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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.
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victorlong1
7 posts
 
Have you tried moving your phono stage around on your rack. Sometimes a few inches will cut the noise way down. Also moving the interconnects a slightly in one direction or another can help. I have mine tied off(with black sewing thread) in the quietest location available. I still have a slight hum, but at my listening position it is not too noticeable and when the music is playing it is gone. The lush sound I get from my tube phono stage makes up for it.
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k9vap
1 posts
 
The powersupply transformer generates alot of hum. I rehoused mine in a separate remote box & solved the problem.....wonderfully quiet now!
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
1,086 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.
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