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INTRODUCING THE 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 300B direct-heated triode as a
voltage regulator. The 300B has justly won the reputation for being a superb output tube in
single-ended amplifier, but it will take some rethinking to imagine this great tube in a role
outside the signal path. The benefit the 300B brings as a voltage regulator is its ability to pass a
fair amount of current at low cathode-to-plate voltages, the result of having a low Rp.
The L-7000 offers world class, holographic sound-staging 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 a reference level 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
Western 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:
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Line output transformer coupling – The L-7000 is "transformer coupled", using transformers
that have been upgraded from those in the L-3000. 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 –
voltage is not affected).
Transformer coupling is superior to capacitor coupling. However, 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 (16Hz ~ 75kHz, -3db), low
distortional, and ultra-flexible (up to 50kHz square wave response) output transformer helps
Allnic Audio to realize the ideal transformer coupled preamplifier. 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.
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 preamplifier. The L-7000 has a 120 ohm (120Ω) 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
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