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Thread: M3-ATX Amplifier Thum Control

  1. #1
    Constant Bitrate besjr69's Avatar
    Join Date
    Feb 2011

    M3-ATX Amplifier Thum Control

    I recently put my first Car PC together. System details are listed below

    Motherboard: Zotac F-Series
    Memory: 2GB DDR2
    HDD: 320GB Toshiba
    Monitor: Lilliput Dual Din (HDMI)
    Power: M3-ATX (125W)
    Operating System: Win 7 64bit

    Everything works fine, but I do have one annoying problem. The documentation for the M3-ATX states that the Thump output delays turning on the amplifiers while the PC is starting to avoid thump. This does not appear to be true. I am not able to avoid the thump at all. I appears it only delays it for about a sec or so. When booting up I hear the HDD spin up and get a steady hiss/crackle until the windows logon screen comes on. This is when I receive my first thump and everything goes quiet until the shutdown/hibernate process. When I cut the ignition, the hiss/crackle sound comes back on until the "Hard Off" stage and I receive another thump. I think it would be best to enable the signal when the 5VUSB rails are turned on and off. As it appears the system is quiet at those points.

    I see there is an option to control the M3-ATX using a serial cable. However, there is little documentation on what you can and cannot control using the serial cable. Do you have config options for the "Thump" control using the software interface? Or do i need to design a small circuit to trigger the output using the 5V USB rails?


  2. #2
    Constant Bitrate besjr69's Avatar
    Join Date
    Feb 2011
    After much more research, I've decided to prototype the following circuit. The idea is to tap into the USB header to get the 5V USB signal. Then I'll switch on a transistor to send the Amp Control signal. I'm going this route because I prefer not to use relays. A simple switch should do the job. I will report back with the results.

    Circuit Diagram:
    Attached Images Attached Images  

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