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Allnic H-1500 II Plus Vacuum Tube Phono Preamplifier

$13,000.00 inc. GST

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Description

The H-1500 II PLUS is Allnic Audio’s mid-line phono-stage model, just under the top of the line H-7000.
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-1500 II PLUS has the following features:

• 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):
– 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.
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D. LCR filters, which are used in the H-1500 II PLUS:
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 construction of
phono stage amplifiers. However, Allnic Audio manufactures a high quality LCR RIAA unit and
has developed a 600 ohms impedance matching method.
• For superior signal to noise ratios, the H-1500 II PLUS is equipped with pure vacuum tube, high
voltage regulation for each channel and a power supply unit separate from the phono stage
itself.
• High quality MC Step-up Transformers with Permalloy cores are used for the H-1500 II PLUS’s dual
MC inputs.
• Pure Class A operation
• As are all Allnic Audio products, the H-1500 II PLUS is fully RoHS (EU Reduction of Hazardous
Substances regulation) compliant in construction and materials.

Allnic H-1500 II Plus Manual
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