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.

--11--

--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

1. Plug the audio cable to the connector on the
daughter card, and notice the orientation of the
hook.

2. Connect the other end of the cable to the
connector on the motherboard, in the same way;
you’ll not be able to plug it in with wrong orientation.

--20--

A

3. Connect your device to the jack on the bracket of this daughter card.

3.5mm Line-IN

6.3mm
Headphone Jack

RCA Output

S/PDIF Output

Left

Right

udio Cable

Connector

--21--

IV. Let’s make things better

Unplugging the tube for replacement

Be Careful - IT'S HOT

Current tube technology requires high internal operating temperatures. As a result, the glass part of the
tube can reach temperatures as high as 250 degrees. Always allow your AX4B-533 Tube to sit switched off for
several minutes before you touch the tubes.

Incorrect ways of pulling up the tube:

1. Never hastily pull out the tube while lights is still
on: The fuse inside the tube could still be red with
high temperature when the power was just being
cut off. Therefore, if you pull out the tube
immediately right after power off, the possibility is
that you might not only be burnt by the high
temperature, but also caused a broken fuse by
violent shaking, and there goes the tube.

--22--

2. Never touching the printed wordings with your
fingers: When you pull out the tube, try not to touch
the printed wordings with your fingers, because if
that’s an earlier-designed tube, the wordings on
tube would be easily rubbed off after few times
touching.

3. Inappropriate pulling angle: Most of the tube basement
could be a little bit tight, but remember not to pull them
too hard bilaterally, for this could break the vacuum seal
and ruin the tube.

--23--

Correct sequence of pulling out the tube:

1. Waiting at least 30seconds right after cutting off the
power for the fuse and inner glass to cool off a bit.

2. Holding the tube with fingers, trying your best not
to touch the printed wordings on tube; Swinging
slightly bilaterally, and pulling the tube upward with
balanced strength.

--24--

g

3. Pull the tube out of the base, and put it into box with care.

--25--

Note: To prevent loud noise caused by
the large current of the huge capacitor
on this motherboard, it is strongly
recommended to turn off your power
amplifier or speaker first before
turnin

off your computer.

Substitution of tube

The following tubes can be used on the AX4B-533 Tube for those of whom looking for different tonal
characteristics or just replacing the tube.

General speaking, a low output tube such as the 6922 will have about 5,000~6,000 operating hours life
span. If you use it 4 hours a day, it will probably last for over 4 years. Of course, many factors also determine
the life of a tube including working voltage, temperature, vibration…etc.

Here is the substitute tube list for Sovtek 6922:

Jan-Philips 6922

Russia 6922 / 6H23

Siemens E88CC / 6922

6N30 or 6N30P

Telsa E88CC / 6922

Telefunken E188CC / CCa

Telefunken E88CC / 6922

Telefunken PCC88 / 7DJ8

Siemens E288CC

Siemens 7308

Sveltana 6N1P

Philips E80CC

Philips E88CC / 6922

MiniWatt ECC88 / 6DJ8

Amperex ECC88 / 6DJ8

Mullard E88CC / 6922

Mullard CV2492 / E88CC

Mullard CV2493 / E88CC-01

Mullard E188CC / 6922

Sylvania 6922 / E88CC

Sylvania 7308 / E188CC

AEG E88CC

--26--

Comparison of different tubes

Please refer to the reference chart below for 6922/6DJ8 tubes comparison:

US code EU code
Normal 6DJ8 ECC88
High-end 6922 E88CC
Advanced 7308 E188CC
Exclusive 8223 E288CC
Compatible 7DJ8 PCC88
Unique CCa (unique german code)

**The CCa here is the same as E88CC, which is made of special quality and low noise, and selected out
among E88CC high-grade tubes, with longevity and less noise.

You may directly change the mentioned tubes whenever you like, but E88CC, E188CC, E288CC, CCa is
the best quality tubes among ECC88/6DJ8 series, with longevity and golden pins mostly. (Most modern or
American tubes do not equipped with golden pins)

PCC88/7DJ8 and 6DJ8 are similar in structure, except one thing, and that is the overheating of filament
(7V). It could be used to replace 6DJ8/ECC88, too.

--27--

The sound trend of various manufacturers of 6DJ8/ECC88/6922/E188CC:

The statement below is just a reference of the sound trend of various manufacturers. You may seek to the
individual pages for their details.

