AOpen TUBE User Manual

I. Introduction

AOpen has been a pioneer in the motherboard field, bringing solid and award-winning products to the PC
community, for many years. These achievements include the first Intel-based 440BX chipset motherboard with
a military-grade black PCB and a 24K gold-plated heatsink for overclockers. AOpen was also the first to offer
space-grade ultra-high precision components for commercial motherboards, providing overall PC system
stability and long-term reliability.

Now, AOpen presents the world’s first vacuum tube motherboard for game enthusiastic and music lovers,
allowing them to totally immerse themselves with their favorite software and enjoy the ultimate in audio
performance. The AX4B-533 Tube is also a true platform for tweakers who wish to not only tweak performance,
but also the tonal quality of the on-board audio tube. Each PC game has its unique sound effect and character,
whether it is engine revs, shotgun pumping or blades chopping through the air and the AX4B-533 Tube can
deeply satisfy a gamer’s cravings and provide audio-grade tonal quality at the same time.

The demands on PC audio today are high, yet little hardware exists that can do games and music
justice

Today, personal computer is playing an even bigger part of one’s daily life compared to just a few years
ago. This is especially the case with multimedia-enriched systems that provide not only sound, dazzling video
and performance, but also are used as video editing gear for digital cameras and camcorders with the
IEEE-1394 interface. With the advent of TV tuner and TV-out capabilities and enormous hard drives, one can
literally turn their PC system into a TV and video recorder. But what about audio?

--1--

What’s Lacking is true audio from a PC that can rival hi-fi stereo systems

Most of today’s motherboards have audio designs that center on the so-called “AC’97” standards that are
certainly sufficient to meet the needs of daily business applications. Technology for both sound cards and
on-board AC’97 emphasize a SNR or (signal-to-noise ratio) that’s unrivaled by ordinary stereo components that
can be purchased from retail electronics chain stores. But what they lack is the ability to reproduce music that
is intended to be played back with faithful reproduction. Certainly SNR has a lot to do with music reproduction.
However, most of all, faithful music reproduction requires more than just excellent SNR, it requires tonality
and depth that truly moves the heart and soul of the listener.

The Perfect PC Audio Solution –Back to The Future

Driven by this premise, a group of geeks at AOpen’s Motherboard Division began to think about a fusion
of the latest digital technology with Thomas Edison’s discovery dating back to 1880 – the conversion of
alternating current into direct current through a device called The Vacuum Tube.

For years audiophiles and musicians have appreciated the warmth and tonal quality that flows from
sound that is reproduced with the utilization of the vacuum tube. Certainly with current materials,
technologies, manufacturing techniques, quality control and measurement equipment, it is possible to
manufacture a significantly improved and accurate audio reproduction machine than what was available 30
years ago. Yet, what is available today lacks the ability to pack the punch that the combination of old and new
can achieve. By introducing the vacuum tube to the new AX4B-533 Tube Motherboard, AOpen is determined to
meet this daunting challenge head-on and deliver a product that will significantly benefit music lovers and
gamers who see personal computer as more than just a personal computer. With this new motherboard, AOpen
is aiming to entice the segment of the user market that wishes to enjoy substantially better sound effects when
playing the latest popular computer games as well as those who desire to use their PC as a bona fide music
playback system.

--2--

Challenges and Creativity – The AX4B-533 Tube Motherboard

The challenges that AOpen engineers have encountered in this endeavor are many-fold in terms of
providing a faithful music reproduction scheme to be combined with the motherboard – commonly referred to
as “On-board”. Our engineers have remained undaunted by those challenges. The design of such a novel
concept involves not only digital know-how, but also linear electronics and acoustic know-how. Musical
aesthetics also play a big role, right from the concept stage, all the way to the testing of such a unique creation.
Meeting the criteria of so many existing playback environments is also a consideration that AOpen engineers
have taken into serious account.

--3--

II. Know more about Tube

What is a Vacuum Tube?

