AOpen AX4B 533 Tube Motherboard Review

Author: Howard Ha, Peter Judson
Editor: Howard Ha
Publish Date: Thursday, November 14th, 2002
Originally Published on Neoseeker (
Article Link:
Copyright Neo Era Media, Inc. - please do not redistribute or use for commercial purposes.

Today we have a unique product on our plate. The first ever consumer motherboard with a vacuum tube as a part of its onboard audio subsystem. This is not only an industry first, it’s one of the many industry firsts introduced by AOpen.

The AX4B-533 Tube is what AOpen terms as the fusion of current day P4 technology, with the century old Vacuum Tube, to create the world’s first true motherboard to claim more lifelike reproduction of music and gaming audio.

At the time of writing this article, the AX4B-533 Tube is no longer cutting edge because it uses the older Intel 845E chipset, but it’s still state of the art, as far as we’re concerned, because of the beautiful Vacuum Tube. Thus we head onwards with our tests and our discussion of just what the AX4B-533 Tube brings to the table.

Why a Vacuum Tube

Almost anyone is an audio enthusiast at some level, and a fair number of audio enthusiasts are well aware of the legendary audio quality attributed to Vacuum Tube amplifiers. Some chalk it up to nostalgic silliness on the part of audiophiles clinging to old technologies, and fearing improvement. And others swear by the richness, the depth, and the purity of audio from Tube amplifiers.

AOpen’s AX4B-533 Tube manual includes a very serious preamble which includes the reasons why they decided to create this P4 - Vacuum Tube fusion, as well as a detailed description of how they addressed various issues surrounding such a fusion design.

So really, why a Vacuum Tube? Aside from looking mighty cool, AOpen and many audiophiles believe that music is… well more musical, more breathtaking, and more soulful. Yes, the harmonic distortion is higher with a Tube system then with a solid state amplifier, but many many people will pick the higher distortion Tube amplifier because they feel the music just sounds BETTER.

In AOPen’s own words: “We love what we hear regardless of harmonic distortion as well as the limited frequency response compared to a solid state device.”

P4 - Vacuum Tube Fusion

I thought I would give you some information about AOpen’s vacuum tube, to curb the curious audiophiles and hardcore enthusiasts alike. AOpen didn’t just go and stuff a tube onto the motherboard and push it out the door, they wanted something that would stand up to some scrutiny.

In fact, they think they’ve succeeded in making the the AX4B a pretty good product:

“Yes, the 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.”

AOpen’s “meticulous journey” to bring this fusion to fruition involved carefully choosing components. They use a 24K plated ceramic 9 pin socket for the tube, Cardas Audi cable, Vishay resistors, and a Maxim 668 DC-DC power supply for the tube.

General Specs and Overview:

CPU    Intel Pentium 4 CPU
   Socket 478
Chipset    Intel 845E
   Intel ICH4
Super I/O    Winbond
Clock Gen.    ICS
   Max Overclocking : 992Mhz
Main Memory    Support DDR266 [PC2100]
   DDR DIMM x 3
   Max 2GB
Graphics    4X AGP slot
LAN    Realtek 10/100Mbps PCI LAN Chip
   Integrated Realtek PHY
Sound    Realtek AC'97 CODEC on-board
   5.1 Channel
   TubeSound Vacuum Tube Technology
USB    USB2.0 x 6
Slots    AGP x 1
   PCI x 3
Storage & Back Panel I/O    Floppy Drive Connector x 1
   IDE Channel : ATA100 x 2
   PS/2 Keyboard x 1
   PS/2 Mouse x 1
   USB Port x 2
   LAN Port x 1
   COM Port x 2
   Printer Port x 1
   Game/MIDI Port x 1
   Speaker_Out x 1
   Line_In x 1
   MIC_In x 1
On Board Connector    Front Panel x 1
   Front Audio x 1
   CPU FAN x 1
   System FAN x 1
   Chassis FAN x 1
   Chassis Intrusion Connector x 1
   AUX_IN x 1
   CD_IN x 1
   Wake_on_LAN x 1
   Wake_on_Modem x 1
   IrDA x 1
   S/PDIF x 1
   USB Port x 4 (optional cable)
   Tube Audio Connector x 1 (Lin-in to Tube AMP, RCA output, S/PDIF output, 6.3mm Headphone)
BIOS    Award PnP 4Mb Flash ROM BIOS
Form Factor    ATX
Board Size    305 mm x 244 mm

The specs on the board itself are pretty standard for a good 845E board, but you will notice that AOpen had to sacrifice a few things in order to fit all the Tube circuitry onto a regular sized motherboard, most notably, there are only 3 PCI slots on this board.

Features wise you have integrated 10/100Mbps LAN, USB2.0 via 2 onboard USB ports, and of course, the very fancy integrated audio with a specially designed expansion bracket that AOpen recommends for the highest quality audio output.

What’s missing? Aside from having only 3 PCI slots, you will note that the package doesn’t come with an expansion bracket for more USB slots, like a lot of other current motherboards (we usually see at least 4 total USB ports on motherboard packages). The board supports up to 6 USB 2.0 ports, but you’d have to buy an expansion bracket yourself, separately. You also don’t have IDE RAID, but for all intents and purposes, AOpen’s engineers did a really good job with deciding what to keep and what to cut out.

If you look at the layout pictures of the board, you can see that the Tube circuitry takes a large chunk of the board’s real estate. In spite of this, we were impressed by what WASN’T lacking, like AOpen’s Dr Voice II voice based boot diagnostics, and AGP Protection (against older, 3.3V AGP cards, which can damage 845 chipsets).