1. German made Siemens: Excellent resolution and stage positioning, however the sound is not as solid
and thick as England made tube. If your system lacks in resolution, then this Siemens made will be your first
choice.

2. England made Mullard, Phlips, Amperex.: Typical England solid style, thick mid range, but of course,
resolution is not as good as Siemens. Suitable for system with delicate sound.

3. Holland made Philips, Amperex, Mullard : As a whole, their performance is average in bass, Treble and
mid range, with full sound and good resolution. They are more tends to neutral style.

4. Telefunken ,TFK: Nobody could hardly ignore Telefunken if they were enthusiasts of tubes! It definitely
is the highest rank among various brands. With impeccable sound, good quality, harmonious sound, longevity,
it has been recognized as the best tubes ever (though some one might do not agree with that). Furthermore,
Telefunken has stopped produce tubes for a while, and folks are earger to seize one, that makes it incredibly
expensive, especially for those Audio tubule, such as E88CC, CCa, ECC82, ECC83...

**Special thanks to WenAudio, www.audio.idv.tw

, for the tube thumbnails.

--28--

The Height comparison of different tubes:

--29--

ECC88 / 6DJ8 type

Amperex Bugle Boy ECC88

This is the famous “Bugle Boy” made in
Netherlands in the 60’s. Excellent
resolution and sound stage positioning.
Clean yet silky sounded infatuated
many audiophiles around the world. As
for the subjective feeling, this tube offers
extended solid bass, wide sound stage,
and sweet mid and airy high. I would pay
for $200 for this tube for its tone and
look.

--30--

Amperex ECC88

The next generation of Bugle boy in the
70’s. Orange globe logo with big “Made in
Holland” print on the glass. Sound
quality very similar to the original Bugle
Boy. An excellent generation. Hard to
find like Bugle Boy.

--31--

Philips MiniWatt ECC88

This 1960’s Philips MiniWatt no-fault
made in Holland ECC88 offers even
better “thickness” compare to the Bugle
Boy. A must for you to own. If you find
this tube in someone’s garage or at the
flea market, don’t barging, just buy it.

--32--

E88CC / 6922 type

Mullard E88CC

This gold-plated pin Mullard E88CC is
made by Philips in Holland like its
cousins Bugle Boy and Philips
MiniWatt. Resolution, solid as rock and
thick like Cappuccino’s thick crème
that makes you feel so comfortable.
Yes, it is also hard to come by tube.

--33--

Mullard E88CC

An England made Mullard E88CC with
shiny gold tone accent. Musically
satisfactory one for the pre.
Voluptuous tonality with seamless
dovetails between mid to high.Its
skin-deep beauty make it best to the
pre-amp that has an open chassis
design.

--34--

Siemens E88CC

Another solid but not hard bass E88CC
with excellent resolution and sound
stage positioning. This one also meets
German’s best – Mercedes Benz and
BMW precision engineering.

--35--

AEG E88CC

AEG is believed to be the parent
company of Telefunken. The original
company name is AEG-Telefunken. A
wonderful sounded E88CC that’s worth
to collect.

--36--

Telefunken E88CC

This Telefunken E88CC is as same as
the AEG one. A work of wonder with
total relaxation.

Telefunken is Telefunken.

--37--

Philips E88CC SQ (6922)

Details, details and details. One can
hear layers after layers of musical
information. Open, airy, a total
harmony. If you love chamber or New
Age music, this is the one that you can
not miss.

--38--

E188CC / 7308

Philips E188CC

Same SQ series from Holland. (Why
Holland makes the best tubes?) When
the ivory keys were hit, you can feel the
notes approaching your ears with force.
A sensational tube for the piano solo
(Bill Evans’s soliloquy)

--39--

Mullard E188CC

England made. Similar with Mullard
CV4108, but better than it in the sense
of space and condensation.

As for its sound stage performance, it
fully stretches to surrounding space
with smooth flow, excellent resolution,
and extended bass and treble as if you
could watch the airy flow of flute.

--40--

Mullard CV4108

Made in England. Thrilled and
impressed it gives us as England Tube
always do. Extravagant and clean, plus
suitable bass and excellent resolution.
Touching people no matter in listening
vocal, instrument or piano etc.

--41--

Siemens 7308 (American made)

Though not made in German, but comes
with a very good quality. Marvelous
resolution that could easily triumph
some modern tubes, like Philips EGG
6DJ8, Sveltana 6N1P, Tesla E88CC, etc.

