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Need help solving hum problem

This one really has me stumped....

The system:
Sony SCD-777ES
analog out into Placette Active Line Stage
digital out into Dodson DAC into Placette
Turntable also into Placette
Placette into CJ11A
ALL front end components plugged into Shunyata Hydra PLC

I get constant, low-volume hum when the Placette is switched to either the Dodson OR the Sony analog out, but not when switched to vinyl or any unused input.

The problem is cured when the Dodson is plugged into another outlet (same circuit). Why would the Dodson contaminate the system at all, and (this is the kicker) for two of the sources (itself and the Sony analog out) but not for the phono?

Any ideas? thanks. --dan
drubin

Showing 4 responses by drubin

drubin OP
3,282 posts
 
Yes, it is.
drubin OP
3,282 posts
 
Thank you. I had tried a cheater on both the DAC and the preamp, with no success. I will try it on the amp, but as I said, the hum goes away if the amp and DAC share the same wall outlet. Based on the results of my various troubleshooting attempts, I don't think that the location or proximity of components and cables is the issue in this case, but I do appreciate that those can be factors in system noise.
drubin OP
3,282 posts
 
(a bit chagrined...) I thought that I had tried lifting the ground on the Dodson. But I happened to try it again, and it seems to have fixed the problem.

Nevertheless, I will attempt to work through the process Sean describes in his excellent other post.
drubin OP
3,282 posts
 
Appears I spoke too soon. It's baaaack.....
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