Interspace cable hum and noise

Well, I switched out my DV 10x5 for a Nottingham Tracer2 on my Interspace/Interspace today, just to compare. The left ground lead clip on the tone arm wire had, previously to my recently purchasing it, been broken off and replaced and resoldered with a slightly larger clip. I had some grounding troubles with the DV, but these seemed to resolve, though I don't actually know how. But now that I've mounted the Tracer, the left channel is many DB quieter than the right, I have a hum, and the left channel interconnect makes lots of noise if I move it or it touches anything. I've tried fixing the grounding at the interconnect plug, and tightening the hot and ground clips at the cartridge, to no avail. What's the problem? What do I do now?

Thanks.

(Same question in VA)