--42--

Sylvania 7308

American made tube, which use the
same structure as E188CC, with
splendid resolution and C/P rate as well.
Worth buy product.

--43--

Telefunken E188CC

1960 German made, with golden pins,
outstanding sound, less interference to
bass, which is considered the best buy
product in TFK E88CC/CCa/E188CC
series.

--44--

E88CC-01 / CCa

Mullard CV2493

England made CV2493 is equal to
E88CC-01, which produces less
interference to bass.

CV2493 has always been famous with
its charming mid range, long life span,
and first-rate quality.

--45--

Mullard CV2493

Holland made CV2493 is equal to
E88CC-01, which produces less
interference to bass.

CV2493 has always been famous with
its charming mid range, long life span,
and first-rate quality.

--46--

Telefunken CCa

1. You will never realize how wonderful

this TFK CCa can bring you unless
you insert and listen realistic sound
coming from it. Nothing was
expected at the beginning when I
changed my Mullard CV4108 with
this TFK CCa, however, when I
insert it on, the miracle happen! It’s
so flawless that no matter from what
perspective you pick at, you can find
nothing wrong! IF you are still not
satisfied with its sound, the only
explanation must be your CD or
your CD Player. Try it and
experience what real sound can
bring you!

2. Though always been a faithful user

of Mullard 6DJ8, I have not satisfied
with its resolution, stage positioning
and its bass and treble performance
actually. While choosing between
Mullard E88CC, which
recommended by friends, and TFK
CCa, I took a risky shot and
purchased this expensive TFK CCa,
but luckily found myself making the

right decision. As whole performance, TFK CCa comes with
appropriate bass-treble range, and sweet mid range, which
produce an excellent elegant sound I ever heard. Highly
recommended product.

--47--

PCC88 / 7DJ8

Telefunken PCC88

No one could resist the incredible sound
of TFK PCC88 once they have
experienced it. Based on Anthem
pre-Amp, try to replace Siemens E88CC
with TFK PCC88, you will be
immediately moved by the music. It is
full of rhythm that you can actually feel
the details and music out of the sound.
It is getting difficult to find a TFK
E88CC/CCa/E188CC lately, you may
try your best to get one to possess
remarkable sound of it.

--48--

After having read so many tubes introduced above, you might be wondering which one is the best?
Furthermore, different people have different views. Everyone will have his/her own different answer in the end.
To get excellent performance, the arrangement of the sound and the design of the machine play an important
role here. I guess you will be able to choose your preferable one once you have personally heard the sound of
them.

Telefunken Series, beyond doubts, remains the highest grade in the realm of tube. The best of the best!
However, from the perspective of the whole function, I would like to recommend Mullard CV4108, which shows
you average or even better performance. Though other tubes such as Mullard E188CC and Holland Made
Mullard E88CC produce similar quality of sound, they are still inferior to Mullard CV4108; as for Holland Made
Philips E188CC SQ, which its sound trend is different from others, suits much better for spacious scenario like
Opera or orchestra, etc.

Basically, the selection of tube depends mostly on the sound trend of your system. If the original sound of
your system is fuzzy, with low resolution, you might need to equip Siemens E88CC for your system. However,
if you are already satisfied with the resolution and positioning, but disappointed with its thinness, then you
might use the thickness England Tube like E88CC to meet your needs. Last, if you would like to improve the
whole performance of your system, Telefunken CCa/E88CC will be your only choice!

--49--

Appendix A

Useful website for vacuum tubes

Useful Information Websites for Vacuum Tubes

www.thetubestore.com

www.sovtek.com

tube.diyzone.net

www.stereophile.com/shownews.cgi?1368

www.bb.wakwak.com/~s-ito/elec/elec.html

www.thlaudio.com/

www.audio.idv.tw

www.tnbstore.com.tw/

home.pchome.com.tw/travel/horobin/

netcity2.web.hinet.net/UserData/bigcwc/

home.pchome.com.tw/art/allen211/

www.jimcom.net/

www.cypress.ne.jp/kouchi/index.htm

www.audiosite-web.com

www.asahi-net.or.jp/~UP2J-KNST/tube.htm

www.jade.dti.ne.jp/~yoshiba/

www.alphapex.co.jp/

oldtube.com/

www.asahi-net.or.jp/~hp6y-isym/index.htm

--50--

Appendix B

Testing equipment list

Music Playback

The following equipment is used to test with AX4B-533 Tube as a preamp for testing and QA before

shipment:

