|While testing this with my in house system, I discovered a low audible noise that seemed to coincide with moving the mouse, or accessing the hard disk. It appears that grounding the preamp through PCI pin 3 was a bad idea and created a ground loop for some of the energy from the data bus to be returned through the preamp. The only way I was able to get the noise under control was to eliminate the ground on the PCI port. The quietest ground scheme I could come up with was to tie the turntable ground directly to the power supply, and ground the preamp through the case. I also added a couple of caps to the board. A 1 uF and .0015 uF across the +/- 12 Volt inputs, and .0015 uF across the 470 uF caps. I posted an updated picture below. Notice the trace cut on pin 3 of the PCI port and the added caps.