Your system, your sound.
We’ve previously described the range of Allnic line-stage preamps, from the recently released L-6500 to the flagships, the L-10000 OTL/OCL and L-8000 DHT. Besides their award-winning sound, praised by owners and reviewers alike, and their exemplary quality/price ratio common across all models, the preamps offer a perhaps unique choice of technologies used to achieve their well-earned reputation for providing world-class sound quality.
Regardless of which of KS Park’s circuit designs is used, every Allnic line-stage will drive virtually any power amp and likely prove to be, in the view of many around the world, an essential component of one’s system. Of course, the ultimate goal is for a preamp not to have a “sound” of its own... However, given that we live “in a material world”, which preamp you prefer will ultimately depend on your preferences for the presentation of recorded music in your home. That presentation will always be the sum of the influences of all elements of your entire stereo system, not only the preamp but also power amp, speakers, your room, cables and, of course, that most incredible system of all, you. Change one thing and rediscover the joys, or frustrations, of this hobby of ours as you seek the balance of all these elements that is “perfect” for you.
As a result of all these variables, we’re not really able to speak in absolute terms about the way that any of the Allnic preamps will affect the sound of any given system. However, besides the points made just above, based in part on the devices’ electrical characteristics and in part on user-based consensus we can say three things with confidence about them: first, that they will measure extremely well, not only according to generally accepted standards for vacuum tube-based equipment but in comparison to benchmarks for all such devices; second, that they will be examples of solid industrial design and build quality; and third, that they are each highly likely to contribute greatly to your satisfaction with the sound of your system.
Consequently, our focuses here are on the technical distinctions between the two output technologies Allnic applies to its line-stages and to make some qualified generalizations about what a person might prefer based on all those factors listed above.
& OTL/OCL Circuits
Transformer and capacitor output coupling:
There are two common coupling methods in tube amp circuitry; one is capacitor coupling and the other is transformer coupling. Both methods are used to separate the AC music signal from a circuit’s DC operating potential. Capacitor coupling is the traditional, low-cost method. It is somewhat stable but transfers only voltage, not wattage (i.e., not real energy). With transformer coupling, about 90% of real wattage is transferred (there is still a transformer loss of about 10% of wattage, while voltage is not affected). Several models of Allnic preamp use transformer coupling.
While transformer coupling is superior to capacitor coupling, all the advantages of transformer coupling depend on the quality of the transformer and on the choice of tubes. Allnic Audio manufactures its own transformers and uses what it views to be the best core material, permalloy. Allnic Audio’s unprecedented, wide (16 Hz ~ 50 kHz, -3db), low distortion, and ultra-flexible (up to 20 kHz square wave response) output transformer helps Allnic Audio realize the ideal transformer coupled pre-amplifier. Gain tubes are also carefully selected for three critical factors for function with the permalloy output transformers: high gm, low internal resistance, and high mu. This is one reason why Allnic preamps often use tubes that are not commonly found in line-stages produced by other manufacturers.
In addition, Allnic’s power supply circuit has “under 1% voltage regulation”. The voltage regulation of the transformer is the percentage change in the output voltage from no-load to full load. To get the best performance out of your transformer, you need the lowest possible voltage regulation. The voltage regulation of Allnic’s power supply circuit is under 1%. It yields an improved power transfer and lower regulation factor, resulting in increased current speed and better dynamics.
Finally, one of the other benefits of transformer coupling is that it can facilitate low output impedance. Low output impedance is critical to the design of a good pre-amplifier, and Allnic’s circuitry achieves constant low output impedance across all frequencies.
Output transformer-less and output capacitor-less (OTL/OCL) coupling:
As noted above, output capacitors and output transformers are used to separate the AC music signal from the DC operating potential. If this is not done, the latter will destroy the power amplifier, the loudspeakers, or both. However, these two coupling devices also introduce their own influences on the transmission of the musical signal, adding their own character (colouration), increasing distortion, and consuming small signals, all as predicted by physical efficiency theory. In addition, they also limit signal dynamics. With superior transformer coupling combined with other carefully designed circuitry, these issues can be mitigated but not entirely eliminated yet, nevertheless, still yield absolutely outstanding sound quality.
For these reasons, the elimination of output transformers and capacitors has been considered the best solution for the design of the most accurate amplifiers. Removal of these two coupling devices from the signal path theoretically achieves the best results possible:
⦁ No colouration of the musical signal
⦁ The lowest possible distortion
⦁ Extremely detailed expression, natural harmonics and subtle musical decay
⦁ The widest musical dynamics
Of course, the success of the OTL/OCL circuit will also depend on the quality of the design of other circuit elements, not to mention the tubes employed in the different gain stages. For example, some circuit experts might be concerned about DC potential in the music signal in an OTL/OCL design. However, the chance of this problem occurring can be 100% reliably eliminated by doing away with the potential for DC in the signal path. To do this, Allnic uses a “floating power supply circuit”, a design which deals with the theoretical issue by simply not creating any significant DC potential in the first place.
Other elements of the power supply, its means of rectification and voltage regulation and the method and materials used for output attenuation, for example, are critical to maximizing the potential of the OTL/OCL output circuit. The Allnic OTL/OCL circuit is basically SEPP, “Single-Ended, Push-Pull”, so a “cancellation circuit” is required to adjust the balance of signal between the upper and lower power output tubes’ input grids. Allnic uses an extremely sophisticated “Active Balanced Positive and Negative Feedback Circuit”, in which the 6AN8 pentode, for example, perfectly controls the circuit’s operation with extremely low distortion and incredible speed.
In Allnic’s OTL/OCL preamp output circuits there is no coupling device between the preamplifier and the power amplifier; that is, the final gain/output tubes are directly connected to the power amplifier. Combined with optimization of other elements of the devices’ complete circuit design, the benefits of the OTL/OCL circuit listed above become a reality with the Allnic OTL/OCL circuits.
