ALLNIC AUDIO H-5000, Owner'S Manual

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THE DHT PHONO-STAGE AMPLIFICATION CHALLENGE
Over a century of research and experience, the grand masters of tube design came to the
conclusion that only a well-made DHT amplifier can have absolutely the most natural and clear
sound. In addition, only the DHT amplifier could combine that pure, undistorted sound with the
ability to reproduce a true 3D sound stage occupied by life-size images of musical instruments,
voices and other recorded sounds.
A number of manufacturers have now introduced DHT power amplifiers, and a lesser number have
released DHT output, if not pure, line level preamplifiers, but no one until now has produced a pure
DHT phono amplification stage. That is because of the increasing difficulty, from power, to line
stage to phono-stage amplification, of implementing a commercially feasible DHT design. Thus,
successful creation of a complete, or pure, DHT phono-preamplifier has been the final goal, the
dream, of tube master designers – now realized by Allnic Audio.
OVERCOMING THE DIFFICULTIES OF DHT PHONO-STAGE DESIGN
•
Rarity of DHT tubes suitable for phono amplification
The essential DHT tubes for phono amplification should have high gain, low internal resistance and
high mutual conductance. It is extremely difficult to make that kind of DHT tube. Among hundreds
of kinds of DHT tubes, there are fewer than 5 that have the specific characteristics required for
phono amplification. To find those tubes requires broad and deep knowledge of tube types and
specifications and much time consuming experimentation.
•
DHTs’ extreme sensitivity to micro-phonic noise
Due to their large, bulky and weak construction, DHT tubes tend to vibrate with the tiniest external
stimuli, so it is almost impossible to use a DHT for phono reproduction without breakthrough
engineering solutions to inhibit sympathetic vibration in the DHT tube. Allnic’s patented GEL tube
damper socket, based on liquid elastomer, mitigate micro-phonic vibrations in the DHT tube.
• Difficulty of properly matching transformers to DHTs
There is no tradition of manufacturing DHT phono-stages, so there are no matching transformers
available in the marketplace. It is, therefore, essential to have in-house capability to design and
wind the transformers specifically required for production of a pure DHT phono-stage. Allnic has
long experience with designing and winding custom transformers, so it is quite natural that a
perfect DHT phono-stage could be made in the Allnic factory. In addition, Allnic has developed and
produces a very small output transformer for DHT phono amplification. The smaller the
transformer, the better sound will be reproduced due to the reduced size of the magnetic field of
the core material, while still providing enough inductance for realistic low frequency reproduction.