L-10000 OTL/OCL

The L-10000 OTL/OCL (Output Transformer-Less/Output Capacitor-Less) is a triple gain stage, remote controlled, line-stage preamplifier, without transformers or capacitors in its single-ended signal path.

  • OTL, OCL Direct Coupled preamplifier
  • Two SEPP 300Bs output
  • True Dual Mono design
  • 61-step Silver Contact Constant Impedance attenuator


Immerse yourself in the original recorded space. The L-10000 OTL/OCL (Output Transformer-Less/Output Capacitor-Less) is a triple gain stage, remote controlled, line-stage preamplifier, without transformers or capacitors in its single-ended signal path. It uses the 300B direct-heated, single-ended triode as its directly coupled output power tubes; i.e., there are no output transformers on the single-ended (unbalanced) outputs, so the 300Bs communicate the signal directly to the connected power amplifier or amplifiers. The 300B has justly won the reputation of being a superb output tube in single-ended amplifiers, and in the L-10000 OTL/OCL preamplifier they fully reveal their inherent accuracy and beauty.

In common circuits, output capacitors or output transformers are required 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. 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 achieves the best results possible:

  • No colouration of the musical signal
  • Extremely detailed expression, natural harmonics and subtle musical decay
  • The lowest possible distortion
  • The widest musical dynamics

In the L-10000, 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. Thus, the benefits listed above are fully present in the Allnic L-10000 preamplifier.

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 DC potential in the first place.

The L-10000’s 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 perfectly controls the circuit’s operation with extremely low distortion and incredible speed.

In addition, Allnic’s newly developed 61 STEP CONSTANT IMPEDANCE BRIDGED TYPE ATTENUATOR, a world premier, is standard with the L-10000 and enhances its lifelike, dimensional sound.

The L-10000 OTL/OCL is a world-class, reference level, line-stage preamplifier. It offers unbelievably realistic, holographic sound-staging combined with incredible resolution, clarity, micro-dynamics, and drive. Instrument and vocal tones and timbres are breathtakingly lifelike, and the placement of instruments and bodies in three dimensions startling, life-size, and addictive. The L-10000 OTL/OCL has no voice of its own, none. It is silent, except for the music emanating from the blackest of backgrounds. In addition, the stunningly realistic sonic quality is matched by the simple elegance, flexibility and ergonomic functionality of the L-10000’s casework and connection options. The L-10000 is truly a masterpiece, and is Allnic Audio’s top line-stage preamplifier. Few preamplifiers can compete.

Technical Specification
Inputs 3 x RCA, 2 x XLR
Outputs 1 x RCA, 2 x XLR
Input Impedance 10k ohms (RCA, XLR)
Frequency Range 5 Hz to 100 kHz
Voltage Gain +18dB
THD (1kHz, 1V RMS) less 0.03%
S/N ratio -100dB
Maximum Output 20V RMS (non clipping)
Output Impedance 200 ohms
Power Consumption 120W
Tubes 300B x 4, 6AN8 x 2, 12AU7 x 2
Fuse 3A/230V, 5A/120V
Dimensions 430mm (16.95 inches. W), 450mm (17.72 inches. D), 280mm (11.02 inches. H)
Weight 23kg (48.4 lbs) unpacked. 28kg (59.5 lbs) packed.

Allnic Audio’s Technology

Remote controlled 61-step constant impedance attenuator

Mr. Park has completed development of the world’s first 61-step, constant impedance, “bridged” type attenuator. Allnic’s new attenuator is now the most sophisticated on the market, and we believe, without a doubt, also the absolute best sounding. With fixed impedance and no (± 0db) channel unbalance at any volume level, the new attenuator will astound users with its elevation of the fidelity and purity of any system in which it is used. This revolutionary and currently unique, oil clutched, motorized attenuator will be standard equipment on the L-8000 preamplifier and L-10000 OTL/OCL, L-9000 OTL/OCL, L-8500 OTL/OCL preamplifier.

OTL/OCL Ciruitry

OTL/OCL means “Output Transformer-Less” and “Output Capacitor Less”. In an OTL/OCL preamplifier, there is no coupling device between the preamplifier and the power amplifier, that is, the preamplifier’s final output tubes are directly connected to the power amplifier. Normally, an Output Capacitor or Output Transformer for separating AC music signal from the DC operating potential; if this is not done, the latter will destroy the power amplifier or loudspeakers. But these two types of coupling devices are effectively obstacles to signal transmission that add their own character (color), increase distortion, and consume small signals according to physical efficiency theory. In addition, they limit signal dynamics. Because of all these adverse effects, OTL/OCL has been considered the best solution for amplifiers in order to maintain signal purity. Some circuit experts might worry about DC potential in the music signal, but there is no need to worry. Allnic uses a “floating power supply circuit” which prevents the creation of any DC potential in the first place.

Soft-start Circuitry

Allnic uses soft start circuitry that, after sufficient warm-up only, provides the high voltage supply to the plate of each tube. This protective design results in prolonged tube life and fewer and less frequent issues with tube performance.

Beautiful 100kHz square wave response

We can show you how beautifully a 100kHz square wave response is reproduced.

New vacuum tube damping technology

Allnic Audio’s patented “Absorb GEL tube damper” technology prevents harmful vibrations from reaching the signal/gain tubes and, therefore, prevents micro-phonic noise propagation in the tubes. The Allnic Audio Absorb Gel damper technology effectively solves a problem that plagues most tube amplification systems. Provided other tube components do not introduce micro-phonic noise into your system, with the Absorb Gel damping system, you will enjoy a degree of transparent sound that will surprise and please you.

Powerful driving circuitry

Allnic believes in the importance of using high-quality, low noise and powerful driving circuitry in all its amplifying devices. Therefore, for example, in the M-3000 mk2, we employ the E282F tube (E55L for M-5000) in triode mode as the second stage driver tube, with a load of about 6 k ohms, and using 20 mA of current. The listener can easily hear and even “feel” the differences between this design and other, more conventional, ones. Please imagine, as you listen to the M-3000 mk2, its sound compared to the sound of an amplifier with conventional 12AU7 or 12BH7’s used as drivers, with a load of about 47 k ohm, and using 2 to 3 mA of current.

Analogue power tube current monitors

In order to provide constant current (bias) monitoring for the power tubes, Allnic uses a separate analogue current meter for each tube. The meters make it exceptionally easy to see the status of each tube at any time and to respond immediately to any variation in bias by use of the bias control knob for the relevant tube. The meters offer a simple, unambiguous indication of each tube’s status compared to conventional LED bias monitors.


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