Homophone

My thanks to Greenmachine and Matt J for your interest and advice on this problem. I have since carried out the following: 1. Checked all grounding of all Audio equipment and find them all OK. 2. Re-recorded the LP to new Mini Disc using the Denon Recorder. 3. Playbacked the MDisc to PC using portable MD R-900 as before but this time not using the adapter and making sure that the MD is well away from the PC or any source of magnetism. The result is the same with unacceptable background hum which I can only construe comes from the portable recorder mechanism.

I use my DENON Minidisc Recorder, which is attached to my audio system to record LPs. I then transfer the recording to my PC using my R-900 Portable Minidisc Recorder through a cable connected to the line in of my sound card. The intention of all of this is to eventually burn the tracks to a CDRW. I know that some will say "why don't you record direct to your PC using the turntable" The problem is my PC is in a room upstairs and the two-minidisc option was the only possibility. However, I find that when I playback the disc using the portable R-900 MD I get a decided background hum on the recording on my PC. My question is: Can this hum be caused by the portable MD and if so how to reduce this. I have no hum problems if I record from the radio or a CD so I do not think the fault lies with the sound card.