Hum Help


I had an interesting case of hum pop up (that I was able to solve) but interested in learning a bit more. 

I have a Technics 1200 Mk5 that is pretty heavily modded. I currently run a Jelco 750D arm on it and have had MM cartridges on it forever, but recently swapped to a Hana SL and picked up a low output Grado Opus3. The table is connected to an ifi iPhono. 

When I made the swap to MC, I started to get a hum on my amp on that line in. I figured it was the iPhono, but I swapped in my Phenomena and it was still there. I tried with both MC cartridges and it remained. I connected the iPhono to the amp using a different rca on a different channel - still a hum. That left the tonearm and phono cable (a Zu Mission). I swapped the phono cable with one from a stock Pro-Ject deck. Hum went away. 

The Zu is not very 'shielded' (?) but I run mostly Zu cables and have never had this issue. I have a long Zu going from the Phenomena to the amp, for example, with no hum. 

Any ideas about what might cause this? I can pretty easily get a better cable, but I'm not sure if that is more like putting lipstick on a pig, as they say, because there is an underlying issue. 
tjnindc
The hum was always there. Lower output source just makes it noticable. The S/N probably went from 70dB to 35.
Happy hunting.
I’d use headphones, turn the level up with no program and start moving the phono cables around. You might be surprised.
If not good luck to ya.
In the 80's Moncrieff said to run the whole cable assembly through a grounded sheath. That definitely helps.
If you do have a constant hum and want to get rid of it completely - read my post at the bottom of this thread
https://forum.audiogon.com/discussions/rega-planar-10-aria-mc-phono-stage-hum

Components with two pin power supplies (i.e. that are not properly grounded) often have hum issues with many amps, but there are some that do not

That simple fix will remedy it.

Regards