L-7000 Line Stage Preamplifier
Immerse yourself in the original recorded space. The L-7000 is a single gain stage, transformer coupled, remote controlled line stage pre-amplifier. It uses the DHT 300B as a voltage regulator. The 300B has justly won the reputation for being a superb output tube in single-ended amplifiers. But it will take some rethinking to imagine this great tube in a non-audio role. The benefit the 300B brings to as a voltage regulator is its ability to pass a fair amount of current at low cathode-to-plate voltages, the result of haveing a low Rp.
The L-7000 offers world class, holographic soundstaging combined with incredible resolution, clarity, micro-dynamics, and drive. Instrument and vocal tone and timbre are lifelike; placement of instruments and bodies in three dimensions startling, life-size, and addictive. The L-7000 has no voice of its own. It 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. The L-7000 is, simply, a revelation.
The L-7000 is Allnic Audio’s reference line stage pre-amplifier. 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 We stern Electric for inventing permalloy for transformer core use, and in so doing, providing an enormous service to recorded music listeners everywhere.
The L-7000 has the following features:
• DHT 300B as a series voltage regulator. The benefit the 300B brings to a voltage regulator is its ability to pass a fair amount of current at low cathode-to-plate resistance, the result of haveing a low voltage drop.
• True Dual-Mono design. 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 this pre-amplifier that both channels share.
• Single gain stage. A single gain stage circuit uses only one tube for amplification (“gain”). This reproduces a purer, more detailed, more spacious and more dynamic sound than multiple gain stages.
• Line output transformer coupling. The L-7000 is “transformer coupled”. In tube amp circuitry, there are two coupling methods; one is capacitor coupling and the other is transformer coupling. 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).
• In-house transformer manufacturing and transformer/tube matching. 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 distortional, and ultra-flexible (up to 20 kHz square wave response) output transformer helps Allnic Audio to realize the ideal transformer coupled pre-amplifier. Of course, 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.
• Power supply circuit with 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.
• Constant and low output impedance. One of the benefits of transformer coupling is that it facilitates constant low output impedance. Low output impedance is critical to the design of a good pre-amplifier. The L-7000 has a 150ohm (150Ω) constant output impedance at all frequencies. In capacitor coupling (C-R coupling), a “cathode follower circuit” is usually used to lower output impedance. Unfortunately, this method of lowering output impedance is accompanied by high distortion and has an “L” shaped output impedance curve. Please compare the two graphs below, especially for low frequency response.
Allnic’s (left), other’s (right)
• 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.
• Precision 41-step single contact attenuator volume control. The L-7000 does not employ a digital IC volume control or a low-cost carbon film volume control with a motor. Allnic Audio has developed a precision oil clutched motorized attenuator; the L-7000 has no (± 0db) channel unbalance at any volume level.
• Pure Class A operation
• Full balanced output circuit
• No negative feedback design
Key features of the Allnic Audio L-7000 line amplifier :
• 300B as a series voltage regulator
• True Dual-Mono design
• Single tube gain stage
• Transformer coupling
• Constant and low (150 OHM) output impedance at all frequencies
• All NOS tubes
• Easy to read tube monitor meters
• Zero negative feedback
• Precision oil clutched motorized single contact attenuator, with zero channel imbalance at any volume
• Ultra high speed, automatic, vacuum tube voltage regulation
• Pure Class A operation
• Full balanced output circuit
• Phase control switch
• 3 RCA and 2 XLR inputs
• 1 RCA, 2 XLR (1 is record out) outputs
• Remote control
• Input Impedance: Unbalanced 10kΩ Balanced 10kΩ
• Frequency Range: 20Hz ~ 20kHz (FLAT) 16Hz ~ 50kHz (-3dB)
• Voltage Gain: +20dB
• THD (1kHz): Output 0.3V, 0.06% Output 1.0V, 0.15%
• S/N Ratio: -90dB (CCIR, 1kHz)
• Maximum Output: 15V RMS (Non-clipping)
• Output Impedance: 150Ω Constant
• Power Consumption: 30W at 110/120V / 60 Hz
• Tubes: E810F × 2 (gain stage, left and right channels–there are no equivalents to these tubes); 300B (no equivalent) × 2(Voltage Regulator); 5654 (similar to EF95, 6AK5) × 2 (Voltage Error Detector)
• Fuse: 2A 250V
• Dimensions: 430mm (W) 410mm (D) 173mm (H)
• Weight: 18 kg (39.7 lbs) unpacked
L-7000 Hificlub(S.Korea’s webzine) review
L-7000 Audio(S.Korea’s magazine) review
Manual: L-7000 Manual