Pre-amplifier for comparison

Audio Research LS-1

Audio Research LS-2

Audio Research LS-7

Audio Research LS-15

Power amplifier

Audio Research VT50

Audi Research VT100

Bryston 4BST

Audio Research LS-16

Golden Tube SEP-1

Sonic Frontiers SFL1-Signature

Jeff Rowland Model 1

PASS X150

USHER R0.8

--51--

CD player

Speaker

Interconnect

Meridian 506.20

Meridian 508.24

Wadia 301

Pioneer DV-S9

ProAc Response 1SC

ProAc Response 1.5

ProAc Response 2.5

ProAc Tablet III

ELAC EL212 Jet

Kimber Kable KCAG

Kimber Kable Silver Streak

Kimber Kable PBJ

Rotel 971

Musical Fidelity A3CD

Philips LHH 100

USHER CD-100

B & W 602 S2

B & W DM303

Dynaudio Contour 2.8

Dynaudio Contour 3.0

USHER CP-8871

--52--

Earphone

Speaker cable

CDs

Audio Technica ATH-W2002

Grado SR80

Kimber kable 8TC (double run)

Kimber Kable BiFocal XL

ZU Cable Julian

Yamamoto Yoshi – Misty - JVC XRCD

Diane Krall – Look in your eyes

Three Blind Mice

Gary Karr – Audiophile Selections

Ennio Morricone – The Legend Of 1900

Groove Note – Jacintha – Here’s to Ben

Rodgers Hart – Blue Moon

Christian Lindberg – Songs for Sunset

B B de Voeux

Dilber – The Art of Coloratura

--53--

Testing Equipment:

Special thanks to REALTEK lab for Audio Precision Test.

Game

Our game experience testing includes the following equipment:

AX4B-533 Tube

Intel Pentium 4 1.8A GHz

AOpen H610-340 cooling fan

AOpen 52X CD-ROM

Apacer 512MB DDR

Seagate 20GB hard drive

Panasonic 1.44MB floppy drive

AOpen 19” monitor

Speaker:

AOpen MS-810

AOpen MS-900

AOpen Titanium GT

Harman Champagne SE

Altec Lansing 621

Klipsch ProMedia 2.1

--54--

Appendix C

A Letter for Tube Lovers

To: Tube Lovers

Sent: June, 29, 2002

From: AOpen Motherboard Team

Cc: AX4B-533 Tube Staffs

Subject: Letter to Tube Lovers

Following a long and challenging road of designing AX4B-533 Tube, we finally present you
this fine piece of product and hoping you will like what you see and hear. This product is
designed for both gamers who rely heavily on performance, reliability and audio capability of a
motherboard and music lovers who will use it as a secondary or even primary music source
when using personal computer.

AX4B-533 Tube is such a rare breed that combines the best of both world – new Pentium
4 performance and old vacuum tube’s sound reproduction capability that brings thrill musical
and sound effect experience – The Ability to Engage You Musically is the Essence of AX4B-533
Tube.

We would like to suggest you to take following steps to ensure unbiased experience and
hoping you will also give us your subjective opinion and comments about our product. These

--55--

steps will assist you to properly set up the system and provide you useful resources when
needed.

Connection

The audio portion of AX4B-533 Tube can be set up in the following ways:

a. Direct connect to PC multimedia speaker

2 channel through tube output stage

2.1 channel through tube output stage

5.1 channel (front left and right through tube output stage and rest of

4 channels through regular AC’97 output stage
b. Direct connect to a headphone through headphone jack (Standard 6.3mm)
c. Connect to a power amplifier which the stereo speakers are connected to the power

amplifier

Warm up / Run-in

Audio components do require a period of run-in (or break-in) to achieve optimum
performance. May we suggest you left the power on of the motherboard for at least 24 hours to
have both vacuum tube and rest of audiophile components fully break-in before doing the
review.

This procedure will greatly help AX4B-533 Tube to achieve its optimum sonic performance.
Do not worry about the thermal since the 6922 is only running at very small current for both
filament and plate and will not generate excessive heat that causes permanent damage to the

--56--

motherboard.

