Dell Dimension C521 and weak line-in signal with Xonar DX audio card

  I am digitizing my vinyl records from a record player via a preamp to the line-in jack of a Xonar DX card. The input signal is so muted that that going ahead with the task is impractical. I set Recording Devices -> Line In -> Levels all the way to 100 but the sound in my recording program rarely gets higher than - 40 decibels. Fortunately my Sigma Tel onboard audio has been able to deliver very good recorded sound through its line-in. In fact a setting of 15 in the Windows Sound applet will deliver audio that approaches 0 decibels or even exceeds it.  To date I have tried four different Xonar DXs in my system and they have all had the same problem. The vendor that sold me the board tested one of them on my computer and determined that the card was defective. I have tried resetting my BIOS and have installed the Xonar DX (after disabling the onboard audio) on a fresh copy of Windows 7 (32-bit). The driver installs properly and playing back music in Media Player works fine but when recording the line-in is always weak. Other things that I have tried are: inserting the Xonar in the PCI-e x 16 slot, testing the PCI-e x 1 slot with a NIC inserted in it and installing the latest chipset driver for my computer. The latter is an update called "nVidia SMBus Driver" and is compatible with Win XP but I read on a forum that it was alright to install it under Windows 7.

  Dell sells the Xonar DX on its Web site (I bought mine elsewhere) and for this reason you might be aware of some incompatibility when using the Xonar DX in a Dimension C521.

  Do you know of an audio diagnostics program? I tried Rightmark's "Audio Analyser" but it did not work as advertised.