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seek advice on hum problem from phono preamp

My EAR 834P phono pre produces quite audible hum at the speakers. It is plugged into a Noisetrapper isolation transformer, which is plugged into another big NT isolation transformer. Probably not a ground loop: cheater plug on the EAR, or anywhere else, doesn't help. Using a Grado Statement Ref cartridge, which is unsheilded and was prone to hum pickup from the motor on a Rega TT, but isn't close to the motor on Thorens TD850; TT is far from the EAR. So the hum comes from the cartridge or the phono pre. Is this just typical of tube phono pre's (meaning, a SS unit is the only real solution), the EAR834P in particular or a defect in same? can the type of tube be a factor, do I need a different cartridge, or what? would greatly appreciate suggestions.
128x128lloydc
mingles
796 posts
 
Is this just typical of tube phono pre's (meaning, a SS unit is the only real solution), the EAR834P in particular or a defect in same? can the type of tube be a factor

This isn't normal behavior and you should be able to get rid of it. My 834P doesn't hum. I've never heard a tube hum so I doubt that's the problem. Try these things:

- Make sure the Grado is wired correctly. Check the connections.
- Move the TT away from any transformers or motors.
- What else is plugged into the Noisetrapper? Unplug it.
- Remove the Noisetrapper transformers from the picture and see if it makes any change.
- Ground the TT to the phono stage. Then remove the ground to see if it makes any change.
- Plug the 834P into a different preamp input.
photon46
1,082 posts
 
You haven't mentioned if this is a recent problem or one that's existed since you installed your phono pre. I was recently befuddled by a phono hum problem, couldn't figure out why it was happening. Then in a moment of Homer Simpson "Duuuhh" clarity, I remembered I'd changed interconnects and that's when the problem started. The unshielded interconnnects were the problem, replaced them with shielded cables and the problem vanished.
lloydc's avatar
lloydc OP
751 posts
 
thanks to everyone, I will try all of the above and keep after it.
f_gates55's avatar
f_gates55
2 posts
 
I have very laud hum from my new modwright ph9 phono stage even when my volume is set to zero, my old phono stage is a ear 834p no hum whatsoever, my amp is ear v20, I have set the power supply as far as it will go from the phono stage but still the same laud hum, my turntable is transrotor with SME309 and PARADOX PULSE MC, I had no hum problems with this system using the ear 834p.
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