The tube is basically an electronic valve that controls the flow of electrons. It consists of an envelope (bulb,
usually glass) from which most air and other gasses have been removed. Inside this near vacuum are two
systems. One is called the heater. This is in the center of the tube and is the portion you will normally see
glowing orange (some tubes may have more than one heater). The other system consists of the cathode, grid(s),
and plate (also called the anode). The plate is the largest metal structure you see inside the bulb. All of this is
held to correct locations by thin disc spacers made of mica or ceramic.

Why The Vacuum Tube?

Before we go further, someone undoubtedly will ask, “Why the vacuum tube?” A quick answer would be:
“The tube looks cool!” But the real answer does not stop here; there are more legends about the tube that wait
to be unveiled.

Why Vacuum Tubes Are Superior for Music Playback

Why use the vacuum tube? Because the tone of the tube attracts listeners in a simple, basic way. There
have been too many arguments between solid-state and tube technologies – many experiments and blind tests
have been conducted. Even statistical gurus have contributed to the argument on the outcome of these tests.

Skepticism has argued that even an average solid-state amplification device is measurably superior to the
best tube device, but the argument may not stand the trial of tonality. So let us make it simple here – We love
what we hear regardless of harmonic distortion as well as the limited frequency response compared to a
solid-state device. With tube technology, the music is more musical!

--4--

Jimmy Page strikes the guitar strings on "Stairway to Heaven" and Angus Young of AC/DC's "Back in
Black" share one common attribute– It is the vacuum tube that powers their guitars’ souls that express what
they want to sound like and what the listener likes to hear.

How The Vacuum Tube Works

Let’s take a look at the fundamentals of how the vacuum tube works. In a modern vacuum tube, there are
four principal elements that work together to make a tube work. The Filament (heater), Cathode, Grid and
Anode (or plate). When the filament is connected with voltage that boils the cathode, the cathode then emits
electrons that pass through the grid and hits the Anode. Through this electron flow, the tube will amplify a
small AC signal into a larger AC voltage, thus amplifying it. By controlling the grid voltage, the current flow can
be regulated and thus creates the desired electronic characteristics, while amplifying the signal (source).

Today, most electric guitar and bass amplifiers are tube-based. Professional audio equipment also
deploys the tube as a preferred amplification device. One can even find tubes in digital-to-analog converter
designs. The vacuum tube is a natural choice for these music-associated vehicles to depend on.

What's that Silver Stuff on the Glass?

The silver deposit is called the "getter" and is there to help increase the vacuum in the tube. Its color may
vary slightly. Sometimes the getter will flow with use, even to the point of becoming evenly and thinly deposited
over the entire envelope. The edge of this flow may have a brown color. None of this is important as long as the
tube biases correctly and stability.

If you see the getter receding leaving a whitish profile the tube is loosing vacuum and should be removed
from service.

--5--

Mechanical Handling

Do not bend or force the metal pins coming out of the base of the tube. This could break the vacuum seal
and ruin the tube. The same is true of any sharp mechanical shock. You can usually tell if the seal breaks, as
the silver deposits that coat the inside of the glass will turn to a white powder.

For The Sake of Nostalgia

As a committed group of computer geeks and jazz music enthusiasts, we at AOpen believe that the
vacuum tube can satisfy the listener’s ear much more than the average AC’97 or a very expensive PCI sound
card. Yes, we understand that we’re dwarfed by the tube equipment giants in a number of ways, but with the
AX4B-533 Tube, we believe we’ve found a better way to get outside the box and really hear the music.

So let the tube glow and enjoy it!

--6--

Technical merits inside AX4B-533 Tube

6922 Tube Specification

Nine-pin miniature tubes (Sovtek 6922 in here) have no plastic base. Locate them in their sockets by
noting the space where there is no pins. Do not wiggle these tubes excessively, as you might damage the
socket or the glass seal.

