ALLNIC AUDIO L?1500, Owner'S Manual

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INTRODUCING THE L ‐ 1500 PREAMPLIFIER
The L ‐ 1500 is Allnic Audio’s mid ‐ line preamplifier model,
just under the top of the line L ‐ 4000. 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 ‐ 1500 has the following features:
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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 multi gain stages.
•
Line output transformer coupling – The L ‐ 1500 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 about10% 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 core 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 ‐ 1500 has a150 ohm (150 Ω ) 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.
•
Advanced tube technology voltage regulation ‐ For
quieter and more dynamic operation, the L ‐ 1500 has
an ultra high speed automatic voltage regulation
circuit, utilizing vacuum tubes. This also protects the
amplifying tubes from change in the AC line supply
and copes with any abrupt, internal current demand.
•
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 microphonic 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 microphonic 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 attenuator volume control – The L ‐ 1500
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 ‐ 1500 has no (± 0db)
channel unbalance at any volume level.
•
Pure Class A operation
•
As are all Allnic Audio products, the L ‐ 1500 is fully
RoHS (EU Reduction of Hazardous Substances
regulation) compliant in construction and materials.
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