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Grounding questions

I’ve had an issue with a slight hum through my system for a long time. System consists of Jolida Fusion Preamp and JD1000P amplifier. Both plugged into Futman Elite 15 power conditioner. It’s not dependent on any sources. Hum is there when amp is on. 
 

I have a dedicated line for the outlet to the Furman. Hum does not increase with higher volume. 
 

Maybe it’s an issue with the power amp but it could be an issue with the house wiring. The house is 62 years old and the fuse box is original and not grounded. Before I pay $800 to have it grounded, what do you think is causing the hum? It’s not cable related as I’ve swapped interconnects. The pre and amp are connected by a balanced cord. 

128x128mschott
kijanki's avatar
kijanki
4,396 posts
 

Hum independent of volume can be a sign of old/dry power supply caps. I would, per maxwave advise, take it to a friend and try it there.

Also, since you have balanced connection between pre and amp, check where shield is connected on both ends. It should be connected to shell/chassis and not to pin 1 (that would cause noise currents induced in shield to flow thru analog grounds causing constant hum). This is very common problem (1994 AES paper, Neil Muncy).

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fuzztone's avatar
fuzztone
5,501 posts
 

Answer your own question with an $8 receptacle tester. Then make sure that the green wire is attached on both ends.

mschott's avatar
mschott OP
129 posts
 

FYI the hum existed before the electrician installed the dedicated line. Im

not home to look at the receptical at this time. 

gs5556
1,211 posts
 

First things first: Power on the amplifier without the preamp. If the hum goes away then connect the preamp. If still no hum connect the source components one at a time to the preamp until there's humming. Then we can narrow it down.

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