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are some phono stages more resistant to hum?

After a tonearm upgrade, which mostly involved "improved" shielded cable, it now hums with tube phono stage (upgraded AR PH3-SE)but no hum with backup ss device (DB Systems). It appears the hum originates with the new wiring, but why would one phono stage be impervious to the hum? Do phono stages have different grounding schemes, making them more compatible with certain tt/tonearm/wiring combos in unpredicable ways? Are ss phono pres less susceptible to hum? Have you ever changed phono pre to cure a hum incompatibility? I see from forums that tt hum problems are common and sometimes difficult to solve. Shouldn't a shielded cable be more immune to hum, not less?
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Showing 3 responses by lloydc

lloydc's avatar
lloydc OP
734 posts
 
thank you, will try all these things. I did try different tubes, not the problem.
lloydc's avatar
lloydc OP
734 posts
 
when I do not connect the ground wire from the tt, just leave it dangling unconnected to anything, the hum is greatly reduced. What does this imply? problem with the way the entire system is grounded? I live in an apartment, and have no control over the non-audiophile wiring setup.
lloydc's avatar
lloydc OP
734 posts
 
thanks to everyone for the responses. It is definitely hum, and not tube or other noise. I suspect that Dhl93449 correctly diagnosed a ground loop. How to solve it, in an apartment with exceptionally noisy wiring (even a flourescent light on the same circuit) and few outlets, is an open question.

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