Two examples of Allnic transformer coupled and OTL/OCL line-stage preamps
Let’s focus on two preamps using the two design approaches and relatively close in price, the transformer coupled L-7000 and the OTL/OCL L-8500, priced at $16,500.00 and $13,500.00 respectively.
Allnic’s unique 61 step constant impedance bridged type attenuator
The L -7000 and L-8500 are both remote-controlled, class A designs using no or minimal negative feedback and Allnic’s exclusive in-house designed and built 61 step constant impedance bridged-type attenuator. This world’s “first of its kind” attenuator maintains a constant impedance at all volumes facilitating a constantly linear output across the frequency spectrum.
They are also true dual-mono designs. Each of the two channels operates completely independent of the other. The chassis, attenuator control and the AC power connection are the only parts of theses pre-amplifier that both channels share.
Allnic L-7000 - Permalloy Output Transformers and 300B Tube Voltage Regulation
The L-7000 is a transformer coupled, remote controlled line stage pre-amplifier. It uses the direct-heated triode 300B tube as a voltage regulator. The 300B has justly won the reputation for being a superb output tube in single-ended amplifiers. The benefit the 300B brings as a series voltage regulator is its ability to pass a fair amount of current at low cathode-to-plate voltages, the result of having a low voltage drop. And, yes, rolling 300B tubes can alter the sound character of the L-7000.
With a single gain stage, the L-7000’s circuit uses only one tube for amplification (“gain”). This reproduces a purer, more detailed, more spacious, and more dynamic sound than multiple gain stages. The L-7000 offers world class, holographic sound-staging with placement of instruments and bodies in three dimensions startling and life-sized (assuming appropriate room and speaker configuration). It combines this capability with incredible resolution, clarity, micro-dynamics, and drive. Instrument and vocal tone and timbre are lifelike. The L-7000 is silent, except for the music emanating from the blackest of backgrounds.
The outstanding sonic quality is matched by the simple elegance, flexibility and ergonomic functionality of the casework and connection options. Few pre-amplifiers can compete.
Like all Allnic Audio products, it uses permalloy (iron and nickel alloy) for its transformer cores. Allnic is grateful to Mr. G.W. Elmen of Western Electric for inventing permalloy for transformer core use, and in so doing, providing an enormous service to recorded music listeners everywhere.
“Serious listening after break-in garnered serious results. The L-7000 is an ultra-musical device that works flawlessly—Allnic’s tube gear I’ve reviewed works as effortlessly as my top-class solid state kit.
The look is industrial and solid, with beautiful casework and those sexy tube chimneys. But the sound is far above that mundane visual description. It’s a very sophisticated unit that sprinkles life, musicality and the most incredible dynamics on everything it touches...
In the Allnic Audio L-7000 Preamplifier, you have a musical instrument that’ll take you anywhere your heart desires, transparently, smoothly, dynamically and embraced in the most wonderful soundstage and gorgeous instrumental and vocal timbres. A life affirming component and very highly recommended.”
Anthony Kershaw, Audiophilia, August 2019. Read the full review here:
Allnic L-8500 - Output Transformer-less / Output Capacitor-less
The L-8500 possesses all the sonic qualities of the L-7000 with, perhaps, slightly more of an ability to present realistic dynamic swings and resolve extemely fine inner-detail, from which the realism of instrumental and vocal timbres benefits. On the other hand, the L-7000 may have a slight edge on the L-8500 in terms of pure “drive” and saturation of tonal colours. However, once more assuming that your room and speaker configuration can communicate it, like the L-7000 the L-8500 produces Allnic’s trademark life-size, holographic sound-stages, sounding true to the recorded venue, whether studio, club or concert hall.
Again, stunningly realistic sonic quality is paired with elegance, ergonomically efficient casework, and flexibility of connections in the L-8500. For example, its two pairs of RCA output connectors take full advantage of the pure OTL/OCL circuitry, while its single pair of balanced (XLR) outputs are coupled to Allnic in-house made permalloy transformers.
The L-8500 sits below the L-10000, Allnic Audio’s top OTL/OCL line-stage preamplifier, and the L-9000 OTL/OCL line stage preamplifier.
The 8500 spun the bits into liquid gold. Accurate, sure, but with timbres so full of life and passion that its sound became, to use Allnic’s word, ‘addictive’. Frigging catnip for my ears.
-Anthony Kershaw, Audiophilia, April 2021
Read the review here: L-8500 Audiophilia Review – April 2021
AND A 2021 PRODUCT OF THE YEAR! Audiophilia Products of the year 2021
In short, though the L-7000 and the L-8500’s circuit designs are quite different, the sonic results are not dissimilar. This is no accident; KS Park worked with both the L-7000 and the L-8500 to optimize the capabilities of their respective approaches to amplification. In a reasonably considered and organized acoustic environment and matched with gear of similar quality, both preamps can facilitate the presentation of recorded music with stunning realism, and an experience of music rich with tonal colour and life-like energy, and deeply emotionally satisfying – the artists will be present. You simply cannot miss, whichever of these two preamps you choose.
Here is a comprehensive list of review publications for Allnic's current product line. Let your system breathe...
To discuss purchasing any of the above products, or any Allnic product, for the first time or to move up the Allnic product line, don’t hesitate to get in touch with me, John Ketcham, at Kevalin Audio.
If you’re in Canada, please contact Don Corby at Corby’s Audio.
And please, remember: quality trades are always welcome.
Website link: Kevalin Audio
Email or call John Ketcham:
Tel: +1 503–292–5592
Website link: Corby’s Audio
Email or call Don Corby:
Tel: +1 905.689.1976
Toll free: 1.877.689.1976