You can also see from the pictures that this is a very good looking board with AOpen’s signature black PCB, a gold coloured aluminum chipset heatsink, the Vacuum Tube itself and it’s surrounding components, and a little “plaque” like sticker signifying the use of “TubeSound Technology” (adding badges and stickers like this is also one of AOpen’s little trademark touches). This is a board that will look very nice indeed with a modified case with window and lighting.

Layout wise, too, there’s little wrong with the design. The location of most of the elements are in good places, though the AGP slot is still too close to the RAM, in this case we’re going to have to give AOpen some slack for this, since the Tube components do take up a good 1/5th of the lower part of the board.

BIOS and Overclocking Features

Before I start talking about the BIOS and overclocking features in the BIOS, I wanted to talk about a very special feature that AOpen has implemented on the board. They call it the “Watch Dog Timer”, which is a system similar to what other manufacturers have used before to prevent jumperless boards from just hanging and requiring a manual CMOS clear via the CMOS jumper.

What Watch Dog Timer does is detect whether the last POST attempt was successful. If the last attempt was a failure, it will restart the system with default values after 5 seconds (you can even manually restart the system by pressing the [ Home ] key). This is a godsend for those of us looking to push the system. Remember during our MSI KT4 Ultra review when I complained about the system giving us black screens when we were overzealous with our overclocking attempts? With the KT4 Ultra and many other boards, we have to clear the CMOS via the CMOS jumpers. Not so with the AOpen AX4B. (Right now I’m reviewing a board that doesn’t even have a CMOS clear jumper K).

Ok on to BIOS overclocking features:

Overclocking Features Overview
FSB Settings 100Mhz up to 248Mhz in 1Mhz increments
RAM Support and settings Up to 2GB, DDR200, DDR266
CPU Vcore 1.1v to 1.85v in 0.025 increments

There are no adjustments for DRAM or AGP voltage on this board, and you can’t set the multiplier. There are memory timings adjustments for those of you who tweak your RAM, but the board will only accept up to 266Mhz for the clock speed setting.

We tested this board with our current test setup:

Intel P4 2.8Ghz CPU
AVC Sunflower P4 Cooler
512MB Corsair XMS3200 DDR RAM
ATI RADEON 9700 Pro 128MB
Seagate 120GB ATA133 Barracuda ST3100

We ran our tests on Windows XP with SP1, using the latest BIOS as of November 1 2002. The system was set to 266Mhz CL2, and the BIOS is loaded with “Optimized Defaults”.

The tests will be compared against the FIC VC19 that we reviewed in September, which also uses the 845E chipset.

Productivity Performance:


The AX4B leads by a very slight margin (around 4%) in the PCMark scores. The advantage that the AX4B has over the VC19 is observed again in the Sisoft Sandra Memory Bandwidth tests shown later.


Sisoft Sandra 2003

In the Sisoft Sandra tests we get somewhat mixed results. The AX4B leads very slightly in the memory bandwidth and multimedia tests, but the FIC VC19 gives higher CPU results.

While productivity tests showed the AX4B-533 to be ahead in most results, the tables are turned on our 3Dmark testing. Note how at all resolutions, in all situations, the FIC VC19 leads the benchmarks, if even by the slightest margin.

The overall performance trends are so slight between the two boards that the most logical conclusion we can draw from this is that the AX4B-533 Tube has performance on par with other 845E boards, in spite of the changes AOpen made in order to get the Tube circuitry in place. It seems our initial concern that such a major “fusion” between two technologies might compromise performance was unfounded.

Audio Performance

We’re far from audiophiles here, but I consider myself a decent audio enthusiast. I have a fairly nice setup at home consisting of a Denon amplifier/receiver, B&W speakers, and a Sony ES CD player for pure music listening, and I have a respectable pair of MidiLand S2 speakers for my computer audio and gaming. So what do I say about the AX4B Tube sound? It definitely has advantages over standard AC’97 that you get from any other integrated sound.

In fact, we did some A-B comparison tests comparing the AX4B Tube against a few other motherboards with integrated audio, and it’s very clear that the Tube brings out a richness and texture to the audio that can’t be heard with the other motherboards. In music of all kinds, there’s a sense of depth, of lushness and vigor that you don’t get with regular audio. Detail in the higher frequencies is especially easy to identify: stringed instruments have a greater sense of depth, with orchestral pieces showing an open and airy soundstage. Deeper sounding instruments like the bass, cello, and the bass portions of piano pieces have a stronger, more subtly guttural impact. The overall experience is definitely more enjoyable than the same experience with regular, integrated audio.

The AX4B-533 Tube is a superb board for the audio enthusiast. There are a number of reasons for this:

  1. The Vacuum Tube pays off with higher quality audio, greater sense of realism, and musical tonality, for those who care
  2. You can’t get Vacuum Tube like sound on the computer ANY OTHER WAY. You certainly can’t buy a Sound Blaster with a mini Tube sticking out of it.
  3. The aesthetic design of the board makes it an ideal centerpiece for an audio enthusiasts’ modded case.

AOPen’s engineering team also managed to integrate the Vacuum Tube onto the motherboard without sacrificing a whole lot on performance on the way. Sure the board’s a little slower when you look at most of the charts in our test results, but for the most part the difference is very minimal. It’s not as if the board runs 10% slower than other 845E boards.

Make no mistake though; this board is now beginning to show its age. It’s now November in 2002, and the board was introduced in June or so. On the Intel platform we’re now a generation or so ahead, and other boards that we have in the lab now sport AGP 8X and DDR400 support, whereas the AX4B-533 Tube only has DDR266 support.

Regardless, if audio is your ticket, and you are a hobbyist, this is THE board to get. AGP8X and DDR400 haven’t really lifted any eyebrows in our performance tests, so you might not miss them much.

This product is an innovation, and an inspiration. I’m very impressed with AOpen for once again introducing a new and unique idea to the market.

Overall Score: 90%


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