User Guide

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Switching Power supply and DC-DC converter
To make 115V DC available from the motherboard or switching power supply for the tube is a
daunting task. The geeks at AOpen have tried different ways to tackle this issue, and have adopted the
switching power method for lighting-up the tube. A Maxim 668 DC-DC converter is the heart of the tube
power supply, supplying ample voltage for the tube to work under optimal conditions for proper music
playback. The design also involves finding a transformer that can work very hard and reliably with
circuitry in tandem. After long hours of experiment, we have determined that four transformers have the
tonal quality that can rival solid-state amplifiers. Four different ferrites and copper wires are measured
subjectively. One stands out and it’s been implemented onto this product.
Amplification
Tube
After audition more than a dozen tubes, we have chosen Sovtek 6922 as standard tube to be used in
AX4B-533 Tube for its well-rounded tonality for both music play back as well as gaming.
A warm and soft mid range, ultra liquid treble can be achieved. Of course you can do your own
experiment by replacing different 6922/ECC88/6H30 dual-triode tube. Please refer to page 26 for
compatible tubes for replacement.