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INTRODUCING THE H‐3000 PHONO STAGE
The H‐3000 is Allnic Audio's top of the line phono stage
model. 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 H‐3000 has the following features:
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LCR TYPE RIAA EQUALIZATION:
RIAA equalization is a specification for the correct
playback of vinyl records, established by the
Recording Industry Association of America. The
purpose of the equalization is to permit longer
playback times and improve sound quality.
RIAA equalization is a form of establishing a flat
frequency response for the playback of recorded
music. The necessity for this equalization process
arises from mechanical difficulties inherent in
record production. In order to prevent the cutting
needle from over‐cutting into the next record
groove in the bass, as a record is cut, some bass
frequencies are attenuated. In the treble region, in
order for high frequency sounds not to be masked
by the noise inherent in moving a stylus over and
through a modulated vinyl surface, some treble
frequencies are boosted. With the application of
the correct filtering techniques on playback, the
result is a flat frequency response with better signal
to noise ratios.
There are four de‐emphasis methods that can be
applied at playback:
A.
Active filters (Negative feedback types):
Different quantities of negative feedback are
applied, with deeper feedback to the high
frequencies and shallower to the low frequencies.
The benefits of this method are improved signal to
noise ratios, low cost and consistent operation.
Some of the shortfalls are looser bass reproduction
and possibly a pinched and compressed high frequency
playback due to excess feedback ratios.
B. Passive filters (CR type):
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The frequencies are filtered to fit the RIAA specification
by varying the amount of attenuation at different
frequencies through a complex capacitor‐resistor
network. This technique results in no voltage overload,
purer reproduction (because there is no feedback), and
more accurate RIAA compensation. However, there are
problems because the system provides no gain, and
insertion loss and impedance matching issues arise.
C. Hybrid filters (use of both CR and negative
feedback types):
In this method, both types of filters applied separately;
an active filter is applied to the low frequencies and a
passive filter to the high frequencies. Unfortunately,
both the advantages and disadvantages of each of
these two types of filters, already discussed, affect the
playback system at the same time.
D. LCR filters, which are used in the H‐3000:
Two pieces of a linear reactor (a kind of choke coil)
comprise the main part of these filters, assisted by
precise CR filters, in order to lower impedances and
insertion loss.
In vacuum tube circuits, active and passive filters usually
are operated on one hundred plus kilo ohms of
impedance. An LCR RIAA filter's impedance is a constant
600 ohms.
Furthermore, an LCR RIAA filter's series resistance is less
than 13 ohms (as a comparative, some famous ones are
31 ohms). The lower the impedance, the more dynamic is
the sound reproduction, with better bass response and
speed.
But LCR RIAA units have drawbacks as well. These
drawbacks are high cost and the difficulty of impedance
matching; the latter has been the primary hindrance to
the commercialization of this superb method in the
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