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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
mschott's avatar
mschott OP
136 posts
 

I have a quote for a new Siemens box. It’s way out of my budget and comfort zone. I’ve been in the home for 24 years with no electrical issues. There is a new supplemental box installed when I had a bathroom reno in 2014. It runs the sump pump in addition to the bathroom circuits. 

russ69's avatar
russ69
3,534 posts
 

Just as a test drop the ground on the amp. Then do the same to the pre-amp. 

kijanki's avatar
kijanki
4,432 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
5,635 posts
 

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

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