I had the USB Phono Plus (http://artproaudio.com/discontinued_products/discontinued_products/product/usb_phono_plus_v2/) set up to record to my laptop via USB and it has worked fine. But my PC is much more powerful so I got a USB cable that is a bit longer and connect the preamp to my tower from the stereo because it needed a few meters. However, I’ve never set up Audacity on the tower so I think I must be missing a setting somewhere because the usb device comes in with a huge buzz sound. It was never a problem with laptop. Could this be feedback of some kind?
It sounds most likely to be an earthing problem.
As you are using a different USB cable, the first thing that I would check is if the problem occurs on the new machine with the old cable.
Phono pre-amps usually have an “Earth” (“Ground”) connection (often a screw terminal). This should be connected with a wire to the Earth/ground connection on the turntable.
It is often beneficial to connect the turntable, computer, pre-amp and speakers to the same power socket.
The ground connection is definitely there.
The USB cable I was using before is too short to reach the computer so that’s not a test I can do and neither is the power test. Again, the distance is too great.
I guess I just have to keep using the laptop. Wasted money on the longer USB cable, I suppose.