama, giving an outstanding acoustic impression of the famous Teatro La Fenice overall. All in all, you feel much more present than usual. This way it just sounds so much more interesting, appealing and moreover: right!

What am I doing connecting my stupid Blu-ray recorder to the big Allnic preamp, you may ask – and will I please connect a real high-end source again? Of course I will, but, apart from the pure sonic pleasure I’m suddenly having with the Panasonic for the first time in five years of operation with many different preamplifiers, not only with music but also with films – something quite amazing can be understood and proven here that is also relevant to high-end components: it is obvious that the Japanese multi-function device has a high degree of contamination or distortion in the signal path. But the Allnic L-10000 is unfazed by this. Why? Obviously its incomparably purist signal path, with no capacitors or transformers in the output, combined with its ability to deliver immense power reserves from its four 300B valves, and finally the unique volume pot, provides a far better signal than any other preamp I’ve tried. And there is one thing you should not be fooled by: the Blu-ray recorder may clearly accentuate this, but moderate-sounding CDs, records, downloads and streams are unavoidable unless you only ever want to listen to “audiophile” recordings (and even those, in fact, especially those can be quite insipid).

Finely balanced and highly complex: Firstly, Kang Su Park’s newly developed cancelling circuit which eliminates any interference, plus an electrical process carefully balanced and controlled on every level allows operation without out- put capacitors or output transformers

Over the years, I have always stressed that the class of a device is not how it plays so-called reference recordings, but how it handles “dirty” content. To shine with demonstration records is not an art; but to get the most out of challenging recordings certainly is. There are two things at stake: On the one hand, a component should not be affected by any kind of technical inadequacy of the medium with which it is fed. In other words, it should not amplify the errors of a signal, but rather process them with a kind of equanimity. And on the other hand, it should also fish out every detail from every signal. If one component combines both these abilities, it is capable of great performance. This is the only way it will bring joy day after day, because it will al- low the listener to hear back to the original source of the recordings.

Until now, Kang Su Park was considered a great advocate of transformer technology. It is no coincidence that he named his company Allnic, derived from the English “all nickel” – in his opinion the best (albeit expensive) material for transformers. In fact, in conversation he turns out to be a fan of Julius Futterman, the first designer to build an output stage without output transformers. And he says that transformers are basically obstacles to good sound, but capacitors are even worse, especially in

the output stage of a preamplifier. They are sup- posed to prevent destructive direct current, but ac- cording to Park they cause coloration and only let voltage through. For a powerful sound, however, power amplifiers need a signal with decent current. So for years he has been developing an OTL/OCL preamplifier (output transformerless and output capacitorless) with output valves that can deliver powerful current. In the L-10000 there are four 300Bs, probably the most famous power amplifier triodes. These feed the connected power amplifiers directly, and thanks to their low output impedance of 200 Ω, it will work with virtually any power amplifier and even long cable lengths, taking full ad- vantage of the dynamics and attention to detail that the 300B is capable of.

Now Park is not the first to come up with the obvious idea of simply omitting sound-impairing components. Yet it is anything but easy when it comes to output stages. Direct current is potentially destructive. And just as transformer technology and coupling capacitors are long-established techniques to keep noise in the case down, an OTL/OCL circuit is sensitive to interference which must be eliminated at all costs, especially in a preamplifier. While the Korean is usually the type of hands-on engineer who has a solution for everything off pat, in the interview on the circuit topology of the L-10000, every few sentences I hear “it’s complicated”, “not easy”, “very difficult to achieve” and you can hear the years of development effort in his voice. In the end, however, in practice his new pre- amplifier works in a completely uncomplicated way and completely problem-free during all the months of testing. Kang Su Park is probably the first to bring this high-flying idea to a completely production-ready device in the really high-end. And with the technology that he has completely mastered, three further, more affordable OTL/OCL preamps are to follow, which should essentially only differ in output valves and a slightly reduced dynamic range. One thing, however, should be kept in mind: in Park’s technological breakthrough, the output stage is directly connected to the output valves, so it is directly dependent on their quality and noise-free operation and of the valves upstream. In order to avoid possible waiting times, it makes sense to have a spare pair for each position.

The input valve in Park’s highly sophisticated circuitry is very rarely seen: the 6AN8 double valve. Its pentode section has control over the feed- back design, is thus responsible for its new “cancellation circuit” and is not in the signal path. It ensures that the split upper and lower phase of the signal remain exactly the same, thus providing a basis for a completely balanced signal path. The other part of the 6AN8 is a triode and represents the first amplification stage. This is followed by the well-known 12AU7 (ECC82) and finally a total of four 300Bs form the output stage in single- ended push-pull configuration. In- stead of the usual phosphor copper sockets, they are plugged into beryllium copper valve bases that Park manufactures in-house because he is not satisfied with what’s available on the market. As he says, there will never be any contact problems with them, as he always emphasizes the necessity of maximum long-term stability in his devices.

The left transformer is responsible for the separate management of the main voltages, the right one provides the heater voltage for the valve filament power supply
The circuit board for the excellent remote control and the push buttons on the front of the L-10000, with their equally impressive haptic feedback
The result of 20 years of development: Kang Su Park’s constant- impedance volume potentiometer has 61 steps and provides the circuit with the ideal state of maintaining the same output impedance regardless of level
On the right side of the picture you can see the beryllium copper valve bases custom built by Allnic for maintaining long-term perfect contact with the 300B valves. On the left, a heatsink with the IC that provides perfect power supply for the valves
An inconspicuous detail: The mu-metal shielding for the capacitor is a small component on the way to a high signal-to-noise ratio, despite the OTL/OCL design

Allnic’s home-grown valve bases are soldered directly to the circuit board, which the Korean developer again emphasizes how difficult it was to get completely balanced and under control as OTL/OCL, for sound quality reasons, but also for safety reasons. He himself designed the board lay- out, with extra thick tracks, which should be safer and sound as good as point-to-point wiring. The complex circuitry would have made point-to-point wiring impossible anyway. To control the uniform operation of the output valves, there are large dis- play instruments on the front panel. If the valves “run away”, the quiescent current can be adjusted with small bias potentiometers above the meters. In order to ensure long-term operation of the 300Bs, their permanently-accurate 5 V filament power supply is ensured by heatsink-mounted ICs.