Specification and max ratings (*)

Filament Voltage 6.3V

Filament Current 365mA

Plate Voltage (max) 130V

Plate Current (max) 25mA

Plate Dissipation (max) 1.8W

Screen Voltage (max) ---V

Screen Current (max) ---A

Screen Dissipation (max) ---W

--7--

TubeSound Technology

Fusion of P-4 and The Grand Old Vacuum Tube

The AX4B-533 Tube Motherboard is a fusion of the latest Intel Pentium 4 technology with the
century-old vacuum tube for the perfect marriage in audio reproduction. This hot-fusion of technologies
over one hundred years apart has merit of imagination that cannot be denied or taken lightly.

Components and Construction

To ensure a full gaming experience and true tonal quality for music playback, AOpen has
meticulously selected the finest components from the world’s top-rated manufacturers. In fact, AOpen
continues to test components that will further enhance tonal quality as well as overall system reliability
for the user’s total enjoyment.

Every AX4B-533 Tube motherboard is patiently and carefully assembled. They are then inspected
and individually tested by AOpen technicians to meet their desired peak performance. Please refer to
Appendix B for testing methods and equipment.

Noise Isolation

In today’s high-performance digital designs, compatibility, stability
and reliability are crucial. EMC, ….(add more) are also part of the

equation of a successful products. By fusing the Pentium 4 and

vacuum tube circuitry, the geeks of AOpen worked for over weeks

exclusively thinking about how to solve tube-inherent technicality issues

as well as their dreaded by-products – NOISE.

The method we developed back in 1998 in another application, is now working again – this time for this
new hybrid product – The method is called the Frequency Isolation Wall (FIW).

--8--

PCB

True to AOpen’s heralded tradition of unique motherboard design, a black PCB is used for the
AX4B-533 Tube. Since the current and voltage of the tube design require more than just a conventional
motherboard PCB, the copper trace has been thickened and several quality improvements have been
made to ensure long term reliability and performance.

Power Capacitor

A magical ELNA electrolytic capacitor is coupled for voltage output for tonality that’s unparalleled.
By using very fine conductive particles of super high purity graphite and other “magical” material, this
Nichicon electrolytic capacitor has drastically lowered many of the distortion mechanism inherent in
electrolytic capacitors design.

Workmanship

Needless to say, AOpen’s workmanship is one of many of our traditions and it is applied to this
product again with “meticulously detailed” steps to ensure quality.

Power Supply for the tube

Max 668 --- Using Maxim 668 DC-DC converter.

Transformer for the Tube

A high quality EI ferrite core with 0.3mm AWG hyper copper wire that not only meets UL standards
but is also able to withstand 266 degree Fahrenheit (130 degree Celsius) operating temperatures. This
transformer supplies more than enough regulated voltage and current to power the tube circuitry.

Power resistor

The Vishay – Military and space-grade resistor is once again fitted seamlessly in this new design,
providing 1% tolerance. Made with high purity ceramic substrate, proprietary nickel-chrome alloy
element, and stainless steel end caps. No magnetic materials are used in any of the construction.

--9--

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.

--10--

Amplification Circuitry

After studying many classic pre-amplifier circuits, we decided to use a single dual-triode (one tube
with stereo channel), as a main amplification device. By complying with many criteria, we also decided to
follow a long path in terms of providing the most faithful, yet economical way, of doing the signal
amplification – Direct Path. In this design, a straightforward amplification is achieved without numerous
coupling devices that could add coloration to the music.

Following is a basic circuit of cathode stage, fully-bypassed cathode implemented in AX4B-533 Tube
for your reference; for intellectual property is su e, we re ve al it in a sim p l e w ay in st ea d o f a
detailed circuit diagram.

