Well Tempered Tonearm clone and hum

Hi,

About 20 years, when I was a still a student, I was heavy into DIY audio and I built a Well Tempered Tonearm clone. The tonearm didn't required precision machining and bearings so I figured it was doable with a similar performance as the original. I used it for about 10 years then the turntable was put into storage because I moved, married, house, etc. Recently I took the turntable out of storage because I was always fond it. The arm always worked well except for one detail: a bit of electrical hum. This is something I want to improve. I have used thin copper wires for the tonearm wiring for which I twisted the strands together. The original WTT doesn't have shielded wiring I wonder if there is a trick to reduce hum. I'm using an MM cartridge (Shure V15 VMR)

Any ideas?

Michel