I had the same problem and tried numerous solutions. You could try different interconnects, did'nt work for me. Someone else suggested aluminium foil+ ferrite beads, wrapped around the phono cable, that did'nt work either. Grounding is an obvious one, but I assume you checked that. My solution was a new phonostage, the unit from K&k audio. Not a blip of pickup since I bought it and that uses tubes. Just shows, there is no substitute for careful design to exclude RFI