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--11--

Common-cathode stage, unbypassed cathode:

Voltage Gain (Output 1):

Av = (mu * ra )/( ra + (mu + 1)*Rk)

Input impedance:

Rin = Rg

Output impedance (Output 1):

Rout = [( ra)/(mu + 1)] //Rk

Frequency response (Output 1):

f1 = 1/(2*pi*Ci*Rg) - highpass breakpoint due to Ci/Rg

f2 = 1/(2*pi*Co*(Rout + Rl)) - highpass breakpoint due to Co/Rout/Rl

Where:

Rg = the grid resistor

Rp = the plate resistor

Rk = the cathode resistor

Rl = the load resistance, or the input resistance of the next stage

Ra = the total load resistance, which is Rp in parallel with the input resistance of the next stage, Rl. If
there is no Rl, Ra = Rp.

ra = the internal plate resistance of the tube

mu = the mu of the tube

--12--

Coupling Capacitors --- MultiCapTM

Polypropylene & Aluminum Foil Multiple-Section Capacitors are used throughout

the amplification except power supply.

Resistors --- Vishay

1% metal film resistors with high purity ceramic substrate, proprietary nickel-chrome alloy

element, and stainless steel end caps.

Tube Socket

A 24K plated ceramic 9-pin tube socket sits on the center of the PCB at a pivotal point. This
high-quality audio grade socket will accommodate years of reliable operation.

Wire – Cardas Cable

Cardas Audio has always been striving to address every detail of cable and conductor
construction. It realized that cable geometry problems are resolved in the cable’s design,
not after the fact with filters, and it also knows that the sound produced by any stereo
system depends on the purity of the audio signal it
produces, so it creates the famous "Silent Conductor" that

allows them to be so uniquely musical and pure. Other than
that, Cardas possess effective methods like enhancing the quality of the
sound by using Constant Q Stranding which could reducing the internal
rise in inductance, exquisite design that incorporates Cross-field
Construction in its manufacture, and so on. It makes perfect sense that
Cardas cables is at the leading edge.

--13--

A

Testing Methods

Frequency Reponses

udio Precision 06/14/02 11:50:52AX4B-533 Tube (Tube OUT) Frequency Response

-10

-12

-14

d

-16

B

r

-18

A

-20

-22

-24

10 20k20 50 100 200 500 1k 2k 5k 10k

Hz

A-A_ FR.a t2

--14--

-10

-12

-14

-16

-18

-20

-22

-24

d
B

r

B

Conclusion

Yes, AX4B-533 Tube is not quite a true “Stereophile” C-class recommended group of components.

Yet, given its original fusion idea and meticulous journey to fruition, we believe it is Class-A for certain.

It is our belief that gamers and music lovers alike will love the AX4B-533 Tube. This unique
motherboard requires a personal audition with ears, heart and soul. Anyone who appreciates
well-reproduced sound, whatever the venue, will appreciate a system built with this innovative
motherboard. Such a system will likely receive as much care and provide as most home and specialty hi-fi
stereo playback systems get from their proud owners.

June 2002

AOpen

--15--

III. Power it up

Unpacking your tube & Insertion

1. Please take out the tube carefully from the packing box.

2. Holding the tube, and try not to touch the printed wordings on it as cautiously as you can.

--16--

J

3. Take a good aim on the pinhole, then slowly inserting the tube pins downward into the white basement with
balanced strength.

Note: Though some of latest version of
Windows support “Digital Audio” through
IDE bus, however, in order to use Open

ukebox player, which is driven under
BIOS, it is a MUST to insert audio cable
to CD-IN connector on the motherboard.

--17--

4. You may “slightly” swing and press down the tube bilaterally at the same time to make sure that it will be
completely inserted.

--18--

Tube Audio Card

This daughter card is specially designed for better analog/digital audio out put, it’s strongly recommended to
connect your speaker to this RCA-output instead of the normal “speaker out” on the back panel of motherboard
for better sound quality.

S/PDIF-IN
Connector

1

+5VSB
NC
S/PDIFIN
GND
S/PDIFOUT

--19--

GND

SPDIFIN

AGND

PHONE_R

SOUND_INR

+5VA

SPDIFO

AGND

PHONE_L

SOUND_INL