• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

A-open’s new motherboard with vacuum tube preamp

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
An engineer at the well-known motherboard manufacture a-open has built a motherboard incorporating onboard audio with a vacuum tube pre-amp stage. The board also uses ELNA caps, Cardas wire, REL Mulitcap Capacitor and VISHAY resistors. The board comes with a sock Sovtek 9622.

More information can be found at http://www.aopen.com/products/mb/ax4b-533tube.htm The board is called the AX4B-533 Tube.


  • (red)-ax4b-533-art-part1.jpg
    38.9 KB · Views: 539
Joined 2001
Paid Member
As was pointed out in another thread, maybe on this board or another, the inside of a computer is a pretty "noisy" place to put an analog tube circuit. Be better just to hang the tube pre off of a FireWire (or even USB) port outside the computer box.

Nice pictures thou. Thanx. A real mix of old electronics and new.

Beats me what putting the sound through a single vacuum tube will do after the sound has already suffered the indignities of wiggling through tens of thousands of semiconductors... I think it's a bit like putting a magic power cord on your amplifier even though the power has already traversed maybe hundreds of miles of wire.

That said, I think the mobo is really cool, not from an audio point of view but simply for the sake of aesthetics.

The engineer or engineers certainly did a great job but I have to agree the insides of computers are too noisy for that board use but maybe outside the output stage should sound better. But I think the "idea" for this design may come from the same idea of putting expensive caps in the signal path for a band-aid. Don't get me wrong I use PP, PS, and Met Poly caps too but I'm mainly interested in the price-to-performance ratio. Cheaper cap parallel with small value premiunm cap.
AOpen motherboards has better filteration and regulation then other motherboard manufactures. AOpen uses 2000uF for the on-board power supply and other manufactures uses either 1000uF or 1500uF. With a good power supply like Turbo Cool or Enermax, the noise can be kept to a minimum.

The tube can be switch off if the user doesn't want to have it on every time they start up.
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.