Speaker Selection

PC multimedia speakers may not be able to reproduce realistic sound stage as well as
presentation compare to stereo speakers due to its build and costs. Therefore, we do
recommend you to acquire a pair of stereo speaker that the tonality suits you for critical
listening. As for the game’s sound effect, nicely built PC multimedia speakers will get the job
well done as well.

There are many inexpensive but solidly built bookshelf stereo speakers that sell for less
than US$300 and we recommend you do test with it to experience the technical merits and
audio reproduction of AX4B-533 Tube.

PC CD-ROM / Audio CD and DVD player selection

Believe it or not, CD drive will greatly affect the sound reproduction too. If you are using pc
CD-ROM, CD-RW or DVD drive, please do swap around with different brands and construction.
We guarantee you will find audible differences among each optical drive during the music
playback.

Your CD / DVD player’s analog output (RCA jack) can be hooked up to the AX4B-533 Tube

--57--

with an RCA-to-mini-phone jack (3.5mm) and serve as source. Please refer to the tube manual
page 21.

Headphone selection

You can use two kinds of headphones

! 6.3mm headphone

! 3.5mm headphone - via a converter to a 3.5mm plug for the lighter and smaller

headphone that can be found in many today’s gear such as MP3 player and portable
CD player to listen the audio through the AX4B-533 Tube connector via the supplied
bracket.

We recommend you acquire a pair of good quality headphone with 6.3mm plug.

Music CD selection

Make sure you have good recording music CDs when testing AX4B-533 Tube. Good
recording music CD will give more realistic sound stage, proper imagine, layers of resolution
and overall presentation. This music CD will then serve as a reference basis when comparing
the sonic performance.

--58--

Accessories

Sonic imperfections such as distortion and noise do occurred during any type of music
playback even with money-no-object high-end stereo equipment. We are not particularly
concerning about the sonic imperfection of AX4B-533 Tube since its technical merit will speak
for itself. However, if you do have audio- graded stereo accessories such as interconnector,
speaker cables, and even anti-vibration tube ring to decrease microphonic effect, we do suggest
you apply to the audition of AX4B-533 Tube for better sonic performance.

Sound quality

Within the audible frequency range, each person does have different subjective
preferences and perceptions on how a musical note is presented. These preferences and
perceptions presented no right and wrong in a simple sense. Where as a person’s dryness may
appear to another person’s cleanness; a relaxed musical sentence may regarded as laidback
and slow to someone else. Airy and openness may be seen as unrealistic soundstage. Again
these subjective observation and perceptions will occurred and suit differently.

What to look for when playing AX4B-533 Tube

Digital portion

--59--

Audio portion

! Overclockability with 1MHz stepping frequency adjustment

! Watch Dog Timer to assist overclockers to achieve optimum system configuration

with highest overclocking capability

! Dr. Voice II

! Ez Winflash for BIOS update and maintenance

! Vivid BIOS for user interface experience

! AGP protection technology to prevent improper AGP card’s voltage damage

motherboard

! EzRestore BIOS and ProMagic Utility for instant restore of your hard disk

! Open JukeBox for music playback without operating system

! SilentPC Technology to minimize fan noise

! Vacuum tube sound quality

! Build and construction

! Aesthetic and virtuoso

! Technology fusion

--60--

The sweetness of a female vocal will touch your heart and soul when playing by the
AX4B-533 Tube. Realistic musical note flows from a wind instrument transpired to your ears
with measurable distance. Trust your heart when auditioning AX4B-533 Tube.

When playing pc games, you will hear more realistic engine revving of racing cars; swords
chopping through the air, punches and kicks have more solid bass and tension of the sound
effect. A gamer’s must own piece!

AX4B-533 Tube can be hooked up WITHOUT the chassis and most of the time immune
from the noise and you will able to see the glow of the tube and the beauty of the motherboard.

If the cooling fan of the power supply does bother you, please use AOpen low noise ATV
Pentium 4 power supply for noise reduction.

Final note

You may find the analog RCA output jack of the supplied bracket may not look appealing
to you due to it is the PCB mount type. But its electrical characteristics and performance are as
good compare to other mounting type ones.

--61--

We do welcome your comments and suggestions on this product and will use it to improve
our future product design. Please feel free to contact us.

http://english.aopen.com.tw/tech/contact/courage.htm.

Enjoy the AX4B-533 Tube

Best regards,

AOpen Motherboard team

--62--